EAPPC & BEAMS 2018

7th Euro-Asian Pulsed Power Conference

22nd International Conference on High-Power

Particle Beams

Book of Abstracts

Changsha, China | September 16-20, 2018

Table of contents

Monday 17 September 2018 ...... 1 Plenary Session 1 - Plenary Speaker: SINARS Daniel...... 1 Plenary Speaker: XIE Weiping...... 1 Oral Session 1 - High Power, Solid State Electronics - Session Chair: REDONDO Luís...... 2 Oral Session 2 - High Power Microwave Devices - Session Chair: ROMANCHENKO Ilya...... 6 Oral Session 3 - Intense Electron and Ion Beams - Session Chair: TAKAYAMA Ken...... 10 Poster Session Ⅰ - Pulsed Power Technology, Systems and Components - Session Chair: YANG Jianhua...... 14 Poster Session Ⅱ - High Power Microwaves and RF Sources - Session Chair: SHU Ting...... 25 Poster Session Ⅲ - Pulsed Power Applications - Session Chair: LIU Jinliang...... 36 Oral Session 4 - High Voltage Insulation; High Energy Density Storage; High Power, Solid State Electronics - Session Chair: LIU Kefu...... 46 Oral Session 5 - Microwave Systems and Sources; Beamless HPM sources - Session Chair: SCHEIDER Markus...... 52 Oral Session 6 - Medical, Biological and Environmental Applications - Session Chair: MUELLER Georg...... 57

Monday 18 September 2018 ...... 61 Plenary Session 2 - Plenary Speaker: CHAIKOVSKY Stanislav...... 61 Plenary Speaker: HE Wenlong...... 62 Oral Session 7 - Closing and Opening Switches -Session Chair: SHAO Tao...... 62 Oral Session 8 - High Power Microwave Devices; THz Technology - Session Chair : HE Wenlong...... 67 Oral Session 9 - Electromagnetic, Plasma, Beam and Laser Applications; Electromagnetic Launchers; Theory and Simulation -Session Chair: YAN Ping...... 71 Poster Session Ⅳ - Pulsed Power Technology, Systems and Components - Session Chair: CHEN Dongqun...... 75 Poster Session Ⅴ - High Power Microwaves and RF Sources - Session Chair: YUAN Chengwei...... 87 Poster Session Ⅵ - Particle Beam Technology - Session Chair: ZHANG Zicheng...... 98 Oral Session 10 - Compact and Repetitive Pulsed Power Systems - Session Chair: MANKOWSKI John...... 109 Oral Session 11 - Antennas -Session Chair: QIAN Baoliang...... 114 Oral Session 12 - Z, X-Pinches and Imploding Liners; High Power Diodes -Session Chair: XIE Weiping...... 119

Monday 19 September 2018 ...... 123 Plenary Session 3 - Plenary Speaker: WANG Xinxin...... 123 Plenary Speaker: TAKAYAMA Ken...... 123 Oral Session 13 - Compact and Repetitive Pulsed Power Systems; High Current and High Energy Systems; Theory and Simulation -Session Chair: CHAIKOVSKY Stanislav...... 124 Oral Session 14 - High Current Accelerators; Plasma, Ion and Electron Sources - Session Chair: CARON Michel...... 129

Oral Session 15 -Pulsed Power Diagnostics - Session Chair: LIN Fuchang...... 133 Poster Session Ⅶ- Pulsed Power Technology, Systems and Components - Session Chair: JIN Xiao...... 138 Poster Session Ⅷ-Radiation Sources - Session Chair: SINARS Daniel...... 148 Poster Session Ⅸ- Pulsed Power Applications - Session Chair: SHI Jinshui...... 159 Oral Session 16 - Compact and Repetitive Pulsed Power Systems - Session Chair : RYOO Hongje ...... 168 Oral Session 17 - HPEM Effects; Theory and Simulation - Session Chair: HE Juntao...... 172 Oral Session 18 -Industrial and Commercial Applications - Session Chair : JIN Yunsik...... 177

Monday 20 September 2018 ...... 184 Oral Session 19 - Generators and Networks - Session Chair: ZURAUSKIENE Nerija…...... 184 Oral Session 20 - High Energy Density Physics; Theory and Simulation - Session Chair: CONG Peitian...... 186 Oral Session 21 - Transmission Lines and Transformers - Session Chair: JAMES Dickens...... 189 Oral Session 22 -High Voltage Power Supplies - Session Chair: YAKOV Krasik...... 192 Oral Session 23 - High Power Microwave Devices - Session Chair: ZHANG Jun...... 195 Oral Session 24 - Free Electron Lasers; Theory and Simulation - Session Chair: YANG Hanwu...... 198 EAPPC & BEAMS 2018 / Programme Monday 17 September 2018

Monday, 17 September 2018

Plenary Session 1 Plenary Speaker: SINARS Daniel - Chair: NOVAC Bucur

(BALL ROOMS 1 & 2#）[08:30-09:20]

08:30 [A3346] Pulsed power science and applications on Sandia’s Z machine SINARS Daniel (Radiation and Fusion Physics Group Sandia National Laboratories, United States) Abstract: Sandia’s 26 MA, 20 MJ “Z Machine” is presently the world’s largest fast pulsed power machine, delivering up to 80 TW of electrical power in a 100-ns pulse. The facility is used for applied research in dynamic materials, radiation sources, and fusion sources. This talk will provide an overview of the research done on the Z Machine, as well as additional pulsed power technology maturation efforts being done at Sandia as we consider possible architectures for a larger-scale driver.

Plenary Session 1 Plenary Speaker: XIE Weiping - Chair: WANG Xinxin

(BALL ROOMS 1 & 2#）[09:20-10:10] 09:20 [A2084] Design of a high reliability 4 MV flash X‐ray facility XIE Weiping (Institute of Fluid Physics, CAEP, China) Abstract: For the use of high valuable fluid dynamics experiment, a 4 MV flash X-ray facility (Sirius，天狼星) has been designed and is in fabrication at Institute of Fluid Physics (IFP). The Sirius has the ability to deliver 4 MV, 100 kA，60 ns electric pulse to a 40 Ω matched diode. It adopts a novel high reliability technical scheme with less active components of high power gas switch, which is based on Tesla Transformer, Induction Voltage Adder (IVA) and rod-pinch diode (RPD). The Sirius consists six-module induction voltage adder (IVA). Each module is identical and composed of a Tesla pulse transformer, intermediate storage capacitor, laser trigger gas switch, pulse forming line, self-breaking oil switch, water transmission line, and one induction cavity. The primary stored energy in Tesla pulse transformer is discharged in 4.0 µs into the intermediate storage capacitor. The operating voltage at the intermediate capacitor is about 1.2 MV when the two capacitors of the Tesla pulse transformer are charged to ±60 kV. The intermediate capacitor is switched out by Page 1

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the laser triggered gas switch to 4.0 Ω, 30 ns pulse forming line which is discharged by the self-breaking oil switch to 7.0 Ω water transmission line. The forwarding going voltage wave at each water transmission line section is about 800 kV, 65 ns and added by six induction cavities. The 4.0 MV, 65 ns voltage pulse with positive polarity could be obtained to drive a 40 Ω RPD. The reliability and stability are the key issue of this facility. As the Tesla pulse transformer has only one gas switch the reliability is very high, it is employed to provide the primary energy instead of Marx generator. Another key factor of high reliability is low pre-fire probability and jitter of the laser triggered gas switch. Every laser triggered gas switch is triggered by one 266 nm laser and each switch can be triggered independently. Conservative electrical stress design is the third key factor of the high reliability. So, the Sirius contains 12 triggered gas switch and 6 oil self-breakdown gaps, which is expected to have the reliability up to 98%, 1.5 mm source diameter, and 10 rad dose at a distance of 1 m. The Sirius is 5 m wide, 5 m high and 17 m long.

Oral Session 1 - High Power, Solid State Electronics - Session Chair: REDONDO Luís

(BALL ROOMS 1#）[10:30-12:30] 10:30 O1-1 [A1592] Compact design of the fast solid‐state pulsed power modulator based on a modular structure BAE Jung-Soo1, YU Chan-Hun2, KIM Hyoung-Suk2, KIM Shin1, JANG Sung-Roc2 (1. University of Science&Technology, Daejeon, Korea; 2. Korea Electrotechnology Research Institute, Korea) Abstract: This paper describes the design of the solid-state pulsed power modulator based on a modular structure for wide applications such as environment, medical, agriculture, and food. The proposed modular structure has the advantages of increasing output voltage and current by stacking series and parallel. The specifications of the high performance unit module are 10 kV, 80 ns (PW), 30 ns (tr & tf), 100 kHz (PRR), 1 kWavg. In addition to fast rising and falling with short pulse width, the developed solid-state pulsed power modulator has the high power density which is achieved greater than 150 W/L. To allow the compact design, the high efficiency resonant converter-based soft switching is designed for charging the six Marx cells. For achieving fast rising and falling with short pulse width, the control loop that provides signal as well as isolated power for gate driving of all the MOSFETs and gate driver circuit for providing fast rising of gate signal are designed with minimized inductance. Finally, the design of the modular pulsed power modulator is verified with Page 2

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Pspice simulation, and the experimental result that will be discussed in following paper. 10:45 O1-2 [A1619] Solid‐state thyratron replacement KEMPKES Michael, SIMPSON Rebecca, ROTH Ian, GAUDREAU Marcel (Diversified Technologies, Inc., United States) Abstract: Thyratrons are typically used as the switch in high power, short pulse modulators with pulse-forming networks. However, thyratrons have a lifetime of only ten to twenty thousand hours, their reservoir heater voltage needs to be adjusted periodically, and reduced overall demand has led multiple thyratron vendors to slow or cease production. In contrast, solid-state switches have a much longer lifetime, need no maintenance, and are based on widely-available commercial items. Despite these advantages, solid-state devices have not historically seen use, due to limited voltage, current, and risetime. Diversified Technologies, Inc. (DTI) has removed this barrier, having developed, built, and tested a thyratron-replacement switch for SLAC based on an array of series and parallel-connected commercial insulated-gate bipolar transistors (IGBTs). This switch has demonstrated operation at very high voltage and current, meeting the full specifications required by SLAC to completely replace (form-fit-function-interface) the L-4888 thyratron: 48 kV, 6.3 kA, and 1 µs risetime. 11:00 O1-3 [A0194] Avalanche S‐diode based on GaAs with deep levels: A high‐current microwave switch PRUDAEV Ilya1, OLEINIK Vladimir1, KOPYEV Viktor1, SMIRNOVA Tatyana1, TOLBANOV Oleg1, ROMANCHENKO Ilya2, PRIPUTNEV Pavel2 (1. Tomsk State University, Russia; 2. Institute of High Current Electronics SB RAS, Russia) Abstract: The results of experimental investigation of avalanche S-diodes operation in different triggering circuits are presented in this work. The diode multilayer structures were made by vapour phase epitaxy and diffusion of Cr and Fe deep acceptors into n-GaAs. Measurements have shown that the switching time of the S-diodes in sharper-type circuit with load resistance of 50 Ω is not greater than 200 ps. It has been found experimentally that the smaller residual voltages and higher currents after switching of the closing S-diode switch are observed in photoelectrical triggering circuit. The using of the S-diodes with large area of an active region (2.5 mm^2) allows one to increase the current in the ON state up to 330-370 A in the photoelectrical circuit with load resistance of 0.94 Ω. The comparison of GaAs S-diodes with the well known high-gain GaAs PCSSes and Page 3

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avalanche GaAs bipolar junction transistors indicates similar nature of switching of these devices. 11:15 O1-4 [A1931] Modular semiconductor‐based pulse power source for pulsed electron beam applications HOCHBERG Martin, SACK Martin, WEISENBURGER Alfons, MUELLER Georg (Karlsruhe Institute of Technology, Germany) Abstract: New generations of power plants such as accelerator driven nuclear power plants or concentrated solar power plants have challenging requirements concerning the materials used in the liquid metal cooling system. Pulsed electron beam surface alloying of the metal components showing promising prospects for increasing the corrosion resistance is therefore investigated at the Institute for Pulsed Power and Microwave Technology at KIT. For increasing the reliability of the process, the Pulsed Electron Beam Device (GESA) is currently being equipped with a modular semiconductor-based pulse power source. The design of the power source allows for a step-wise arbitrary output waveform of up to 120kV for a duration of 100µs at pulse currents of up to 600A. The required fast voltage rise time in the order of 100kV/100ns is achieved by using fast switches, fast optical signal transmission, a low inductance circuit layout and minimizing the stray capacitances to ground. The dynamic load behavior of GESA demands for a fast overcurrent protection scheme, which is implemented by distributing the control circuitry over the whole generator. This contribution highlights selected features of the design and presents the latest measurements. 11:30 O1-5 [A2209] Characterization of a vertical 6H‐SiC PCSS for high‐electric field application WU Qilin1, XUN Tao1, YANG Hanwu1, HUANG Wei2 (1. College of Advanced Interdisciplinary Studies, National University of Defense Technology, China; 2. Shanghai Institute of Ceramics, Chinese Academy of Sciences, China) Abstract: A high-power photoconductive semiconductor switch (PCSS) package is constructed of a bulk semi-insulating 6H-SiC substrate and its characterization under high electric field is presented. First, to optimize the high voltage withstanding, the field enhancements of the PCSS were simulated with various substrate thickness, electrode profiles and encapsulation materials and structure. Then the PCSS is tested in the laboratory, and the 0.8 mm thick 6H-SiC PCSS is able to work with electric fields up to 225 kV/cm and the power capacity up to 10.65 MW without failure, when triggered by a Nd:YAG laser (532 nm, 0.45 ns FWHM); By changing the triggering optical energy from 25.1 mJ to 31.9 mJ, the minimum Page 4

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resistance and the peak photocurrent of the PCSS as a function of input optical energy are obtained. The PCSS fails with further increasing voltage and the cause of the failure was identified to be surface flashover. This work forms the basis for developing very compact high-voltage PCSS used for high-electric field. 11:45 O1-6 [A0417] SOS generator with a primary thyristor switch triggered in impact‐ionization wave mode GUSEV Anton, LYUBUTIN Sergei, PONOMAREV Andrey, RUKIN Sergei, SLOVIKOVSKY Boris, TSYRANOV Sergei (Institute of Electrophysics UB RAS, Russia) Abstract: To increase SOS generators efficiency the simplest pumping circuit containing only one magnetic element, namely a step-up pulse transformer, should be used. But this approach needs a develop-ment of a superfast high power solid-state primary switch, which is capable of passing the currents with amplitude of tens of kA at dI/dt up to 100 kA/µs. Recently we found that such a switch can be developed on the base of usual commercial thyristors of tablet design triggered in impact-ionization wave mode. It turned out that when the voltage rise rate across the thyristor is around several kV/ns, the thyristor switching time to the conducting state is within several hundreds of ps. Within this switching time the semiconductor structure is filled with dense electron-hole plasma on significant part of the surface area. This allows significant increase in dI/dt and peak current through the switch. In experiments the thyristor based switches contained 2 to 9 series connected thyristors and operated in this triggering mode in different discharge circuits. Operating voltage was 5 to 20 kV, capacitance of discharge capacitors was 2 μF to 1.2 mF, and stored energy was 0.4 to 15 kJ. The experimental results obtained covered the following range of discharge parameters: discharge current amplitude of 10 to 200 kA, current-rise rate of 15 to 130 kA/μs, current rise time (0.1-0.9 level) of 0.4 to 5 μs, pulse duration (FWHM) of 1 to 20 μs, and switching efficiency of 0.85 to 0.97. In this paper we present SOS generator with a primary thyristor switch triggered in impact-ionization wave mode. The switch operates at 6 to 12 kV charging voltage and discharges a capacitive store with stored energy of up to 16 J. At pulse duration of 400 to 500 ns the peak current is several kA with dI/dt up to 50 kA/μs. Effect of the voltage rise rate at the triggering stage on the thyristor switch main characteristics will be shown. Results of the SOS generator testing will be given.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 12:00 O1-7 [A2474] Design of the drive circuit for IGBT array ZHU Xiaoguang, WANG Qingfeng, ZHANG Zhengquan, LIU Qingxiang (School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, China) Abstract: For improving voltage and current capability of switches for pulse power application, series-parallel IGBTs have their advantages. Hence the drive circuit must supply enough power to several IGBTs in series accordingly, which ensures IGBTs could turn on as soon as possible. At the same time, gate drive circuit needs to have equal propagation delay for each IGBT in parallel. Considering about these requirements, drive circuit for the IGBT array has been designed with the help of simulation, based on drive strategy for single IGBT. There are 25 IGBTs in this array, and every five paralleled IGBTs are in series. Its operating principle and circuit are introduced. The pulse forming network was used to verify its viability. The result of experiment was consistent with simulation. It is proved that this circuit could drive IGBTs switch fast in the same time.

Oral Session 2 - High Power Microwave Devices - Session Chair: ROMANCHENKO Ilya

(INTERNATIONA L HALL）[10:30-12:30] 10:30 O2-1 [A1426] A compact relativistic magnetron with novel axial output configuration QIN Fen, LEI Lurong, XU Sha, JU Binquan, WANG Dong (Key Laboratory on High Power Microwave Technology, Institute of Applied Electronics, CAEP, China) Abstract: Relativistic magnetron (RM) is an important high-power microwave source which could be designed to be compact and lightweight. A novel RM configuration for more compact operation with high efficiency is proposed. In this output configuration (namely, multi-antenna output structure), several conducting rods connected to the anode vanes of the magnetron are arranged in the axial direction to serve as the extraction antennas. Lower order cylindrical RF mode such as TE11 mode or TM01 mode is selected as the output mode which makes the dimensions of the output waveguide equal or slightly larger than the anode block, which leads to a more compact magnet system than previous RM configurations. High frequency analysis for an L-band RM with the multi-antenna output structure

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with CST Microwave studio demonstrates that this output structure excites lower-order cylindrical RF modes efficiently. PIC simulation with CHIPIC code demonstrates that this configuration has a power conversion efficiency of 50%. These results make this novel RM configuration more attractive for compact applications. 10:45 O2-2 [A1439] Prospective schemes of relativistic virtual cathode oscillators BADARIN Artem1, KURKIN Semen2, KORONOVSKII Alexey1, RAK Alexey3, FROLOV Nikita2, Alexander HRAMOV2 (1. Saratov State University, Russia; 2. Yuri Gagarin State Technical University of Saratov, Russia; 3. Belarusian State University of Informatics and Radioelectronics, Russia;) Abstract: This work is devoted to the presentation and analysis of promising modifications of vircators. The results of numerical modeling and investigation of the following schemes are presented. 1) Multibeam scheme of vircator, in which several beams with supercritical currents are loaded onto a common resonator. Such scheme can be considered as promising for further increasing the power and frequency of the generators with a virtual cathode. 2) Relativistic vircator with elliptical resonator. We have analyzed dynamics of the electron beam in such system. We have shown that the elliptical type of the resonator makes it possible to provide a better efficiency of interaction between the relativistic electron beam and electromagnetic field due to better localization of the field being excited in the electrodynamic structure. It leads to a significant increase in the system efficiency. 3) Relativistic vircator with photonic crystal. The analysis of the simulation results has shown a high generation efficiency when using a photonic crystal structure as power output, in comparison with the classical scheme of axial vircator. The work has been supported by the Ministry of Education and Science of the Russian Federation (Project 3.859.2017/4.6) and the Russian Foundation for Basic Research (Project 17-52-04097). 11:00 O2-3 [A1486] Investigation of an X‐band high power long pulse multibeam relativistic klystron amplifier LIU Zhenbang, HUANG Hua, JIN Xiao (Institute of Applied Electronics, CAEP, China) Abstract: To realize coherent high power microwave combining, an X-band long pulse multibeam relativistic klystron amplifier is designed, and the relative phase stability is investigated by three-dimension particle-in-cell simulation and high power microwave experiment. The simulation shows that the relative phase difference can be stabilized at gigawatt level radiation power. But the Page 7

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relative phase jitter increases in the experiment, then some measures are proposed to improve the stability of relative phase difference and avoid pulse shortening. A gigawatt level radiation power with long pulse duration is obtained in the experiment, the pulse shortening is avoided. And the experiment shows that the relative phase difference can be stabilized at a steady level between the flat top time at gigawatt level radiation power. 11:15 O2-4 [A1889] Design of a C‐band Cerenkov‐type oscillator without guiding magnetic field GUO Liming, SHU Ting, LI Zhiqiang, JU Jinchuan (College of Advanced Interdisciplinary Studies, National University of Defense Technology, China) Abstract: To improve the compactness and miniaturization of the high power microwave (HPM) systems, an efficient C-band Cerenkov-type oscillator without guiding magnetic field is presented in this paper. Through the investigation of slow-wave-structure and diode design, an optimized structure is achieved in particle-in-cell simulations. With an input pulse power of several hundred MW, this oscillator can generate one hundred MW level microwaves with an efficiency of about 30%. When the diode voltage changes from 130kV to 205kV, the oscillator generates a microwave at the frequency of 6.0GHz with the power changing from 30MW to 130MW, and achieves the highest efficiency of 35% at 145kV. 11:30 O2-5 [A1894] Research on the characteristics of radial TTO with different radial overall sizes WANG Haitao, ZHANG Jun (National University of Defense Technology, Changsha, China) Abstract: Performance of radial Ka-band TTOs with cathodes of different length is studied in this paper. Through physical analysis and simulation study, some meaningful laws have been be found. As radial length of cathode is increased, keeping sizes of the other components unchanged, mode of RF field and resonant frequency will not change. By PIC simulation, it can be found that if the length of cathode grows larger, the diode impedance will decrease and the input power will grow, consequently. However, frequency as well as efficiency of the generated wave will remain about the same, so the output power of the radial TTO will be improved. Compared with the traditional axial oscillators, assuming the power of output microwave is the same, amplitude of the maximum electrical field in radial TTO is much smaller. These show that radial device is a promising way to solve the power capacity problem of millimeter wave devices.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 11:45 O2-6 [A1908] An improved X‐band triaxial klystron amplifier with two‐stage cascaded bunchers ZHANG Wei, JU Jinchuan, ZHANG Jun, ZHONG Huihuang (National University of Defense Technology, Changsha, China) Abstract: Relativistic triaxial klystron amplifier (TKA) is considered to be a credible device to achieve GW-level amplification output radiation at X-band. In this letter, we present an improved X-band TKA to generate GW-level radiation. The two-stages cascaded bunchers are designed to strengthen the electron beam modulation and, moreover, to obtain a high output radiation power. Meanwhile, compared with the single buncher structure, a shorter drift length is adopted in the improved TKA, which is significant for the compactness of the system. The improved TKA is demonstrated to be capable of generating the X-band output radiation with the power of 1.25 GW and pulse duration of 100 ns in experiment. Furthermore, the phase of the output radiation is locked by the seed signal over 60 ns. 12:00 O2-7 [A1968] L‐band metamaterial high power microwave source Presenter: DAI-OU Zhixiong, HE Juntao, LING Junpu (College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, China) Abstract: In this paper, we present an L-band compact metamaterial high power microwave source, which is based on a new all-metal metamaterial slow wave structure and a rectangular output coupler. Due to the reverse Cherenkov radiation of the metamaterial, this metamaterial microwave source can be considered as a new sort of backward wave oscillator (BWO), the L-band metamaterial microwave source has been further studied and analysed by using electromagnetic simulation software. Through the optimized design of the rectangular output structure that the electronic efficiency of this L-band metamaterial microwave source can grow up to 30% with the average output power of 250 MW. When compared with conventional BWOs, it has obvious advantages such as miniaturization and high electronic efficiency

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 12:15 O2-8 [A3278] A repetitively‐operating relativistic backward wave oscillator SUN Jun, CHEN Changhua, SONG Wei, SHAO Hao, ZHANG Xiaowei, ZHANG Yuchuan, HUO Shaofei, SONG Zhimin, WU Ping (Northwest Institute of Nuclear Technology, China) Abstract: Relativistic backward wave oscillator (RBWO) is a promising high power microwave (HPM) generator. In past decades, many efforts have been devoted to improving its practicality, in which the repetitively-operating RBWO has drawn much attention. However, two bottlenecks once limited its development. One is the generation of massive anode plasmas or even damage of the collector caused by the energy deposition of the relativistic electron beam on the collector, and the other is the strong field breakdown of the RBWO, which will be aggravated in the case of long pulse duration or high conversion efficiency. This paper describes an RBWO which can operate repetitively with 3 GW microwave power by mitigating those two problems. First, a titanium collector, which shows better performance in resistance to ablation than the conventional stainless steel collector, is adopted. Meanwhile, water-cooling technology is applied in the collector to expedite heat dissipation. Second, since our research results demonstrate that an “anode” mechanism, not the conventional “cathode” mechanism, is the direct cause for breakdown under strong guiding magnetic field, the titanium material is used to manufacture the RBWO in order to increase the power capacity, and the advantage of the titanium RBWO is verified in experiments. The application of these techniques, as well as some important surface treatment techniques such as polishing, ultrasonic washing and vacuum baking, leads to the stable repetitive operation of the RBWO with 3 GW output power, 25 ns microwave duration and 50 pps repetition frequency. The successive operation time of the device reaches 20 s.

Oral Session 3 - Intense Electron and Ion Beams - Session Chair: TAKAYAMA Ken

(BALL ROOM 3#）[10:30-12:40] 10:30 O3-1 [A0613] Operation of cylindrical triode‐type electron accelerator under the influence of circling electrons FETZER Renate, AN Wladimir, WEISENBURGER Alfons, MUELLER Georg (Karlsruhe Institute of Technology, Karlsruhe, Germany) Page 10

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Abstract: Recently, the new cylindrical pulsed electron accelerator GESA-5 with radially converging electron beam for surface treatment of target tubes was put into full operation at the Efremov Institute in St. Petersburg, Russia. Simulations of the electron beam characteristics showed two different operation regimes of the new facility: stable operation with homogeneous beam profile for low cathode-grid voltages and unstable operation with the formation of a virtual cathode between grid and anode for large cathode-grid voltages. Although the voltages were chosen to obtain stable operation, first experiments showed an inhomogeneous beam profile and an enhanced current to the grid. An advanced simulation study reconsidered the operation of the cylindrical triode system taking into account a larger number of electrons that miss the target and circulate inside the accelerator. The circling electrons shift the limit of the stable operation regime to much lower beam currents. Additionally, the beam profile becomes inhomogeneous and the electron current to the grid increases. Various causes for an enhanced amount of circulating electrons are discussed. 10:45 O3-2 [A1120] Study of pollution‐free targets for beam bombardment ZHANG Guangshuai, SUN Jun, WU Ping, CAO Yibing, SONG Zhimin, FAN Zhiqiang (Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: High-quality intense relativistic electron beam (IREB) is an indispensable condition to ensure high efficiency and stable operation of high power microwave (HPM) devices, IREB Bombardment on the target is a common solution to evaluating the quality of IREB and the concentricity of the system. So far, as widely used target materials, pure metals seriously pollute the foilless diode, which could result in unexpected breakdown and thus lowering the performance of the HPM devices. In this paper, the graphite with a metal coating is proposed as a pollution-free target. First, with an incident 796kV, 5.5kA IREB guided by an external magnetic field of ~0.8T, the energy deposition of the IREB in the graphite targets with different metal coatings is theoretically and numerically investigated. The slightest ablation of targets is achieved by optimizing the thickness of the coatings, which means the pollution caused by sputtering from the target material is effectively reduced and simultaneously obvious ablative marks on the target can be obtained. The related experiment has been carried out in our laboratory. The experimental results are well consistent with those from the theoretical and numerical analyses.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 11:00 O3-3 [A1154] The study of LIA focal spot evolution in two pulse mode of operation LI Elena1, KOLESNIKOV Petr1, SKOVORODIN Dmitriy2 (1. Zababakhin All-Russian Scientific Research Institute of Technical Physics, Snezhinsk, Russia ; 2. Budker Institute of Nuclear Physics of Siberian Branch Russian Academy of Sciences, Russia) Abstract: The study of dynamic processes in optically opaque objects of high density is mainly carried out by the flash radiography method. One of the most prospective X-ray sources is Linear Inductive Accelerator of electrons (LIA). As a result of intense electron beam focusing on the accelerator target, energy release exceeds vaporization and ionization threshold that leads to dense target plasma formation. Back-streaming plasma ions flux causes electrons beam defocusing. The study of focal spot evolution in one and two pulse mode of operation is presented in this work. The study shows that the first beam defocusing is caused by light surface molecules vaporization and can be minimized by target melting (pre-pulse). The second LIA pulse defocusing is supposedly caused by target plasma formation after the first pulse was observed. The focal spot increasing time dependence was obtained. 11:15 O3-4 [A1705] The first proton beam accelerated by a dielectric wall accelerator XIA Liansheng, SHEN Yi, LIU Yi, WANG Wei, Mao YE, SHI Jinshui, ZHANG Linwen, DENG Jianjun (Institute of Flude Physics, Mianyang, China) Abstract: Dielectric Wall Accelerator (DWA) is a potential compact induction accelerator under development, and originated with a desire for compact flash X-ray radiography source. it is firstly developed at LLNL using fast switched high voltage transmission lines to generate pulsed electric field on the inside of an accelerator tube, which consists of many alternating fine layers of floating conductors and insulators. The authors were also trying to develop DWA in the past years and make some progress on solid-state dielectric pulse forming line, photoconductive semiconductor switching system and high gradient insulator. Based on the work, a DWA was built to accelerate proton beam. The proton energy gain is more than 300 keV.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 11:30 O3-5 [A2083] Investigation on high injection efficiency of intense relativistic multiple electron beams HUANG Hua, LI Lele, LIU Zhenbang, WANG Ganping, HE Hu, LI Shifeng, JIN Xiao (Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics, CAEP, China) Abstract: Intense Relativistic Multiple Electron Beams generated by multi-beam cathode inject into multi-beam drifting tube and then take part in beam-wave interaction in High Power Microwave device. The uniformity of space distribution, energy and its injection efficiency will make a direct influence on the efficiency and the stability of the whole device. At first, the reason of the lower injection efficiency in our previous research is analyzed by the combination of the theory, simulation and experiment in this report. It is introduced that some kinds of new multi-beam cathode structures that improve the injection efficiency are proved, and it is demonstrated by experiment. The result of the research indicates that multi-beam cathode with a skew forepart can restrain the radial emission of the base of the cathode and improve the injection efficiency remarkably on the foundation of all-around optimizing the structure of the diode; the injection efficiency is 99% in simulation and more than 90% in experiment for a 7GW electron beam. The cathode is applied in X-band multi-beam Relativistic Klystron Amplifier and it improves the beam-wave efficiency of the tube remarkably. 11:45 O3-6 [A0535] A 2D3V electrostatic/electromagnetic particle‐in‐cell code for high plasma‐density charged‐particles diffusion and transportation ZHANG Heng1, DONG Ye2, ZHOU Haijing2, DONG Zhiwei2 (1. CAEP Software Center for high Performance Numerical Simulation, China; 2. Institute of Applied Physics and Computational Mathematics, China) Abstract: When simulating the process of charged-particles diffusion and transportation especially in high plasma-density condition, the computation time is usually rather long due to large number of macro-particles and lots of time steps. In this paper, we develop a massively parallel 2D3V ES (Electrostatic) / EM (Electromagnetic) PIC (Particle-In-Cell) code in r-z coordinates system. In this code, plasma is described as charged-particles model. The charged-particles could emit from metal surface and also could be loaded in a fixed volume. Now, up to six sorts of charged-particles are supported in the code which could be tracked by solving the Newton-Lorentz equations. EM field is calculated by using standard FDTD (Finite-Difference Time-Domain) method. For solving Laplace and Poisson equations in ES field model, many linear solvers are Page 13

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implemented, such as SOR (Successive Over Relaxation), GMRES (Generalized Minimal Residual), and AMG (Algebraic Multi-Grid) preconditioner, etc. As an example, the fully diffusion and + + transportation process of four charged-particles (H2 -e and H -e pairs) in the extraction structure of Penning tube are numerically simulated and investigated by using this code. Considering the characteristic of r-z coordinates system, a non-uniform particle-weighting technology is applied for decreasing the total number of macro-particles and saving the running time.

Poster Session I - Pulsed Power Technology, Systems and Components - Session Chair: YANG Jianhua (BALL ROOM 2#)[13:30-15:00] P1-1 [A0325] The statistics characteristics of self‐breakdown time delay in high electric field under hundreds of nanoseconds pulse for mm gap GUO Fan1, HE Shi1, JIA Wei1, LI Junna2, CHEN Zhiqiang1, XIE Yanzhao1 (1. State Key Laboratory of Electrical Insulation and Power Equipment, China; 2 State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, China) Abstract: Self-breakdown probability and breakdown time delay statistics distribution in high electric field under hundreds of nanoseconds pulse for mm gap has been studied by employing the statistics experimental method. The experimental results are indicated that as the voltage pulse slope is increased, the self-breakdown time delay and jitter basically decreased. And they have reached the saturation point. There is a threshold value which can be made that standard deviations of breakdown voltage and time delay are both the extreme minimum value. The statistics characteristics of breakdown probability have been analyzed and a 100% breakdown probability experimental method is proposed which can be used for evaluating the statistics distribution of breakdown time delay. The breakdown time delay follows Gaussian distribution when the experiment condition is 100% breakdown probability. P1-2 [A0491] Research on stability for insulator linked structure of transformer XU Xiudong, SU Jiancang, LI Rui, ZHANG Yu, ZHENG Lei, QIU Xudong, SHEN Zhiyuan (Northwest Institute of Nuclear Technology) Abstract: The insulator is one important mechanical part for connecting inner and outer cylinder of Transformer, which influenced structural stability of

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transformer. Generally, the material of insulator was nonmetallic because of the insulative requirement between the inner and outer cylinders. In order to compensate stability shortage of nonmetal material and improve joint stiffness, a new linked structure between the outer cylinder and the insulator was proposed in this paper. This structure considered the creep characteristics of the insulator. The insulator was compressed by pre-tension force between two outer cylinders. And the steady contact was established between the outer cylinder and the insulator. Furthermore, the stability of this linked structure was analyzed in the paper, which obtained the influencing factors of structural stiffness. And the creep model of the insulator was established by utilizing creep experiment results. The simulation result showed that the steady contact can be obtained. And the structural stiffness can be improved by considering the compressed creep characteristics. P1-3 [A1746] Experimental study on the improvement of breakdown voltage of glycerin gap by combination insulation CHENG Xinbing, YANG Jianhua, CHEN Rong, GENG Jiuyuan (College of Advanced Interdisciplinary Studies, National University of Denfense Technology, China) Abstract: Glycerin is a kind of ideal energy storage medium in the compact pulse forming line for its high relative permittivity of 40, high breakdown electrical field, and high resistivity. Meanwhile, to improve the dielectric strength in the high voltage electrical apparatus, it is usual to equalize the electric field by the combination of different insulating material with different permittivity. So in this paper, the insulated characteristics of glycerin gap, glycerin-nylon gap, and glycerin-high density Polyethylene plastics (HDPE) gap are investigated by theoretical and experiments. Firstly, the breakdown voltages of glycerin-nylon gap and glycerin-HDPE gap are tested for plate electrodes, the experimental results show that the breakdown voltage of glycerin-nylon gap is 3-4 times higher than that of glycerin gap, and the breakdown voltage of glycerin-HDPE gap is 2-3 times higher than that of glycerin gap. Secondly, the breakdown voltage of glycerin-nylon gap and glycerin-HDPE gap is tested for the coaxial electrodes, and compared with the breakdown voltage of the pure glycerin gap, the breakdown voltages of glycerin-nylon gap and glycerin-HDPE gap are all increased significantly. At last, the breakdown voltages of transformer oil-nylon gap and transformer oil-HDPE gap are tested, and the results show that the breakdown voltage is not affected by the nylon or HDPE materials. These experimental results show that the breakdown voltage of glycerin gap can be improved by adding the HDPE or nylon material to the insulation gap.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 P1-4 [A2339] Lifetime characteristics of high temperature capacitor LI Lu (Key Laboratory of Pulsed Power Technology (Huazhong University of Science and Technology)，Ministry of Education, Wuhan, China) Abstract: Pulsed capacitor has been gradually applied to diversified fields including aerospace and power electronics. These applications highlight the need to develop the capacitor technology which can work reliably over a wide range of temperature. Taking the high temperature capacitor made of metallized films as an example, this paper mainly concentrates on the failure mechanisms of capacitor, and the effect of temperature-voltage-discharge current on the lifetime characteristics of capacitor. And then, the lifetime of capacitor under different discharge current and voltage is predicted by the empirical law. The results show that, (1) the electrode end connection of capacitor is significantly degenerated at high temperature. When the temperature rises from 60 ℃ to 100 ℃, the resistance of electrode end connection increases by 72.92%. (2) The electrode end connection degeneration of high temperature capacitor leads to the sudden drop of capacitance, thus resulting in the failure of capacitor. When the temperature is 40 ℃, 100 ℃ and 110 ℃, the lifetime is 3.19 L0, 1.43 L0, and 0.72 L0, and the probability of the electric sparks at the electrode end connection is same to the sudden drop of capacitance, which is 0, 50% and 83.33% respectively. (3) When the temperature is 110 ℃, the lifetime of high temperature capacitor decreases with the increase of voltage and discharge current. When the voltage is 3.75 kV, the lifetime of capacitor corresponding to the discharge current of 4.12 kA and 4.96 kA is L0 and 0.31 L0 respectively; and when the voltage is 4.5 kV, the lifetime of capacitor corresponding to the discharge current of 4.48 kA and 4.96 kA is 0.31 L0 and 0.17 L0 respectively. P1-5 [A0297] Dynamic characteristics of magnetic switch core under fast pulse excitation WANG Meng, WANG Jue, YAN Ping (Institute of Electrical Engineering Chinese Academy of Sciences,Beijing, China) Abstract: Magnetic switch is the key part of magnetic pulse compression system. It is necessary to focus on the characteristics of the magnetic core and its effects on switching operation. A one-stage magnetic pulse compression system was designed and manufactured to test the dynamic characteristics of the magnetic cores under fast pulse excitations including microseconds and hundreds of nanoseconds. The hysteresis loops of the magnetic cores were derived from the measured voltage and current waveforms, thus the saturated magnetic flux intensity and coercivity could be obtained. The simulation of magnetic pulse compression system was built to analyze the dynamic characteristics of the magnetic cores and the magnetic switch operation.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 P1-6 [A0798] Experimental study on breakdown characteristics of trigger gap and overvoltage gap in a gas switch ZHAI Rongxiao (Skate Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, China) Abstract: Gas pressurized closing switches are one of the most important elements in FLTD-based systems. Improving the trigger performance of gas switches is useful for improving the output parameters and the reliability of the FLTD. In this paper, the breakdown characteristics of the trigger gap and the overvoltage gap are studied experimentally. The reasons for the different breakdown characteristics of the two gaps are also investigated. The results show that the breakdown delay of the trigger gap is more influenced by the trigger voltage, while the breakdown delay of the overvoltage gap is more influenced by the working coefficient and always higher than that of the trigger gap. The jitter of the trigger gap is more influenced by the trigger voltage and accounts for 60% of the total switch jitter, while the jitter of the overvoltage gap is hardly changed with the trigger voltage as well as the working coefficient and maintains less than 1.4 ns. It is proved that the discharge products of the trigger gap can effectively reduce the breakdown delay and jitter of the overvoltage gap. Based on that, the effect and improvement of pre-ionization on the two gaps are also studied. It is concluded that the jitter of the trigger gap reduces obviously when the pre-ionization is added, while the pre-ionization almost has no effect on the jitter of the overvoltage gap. The jitter of the overvoltage gap is about two times higher than the trigger gap in the pre-ionizing switch. P1-7 [A1122] The effects of 2.6‐MV low‐inductance PFL switch on output pulse of IVA device YIN Jiahui, QIU Aici, SUN Fengju, WEI Hao, JIANG Xiaofeng, CONG Peitian (Northwest Institute of Nuclear Technology, China) Abstract: At Northwest Institute of Nuclear Technology (NINT, China), a 2.6 MV, 200 kA electrical triggered gas switch with 130~160 nH self-inductance is developed as the pulse forming line (PFL) switch in an induction voltage adder (IVA) device. In this paper, the effects of switch characteristics on the output pulse of IVA device are discussed. It shows that the increased switch self-inductance will reduce the amplitude of the driven pulse and the instability of switch self-inductance will lead to an unstable breakdown of the peaking switch. Then the influence of switch jitter on the output characteristics of IVA device is also discussed. It shows that as the driven pulse of induction cells are deviated ±10 ns from the ideal sequence, there is no obvious effect on the amplitude and rise time of output current in the IVA devices. The theoretical analysis and the corresponding equivalent circuit simulation are in good Page 17

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agreement with the experimental results. At present the range of output time of four driven pulses is 15 ns, which can basically meet the synchronization requirement of IVA device. P1-8 [A1341] Investigation of initially unbiased layered silicon structure operating in impact‐ionization mode WANG Ganping, LI Fei, WU Chaoyang, SONG Falun, JIN Xiao (Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics, CAEP, Mianyang, China) Abstract: A possibility of superfast switching of initially unbiased silicon high-voltage diode with p+nn+ structure was studied. In experiments, a reverse overvoltage pulse with a rise rate in the range of 0.7 to 2 kV/ns was applied to a layered silicon diode with operating voltage of 2 kV. Under these conditions, the diode closing process occurred when the impact-ionization front started to propagate across the structure and then became quite distinctive. Experimental results showed that, due to different dynamic mechanism, the switching process could be divided into two stages, which is qualitatively in agreement with theory. For the high velocity of ionization front, the first stage with a steep voltage drop was just following the initiation of ionization front, whereas as the front collided the extraction front before arriving at the p+ region, the second stage emerged with slower ramp due to low plasma density caused by homogeneous breakdown. By increasing the reverse biased voltage, the second switching stage would vanish gradually, thus the structure could be transited from blocking state to conducting state within 1 ns. P1-9 [A1268] Space and time resolved optical emission spectroscopy characterization of ejected plasma used as a trigger method in low‐working coefficient gas spark switch SHEN Xi, LIU Xuandong, ZHANG Mingkang, ZHOU Chenhui, ZHOU Feiyan, ZHANG Qiaogen (Xi'an Jiaotong University, China) Abstract: Gas spark switch, triggered by ejected plasma, can operate reliably when the working coefficient is lower than 10%. The ejected plasma is generated by spark discharge in a micro-cavity, and it has a broad application prospect in pulsed power system. When gas spark switch is firing at low switching coefficient, the ejected plasma as the initiating electron of the main gap has very important significance for the switch breakdown or closure process. Therefore, it is necessary to acquire the parameters of the plasma ejection to support the design and application of this kind of gas switch. In this paper, the ejected plasma was generated by spark discharge in the micro cavity embedded in the ground electrode in a two-electrode switch. The insulation material between trigger pin and ground electrode was PTFE. An optical measurement platform for plasma spectroscopy was set up. The luminescence of a specific area of the plasma channel was captured by ICCD

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through a slit, and a time delay system was used in conjunction with a grating spectrometer to obtain the plasma emission spectrum characteristics with time and space resolution. The influences of gas pressure and trigger voltage polarity on the plasma parameters were studied. When there was no voltage applied across the main gap, the whole ejection turned to be an energy dissipation process since no external energy could support plasma impact ionization after plasma was ejected from the micro cavity. When the plasma was ejected from the micro cavity, under high pressure conditions, the electron energy loss was exacerbated due to the higher collision frequency, so the electron temperature of the plasma under relatively high pressure was lower. The influence of the gas pressure on the plasma parameters was much more remarkable or obvious on the initial stage of plasma ejection. The maximum difference in electron density was up to 17.3%. When the pressure was 0.1 MPa, the electron temperature at the plasma of 0-5 mm was 0.73~0.98 eV and 0.74~1.12 eV in positive and negative polarities, respectively. When the pressure raised to 0.5 MPa, the electron temperature at 0-5 mm was reduced to 0.72 ~0.90 eV and 0.73~0.93 eV, respectively. In addition, as the electron energy was easier to dissipate under high pressure so the electron density of the plasma under relatively high pressure was lower. When the gas pressure was 0.1 MPa, the electron density of the plasma at 0-5 mm was 1.931011 ~3.171012 cm-3 and 2.181011~5.791012 cm-3 at positive and negative polarities, respectively. When the pressure was raised to 0.5 MPa, the electron density of the plasma at positive and negative polarity at 0-5 mm decreased to 1.021011~8.551011 cm-3 and 8.331010 to 3.041011 cm-3, respectively. No matter what polarity the trigger pulse was, the trend of electron temperature and electron density with time and space under different gas pressures were almost the same, but the electron temperature and electron density under the positive polarity were lower than that of negative polarity. When the negative polarity trigger pulse was applied, the amplitude of breakdown voltage of the micro cavity was higher, so the energy deposited in the discharge channel was higher. During this process, the discharge channel could obtain a higher electron density, and the energy of electrons was also relatively higher, so the probability of generating electrons through impact ionization in the main gap was also relatively higher. When the gas pressure was 0.1 MPa, the electron temperature at 0-5 mm was 1.12 eV at the negative polarity and 0.97 eV at the positive polarity. When the gas pressure was 0.5 MPa, the electron density at 0-5 mm was 2.211012 cm-3 in the negative polarity and 8.551011 cm-3 in the positive polarity.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 P1-10 [A1546] A novel gas switch triggered by ejected plasma of three‐electrode two‐gap capillary in SF6 ZHOU Feiyan, LIU Xuandong, SHEN Xi (State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China) Abstract: In this paper, the author designed a SF6 plasma ejector with 3-electrode, 2-gap plasma jet device based on capillary discharge. The capillary is divided into the trigger channel and the main discharge channel by introducing the intermediate electrode. The main discharge channel is ignited after the initial stage when the trigger gap is flashed over under the high-voltage pulse, and then the plasma ejects. The experiment studies the influence of structure and circuit parameters on capillary discharge in SF6 and records the plasma’s height by photograph. Experimental results show that, the duration of discharge is within 100 μs and with the increase of the capacity or the trigger voltage, the current through the main channel ranges from 3.5 kA to 11.3 kA. Although the peak current of the main channel hardly varies when we used a 15 mm capillary to replace the 10 mm one, the height of the plasma ejection dramatically increases, from about 3 mm to 14 mm. P1-11 [A2015] Application of high speed frame camera on discharge processes of the corona stabilized triggerred switch YANG Jianhua1, CHENG Xinbing1, YANG Xiao1, CHEN Rong1, 2 GENG Jiuyuan (1. National University of Defense Technology; 2. National University of Defense Technology, Changsha, Hunan, China) Abstract: The discharge processes in the gap of Corona Stabilized Triggered Switch (CSTS) which works as the main switch of IEBA could be diagnosed by a High-Speed Framing Camera (HSFC). Because of the complex point-field configuration in CSTS, the discharge processes are divided into three stages: corona discharge, streamer discharge, and insulation recovery. In the experiment, discharge processes were diagnosed by a ns-level HSFC. The changes in volume of corona and streamer, and time of insulation recovery were studied by varying gap voltage, pressure of the insulating gas and partial field enhancement. It was obtained that a multi-channel phenomenon could be observed between the gap. The probability of multi-channel increased with gap voltage and gas pressure increasing. At the same time, the time of insulation recovery was tens of microseconds. P1-12 [A2579] Triggering characteristic research of ±80kV three‐electrode field‐distortion gas spark switch DENG Haojie, CONG Peitian , ZHANG Tianyang , ZENG Jiangtao , HUANG Tao , WANG Zhiguo (Northwest Institution of Nuclear Technology, Xi'an, China) Page 20

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Abstract: A three-electrode field-distortion gas spark switch used for Marx generator is developed. With different trigger voltage polarity, the triggering characteristics are experimentally investigated for the switch with SF6 and dry air, respectively. The triggering experiments demonstrate that, the close jitter with the negative trigger voltage is lower than that positively triggered. The triggered close jitter of air is lower than that of SF6. For air switch with the ±80 kV charging voltage and the 70% ratio of charging voltage to self-breakdown voltage, the delay time of the switch closing is about 21 ns, and the close jitter time is about 2.1 ns, which meets the performance requirements of the developing Marx generator. P1-13 [A2974] A subnanosecond bipolar pulse former based on combined chopping‐peaking switches SHI Lei, FAN Yajun , ZHU Yufeng , XIA Wenfeng , LU Yanlei (Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, China) Abstract: A bipolar pulse can form when the single-polar pulse goes through a combined chopping-peaking switch. A high power bipolar pulse former with combined chopping-peaking switches is designed and developed. The peak-to-peak voltage of the bipolar pulse is double of the input pulse voltage in ideal, the duration of the bipolar pulse can be changed by adjusting the gaps of the chopping-peaking switches. Experimental results show that the bipolar pulse former can generate bipolar pulses with peak-to-peak voltage nearly two times of the input single-polar pulse. P1-14 [A3035] Post‐breakdown characteristics of a plasma closing switch filled With environmentally friendly gases YAO Yuan, TIMOSHKIN Igor, MACGREGOR S. J., GIVEN Martin, WILSON Mark, WANG Tao (Department of Electronic and Electrical Engineering University of Strathclyde, U K) Abstract: Gas-filled Plasma Closing Switches (PCSs) are important components of different high energy density pulsed power systems, used to generate short, high-power (10s MW to several GW) impulses. In multiple practical applications, PCSs are required to operate in high current (10s kA), high voltage (10s-100s kV) regimes, to produce fast rising (ns and sub-ns) HV impulses. The transient/ time-dependent resistance of a PCS significantly affects the maximum power delivered to the load and the rise time of the generated impulses. The present paper is focused on an investigation of the time-dependent resistance of the plasma channel(s) formed between the electrodes of the PCS. Experimentally-obtained current and voltage waveforms were used to calculate the transient plasma resistance associated with the PCS, when filled with different environmentally-friendly gases (air, N2, CO2, Ar/O2). Different analytical approaches, that attempt to describe the dynamic resistance of the plasma channel were used to model the transient spark resistance in the PCS. These analytically-obtained transient plasma Page 21

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resistances have been compared with the experimental results. This analysis will help in optimisation of the operational performance of PCSs filled with environmentally-friendly gases and to determine the suitability of the analytic methods to determine the transient resistance associated with breakdown in these gasses. P1-15 [A0240] Anode failure mechanism of GaAs photoconductive semiconductor switch triggered by laser diode SHEN Yi, LIU Yi, WANG Wei, YE Mao, ZHANG Huang, XIA Liansheng (Institute of Fluid Physics, Mianyang, China) Abstract: This paper presents an experimental study on the failure mechanism of high current gallium arsenide photoconductive semiconductor switches (GaAs PCSS) triggered by laser diode. We propose a Blumlein pulse forming line to test the GaAs PCSS. The result shows that damage of GaAs PCSS almost occurred on the anode side nearby the electrode either by anode illumination or by cathode illumination. Since the highest amplitude of Gunn oscillating always occurs on the anode, we speculate that the failure of high current GaAs PCSS is attributed to the Gunn effect according to the statistics about failure factor of GaAs PCSS. And we use a scanning electron microscope to semi-quantitative analysis of composition of the erosions micro ball or granules, whose compositions are gallium and arsenium. It further proves our speculation. P1-16 [A1195] Mechanism of fast current interruption in SiC picosecond high‐voltage semiconductor opening switches HAO Yong1, LI Yongdong1, DING Zhenjie1, WANG Hongguang1, FANG Xu2 (1. Electronic Science and Technology, School of Electronic and Information Engineering, Xi'an Jiaotong University, China; 2. Northwest Institute of Nuclear Technolog, China y) Abstract: This paper simulate the SiC semiconductor opening switches with 10 dies stack in series by using Silvaco Atlas. A picosecond rise-time high-voltage pulse output which is far faster than silicon devices with the same structure is obtained. We investigate the evolution of carrier concentration and electric field in SOSs during forward and reverse pumping stages and analyze the interruption mechanism of high density current both in SiC and silicon devices. High carrier mobility and wide bandgap of SiC leads to the different interruption process comparing with silicon devices.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 P1-17 [A1473] Research on the effect of conducting current to conducting resistance of GaAs‐PCSS in nonlinear mode LIU Yi, XIA Liansheng, SHEN Yi, WANG Wei, YE Mao, SHI Jinshui, ZHANG Linwen (Institute of Fluid Physics, China) Abstract: By utilizing high power laser diode as trigger source, the GaAs Photoconductive Semiconductor Switch (GaAs-PCSS) nonlinear conducting experiment is performed to research the effect of conducting current to conducting resistance. The experimental platform is a Blumlein line constructed of glass-ceramic pulse forming lines with different characteristic resistances and the same electrical length. The results demonstrate that the conducting resistance decreases with increasing conducting current in nonlinear mode while all other factors remaining unchanged. By primary analysis, conducting current and avalanche effect of carrier enhance each other. Consequently, conducting current affects the conducting resistance independently. P1-18 [A1913] Design and primary realization of a megahertz solid‐state pulse power source HE Yang, DAI Wenfeng, FENG Chuanjun, GENG Lidong, YUAN Jianqiang, LIU Hongwei (Institute of Fluid Physics, CAEP, Mianyang, China) Abstract: With the latest solid-state switching technologies, a pulse power supply may achieve a repetition rate as high as megahertz, which is of great use in some industrial applications, like dust and water treatment. However, the rated voltage and current parameters of solid-state switches are not satisfactory in most cases. Therefore new structure designs have to be proposed for better performance. This work presents the basic module design of a solid-state pulse power source, which features short pulse width (dozens of nanoseconds) and high repetition rate (megahertz). In this design, multiple solid-state switches are placed in a circle in parallel connection to share the pulse current, and RF MOSFETs are selected as the main switches to guarantee short switching time. Multiple modules are stacked up as an accumulator to achieve higher pulse voltage. Optical fiber trigger links and the timing control mechanism are also proposed for insulation and timing accuracy. Finally a two-module stack of pulse power source is realized, and the test results reveal a 1kV pulse peak over 1Ω resistive load, as well as running at the repetition rate of 1MHz. This result is good for current research stage, and discussions of further developments are also included in the end of this work. P1-19 [A2752] Improvement of compact pulsed power supply for ion source using 13 kV SiC MOSFETs

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 TOKUCHI Akira1, BOKUDA Yasuo1, SHINTO Katsuhiro2, FUKUDA Kenji3 (1. Pulsed Power Japan Laboratory Ltd., Japan; 2. Japan Atomic Energy Agency, J-PARC Center, Japan; 3. National Institute of Advanced Industrial Science and Technology Advanced Power Electronics Research Center, Japan) Abstract: In the J-PARC accelerator, a 54 kV ion beam was extracted for 1 ms by using a power supply superimposed with a pulse voltage of 9 kV for 1 ms to a direct current voltage of 45 kV, and passed through the RFQ to generate a 1 μs ion beam. To generate the 9 kV pulses, 16 MOSFETs with 1.2 kV withstand voltage were connected in series. Therefore the trigger circuit was complicated and the switch became large-sized. In this year, by replacement of newly developed SiC MOSFETs with withstand voltage more than 13 kV, the pulsed voltage was increased higher than 15 kV and the switch became more compact. A part of this work has been implemented under a joint research project of Tsukuba Power Electronics Constellations (TPEC). P1-20 [A2811] Improvement of bipolar LTD using SiC MOSFETs MUSHIBE Yoichi1, TOKUCHI Akira1, TAKAYANAGI Tomohiro2 (1. Pulsed Power Japan Laboratory Ltd. , Japan; 2. Japan Atomic Energy Agency, J-PARC Center, Japan) Abstract: We are developing a new power supply that can be used for a kicker magnet in J-PARC accelerator. The power supply is a pulse generator using SiC MOSFETs based Linear- Transformer-Drivers (LTDs). The output unit part is equipped with the circuit which absorbs a reflective wave of the bipolar voltage. It is also possible to adjust the output waveform by adding circuit boards for voltage correction. P1-21 [A3004] Fast multiple‐protection of short circuit for solid‐state Marx generator DONG Weigang, LIU Kefu, TONG Liqing (Institute of Electrical Light Source, Fudan University, China) Abstract: All solid-state Marx generator is widely used in various fields such as industrial and medical fields. These applications require solid-state Marx generators with higher safety, stability and reliability. The voltage and current capacity of solid-state devices have become the main factors restricting the Marx generator’s performance. How to make the solid-state device maximize its performance is a meaningful research. This paper deals with the operating characteristics of a MOSFET at pulsed high current exceeding the DC rated current and we proposed a detail design of the fast multiple-protection of short circuit for solid-state Marx generator based MOSFET switches. The fast multiple-protection is divided into three parts: CLP (Current-Limiting Protection), DP (Device Protection), and BP (Backup Protection). The CLP works when the current fluctuates. A nonlinear resistance characteristics module is used to maintain the load current within the normal range. If the load is short-circuited, the current rises rapidly and the DP then works. A driver Page 24

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circuit with gate-source capacitance discharge function for MOSFETs is used to ensure instantaneous shutdown when the switch is overcurrent. Simultaneously, to protect the Marx generator from secondary damage at the moment of breakdown, an overload monitoring part which can turn off the control circuit is included. Some experimental and simulated results are included to verify the fast multiple-protection performances in this paper. P1-21 [A3004] Fast multiple‐protection of short circuit for solid‐state Marx generator DONG Weigang, LIU Kefu, TONG Liqing (Institute of Electrical Light Source, Fudan University, China) Abstract: All solid-state Marx generator is widely used in various fields such as industrial and medical fields. These applications require solid-state Marx generators with higher safety, stability and reliability. The voltage and current capacity of solid-state devices have become the main factors restricting the Marx generator’s performance. How to make the solid-state device maximize its performance is a meaningful research. This paper deals with the operating characteristics of a MOSFET at pulsed high current exceeding the DC rated current and we proposed a detail design of the fast multiple-protection of short circuit for solid-state Marx generator based MOSFET switches. The fast multiple-protection is divided into three parts: CLP (Current-Limiting Protection), DP (Device Protection), and BP (Backup Protection). The CLP works when the current fluctuates. A nonlinear resistance characteristics module is used to maintain the load current within the normal range. If the load is short-circuited, the current rises rapidly and the DP then works. A driver circuit with gate-source capacitance discharge function for MOSFETs is used to ensure instantaneous shutdown when the switch is overcurrent. Simultaneously, to protect the Marx generator from secondary damage at the moment of breakdown, an overload monitoring part which can turn off the control circuit is included. Some experimental and simulated results are included to verify the fast multiple-protection performances in this paper.

Poster Session II - High Power Microwaves and RF Sources - Session Chair: SHU Ting (BALL ROOM 2#)[13:30-15:00] P2-1 [A0308] Studies on the mode competitions in a magnetically insulated line oscillator YANG Wenyuan, DONG Zhiwei, SUN Huifang (Institute of applied physics and computational mathematics, Beijing, China) Abstract: For a MILO(Magnetically Insulated Line Oscillator) operating on the pi mode of the fundamental mode，various mode competitions are prone to appear during the initial stage of the development of the radiated Page 25

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electromagnetic field. From the dispersion relations between the electron beam mode and the lower order eigen modes in MILO, a brief description of the characteristics and possible appearing reasons of three kinds of mode competitions are given. The first kind mode competitions is between the axial modes of the fundamental mode. The second is the competitions between the fundamental and higher order modes. The third is the competitions between the fundamental and low order dissymmetric modes. Numerical studies and physical analyses on the mode competitions in an L-band MILO are carried out. The study results show that the competition in the initial stage comes mainly from the dissymmetric HEM11 mode. After a short time, the fundamental mode increase rapidly and the competition modes are inhibited. High and stable output microwave power is obtained in the end in the L-band MILO. P2-2 [A0550] Effect of the cathode emission pre‐initiation on the generation phase of Ka‐band relativistic backward‐wave oscillator SHARYPOV Konstantin1, ROSTOV Vladislav2, SHPAK Valerii1, SHUNAILOV Sergey1, ULMASKULOV Marat1, YALANDIN Michael1 (1. Institute of Electrophysics UB RAS, Russia; 2. Institute of High Current Electronics SB RAS, Russia) Abstract: Conditions of a phase-stable generation of a subgigawatt, superradiant (SR) relativistic backward-wave oscillator (BWO) are studied at the accelerating pulse front parameters (its shape, steepness, and stability) realized in the experimental conditions. Alongside the necessary excess of a seed electromagnetic (e.m.) signal from the front of a high current beam over some threshold level, the generation phase reproduction requires a stable explosive electron emission (EEE) onset at the cathode. In our experiments, for the fast-rise voltage (up to 1.5 MV/ns), this stability is provided by advanced field-emission (FE) activation of graphite cathode during the voltage prepulses. Nanosecond high-voltage generator RADAN-303 with additional inductance-capacitive unit based on a short pulsed forming line and uncontrollable high-pressure nitrogen spark-gap was used for the formation, compression and sharpening of the pulse feeding the electronic injector of Ka-band BWO. When the sharpening voltage edge rise on the cathode to the amplitude value (~ minus 250 kV) for ~ 200 ps, the prepulse (~ minus 10-15 kV) with a duration of ~ 3 ns provides the transition of FE to EEE stage with a picosecond accuracy. The seed e.m. signal of sufficient power is formed by the front of the beam emitted at some point of subnanosecond voltage front which is reproducible during initial front section despite of essential amplitude dispersion. As a result, high-frequency beam modulation in the SR BWO develops at a rising voltage due to high amplification increment of a seed e.m. signal. That is, the phase establishment is a little sensitive to the variation of accelerating pulse amplitude. It was shown in the experiments and in numerical modeling (KARAT code) with the amplitude dispersion of up to 15%. Phase stabilization is also possible when a seed e.m. signal is formed by the current burst arising due to kinematic sharpening of the beam current front.

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The work was fulfilled in the frame of the IEP state task No. 0389-2015-0026, supported by the RAS Program No.10, and, in part, by RFBR Grant No. 18-08-00133. P2-3 [A0590] Experimental verification of the elimination effect of the asymmetric modes in a Ka‐band super overmoded coaxial Cerenkov oscillator BAI Zhen1, ZHANG Jun2, ZHONG Huihuang2, SONG Xumin1, CHAI Hua1, TAN Bitao1 (1. Space Engineering Technology University, China; 2. National University of Defense Technology, China) Abstract: The issue of asymmetric modes output of a Ka-band super overmoded coaxial Cerenkov oscillator is analyzed and the methods to suppress asymmetric modes competition are present in a previous paper. By inserting a taper waveguide at a specific position to achieve destructive interference of the reflected TM11 mode, and designing a special support structure to avoid reflection of TE11 mode, a good suppression effect was obtained in simulation. In this paper, experimental verifications of the elimination effect are implemented. The experiment results are basically consistent with the simulation results, and finally a relatively pure TEM mode output with the power of 291 MW, the pulse of 25 ns is achieved. P2-4 [A0772] High‐current large‐orbit gyro‐like relativistic backward wave oscillator operating at low guiding magnetic field XIAO Renzhen, SONG Zhimin (Northwest Institute of Nuclear Technology, Xi'an, China) Abstract: A gyro-like relativistic backward wave oscillator (RBWO) is presented. In the device, the slow wave structure with axial corrugations and the large-orbit beam with electrons encircling about the structure axis are used. Due to the existence of the axial electric field, the axial bunching and azimuthal bunching are cooperative. Both Cerenkov radiation and bremsstrahlung radiation are expected to play significant roles in the beam-wave interaction. Preliminary particle-in-cell simulations show that when the beam energy is 900 keV with an initial velocity ratio of 1.0, beam current is 1.2 kA, and the external magnetic field is 0.23 T, the generated microwave is 320 MW, corresponding to a beam-wave conversion efficiency of about 30%, the frequency is 13.3 GHz, and the operation mode is hybrid TE21 mode.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 P2-5 [A1375] Investigation of an L‐band relativistic magnetron with low guiding magnetic field LEI Lurong1, FEN Qin2, DONG Wang2, SHA Xu2 (1. Science and Technology on High Power Microwave laboratory, Institute of Applied Electronics, CAEP, China; 2. Science and Technology on High Power Microwave laboratory, Institute of Applied Electronics, CAEP, Mianyang, China) Abstract: In order to reduce the volume and weight of the relativistic magnetron system, a low magnetic field relativistic magnetron with diffraction output is investigated in this paper. By analyzing the resonance characteristics of magnetron, it is found that the magnetic field can be reduced by optimizing the anode radius. Furthermore, it can decrease the volume and weight of the magnetic coil subsystem and finally realize the miniaturization of the magnetron system. A compact L-band six-cavity relativistic magnetron with diffraction output is simulated and investigated experimentally based on the analysis. Preliminary experimental investigation is carried out to verify the simulation results. When the applied voltage is ~330 kV and the magnetic field is ~0.21 T, the output microwave power is ~650 MW with the efficiency of about 35%. The radiating frequency is 1.582 GHz which is in agreement with the π mode frequency. The radiation pattern is TE31 mode which is also in agreement with simulation result. P2-6 [A1566] Investigation of plasma effects in intense relativistic electron beams BADARIN Artem, KURKIN Semen, HRAMOV Alexander (Yuri Gagarin State Technical University of Saratov, Russia) Abstract: This work presents the results of investigations of ionization effects influence on processes occurring in promising high-power microwave devices – relativistic vircators (generators and amplifiers on a virtual cathode (VC)). The results are obtained using electromagnetic PIC code. We have carried out the detailed studies of critical current of a relativistic electron beam (REB) with change of the control parameters of the system: concentration of residual gases, external magnetic field value, electron beam energy, and shape of the current pulse. We have obtained analytical estimates that explain the characteristic shape of the dependence of critical current on external magnetic field value. The rate of VC formation and its lifetime are studied depending on the concentration of residual gases. We have investigated the influence of plasma effects on the formation of electron-plasma structures in a REB. The results obtained within the framework of the research are intended to broaden the fundamental ideas about the dynamics of intense electron beams in a plasma. The work has been supported by the Ministry of Education and Science of the Russian Federation (Project 3.6723.2017/8.9).

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 P2-7 [A1990] Simulation investigations of a Ku band relativistic magnetron ZHANG Jun, YAN Hanwu, LI Zhiqiang, LI Wei (National University of Defense Technology, China) Abstract: Simulation investigations of a Ku band relativistic magnetron are proposed in this paper. The magnetron has multi-resonant cavities and an axial structure. According to apparatus optimizing, the magnetron can output microwave as follows: central frequency of 14.4 GHz, microwave power of 500 MW, power conversion efficiency of 35%. The radiation pattern is TE01 mode. P2-8 [A2160] A novel TM01‐TE01 mode converter YUAN Chengwei1, ZHAO Xuelong2, HAO Dongqing1, ZHANG Qiang1, YU Longzhou1, SUN Yunfei1 (1. College of Advanced Interdisciplinary Studies, National University of Defense Technology, China; 2. Beijing Institute of Radiation Medicine, China) Abstract: A novel TM01-TE01 mode converter for high power microwave (HPM) applications is proposed in this paper, which can efficiently convert TM01 mode into TE01 mode in circular waveguide. The converter is composed of three sections: power-dividing section, twist-waveguide section and power-combing section. These sections are analyzed and discussed, respectively, and the electronic behaviors of the assembled converter were investigated in simulation. The simulation results show that the TM01-TE01 conversion efficiency of the converter at the central frequency of 12.5 GHz is nearly about 0 dB, and the bandwidth for conversion efficiency more than 0.25 dB is 22%. Moreover, the power handling capability of the converter is estimated about 2.65 GW. P2-9 [A2260] Preliminary study of thermal characteristics of the RBWO high frequency structure HUO Shaofei1,2, ZHANG Xiaowei2, SHAO Hao2, LIU Chunliang1, MIAO Tianze2, BAI Xianchen2 (1. Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi’an Jiaotong University, Xi’an, China; 2. Laboratory on Science and Technology of High Power Microwave, Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: The increase of microwave power, repetition frequency and successive operation time of Relativistic Backward Wave Oscillator (RBWO) aggravates the surface heating and thus the temperature rise of high frequency structure (HFS), in company with significant power losses. That may results in severer breakdown and worsen the operation stability of the RBWO. In this paper, the temperature variations of the HFS versus cathode voltage, microwave power and so on, are obtained by thermocouples in the experiment. The results show that the temperature rise may be associated with the RBWO Page 29

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output performance. The temperature increment seems to reach the minimum when the microwave generation efficiency comes to the maximum. Theoretical analysis and numerical simulations are also performed regarding this phenomenon for an explanation. P2-10 [A2286] Performance improvement of a MILO with a preprocessed and conditioned carbon fiber array cathode LI Ankun, FAN Yuwei, QIAN Baoliang, LUO Ling, ZHU Weixing (National University of Defense Technology, Changsha, China) Abstract: The carbon-fiber-based cathodes have shown advantages in lifetime and vacuum compatibility over traditional polymer velvet cathode, but the fabrication of the carbon-fiber-based cathode is usually more complicated than the polymer velvet cathode. A carbon fiber array cathode was presented and tested in a Magnetically Insulated transmission Line Oscillator (MILO) in previous papers; however, the performance (power conversion efficiency and pulse duration) of MILO with this cathode was not as good as the polymer velvet cathode, and we think the unsatisfactory fiber distribution on the cathode surface may be a reason for this drawback. In this paper, after this carbon fiber array cathode was carefully preprocessed and conditioned, the performance of MILO with this cathode is improved a lot and reaches a level that is as good as the traditional velvet cathode. In the pretreatment, firstly, the fiber rings were taken down and the fibers were shaved once again to make the fibers’ length more consistent; secondly, all fiber rings were cleaned in alcohol with assistance of ultrasonic; thirdly, these fiber rings were baked out and put on the cathode shank. After pretreatment, the distribution of the fibers on the cathode surface is more uniform than it was before this pretreatment, and we believe this will contribute to the performance of MILO. In experiments, after tens-pulses’ conditioning process, with this carbon fiber array cathode, the performance of MILO is as good as the traditional velvet cathode under similar conditions. In this way, this carbon fiber array cathode provides a possible substitute for the polymer velvet cathode. Also, the improved results demonstrate that the pretreatment and conditioning of cathode are essential for the carbon fiber based cathode to reach satisfactory performance. The reason of this phenomenon should be further researched. P2-11 [A2301] An L/C double‐band magnetically insulated transmission line oscillator FAN Yuwei, YU Yuanqiang, WANG Xiaoyu, LI Ankun, LIU Zeyang (National University of Defense Technology, Changsha, China) Abstract: The magnetically insulated transmission line oscillator (MILO) is a promising high-power microwave (HPM) source designed specifically to generate microwave power at the gigawatt level and a major hotspot in the field of HPM research. However, because of the fact that a large fraction of the dc input current forms the load current, its power efficiency is not very high for most applications. In order to increase the power efficiency, a complex MILO Page 30

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has been presented and its power efficiency has an increase of about 50% compared with the conventional load-limited MILO. In simulation, the power efficiency of the original complex MILO is 19.9%. According to the theoretical anticipation, the power efficiency of the complex MILO can be above 25%. In order to enhance the power efficiency and the microwave power, an L/C double-band MILO is presented and investigated numerically in this paper. In the L/C double-band MILO, the C band MILO is used as the load of the L band MILO. In simulation, when the voltage is 682 kV and the current is 69 kA, HPMs with frequencies of 1.71 GHz and 4.17 GHz can be achieved with powers of 8.4 GW and 3.9 GW, respectively. The corresponding total microwave power and the power efficiency are 12.3 GW and 26%, respectively. P2-12 [A2536] Dispersion characteristics of X‐band coaxial relativistic oscillators with periodic rectangle grooves WANG Jiayu, ZHANG Jun, JIN Zhenxing (National University of Defense Technology , Changsha, China) Abstract: In order to achieve high power, high efficiency and long pulse HPMs in X band, a new structure, the coaxial relative oscillator with large radius, is proposed. The structure is similar to a multi-gap resonant cavity, which is formed by loading the rectangular grooves on the coaxial structure’s inner and outer conductor. Based on Cherenkov radiation theory, this paper deals with the distribution, dispersion curve, growth rate, coupling impedance and power capacity of the large radius coaxial slow-wave structure. It then analyzes the working frequency and working mode of certain structural parameters and electrical parameters. But as this new structure is expected to adopt fewer gaps (about three), the field distribution may be not satisfied with the floquet theorem. Thus the simulation software CST is used to simulate the cold cavity of the slow-wave structure, to compare the the dispersion curve got from simulation and the theoretical derivation, to verify the correctness of the derivation based on the Cherenkov radiation theory. P2-13 [A2642] High power microwave pulse sharpening utilizing a waveguide spark gap SHAW Zachary, MANKOWSKI John, POWELL Melvin, BARNETT David, NEUBER Andreas, DICKENS James (Texas Tech University, United States) Abstract: This paper presents the experimental results of a waveguide sparkgap used to reflect an incident high power microwave pulse. The incident pulse is generated by a coaxial magnetron with a nominal output power of 3.2 MW with a 3 µs pulse width. The triggering of the spark gap takes place at the peak of the incident waveform, in which the sudden short reflects the incident waveform with sub 50 ns risetime. Multiple setups are implemented to compare the reflected risetime. The discuss begins with the incorporation of an LC Page 31

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inversion generator (~2.25 J), and eventually leads to a solid state pulser driven peaking gap of significantly less energy (~15 mJ). The switch itself is housed in a WR284 waveguide, operating in the dominant TE10 mode, centered about the E-field peak. A quartz tube surrounds the spark gap electrodes so that specific gases may be used within the gap that do not affect the gas within the waveguide itself. To avoid breakdown inside the waveguide, SF6 was used (1 atm absolute), while argon used as the medium in the quartz tube. The experimental setup involves the previously described coaxial magnetron, coupled to a high power circulator which is then connected to the plasma switch, and a high power microwave load. Two envelope detectors are implemented, placed at the magnetron output, and the HPM load in which the reflected signal is terminated. These envelope detectors (along with 40 dB of inline attenuation) are used to measure the power levels of the incident and reflected microwave pulses. Waveforms demonstrate the effectiveness of the pulse sharpening with varying pressures of argon in the quartz tube housing the spark gap (1-3 atm) and by also flowing the gas through the housing. Waveforms also demonstrate the effectiveness of these techniques while rep-rating the magnetron at 10 Hz. P2-14 [A2693] Design and realization of magnetic field automatic measurement system for TWT permanent magnet system YAO Zeqin, WANG Zhanliang, GONG Yubin, DUAN Zhaoyun, GONG Huarong, LU Zhigang (School of Physics, University of Electronic Science and Technology of China) Abstract: The permanent magnet system is an important part of the Traveling-Wave Tube(TWT), which is mainly used to limit the electron beam divergence. And it enables the electron beam to pass smoothly through the slow wave structure, so that electrons can not be captured and dissipate energy. Further, the electron beam can function fully with the electromagnetic wave to achieve the amplification of the microwave signal. This paper introduces a system for automatic measurement of TWT permanent magnet system, which is mainly used to measure the distribution of magnetic field intensity in the axial direction of the TWT. The system consists of a horizontal test bench, a longitudinal mobile device, a motion control system, a magnetic field measuring device and a data acquisition and processing system. Through the modular programming of the software to the control system, the automatic measurement of the magnetic field can be carried out in the axial direction of the TWT, and the data are collated, analyzed and plotted through the data acquisition system.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 P2-15 [A2739] A coaxial transit‐time oscillator operating in TM02 mode with traveling wave output structure DENG Bingfang, HE Juntao, LING Junpu (College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, China) Abstract: A 60 GHz coaxial transit-time oscillator with traveling wave output structure is presented. The beam-wave interaction region consists of a four-gap pre-modulation cavity, a five-gap modulation cavity and a traveling wave output structure. All the interaction regions operate in TM02 mode. The pre-modulation cavity is used to pre-modulate the electron beam and prevent the microwave from leaking into the diode region. The beam is further modulated in the modulation cavity to ensure the sufficient beam-wave interaction in the output structure. By using a traveling wave output structure, the power handling capacity is increased. The output structure is also good for improving beam-wave interaction. The dispersion relation of the SWSs in the output structure is analyzed by mode matching method. In numerical simulation, a 610 MW microwave pulse at 60.0 GHz is obtained with a diode voltage of 400 kV and beam current of 5 kA. The power conversion efficiency is about 30.5%. P2-16 [A2767] Study of an S‐band triple cavity high power microwave oscillator WU Yang (Institute of Applied Electronics, CAEP, Mianyang, China) Abstract: By use of the intermediate cavity and optimizing the phase of the modulated electron beam into the cavity, the triple cavity oscillator could improve the interaction efficiency of the dual cavity oscillator. In this paper, an S-band triple cavity oscillator is proposed, and the effect of the intermediate cavity on enhancing the fundamental harmonic current is also investigated. Moreover, 3D particle-in-cell (PIC) simulation is carried out, and the mechanism of the non-working mode oscillation and its influence on working characteristics of the device are explored in the simulation. It indicates that the TE11 mode’s reflection due to the support posts and the TM11 mode’s excitation in the cavities are the main causes of non-working mode self-oscillation. Finally, mode control of the triple cavity oscillator is accomplished by adjusting the axial position of the support posts without affecting the characteristics of the working mode. And the 3D simulation result agrees with the 2D result, which indicates that the non-working mode excitation is fully eliminated.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 P2-17 [A2789] Evaluation of microwave pulse emitted from multistage axially‐extracted vircator with reflectors NIWA Fumiya, SATOU Tomoya, ITO Hiroaki (University of Toyama, Japan) Abstract: The high power microwave generated in an axially extracted virtual cathode oscillator (vircator) has been studied experimentally. The vircator is driven by a Marx generator and pulse forming line. To improve the efficiency, we installed reflectors in the vircator to improve the microwave conversion efficiency and oscillation frequency control. The electron beam diode was an axially extracted vircator with the solid type aluminum cathode of 60 mm in diameter and the stainless steel mesh anode. The output power of the microwave was measured by varying the refrector spacing length and the number of reflector. In addition, we evaluated the characteristics of output microwave by the time-dependent frequency analysis. These experimental results show that the microwave conversion efficiency with reflectors is several times higher than that without reflectors. P2-18 [A2835] A multi‐band relativistic backward wave oscillator LI Hailong1, YE Qicheng2, WANG Maoyan2, WANG Bin1, YIN Yong1, MENG Lin1 (1. School of Electronics and Engineering, University of Electronic Science and Technology of China; 2. School of Physics, University of Electronic Science and Technology of China) Abstract: This paper presents a relativistic backward-wave oscillator that can produce multiple frequency electromagnetic waves. By connecting two different slow-wave structures with different parameters, multiple high-frequency electromagnetic waves with similar frequencies can be generated at the same time, so that electromagnetic waves with beat wave effect can be output. The preliminary simulation results show that the four frequency microwave output at about 8.7 GHz and 9.4 GHz has been produced on the condition of the beam voltage 460 kV, current 4.3 kA and guided magnetic field 1.9 T. By optimizing these parameters, device efficiency can be significantly improved. P2-19 [A3044] Measurement of field distribution of coaxial multi‐beam microwave resonant cavity ZENG Fanbo, YIN Yong, BI Liangjie, PENG Ruibin, XU Che, ZHU Sairong, CHANG Zhiwei, WANG Bin, LI Hailong, MENG Lin (University of Electronic Science and Technology of China) Abstract: The application of multiple beams in the Extended-Interaction Oscillator(EIO) with coaxial structure permits a significant increase in the average output power at millimeter wavelength. A simulation has been accompolished by a 3-D Particle-in-Cell-code computer simulation technology predicting an output power up to 25 kW at 35 GHz. The performance Page 34

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parameters of the EIO depend to a large extent on the distribution of microwave fields in the cavity. This article describes a technique to measure the field strength of the coaxial multiple-beam microwave resonator and discusses perturbation in the microwave resonator. This solution can be used for the measurement of coaxial multiple-beam microwave resonators. The method is simple and practical, the introduced error is small, and it is verified by experiments that the method is consistent and reliable. P2-20 [A3088] Development of a solid state pulsed high power supply for gyrotron PU Youlei, WU Zewei (University of Electronic Science and Technology, Chengdu, China) Abstract: This paper describes the development of a solid state pulsed power supply (SSPPS) for high power millimeter wave gyrotron. Because the power output of gyrotron is varied with different pulse width, repetition rate and amplitude, the SSPPS should output high power with wide tuning range of pulse width and repetition rate. In order to meet the requirement of the output power and compact the volume, there are some special designs for the source part and the modulator part of the SSPPS. The source part of the SSPPS consists of four phase-shifted full-bridge (PSFB) converters. The zero-voltage-switching (ZVS) technology and some auxiliary circuit are implemented in the PSFB converter to reduce the loss of switching process. The modulator part is made up of series-connected insulated gate bipolar transistors (SC-IGBTs). In addition, distinctive design of the driving method for the SC-IGBTs is introduced, which combines the digital circuit technology and magnetic coupling method. The overcurrent protection is implemented to protect the SSPPS working stably. Finally, the developed SSPPS can output the pulse with the maximum repetition rate of100 kHz and the pulse width from 5 s to DC P2-21 [A3270] Research on output cavity with tungsten coating layers in high power microwave source XIE Jialing, CHA Changhua, YANG Dewen, WU Ping, LIU Wenyuan, HUO Yankun (Northwest Institute of Nuclear Technology, China) Abstract: The output cavity in a relative backwardwave oscillator is made of titanium, the surface is tungsten plated with varing thickness. The results indicate that the radiaton waveforms of output cavity with tungsten coating layers shorten, and the thicker the layer, the greater the shortening. The breakdown tracks on the output cavity are analyzed. On the output cavity with 2 m tungsten coating layer, the coating layer on the side near the collector exfoliates greatly. The tracks on the side near the collector are developed into microcraters. And on the side near slow wave strctures, there are sputtered tracks, when getting through thousands of shots, there are erosion tracks on

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this side. The breakdown process is discussed. P2-22 [A2356] Design of a compact radial‐line relativistic klystron oscillator with low guiding magnetic field DANG Fangchao (National University of Defense Technology, Changsha, China) Abstract: Owing to its merits of high power capacity and weakened electron density, the radial-line relativistic klystron oscillator (RL-RKO) is one of the most promising high power microwave (HPM) sources in high frequency band. In previous work, we have experimentally demonstrated its feasibility by generating Ku-band gigawatt-level microwaves with a beam-wave interaction efficiency of 24% in our lab. Notwithstanding, the previous oscillator exhibits an oversized radial dimension, which greatly limits its actual application. In this paper, we are intended to miniature the dimension of this HPM device. On the one hand, a soft magnetic material is adopted in the cathode base design, constituting a soft magnetic cathode (SMC). The SMC can be able to compensate the guiding magnetic field in the diode region and to decrease the diode radius. Meanwhile, the diode electrodynamics structure is improved to weaken the transverse electric field and the guiding magnetic field strength. On the other hand, we designed a three-gap buncher based on transit-time effect, and the electron beam is deeply bunched with a fundamental current modulation depth of 120%. After employing a dual-gap extractor, a microwave beam is generated with a power of 2.2 GW, center frequency of 14.15 GHz and efficiency of about 40% in the particle-in-cell (PIC) simulation. The radius of the whole RL-RKO is less than 12 cm and the guiding magnetic field strength is only 0.4 T.

Poster Session III - Pulsed Power Applications - Session Chair: LIU Jinliang (BALL ROOM 2#)[13:30-15:00] P3-1 [A0250] The controller design of the auxiliary power module for magnetically compressed plasma fusion WENG Zhiyuan1, LI Ge1, MIAO Pengcheng1, WENG Zhigang2 (1. The Institute of Plasma Physics, Chinese Academy of Sciences, China; 2. West Anhui University, China) Abstract: In order to improve the operating parameters of plasma in Tokamak, at high density, high temperature and high beta, it has been proved that the magnetically compressed plasma is one of the effective methods. In this paper, a high frequency and high power dc–dc converter is proposed, used for the power supply system for radius magnetic compression coil. The basic of power modules is full-bridge phase-shift pulse-width-modulated (PWM) dc–dc converter. Also, the control method adopts current closed loop PI control and

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has short current response time (less than 1 ms). The converter is analyzed and the design procedure is discussed. Experimental results obtained from a 30 kW converter prototype are presented to validate the converter’s performance and the concepts presented. P3-2 [A0450] Shockwave characteristics and ignition mechanism of nitramine powder ignited by microsecond exploding wire plasma LIU Qiaojue, YAO Weibo, WANG Yu, ZHANG Yongmin, TANG Junping, YANG Li, QIU Aici (State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China) Abstract: Based on high pulsed power technology, electrical explosion is increasingly utilized to generate shock waves with high pressure. To further magnify the shock wave pressure, we have proposed a novel technique by using energetic materials ignited by the plasma of microsecond wire explosion. Organic derivatives of nitramide, termed nitroamines, are widely used as powerful and relatively insensitive explosives, including RDX and HMX. In this paper, we investigated the underwater shock wave characteristics of nitramine (RDX and HMX) powder ignited by exploding Cu and Mo wire (diameter 0.2 mm, length 60 mm) plasma. With charge voltage ~24 kV and powder mass ~6.0 g, the most evident experimental results suggested that the RDX load possessed higher peak pressure 10.66 MPa and larger areal impulse 513.98 MPa·μs, comparing with the shock wave of HMX load (7.06 MPa and 303.43 MPa·μs). Moreover, the RDX load also had greater ascent rate of pressure, which was nearly twofold of that of HMX load. In addition, it was implied by quantum chemical calculation that the light emission during the wire explosion process was one of the key factors that would affect the ignition characteristics. Finally, a simple multi-factors ignition mechanism for nitramine powder under microsecond exploding wire plasma was proposed and discussed. P3-3 [A0717] Recent upgrade of the hydrodynamic experimental platform (FP‐1) at CAEP ZHANG Shaolong, ZHANG Zhengwei, SUN Qizhi, LIU Wei, LI Jun, CHI Yuan, ZHANG Nanchuan, QIN Weidong (Institute of Fluid Physics, CAEP, China) Abstract: FP-1 is a pulsed power generator used for investigation of the hydrodynamic behavior of materials under strong shocks. The facility was constructed in 1990s at Institute of Fluid Physics, CAEP. The facility consists of a capacitor bank of total 216 μF which could store 172 kJ electricity energy at charging voltage of ±20 kV. Peak current of 2 MA could be delivered to the aluminum liner load with a 7 μs rise time (0-100%). Magnetic pressure generated by the current could drive a 31 mm aluminum liner impacting on a 22 mm target with velocity of about 1 km/s. Recently, some upgrade of this facility was made to enhance the current repeatability and experiment

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efficiency. In this report, details of the upgrade will be shown, including modification of the opening switch, reformation of the trigger method, addition of a monitor system for switch action. Some applications of this facility after upgrade will also be shown. P3-4 [A0814] Isentropic compression of LiH studied by means of ultra‐high magnetic field pressure KORSHUNOV Alexey, BORISKOV Gennady, BYKOV Alexander, EGOROV Nikolai, PAVLOV Valery, STRELKOV Illiya, TIMAREVA Valentina, BELOV Sergey (Russian Federal Nuclear Center – All-Russian Research Institute of Experimental Physics, Russia) Abstract: The authors provide the experiments description regarding the isentropic compression of metalhydrides by means of ultra-high magnetic field pressure in the device based on the magneto-cumulative generator MC-1. There are the results of the set of three such experiments data analysis, where a lithium hydride (n)LiH was studied as the investigated substance. The experimental points on the P-rho diagram are compared with a normal adiabat obtained earlier on the diamond anvil cells experiments, and with ab initio theoretical curve. P3-5 [A1800] Design of high‐power plasma phase shifter HAO Dongqing, YUAN Chengwei, ZHANG Qiang (National University of Defense Technology, Changsha, China) Abstract: Phase-shifters are used to adjust the phase of microwave output, which is one of the most important devices to realize two-dimensional beam scanning of array antennas. Common phase shifters cannot be directly applied to high power microwave field because of the power capacity problem, so it is necessary to study a new type of phase shifter which has high power capacity. In this paper, a plasma phase shifter is proposed by controlling the excitation and quenching of plasma. Through theory analysis, model construction, simulation and experiments, its power capacity is analyzed and the feasibility is verified. Also, the state of the plasma under different gas parameters and its influence on the phase shift are analyzed. Results show that the power capacity of this S-band reflection type plasma phase shifter can reach tens of megawatts, and the phase shifter can achieve 360 ° phase shift rapidly. P3-6 [A2249] Long lifetime, large plasma waveguide using segmented electrodes for laser particle acceleration SASAKI Toru, SAWADA Kyohei, KAJIUCHI Yuki, Osawa Makito, TAKAHASHI Kazumasa, KIKUCHI Takashi (Nagaoka University of Technology, Nagaoka, Japan) Abstract: In the laser particle acceleration, the acceleration region is limited to the Rayleigh length of laser. In this study, to realize a plasma waveguide using Page 38

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capillary discharge, segmented electrode type capillary was proposed. The plasma generated in the capillary by the discharge has a concave electron density distribution, and the concave electron density distribution depends on the capillary diameter and the main discharge current. The laser intensity through the plasma waveguide also improves in the proposed capillary. P3-7 [A2887] Numerical analysis and finite element simulation for the high current planar spiral inductor WU Haibo, LI Lee, DAI Hongyu, XIONG Jiaming, YU Bin, PENG Mingyang (Key Laboratory of Pulsed Power Technology (Ministry of Education), School of Electrical & Electronic Engineering, Huazhong University of Science and Technology, China) Abstract: Pulsed inductors are widely used in the capacitive pulsed power supplies as pulse shaping elements and protection elements. Compared with the solenoid pulsed inductor, the planar spiral inductor is helpful to the miniaturization of the pulsed power supply. In this paper, a numerical method for the inductance of the planar spiral inductor is proposed based on Bartky transformation method of elliptic integral calculation, and the corresponding numerical analysis program is developed. On this basis, the parameter design of the inductor is carried out based on particle swarm algorithm, some constraints are considered in the design such as space, temperature and current density. By the finite element simulation for the electromagnetic force of the planar spiral inductor under hundreds kiloampere of current pulse, it is found that the maximum von Mises stresses in the components of the inductor are lower than the ultimate tensile strengths of the materials. Analysis and simulation of the planar spiral inductor can provide guidance for design of the high current inductor. P3-8 [A3240] Research on electro‐plasticity in metals generated by pulsed currents ALOTAIBI T., NOVAC B. M., SENIOR P., COLES L., ROY A., SILBERSCHMIDT V. (Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, U.K.) Abstract: Application of high-intensity currents is known to enhance materials’ deformability. For instance, a high-density electric current applied continuously (CC, continuous current) or in short pulses (PC, pulsed current) on a metal may significantly affect its deformation response to external loads. This phenomenon is commonly referred to as electroplasticity or electroplastic effect (EP). In the present study, mechanical tensile experiments were performed in combination with the application of a high intensity electric current for very short durations in copper samples. The study demonstrated the enhanced plasticity was induced in the metal due to EP. Post-event microstructural studies highlight the effect of the high intensity electric current in the material.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 P3-9 [A0235] Toluene removal using nanosecond pulsed discharge plasma supported by MnOx catalysts TORIGOE Yasuaki1, KORI Shintaro1, IWASAKA Asuki1, ZHANG Pengyi2, NAMIHIRA Takao3, WANG Douyan3 (1. Graduate School of Science and Technology, Kumamoto University - Japan; 2. School of Environment, Tsinghua University - China; 3. Institute of Pulsed Power Science, Kumamoto University – Japan) Abstract: Volatile organic compounds (VOCs) adversely affect the human health. Efficient removal methods of VOCs are essential to meet global emission regulations. The authors’ research group also developed a nanosecond (ns) pulsed discharge system utilizing 5 ns of pulse duration which demonstrated higher energy transfer efficiency compared with a DBD; efficient NOx decomposition; dependence between pulse width and O3 yield (i.e. energy efficiency); and O3 generation with a yield higher than reported non-thermal plasmas. To expand on this, our present work aims to clarify combined effects of the catalyst and its position using plasma alone (PA, i.e., without catalyst) and the three methods mentioned above, IPC, PPC, and I-PPC with an ns pulsed discharge system for the decomposition of a VOC in atmospheric pressure at room temperature. MnOx catalyst supported by Ni-foam was selected as the most cost-effective catalyst for complete oxidation of hydrocarbons and decomposition of O3. Toluene was selected as a common model VOC existing in home or workplace interiors under WHO guidelines, which recommends maintaining 30 min average concentrations below 0.27 ppm. Toluene is also the most studied VOC for abatement at the laboratory scale, while 110-120 ppm was selected because it is the most frequently investigated initial concentration. P3-10 [A1040] Influence of pulsed electric field to leaf lettuce evaluated by photosynthetic measurement SATO Ryusei1, HAYASHI Yu1, HIGASHI Yuya2, NAMIHIRA Takao2, WANG Douyan2 (1. Graduate School of Science and Technology Kumamoto University, Kumamoto, Japan; 2. Institute of Pulsed Power Science Kumamoto University, Kumamoto, Japan) Abstract: Physical phenomena in biological cells caused by external pulsed electromagnetic energy, known as bioelectrics, have been studied in a variety of applications. The use of pulsed power technologies to organisms is expected to open up new science and technology, especially, plant biology. For example, nanosecond pulsed electric fields (ns-PEF) give a unique stress based on dielectric and electrostatic effects to subcellular biomolecules and organelles of plants and animal species, being expected to lead to new biological reactions. However, it remains unknown correlations between pulsed power and biomechanisms. To clarify these correlations, this study focused on photosynthetic mechanism of plants and fundamental research was carried out. Leaf lettuce was chosen as the material of this experimental study. Pulsed Page 40

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electric field (PEF) was generated by pulsed forming networkand arranged to make a single pulse with 400 ns pulse duration and irradiated to a leaf of leaf lettuce. Number of pulses, electric field strength, and pulse repetition rates were set to 500 shots, 0.2 kV/cm, and 1 pps, respectively. Following PEF treatment, the Portable Photosynthesis System measurement was conducted to get some photosynthetic parameters. Results showed that carbon fixation rate (A) was increased by the PEF treatment compared to control samples. P3-11 [A1393] Stability of pulsed discharge plasma with porous electrode without dielectric barrier at atmospheric pressure LI Jie, DONG Pan, LI Xi, XIE Yutong, LONG Jidong, ZHANG Linwen (Institute of Fluid Physics, China) Abstract: Stable and uniform large-volume plasma generated at atmospheric pressure attracts much attention in recent years in gas discharge physics for the potentials for numerous applications. In this study, one of the parallel plate electrode is designed with barrier-free small apertures distributed uniformly, so the working gas could flow uniformly to the operating discharge gap. Both of the electrodes are barrier-free with their diameter of 130 mm. A repetitive unipolar sub-microsecond pulse power (0~100 kV, 130 Hz~1 kHz, pulse width 230 ns, rise time 120 ns) is used to drive the barrier-free gas gap. Uniform discharge plasma can be steadily sustained even the gap distance exceeds 20 mm in atmospheric pressure He with a flow rate of 5 L/min. Characteristics of the discharge have been studied by experiments. Temperature of the electrode nearly remained unchanged after 30 min’ discharge with the frequency of 500 Hz. Tests of electrical parameters showed that plasma generation occurred in the voltage-falling phase. Experiments of high speed photography with exposure time of 5 ns proved the discharge worked at homogeneous glow discharge mode. It is found that type of the working gas, proportion of mixture gases, waveform of the applied voltage (especially the rising and falling time of the pulse) are the key factors for the stability of the discharge. Also, spectrometer was used in our research to study the plasma parameters (such as spectral line intensity of emission spectrum, electron temperature) of the discharge. Some recent results will be mentioned in the report. P3-12 [A1463] Quantitative assessment of reactive oxygen species oxidizing aqueous organic pollutants in pulsed corona discharge PREIS Sergei1, WANG Yixian2, KORNEV Iakov3, WEI Chaohai2 (1. Tallinn University of Technology, Tallinn, Estonia; 2. School of Environment and Energy, South China University of Technology; 3. School of Advanced Manufacturing Technologies, National Research Tomsk Polytechnic University) Abstract: Conventional potable water treatment often does not meet drinking water standards in contents of unwanted admixtures. Industrial application of refractory compounds of highly potent character results in their accumulation in Page 41

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the environment. Solving these problems with application of ozone-based advanced oxidation processes meets the obstacle in unaffordable cost of ozone generation and application. Substantial improvement of the energy efficiency of water treatment is acquired by using gas-phase pulsed corona discharge (PCD) organized between electrodes with the water showering through the plasma zone. Involving short-living reactive oxygen species (ROS) to the water treatment, the plasma application allows minimum two-fold surpassing of conventional ozonation in energy efficiency. Experimental research was undertaken for quantitative assessment of ROS contributions to oxidation of aqueous pollutants of various oxidation kinetics – phenol (rapid oxidation), humic substances (medium-rate oxidation) and oxalate (slow oxidation). Radical-scavenging admixtures of surfactant and non-surfactant properties of various concentrations were used to estimate the surface character of oxidation reactions and the role of short-living ROS in the overall balance of oxidants. The results of the research showed noticeable radical-scavenging effect of both surfactant and non-surfactant admixtures to the oxidation of target pollutants, although the surfactants appeared to act more effectively. The slowing effect of sodium dodecyl sulphate, tert-butyl alcohol and sodium bicarbonate at various concentrations was quantitatively estimated. The comparison of radical-scavenging effects gives a possibility to assess the ROS balance in target reactions of pollutants elimination. The oxidation efficiency assessment was made at various pulse repetition rates to estimate the role of this parameter in the ROS balance. The results allow quantitative forecast of optimum pulse repetition frequency for maximum energy efficiency dependent on the character of pollutants. P3-13 [A1664] Generation of plasma activated water by hybrid plasma source JIN Yun Sik, CHO Chuhyun, KIM Jong Soo (Korea Electrotechnology Research Institute, Korea) Abstract: Recently plasma activated water (PAW) has been studied actively since it can be applied for various applications such as biomedical, food, and agriculture. Especially PAW is known to inactivate microbial cells effectively. In this study, PAW was generated by a hybrid plasma source of thermal and non-thermal plasma. As a thermal plasma source, gas-jet assisted pulsed discharge in the water was used to produce PAW. And a coaxial cylindrical dielectric barrier discharge (DBD) was used as non-thermal plasma source for PAW preparation. Characteristics of PAW formation were investigated when the two plasma sources were used simultaneously or in succession. P3-14 [A1696] Nanosecond pulse discharge in air gap between water electrodes for plasma activated water production CHO Chuhyun, JIN Yun Sik (Korea Electrotechnology Research Institute, Korea) Abstract: It is reported that the underwater discharge mechanism due to the Page 42

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nanosecond pulse is caused by bubbles generated at the electrode surface. From these results, a method of supplying gas to generate a discharge in water/underwater has been extensively studied. In this study, an air gap was formed by using a separator in water, and a discharge was generated by applying a nanosecond pulse between them. At this time, the electrodes were immersed in water so that the discharge occurred at the surface of the water in contact with the gas. Through this, the generation of metal nanoparticles could be suppressed. The water produced through this discharge shows the characteristics of the plasma activated water. From the analysis of the prepared activated water, it was confirmed that the energy efficiency was better than the DBD discharge method. P3-15 [A1862] A repetitive nanosecond pulse generator with photoconductive semiconductor switch and application for atmospheric pressure plasma jets XIAO Jinshui, LUAN Chongbiao, LI Hongtao, MA Xun, WANG Chuanwei, HUANG Yupeng (Key Laboratory of Pulsed Power, Institute of Fluid Physics,CAEP, China) Abstract: In this paper, a compact repetitive nanosecond pulse generator is designed for exciting the atmospheric pressure plasma jets (APPJ) in noble gases. To realize the ultrashort pulse output, a novel Si photoconductive semiconductor switch (PCSS) with reflected cavity and two pulsed formed lines is used. Based on the Blumlein topology, the nanosecond pulse generator can produce repetitive pulses with rise time of ~5 ns, pulse width of ~7 ns, and pulse repetition frequencies of 1 Hz~1 kHz. Using the designed repetitive nanosecond pulse generator, the characteristics of the APPJ are investigated by measuring the voltages and currents and obtaining images of the discharges. Experimental results show that the nanosecond pulse generator has been successfully used to sustain stable APPJs in helium. The length of plasma plume is over 2 cm. Furthermore, the effects of flow rate, the applied voltage, and the pulse frequencies on the He APPJs are investigated. P3-16 [A2039] A pilot‐scale pulsed electric field treatment for a continuous flow system and its use for microorganism inactivation DENG Weijun, XIAO Jinshui, KANG Chuanhui, DING Mingjun, MA Xun, LI Hongtao (Key Laboratory of Pulsed Power, Institute of Fluid Physics,CAEP, China) Abstract: As a non-thermal sterilization technology, the pulsed electric fields (PEF) treatment has the capabilities to inactivate microorganisms in foods without significant loss of flavor, color, and nutrients etc. To improve the process capacity, a pilot-scale pulsed electric field treatment for a continuous flow system has been designed and fabricated. The system mainly consists of an HV pulse generator, a novel guide-flow chamber, a cooling system, a pump and controlling unit. As the key part, the generator produces monopolar pulses Page 43

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with operational pulse voltage 1-100 kV, pulse duration 1-20 μs, pulse repetition rate 1-100 Hz. The flow rate is controlled within 1~3 L/min. To achieve high electric field, two or three treatment chamber are in series and applied with an electric field almost 30-100 kV/cm. With the pilot-scale system, the performance of microorganism inactivation by PEF has been investigated. Experimental results show that when using PEFs of E=30-100 kV/cm and tp=5 μs, the Saccharomyces cerevisiae reduction can reach 4~6log10 with the treatment temperature rise below 30℃. P3-17 [A2172] The effect of different parameter of electromagnetic pulse on blood brain barrier permeability CHEN Qin1, GAO Peng1, HU Junfeng1, LIN Yanyun1, DING Guirong2, GUO Guozhen1 (1. Department of Radiation Medicine, Faculty of Preventive Medicine, Fourth Military Medical University, Xi’an, China; 2. Department of Radiation Biology, Faculty of Preventive Medicine, Fourth Military Medical University, Xi’an, China) Abstract: To study the effect of electromagnetic pulse (EMP) on permeability of blood-brain-barrier (BBB). Sprague-Dawley(SD) rats were randomly divided into positive control group, negative control group and EMP exposure group, the exposure group was exposed to EMP at field intensity of 350 kV/m and 750 kV/m, respectively. The BBB permeability was assessed by methods of the tracer of exogenous EB（Evans Blue）and the staining of endogenous albumin at different time points of 0.5, 3, 6 and 12 h. The results showed that the EB extravasation and albumin immunohistochemistry intensity around brain microvessel of EMP-exposed group significantly increased compared to control group, the field intensity of 720 kV/m showed stronger effect than 350 kV/m. The EB and albumin began to extravasate from microvessel at 0.5 h after exposure, reached the peak at 3 h and 6 h, and fell to minimization at 12 h after EMP exposure. EMP exposure can reversibly increase the BBB permeability and the field intensity may play a vital role in the effect. P3-18 [A2439] Subnanosecond pulse forming line generator for NO removal with transient plasma RIVALETTO Marc1, PECASAING Laurent1, DE FERRON Antoine1, HUISKAMP Tom2, KUMAR Siddharth2, DEURSEN Armand v.2 (1. Univ Pau & Pays Adour, France; 2. Eindhoven University of Technology, Department of Electrical Engineering, Electrical Energy Systems Group, Eindhoven, The Netherlands) Abstract: Regulations concerning air pollution by industry and the transportation sector, as well as indoor air quality are continuously increasing in number and stringency to work towards a cleaner and healthier environment. A versatile and promising technology that combats air pollution efficiently uses transient plasma. Recent research has shown that using ultrashort high-voltage pulses to generate these plasmas increases the efficiency of this technology to the point where it becomes a viable alternative to existing

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technologies, which are not as versatile and have other significant disadvantages. Previous works at Eindhoven University showed that the main parameter that caused high efficiency is the very short rise time of the pulses. In this context, a new pulsed generator was developed at the SIAME laboratory of Pau University to try to improve the efficiency of the air treatment pulsed plasma reactor developed by the Electrical Energy Systems section of Eindhoven University. This generator, based on a pulse forming line, operates with a 60 bar hydrogen spark gap switch, and produces 30 kV pulses with 3 ns of duration with a very fast rise time of 100 ps. Its repetition rate can reach 300 Hz. Its modeling under CST MW Studio, its design (CATIA), its construction, its performances and first tests of the combination of this source with a plasma reactor are presented in this contribution. P3-19 [A3187] Investigation on the water treatment by nanosecond pulsed dielectric barrier discharge based with water mist JIANG Song, ZENG Tong (University of Shanghai for Science and Technology, China) Abstract: The application of non-thermal plasma is more and more extensive especially in wastewater treatment and its treatment effect is obvious. In this paper, the dielectric barrier discharge water treatment is studied under the condition of water mist by nanosecond pulsed power. The reactor uses coaxial structure and the treated solution enters the discharge area in the coaxial reactor with the form of water mist. The effect of discharge time, voltage amplitude, frequency and pulse width for treatment results were studied. The concentration of ozone, hydrogen peroxide and hydroxyl radical was measured in the flow of oxygen and air respectively. The possible products of the reaction were analyzed by using spectra. Finally, indigo carmine was used as simulated wastewater to analyze the degradation efficiency of indigo carmine and the energy consumption of the whole system. The experimental results show that the treatment system has good degradation effect on indigo carmine solution. The degradation efficiency increases with the increase of voltage amplitude and frequency. The degradation efficiency of indigo carmine solution in the flow of oxygen is higher than that of air.

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Oral Session 4 - High Voltage Insulation; High Energy Density Storage; High Power, Solid State Electronics - Session Chair: LIU Kefu (BALL ROOM 1#)[15:00-17:30]

15:00 O4-1 [A1960] Comprehensive diagnosis study of surface flashover characteristics across large‐scale ceramic vacuum interfaces in high‐current diodes SUN Xiaoliang, XUN Tao, ZHONG Huihuang, ZHANG Jun (College of Advanced Interdisciplinary Studies, National University of Defense Technology,China) Abstract: In this paper, a comprehensive diagnostic platform for investigating the surface flashover characteristics of vacuum interfaces is presented and the experimental results for the flashover evolution across a large-scale ceramic vacuum interface under a high-voltage pulse are reported. Besides the pulse power modulator and the sample chamber, the platform contains the optical diagnostic instruments such as the high-speed framing camera, spectrograph, X-ray spectrometer and electrical measurements including capacitive voltage divider and self-integrated Rogowski coil as well. For the system in this paper, the surface flashover is initiated from a velvet ring attached to the cathode triple junctions. With the high-speed framing camera, the flashover plasma light emission process was observed and an average light propagation velocity of 2×108 cm/s was obtained. The radial and angular velocity components characteristics were analyzed by digital imaging processing method. An average electron temperature of 4.57 eV for flashover plasma was also acquired. X-ray measurements of the surface flashover plasma across the large-scale ceramic vacuum interface under high-voltage pulse were analyzed as well. These results confirm that besides the impacted electrons, the trapped electrons on the ceramic surface also play an important role for the flashover process across a ceramic vacuum interface. This work can give a further understanding of flashover along the ceramic interface with high-voltage pulse and promote their applications in high-current diodes.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 15:15 O4-2 [A2440] Insulation technology of propylene carbonate‐based nano‐fluid in pulsed power source ZHANG Zicheng, HOU Yanpan, LIU Shifei, YANG Hanwu, ZHANG Jiande (College of Advanced Disciplinary Studies, National University of Defense Technology, Changsha, China) Abstract: Development of pulsed power technology is towards high power, longer duration and more compact structure. Propylene carbonate, due to its great permittivity, high insulation strength, good self-healing, and easy shaping, has a good potential in compact pulsed power source as the energy storage medium of pulse forming line. Nano science is considered as one of the six major disruptive basic research field in the future by Department of Defense, United States. In this paper, nano-particle modification technology is introduced in the pulse power source to improve the insulation characteristics of propylene carbonate. Investigations are focused on the pulsed insulation characteristics, breakdown mechanism and engineering application of propylene carbonate. Firstly, the nanoparticles are uniformly dispersed into propylene carbonate by ultrasonic dispersion method. Thus, the stable and reliable nano-fluids are prepared by means of microstructure analyzing. And then their pulsed insulation characteristic is experimentally investigated in the microsecond regime, using the liquid dielectric breakdown setup with test cell. The insulation strength of nano-fluid is 40% higher than that of the base liquid, propylene carbonate. Moreover, the effects of the polarity and temperature on the pulsed insulation strength are explored. Secondly, by using the optical diagnosis method of ultrafast high-speed camera, physical images of streams during pulsed breakdown are captured. Based on the images of generation, propagation, cut-off for shock wave, sub-microscopic fracture surface, a physical model of breakdown for nano-fluid is proposed, revealing the physical mechanism of nano-modification to improve the pulsed insulation of the base fluid. Finally, the nano-fluid is applied in a liquid forming line of pulsed power source. The compact level of the pulsed power source is doubled. These efforts promote the interdisciplinary development of nano-science and pulsed power technology and show a promising application of nano-fluid in the pulsed power source for the future. 15:30 O4-3 [A2271] Research on improving energy density of pulsed inductor MIAO Jianhua, DAI Ling, ZHU Qi, WANG Shaojie, LIN Fuchang (State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Page 47

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Huazhong University of Science & Technology, Wuhan, China) Abstract: The inductive pulsed power supply (IPPS) gains wide attention in the field of electromagnetic launch. In order to improve the overall energy storage density of IPPS, the volume of the energy storage inductor needs to be reduced. Firstly, this paper investigates the multi-layer solenoid inductor, and establishes the inductance analytical expressions based on the calculation formula of self and mutual inductance. Comparing the results of the calculation with the finite element simulation, the error is less than 2%. Secondly, the optimal design algorithm of structural parameters is programmed. There are several decision variables contained in the algorithm, such as coil diameter, number of turns and layers, etc. The inductance value (L) and rate of current change (di/dt) are set as the equality constraints. Inequality constraints consist of the flow capacity, the ratio of inductance and resistance (L/R). The energy storage density is set to the objective function. Same method is applicable for other kind of inductor. Based on the MATLAB platform, the results show that the optimization method can obtain the optimal solution effectively. Finally, an inductor of 10 H is designed according to the algorithm. It possesses the expected flow capacity. The energy storage density reaches 18 MJ/m3. 15:45 O4-4 [A2524] Electric field force and temperature rise simulation of LTD capacitor to improve the life XIAO Haolong (Huazhong University of Science and Technology, Wuhan, China) Abstract: In the LTD system, the energy storage capacitor is an important component that requires low inductance and long life. According to experiments, LTD capacitor failure is generally due to surface breakdown between aluminum foils or breakdown at the junction of aluminum foil and polypropylene film. This paper uses simulation software to simulate the electric field, electric field force and temperature rise effect, and studies: (1) the distribution of electric field in the capacitor; (2) the distribution of the electric field force on the polypropylene film, and the influence of the electric field force on the stretching effect of the polypropylene, especially the deformation of the polypropylene film during the charge and discharge process resulted in fatigue breakdown and breakdown of the capacitor; (3) the temperature rise effect of the capacitor during charge and discharge, especially the uneven distribution of the current on the electrode, which leads to uneven heat production distribution and ultimately leads to the influence of the internal core temperature distribution difference on the capacitor life. Based on the conclusions drawn from the simulation, a scheme for improving the life of the capacitor was proposed and will be verified in the next experiment.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 16:00 O4-5 [A2706] Key techniques of energy storage dielectrics for “Triple Highs” pulse capacitor WEI Meng1, DENG Bowen1, WANG Wenjun2, CHEN Hongwei1, ZHANG Jihua1, ZHANG Wanli1 (1. State Key Laboratory of Electronic Thin Films and Integrated Devices, Collaboration Innovation Center of Electric Materials and Devices, University of Electronic Science & Technology of China; 2. Chengdu Micro-Tech Science &Technology Company Ltd) Abstract: High energy density storage components play an important role in the high power applications, such as electromagnetic, plasma, beam, laser, medical, biological and environmental. The pulsed energy storage components categorize into four groups: mechanical energy storage, chemical energy storage, inductor energy storage and electrostatic capacitors energy storage. Mechanical energy storage has the advantage of large storage density (~102 J/cm3), but the high cost of the core material (carbon fiber) and the huge control system for electromagnetic shielding and heat dissipation limit the development of miniaturization. Though chemical energy storage has the larger storage density (~104 J/cm3), one-time characteristic and superstrong destructive force cause its application to be unsatisfactory. Inductor is used to energy storage, with high storage density (~102 J/cm3). However, the hard work conditions (working temperature below 77 K or 4.2 K) need huge environmental control system for realization of superconductivity. Electrostatic capacitors energy storage, exhibiting broad temperature-, frequency-, and bias voltage-stability, is an attractive candidate for energy density capacitors, while the only weakness is attribute to the relative low energy density. Nowadays, four candidate materials with high energy density have been reported: ferroelectric, relaxor ferroelectric, antiferroelectric and linear dielectric. Ferroelectrics possess larger Pm and moderate BDS, but their energy density values and efficiency are lower due to their larger Pr. Comparatively, relaxor ferroelectrics with larger Pm, smaller Pr and moderate BDS are more likely to be used for high energy storage. Further improvement of energy density is limited by the nonliearity. Most antiferroelectrics, with larger Pm, smaller BDS and relatively high energy density, are lead-based materials, such as Pb(Zr/Sn/Ti)O3, (Pb/La)ZrO3 and (Pb/La)(Zr/Ti)O3. However, the disadvantages are obvious, such as fatigue effect, strain effect, not environmentally friendly and so on. Linear dielectrics usually exhibit higher BDS and lower energy loss, but the only limit is low permittivity. Obviously, linear dielectrics stand out and serve as realizing "Triple Highs" (the HIGH output power of traditional electrostatic capacitance with the HIGH energy storage density of electrochemical super-capacitors, and with HIGH temperature/voltage /frequency stability) pulse energy storage Page 49

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capacitors. In this paper, we introduce a dielectric material based on TiO2 single cation oxide with strong binding energy and high dielectric constant (80-120). We intend to design the structure of high withstand voltage with blocked conductive channel. The mechanisms of self-catalytic fully sintering, defect balance and fine grain control are investigated systematically. It is expected to provide material support for promising candidate materials for "Triple Highs" energy storage ceramic capacitors. 16:15 O4-6 [A1631] Daresbury Laboratory short pulse klystron modulators KEMPKES Michael, CHIPMAN Christopher, SIMPSON Rebecca, GAUDREAU Marcel, KINROSS-WRIGHT John, JASHARI Luan (Diversified Technologies, Inc. , United States) Abstract: Diversified Technologies, Inc. (DTI) has developed a unique short pulse klystron modulator system for the Compact Linear Advanced Research Accelerator (CLARA) Project at Daresbury Laboratory. Two units have been delivered and two more are on contract. This system is based on the combination of a high voltage solid-state switch, with a conventional 1:7 pulse transformer, and a passive pulse corrector with automated adjustment. This unique passive circuitry delivers the extremely flat output pulse required for advanced accelerator applications. The CLARA modulators share design elements with previous DTI modulators which provides both a lower cost and easier to maintain system. The modulators are designed to pulse 80 MW-class klystrons at an avg power of 250 kW and provides adjustable high efficiency operation in the 45 kV to 450 kV range for currents up to 545 A and pulse lengths of 1.5 to 4.0 µs. One key objective of modulator development is optimization of voltage flatness (± 0.02 %), stability (± 0.05 %), and reproducibility (± 0.05 %). 16:30 O4-7 [A2424] Design of high‐speed IGBT drive circuit for pulse power applications ZHU Xiaoguang, WANG Qingfeng, ZHANG Zhengquan, LIU Qingxiang (School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, China) Abstract: Fast switching of semiconductor switches is required by the pulse power systems. In this work, a strategy to improve switching time of IGBT has been investigated, which used 60 V gate-drive voltage. The principle and design of drive circuit is clarified. There was an experiment to test the drive circuit by pulse forming network. Page 50

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Meanwhile three different types of IGBT were tested based on this drive strategy. Comparing performances of this three types of IGBT, the one whose model is IRG7PH50UPbF has been employed. The collector current’s rise rate could be up to 9.41A/ns, when working voltage is 1kV, which is well above the results using traditional ways. The repeated experiment has verified that the circuit and IGBT could operate stably for over 107 times with frequency of 100 Hz. Hence, this drive strategy could be applied to pulse power systems, which requires long-lifetime and high reputation. 16:45 O4-8 [A1689] Marx generator technology for accelerators based on SiC MOSFETs REDONDO Luis1, KANDRATSYEU Aleh2, BARNES Mike3 (1. Lisbon Engineer Superior Institute, GIAAPP/ISEL, Portugal; 2. EnergyPulse Systems, Lisbon, Portugal; 3. ABT Group, TE Department, CERN, F-01631 Geneva, Switzerland) Abstract: This work describes the design strategy for a new Marx generator, based on SiC Metal Oxide Semiconductor Field-Effect Transistors (MOSFETs), proposed for accelerator applications, such as replacement of thyratrons and PFLs in kicker magnet power supplies. The use of semiconductor switches in areas that were traditionally dominated by hard tubes, such as thyratrons, can be explained by the vertiginous progress of semiconductor devices and associated electronics, driven by the irresistible need for more economic equipment with lower maintenance costs and with increased flexibility. This paper presents design strategies and preliminary test results for a Marx generator, for possible replacement of a thyratron and PFL in an existing kicker at CERN (European Organization for Nuclear Research), with specifications of 40 kV, 3.2 kA, 3 s pulse width, 30 ns rise and fall time, and 1 Hz repetition rate. The novelty presented in this work is the use of off-the-shelf components, such as SiC MOSFETs, in a Marx topology. First tests using 900 V/90 A pulse MOSFETs in a four-stage Marx generator, producing 3200 V/2700 A, 2 s pulses, are described and the concept is evaluated, considering scale up to 40 kV. 17:00 O4-9 [A0609] Vertical SiC photoconductive switch with AZO transparent electrode and potential of SiC as substrate for photoconductive switch HUANG Wei1, GUO Hui2 (1. Shanghai Institute of Ceramics, Chinese Academy of Sciences, China; 2. Xidian University) Abstract: High voltage photoconductive switch (PCSS) is an attractive device required in high pulse power systems like Page 51

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accelerators, radars, and high power sources. For the wide bandgap (3.26 eV), high critical field strength (3 MV/cm), and high thermal conductivity [4.9 W/(cm·K)] , semi-insulating 4H-SiC was considered an ideal material for PCSS. The PCSS is a switch controlled by the nanosecond laser pulse. The dark resistivity of semi-insulating 4H-SiC should be as low as 1011 Ω·cm for microampere leakage current. The on-state switch resistance should be as lower as better for high power output, but only about 1 Ω on-state resistance was achieved so far, which may due to the low carrier mobility of SiC. It is important to check the limit of SiC material as substrate for PCSSs. A new vertical SiC PCSS structure with a transparent Al doped ZnO (AZO) anode, semi-insulating SiC substrate, and high reflection silver cathode was introduced. A circular aperture was used to change the area of laser illuminating the transparent anode. Under a 2 kV bias and the 532 nm laser with power density of 18.2 MW/cm2, the resistance of the PCSS using different area of aperture was tested. The on-sate resistance was made of the resistance of SiC under laser excitation (Ron_SiC), and the inductive impedance (RL) in the switch and test circuit. The expression is given as Ron_test = Ron_SiC + RL = ߩH/S+ RL [Formula (1)] , where ߩ is the resistivity of SiC under laser excitation, H is the thickness of SiC substrate, S is the area of the aperture. The measurement data and the fitting result by Formula (1) show a good linear relationship between Ron-test and 1/S. The resistivity of SiC excitated by 18.2 MW/cm2 laser was 0.96 Ω·cm by linear fitting, resulting in a resistance of 0.34 Ω for 1 mm thick SiC under a circular aperture with diameter of 6 mm. In this work we present a new vertical SiC PCSS structure with AZO transparent electrode, by which a new concise method for measurement of transient resistivity of semi-insulating SiC excitated by nanosecond laser pulse was introduced. Sub-ohm on-state resistance is revealed for SiC PCSS.

Oral Session 5 - Microwave Systems and Sources; Beamless HPM sources - Session Chair: SCHEIDER Markus (INTERNATIONAL HALL)[15:00-17:30] 15:00 O5-1(Invited) [A3093] Nonlinear transmission lines in pulsed power and applications ROMANCHENKO Ilya1, ROSTOV Vladislav1, SHARYPOV Konstantin2, SHUNAILOV Sergei2, UL’MASCULOV Marat2, YALANDIN Michael2 (1. Institute of High Current Electronics, Tomsk, Russia; 2. Institute of Electrophysics, Ekaterinburg, Russia) Abstract: The principle of synchronism of the magnetization wave

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with the shock front is shown to be responsible for RF oscillations generation in gyromagnetic nonlinear transmission lines (NLTL). The equation describing the magnetization wave dynamics can be written as the modified Korteweg-de Vries equation in a simplified model. The technical solutions for high power RF generators based on gyromagnetic NLTLs are surveyed. The applications of gyromagnetic NLTLs such as exposure of biological objects to ns RF pulses, generation of electron beams and development of relativistic vacuum tubes are discussed. 15:25 O5-2 [A0343] Millimeter‐wave Cherenkov oscillators based on compact high‐current accelerators with nanosecond pulse duration ROSTOV Vladislav1, TSYGANKOV Ruslan1, KURKAN Ivan1, GUNIN Alexander1, KONEV Vladimir1, YALANDIN Michael2, SHARYPOV Konstantin2, SHPAK Valery2, UL’MASCULOV Marat2, SHUNAILOV Sergei2 (1. High Current Electronics Institute, Russia; 2. Institute of Electrophysics UB RAS, Russia) Abstract: We have designed and tested two Cherenkov type oscillators of 8 and 4 mm wavelengths with moderately oversized slow wave structures (SWSs) when the average diameters were about 2.5 λ. In the first case, the SINUS-200 high-current accelerator with maximum diode voltage up to 440 kV and beam current of 4 kA at 10 ns pulse width was used. It is relatively compact driver with the weight of about 150 kg. The main goal of this research was increasing the beam-to-microwave power conversion. Identical structures were made from stainless steel (SS) and titanium. The tubular beam was formed and transported through SWS in the magnetic field of 2.5 T. The calorimetric measurements have shown the microwave energy up to the 2.1 J for SS material and up to the 3.2 J for titanium SWS. For SS material, the pulse width had the tendency of degradation after few hundreds of pulses from 3 ns to 2.0-2.4 ns. There were no such effects for the titanium which is characterized by lower density and lower secondary electron emission. The report will also present the results of experiment with 4 mm wavelength which is performing now by the min-accelerator RADAN 303 (about 40 kg of the weight). We suppose that, due to the decreased beam power (300 kV, 2.5 kA) and current duration (4 ns), the risk of the microwave pulse shortening is eliminated. The particle-in-cell simulation predicts the generation of about 100 MW pulses with 2 ns pulse duration. In the experiment, a detector and calorimetric measurements confirmed a quite similar peak power with somewhat shortened pulse duration. The last is explained by irregular voltage pulse waveform which is resulted in the less Page 53

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effective accelerating voltage duration at the pulse top. 15:40 O5-3 [A1521] Diagnosis of temporal evolution of the collector plasma discharge in high power microwave sources by spectrum analysis FAN Zhiqiang1, CAO Yibing2, SONG Zhiming2, ZHU Meng2, WU Ping2, TENG Yan2, SUN Jun2 (1. Department of Engineering Physics, Tsinghua University, Beijing, China; 2. Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: The temporal evolution of the collector plasma discharge in high power microwave source was studied by spectrum analysis. Optical fiber implanted into the extraction cavity, together with a spectrometer and an intensified-charged-coupled device, is designed to detect the collector plasma discharge spectra in the experiments. Using the representative Hα and Hβ lines of hydrogen detected in the experiments, the electron density and temperature of the collector plasma were obtained by calculating the ratio of emission coefficients and by de-convolving the Stark broadening. The temporal evolution of the electron density and temperature of the collector plasma were measured based on statistical analysis of the spectra results. The typical values of the plasma electron density and temperature were approximately 1015 cm-3 and 0.5 eV, respectively. The results demonstrated that the collector plasma is sufficient to destroy the microwave generation and transmission and even resulted in severe pulse shortening. 15:55 O5-4 [A1624] High efficiency high power resonant cavity amplifier SIMPSON Rebecca, KEMPKES Michael, JOHNSON Erik, GAUDREAU Marcel, COPE David, KINROSS-WRIGHT John (Diversified Technologies, Inc. , United States) Abstract: Diversified Technologies, Inc. (DTI) is developing an integrated resonant-cavity combined solid-state amplifier for the Proton Improvement Plan-II (PIP-II) at Fermilab. The prototype has demonstrated multiple-transistor combining at 71% efficiency, at 675 watts per transistor at 650 MHz. The design simplifies solid-state transmitters to create straightforward scaling to high power levels. A crucial innovation is the reliable “soft-failure” mode of operation; a failure in one or more of these myriad combined transistors has negligible performance impact. The design couples the transistor drains directly to the cavity without first transforming to 50 ohms, avoiding the otherwise-necessary multitude of circulators, cables, Page 54

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and connectors. DTI’s design increases the power level at which it is cost-effective to employ a solid-state transmitter. DTI is upgrading the system to accommodate more transistors in each cavity module, and then will design and build a complete 100 kW-class transmitter which will consist of four or more such cavity modules and a combiner. 16:10 O5-5 [A2637] Vircator validation using particle‐in‐cell modeling BARNETT David, MANKOWSKI John, DICKENS James, NEUBER Andreas (Texas Tech University, United States) Abstract: This study compares results of a tunable virtual cathode oscillator (vircator) developed at Texas Tech University (TTU) to a CST three dimensional particle in cell simulation (PIC). The CST model is validated using experimental data from the tunable compact hard-tube reflex-triode vircator developed at TTU. The vircator is capable of burst-mode operation at pulse repetition rates (PRFs) up to 100 Hz. A Marx generator is used to drive the vircator. The Marx generator storage capable of storing 158 J and delivering a pulse of 300 kV, 3 kA into a 10  load. Using a pulse forming network (PFN) the pulse is a pseudo-square of approximately 100 ns pulsewidth. The vircator utilizes a bimodal, carbon fiber cathode and pyrolytic graphite anode. This provides long lifetime and higher achievable rep rates. The vacuum tube structure features a square waveguide that allows the distance between the anode-cathode (A-K) gap, backwall distance, and bottom plate distance to be manipulated. This movement allows the frequency to be shifted and the cavity to be tuned to a frequency allowing for optimum efficiency. The PIC simulations have been performed using CST PIC Solver, by Dassault Systemes. The 3D model shows virtual cathode formation and the subsequent extraction of radiated microwave power for several of cavity geometries. A working three-dimensional, relativistic, electromagnetic, particle-in-cell model of a vircator allows for quick, predictive results relative to building an experimental setup. The CST model aids in determining the necessary driving voltages, A-K gap distances, and cathode current densities to extract microwave radiation. Simulation is used to identify mode contributions and the dominate mode of the radiated waveform. Voltage, current, and microwave data are presented and compared against experimental results at different operating conditions.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 16:25 O5-6 [A0305] CARM project at ENEA SPASSOVSKY Ivan (ENEA, Frascati, Roma, Italy) Abstract: In this report we present the design elements of Cyclotron Auto Resonance Maser (CARM) for additional plasma heating. Various steps of a mid-size, long term theoretical and experimental project are described. Most of the components and units are designed by ENEA CARM team. Some of the parts like the high voltage modulator and the superconducting magnet will be fabricated by private companies with participation of ENEA. We are in close collaboration with the Institute of Applied Physics in Nizhni Novgorod to study and realize the RF circuit and various components for cold testing experiment. The working characteristics of the proposed CARM source are chosen according to the demands of reactor-relevant machines like DEMO. The oscillator would be used for plasma heating and diagnostic as well. We are planning to develop the project in two steps. The first one considers s pulsed regime for testing of all components and parts. The second step will be a transition from long pulse (ms) to continues wave (CW) operation. For that purpose a new modulator will be designed and constructed together with a depressed collector for energy recovery to address the efficiency problems. Later we will consider developing an amplifier which would be applicable for diagnostics or where the phase and frequency control is needed. 16:40 O5-7 [A0432] Compact generator of a 10 GHz, deep‐modulated high‐voltage pulses based on gyromagnetic nonlinear transmission lines and the RADAN driver ULMASKULOV Marat, SHUNAILOV Sergei, SHARYPOV Konstantin, YALANDIN Michael, SHPAK Valery (Institute of Electrophysics UB RAS, Ekaterinburg, Russia) Abstract: Increase in deep modulation frequency of high-voltage pulse of a gyromagnetic nonlinear transmission line (NLTL) with saturated ferrites to 10 GHz was provided by preliminary preparation (compression and sharpening) of a nanosecond driver RADAN-303 pulse using a two stage converter. The driver formed voltage pulse with amplitude of U0~150 kV at a matched load. The full width at a half magnitude (FWHM) of the pulse was 4.5 ns with a risetime tf~1.5 ns and repetition rate up to 25 Hz. The first stage of compression consisted of serial connected high impedance spiral and coaxial forming line with oil insulation. The forming line was charged through the high impedance line in a traveling wave mode, and its next commutation across a load with a nitrogen high-pressure discharger. As a result, the pulse amplitude of the driving pulser RADAN-303 Page 56

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increased from 150 kV to 240 kV with front ~200 ps while the duration was shortened to ~ 1ns. The second stage of compression was the NLTL with an external biasing of ferrite filling. The NLTL could increase the peak voltage amplitude up to ~300 kV with pulse duration (FWHM) ~350 ps. The high modulation frequency was provided by both high rate of voltage rise of an input pulse (dU/dt ~ 0.9 MV/ns) and small sizes of the ferrite rings (dia of several mm). In this case, it was necessary to ensure the high electrical field strength of NLTL waveguide elements because the electric field intensity at a central electrode of the line could reach high values ~1700 kV/cm. As a result, the generating NLTL provided at its output rapidly damped microwave modulation with effective frequency as high as 10 GHz and peak voltage amplitude to ~300 kV. Delay time of the output pulse could be controlled within oscillation period by varying the external magnetic field (in the range of 15-80 kA/m) of the ferrate line, which is important in utilizing such lines as part of multichannel system. This work was supported by grant of RFFI №16-08-00058.

Oral Session 6 - Medical, Biological and Environmental Applications - Session Chair: MUELLER Georg (BALL ROOM 3#)[15:00-17:30] 15:00 O6-1(Invited) [A0126] About possibility of the pulse electrical strength and energy density increase in water KOROBEYNIKOV Sergey (Novosibirsk State Technical University, Novosibirsk, Russia) Abstract: Prebreakdown processes in water with screening electrodes were investigated by optical and electrooptical methods. I am sure that the pulse electric strength can be increased only by influencing the stage of the streamer initiation. The creation of conductive layers at the electrodes is a way of influencing the generation of streamers. In this paper layers were prepared by electrodes coating by ion exchange membranes. The results of experimental studies of the electric field intensity distribution in the gap with modified electrodes by using the Kerr effect in water is presented. Pulse electric strength is increased, nonelectrode and postbreakdown streamers are registered. The possible application for pulsed power systems are discussed.

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EAPPC & BEAMS 2018 / Programme Monday 17 September 2018 15:25 O6-2(Invited) [A0749] Atmospheric‐pressure pulsed discharge and its application for surface insulation improvement SHAO Tao (Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China) Abstract: Non-thermal plasma treatment is a promising approach owing to environment- friendly, controllability and flexible structure for surface modification. In the Institute of Electrical Engineering, Chinese Academy of Sciences, characteristics of pulsed discharge and its application on surface treatment have been conducted since 2006. In particular, pulsed plasma has been used for polymer and metal surface modification to inhibit micro-discharge in high voltage insulation system. Regarding the non-thermal plasma generation, dielectric barrier discharge (DBD) and atmospheric-pressure plasma jet (APPJ) were developed for surface modification. Experimental results showed that the plasma modification could significantly improve the surface flashover voltage of the polymers. The experiments also showed that, by introducing SiOx on polymer surface, the surface charge dissipation rate was accelerated and the surface flashover voltage was increased. In summary, the pulsed plasma surface modification technology developed by our laboratory has been proven a feasible method for high voltage insulation performance improvement. 15:50 O6-3 [A0690] ROS measurement for treatment of produced water using nanosecond pulsed power discharge plasma OISHI Kazuki1, KODAMA Shintaro1, WANG Douyan2, NAMIHIRA Takao2 (1. Graduate School of Science and Technology, Kumamoto University, Kumamoto, Japan; 2. Institute of Pulsed Power Science, Kumamoto University, Kumamoto, Japan) Abstract: Produced water is the largest volume byproduct stream in oil and gas production, and has an adverse environmental impact due to its complex composition and high disposal costs. Therefore, new efficient treatment method is required. In this work, produced water treatment experiments using nanosecond (ns) pulse generator which has a 5 ns pulse width and 40 kV peak voltage were conducted. In this research, plasma is generated in gas phase and produced water is sprayed and supplied into the plasma region. The experimental results showed 92 % of TOC (Total Organic Carbon) removal ratio of the produced water under the discharge condition of 11 hours operation. Moreover, the results achieved 4.1 g-TOC/kWh for produced water treatment (initial TOC concentration = 1500 mg-TOC/L). In this research, produced water is treated using ROS (Reactive Oxygen Species) which is generated by ns pulsed Page 58

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discharge. In particular, OH radical has a very strong oxidizing potential. In this study, the OH radicals were measured by using a chemical probe method. Hydrogen peroxide and ozone concentrations were also measured as the indicator of water treatment. The experimental results showed that 20.5 µM of OH concentration were obtained during single pass in the discharge reactor. 16:05 O6-4 [A0694] Effect of coaxial reactor direction on performance of nanoseconds pulsed discharge based ozonizer SASAKI Kanji1, ICOMA Daichi1, IIDA Shuhei1, NAMIHIRA Takao2, WANG Douyan2 (1. Graduate School of Science and Technology, Kumamoto University-Japan; 2. Institute of Pulsed Power Science, Kumamoto University - Japan) Abstract: Ozone has several characters  it has strong oxidizability, it's naturally decomposed into oxygen in the air and it has no residual toxicity. Therefore, the application of ozone is expanding into sterilization, deodorization, decoloration, bleach, and so on. Nanoseconds (ns) pulsed discharge based ozoneizer which was developed in recent years has the higher ozone generation yield than the DBD one. However, the ozone concentration formed by the ns pulsed discharge saturates at approximately 40 g/m3. It is assumed that a main cause of the saturation is the decomposition of ozone by the electron collision and thermal load. Typically, the coaxial reactor used in the ns pulsed discharge based ozonizer was put in horizontal attitude. However, in this paper, the coaxial reactor was placed in vertical attitude to enhance the moving of heat caused by the discharges. As the result, the direction effect of coaxial reactor used in the ns pulsed discharge based ozonizer on its performances was investigated. From the experimental results, the elevation of the heat in the vertical coaxial reactor was confirmed. However, it is also demonstrated that the heat elevation has no significant influence on the performance of the ns pulsed discharge based ozonizer. 16:20 O6-5 [A1261] Proliferative activity of tumor cells after exposure to high power nanosecond RF pulses ROMANCHENKO Ilya1, ZHARKOVA Lubov1, BULDAKOV Michael2, PRIPUTNEV Pavel1, BOLSHAKOV Michael1, ROSTOV Vladislav1 (1. Institute of High Current Electronics, Tomsk, Russia; 2. National research Tomsk state university, Tomsk, Russia) Abstract: Tumor cells suspensions (HeLa, K562) were exposed to electromagnetic nanosecond RF pulses generated by gyromagnetic nonlinear transmission line. The pulse parameters were as follows: center frequency of about 1.0 GHz, pulse duration of 4 ns, peak Page 59

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amplitude of electric field of about 30 kV/cm, pulse repetition rate in the range from 8 to 25 Hz, number of pulses in the range from 1000 to 8000. The proliferative activity of tumor cells was estimated by MTT assay and the method of colonies. The reduction in proliferative activity estimated by both methods was observed for certain RF pulse exposure parameters. 16:35 O6-6 [A3143] Non‐invasive generation of intense PEF in water NOVAC Bucur1, SENIOR Peter1, XIAO Renzhen2, PECASTAING Laurent3 (1. Loughborough University, UK; 2. Northwest Institute of Nuclear Technology; 3. Université de Pau et des Pays de l’Adour, France) Abstract: A prolate spheroidal reflector was designed, manufactured and attached to a bipolar former at the output of a 10 GW Tesla-driven Blumlein pulsed power generator. The output from the bipolar former has a peak to peak voltage in excess of 600 kV, a rise time of 300 ps, with the bandwidth peak close to 1 GHz. The reflector, operated in water, is capable of producing intense pulsed electric fields of the order of 50 kV/cm. Constructional details will be provided, together with experimental results and a detailed analysis using 3D software modelling of the reflector that provides results in good agreement with experimental data.

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Tuesday, 18 September 2018

Plenary Session 2 Plenary Speaker: CHAIKOVSKY Stanislav - Chair: ROSTOV Vladislav

(BALL ROOMS 1 & 2#）[08:30-09:20] 08:30 [A1061] Compact pulsed power systems for X‐pinch based soft X‐ray backlighting CHAIKOVSKY Stanislav ( Institute of Electrophysics of the Ural Division of the Russian Academy of Sciences, Russia) Abstract: Soft X-ray radiography with high temporal and spatial resolutions is a powerful tool of plasmas diagnostics. An X-pinch is two or more fine wires which are crossed in the shape of “X” and exploded under the action of the current pulse. The high-temperature plasma “hot-spot”, which serves as an X-ray source, is generated at the cross point of the wires. The “hot spot” has several micrometers in size and lifetime about 1 ns. The parameters of such X-ray sources make them attractive for use in the projection radiography of various short-lived physical objects. The main requirements imposed on the pulsed power generator are the current amplitude 100-300 kA and the rate of the current rise 1-2 kA/ns. The design of a compact pulsed generator which provides the required parameters makes it possible to use X-pinch backlighting techniques in any laboratory worldwide. In this report, a number of compact capacitor bank generators with the current peak of 150-250 kA and the rise-time of 150-200 ns are described. Such X-pinch driver could be placed within a 1 m x1 m laboratory area. The driver could be connected to the X-pinch load unit by means of a flexible low-inductance transmission line. The flexibility of the transmission line is an additional advantage, since it allows precision of the X-ray radiography system adjustment to be improved and the X-pinch to be located near the sample investigated. Two (or more) separate drivers could be synchronized well with arbitrary delay in order to realize multi-frame X-ray backlighting system. The driver’s design, their operation and backlighting experimental results will be presented.

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Plenary Session 2 Plenary Speaker: HE Wenlong - Chair: DENG Jianjun

(BALL ROOMS 1 & 2#）[09:20-10:10] 09:20 [A3342] High‐power (kilo watts) broadband Gyro‐amplifiers operating in terahertz range HE Wenlong (University of Strathclyde, Glasgow, United Kingdom) Abstract: The gyrotron travelling wave amplifiers (Gyro-TWA) are high power coherent broadband sources that excel at high frequencies (up to the terahertz range) and have many applications including electron spin resonance, fast data-rate communications, high resolution RADAR, plasma diagnostics and remote sensing. Recent breakthrough in the research and development of the gyro-TWAs at University of Strathclyde has resulted in unprecedented operating frequency bandwidth and output power. This is due to ideal dispersion properties existed in a helically corrugated interaction region (HCIR). The principle and frequency scalability of the gyro-TWAs using HCIRs are discussed with a review of operation and achievements in the X-band frequency. Demonstration and experimental results at 90-100 GHz frequency will be presented. Current work of the gyro-TWAs operating in the higher terahertz range will also be presented.

Oral Session 7 - Closing and Opening Switches -Session Chair: SHAO Tao

(BALL ROOM 1#）[10:30-12:30] 10:30 O7-1 [A0774] A method to reduce the trigger‐threshold voltage of the multi‐gap gas switch JIANG Hongyu, SUN Fengju, WANG Zhiguo, JIANG Xiaofeng, CONG Peitian, YIN Jiahui, HUANG Tao, LUO Weixi, ZHANG Tianyang, ZHAI Rongxiao (State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: In order to reduce the trigger-threshold voltage of the multi-gap gas switch used for fast linear transformer-driver (FLTD), the gap voltage distribution during the triggering process is analyzed based on an equivalent circuit model. And a method is proposed to make the trigger gap achieve nearly entire trigger voltage by paralleling resistors and capacitors with the switch gaps, and the ultraviolet (UV) pre-ionizing structure is also applied to make the Page 62

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trigger gap discharge more easily in the triggering process. The effects of capacitor parameters and the UV pre-ionizing structure on the triggering characteristics of the switch are experimentally investigated. Compared with the original switch, the results indicate that, at the charging voltage of ±80 kV, and operating at 60% of self-breakdown voltage, the trigger voltage is reduced from 110 kV to 40 kV, while the jitter of the switch remains the same as 3.2 ns. 10:45 O7-2 [A1674] Research on LTD gas switch at NINT CONG Peitian, LUO Weixi, HUANG Tao, ZHANG Tianyang, ZHAI Rongxiao, JIANG Hongyu, JIANG Xiaofeng, SUN Tieping, WANG Zhiguo, YIN Jiahui (State Key Lab of Intense Pulsed Radiation Simulation and Effect), Northwest institute of Nuclear Technology, Xi'an, China) Abstract: This paper mainly focus on the LTD gas switch research undertaken at NINT, including a few theoretical and experimental studies. Firstly, a probability analysis method for evaluating the self breakdown voltage of a multi-stage gas switch (MGS) is proposed. Secondly, Townsend theory considering the electrode surface morphology is further developed. Thirdly, an electrode consisting of different types of materials is produced to disperse the arc-channel positions along the circumference. Fourthly, a circuit model is set up to analyze the influence of stray parameters on the MGS before taking voltage-equalization and pre-ionizing measures to achieve a close jitter of 3.2ns at 40kV trigger voltage. Fifthly, switch static and trigger performance tests show that Graphite as the electrode material is better than stainless steel, brass and copper-tungsten alloy. Sixthly, under ±100kV and 65% operation ratio, the MGS featuring with an electrode-insulator stack survives over 175’000 triggered shots, with a statistical jitter and pre-fire rate to be 3.5ns and 2×10-5, respectively. Finally, by incorporating the MGS into two cylindrical capacitors, an integrated LTD brick is invented to have an inductance of only 100nH. 11:00 O7-3 [A1693] High‐voltage, high‐repetition nanosecond pulse generator using rotary triggered double spark gap switches CHO Chuhyun, JIN Yun Sik (Korea Electrotechnology Research Institute, Korea ) Abstract: The high-voltage, high-repetition nanosecond pulse generation technology is a necessary technology for applications such as water treatment and nanocolloid production through underwater discharge. For this application, a high-voltage, high-speed switching technology is crucial for quickly transferring the energy stored in the capacitor to the load. In this study, we proposed a method of using rotary triggered double spark gaps interlocked Page 63

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with both charge and discharge switches as a method of mechanical switching. This solves the problem of irregular and unstable pulses generated by removing arcing due to charging current. Using this technique, a 10 kV, 100 ns rising pulse was generated at a repetition rate of 1000 pps and applied to a silver electrode placed in water to generate a discharge to produce silver nanocolloid. 11:15 O7-4 [A1792] Investigation on amorphous material with varying motivation current LI Song, GAO Jingming, YANG Hanwu, QIAN Baoliang, CUI Yancheng, WU Qilin, LIU Shifei (Institute of High Power Microwave Technology, Changsha, China) Abstract: High voltage pulse generators have been investigated for their potential applications including plasma science, high power microwave, food preparation, and environment protection. It is generally believed that high power switches are of importance to the performance of the generator. As important candidate, magnetic switch can work at high repetitive rate with high reliability, which meets the requirements of the applications. As crucial component, magnetic material decides the performance of the magnetic switch. In this paper, amorphous material was investigated with saturable time range from 0.1T/s to 5T/s. Importantly, the motivate current is changing with different circuit of test stand. Key parameters of the material were studied numerically and experimentally. Saturation process was concluded and analyzed. The results are valuable for the applications of magnetic switch. 11:30 O7-5 [A1821] Calculation model of a gas switch static performance LUO Weixi, CONG Peitian, HUANG Tao, QIU Ai.ci (Northwest Institute of Nuclear Technology, China) Abstract: Stability of an FLTD system is determined from the static performances of the gas switches used in the primary energy storage units (bricks). In this paper, the static performance of the switched is described as the probability density distribution of self-breakdown voltage. In order to study the random distribution mechanism of the self-breakdown voltage, some random variables has been introduced into Townsend theory. These random variables include the time and position of a freedom electron appearing in the switch gap, and the number of the secondary electrons. Base on the mathematical relation between the random variables and breakdown voltage, a Monte-Carlo model is built to describe the process of gas switch self-breakdown. On the other hand, the mathematical relation between the random variables and experiment conditions (like gas pressure, gap structure, atmospheric ionization rate, and so on) is Page 64

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studied to build the sample methods used in the Monte-Carlo model. Based on the findings above, calculation model of gas switch static performance has been built. At last, the calculation model will be illustrated by experiments. 11:45 O7-6 [A1846] Study on operating characteristics of UV‐preionization gas switch LI Yuansheng (Huazhong University of Science and Technology, China) Abstract: The operating characteristic study on previous UV-preionization gas switch for linear transformer driver (LTD) has been conducted. The minimum operating voltage and the triggering breakdown time and jitter versus various switch operating conditions have been tested to achieve optimal triggering performance of the switch. Moreover, a life-time 5Hz-frequency repetitive switch experiment has been done. Analysis of SCAN ELECTRONIC MICROSCOPE and ENERGY DISPERSIVE SPECTROMETER of the attachments on the switch insulation chamber surface after 10,000 discharging shots has been done. It was found that the main cause of the switch failure is the insulation deterioration caused by the electrode erosion mass ejection. 12:00 O7-7 [A2377] Numerical simulation and experiment of pulsed switching of a ferromagnetic core SHI Chengyu, GAO Minghao, LI song, CUI Yancheng, YANG Hanwu (National University of Defense Technology, Changsha, China) Abstract: Magnetic switches in pulsed power systems are usually made of ferromagnetic tapes which have very low coercive force and high saturation magnetic induction. However, the high conductive of the tapes cause eddy losses in high frequency and frequency dependent hysteresis of the cores. To study the detailed pulsed switching characteristics of the ferromagnetic cores, this paper models a ferromagnetic core by solving the coupled circuit equation and magnetic field diffusion equation, and detailed space-time distribution of magnetic field and electric field is obtained. The model can predict the frequency dependent hysteresis, the inter-lamination voltage, eddy loss and hysteresis loss. Experiments are carried out with samples cores, and the results verified the numerical simulation. Limitations of the numerical model are discussed.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 12:15 O7-8 [A3008] A three‐electrode gas switch triggered by micro‐hollow cathode discharge with low trigger voltage LIU Kefu, ZHANG Chengbo, QIU Jian (Fudan University, China) Abstract: The trigger voltage is generally high (usually at least a few hundred kV) in traditional field distortion three-electrode gas switch, which puts high demand for the design of trigger device in large scale pulsed power system such as Linear Transformer Driver (LTD). On the other hand, the erosion for third electrode in field distortion switch is inevitable, leading to a restriction in the aspect of the frequency rate and lifetime of such gas switch. Therefore, a novel three-electrode gas switch triggered by micro-hollow cathode (MHC) discharge is put forward and introduced, and its working mechanism and turn-on characteristics are studied. Micro-hollow cathode discharge is a kind of micro-discharge with some unique features: a) tiny size and simple structure. The size of the electrode and gap channel can be as small as a few hundred μm, which is easier to be integrate inside the gas switch; b) low trigger voltage (as low as 1~3 kV in pulsed mode), which is beneficial to reducing the trigger voltage of field distortion switch; c) high electron density (especially in pulsed mode), which provides large numbers of seed electrons into the gap of the switch and induces the breakdown of the switch faster. Based on the features of MHC described above, the MHC trigger for gas switch is firstly designed and tested. The MHC trigger consists of two electrode layers and one dielectric layer with 0.5mm diameter hollow size and 0.4mm dielectric thickness. The trigger voltage in pulsed mode can be lower than 3 kV at atmospheric pressure, and peak current can be up to 80 A. Three such MHC triggers working synchronously are located in the center of the gas switch, where two main electrodes are set at the top and bottom of gas body separately. Experiment shows that the newly designed gas switch with MHC trigger can work under the condition of up to ±50 kV working voltage, 3 kA current, and 0.3 MPa pure nitrogen gas pressure, while the trigger voltage can be as low as 6~8 kV. Then, two working modes and its influences of MHC switch are investigated, which are three-electrode mode (T-mode) and two-electrode mode (D-mode). At last, the turn-on parameters including delay time, jitter, and rise time are tested to help optimize and improve the design of such MHC switch for better behavior.

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Oral Session 8 - High Power Microwave Devices; THz Technology - Session Chair : HE Wenlong

(INTERNATIONAL HALL）[10:30-12:30] 10:30 O8-1 [A2063] Research progress on the high power relativistic klystron amplifier at Ka band LI Shifeng1, DUAN Zhaoyun1, HUANG Hua2, LIU Zhenbang2, HE Hu2, GE Yi2, DENG Derong2, WANG Zhanliang1, GONG Yubin1 (1. School of Electronic Science and Engineering, University of Electronic Science and Technology of China; 2. Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics) Abstract: In this paper, we present in detail the research progress on the high power relativistic klystron amplifier at Ka band. We propose an extended interaction oversized coaxial relativistic klystron amplifier (EIOC-RKA) to generate a gigawatt-level output at Ka band. We design the EIOC-RKA by using the 2.5D particle-in-cell (PIC) simulation. In the simulations, we use an electron beam with a current of 6 kA and a voltage of 525 kV. The simulation results demonstrate that the saturated output power is 1.17 GW, the electronic efficiency is 37.1%, and the saturated gain is 57 dB at 30 GHz. At the same time, we also analyze more complex physical problems, such as high-order mode self-oscillation, high efficiency input and output coupler, different device materials (stainless steel, copper), and so on, by using 3D PIC simulation. Finally, the “Cold” test of the high-frequency structure and “Hot” test are shown and discussed. The proposed EIOC-RKA have plenty advantages such as large power capacity, high electronic efficiency, low focusing magnetic, high gain, and simple structure. 10:45 O8-2 [A2951] Determination of input impedance of cylindrical axial vircator TIMUR Busra, KUCUK Ibrahim Semih, TANC Zafer, DEMIR Simsek (METU, Ankara, Turkey) Abstract: The virtual cathode oscillator (vircator), which is one of the HPM sources, has been frequently studied regarding output characteristics such as enhancement of output power, stability, and tunability of operating frequency. Besides, analyzing input characteristics of the vircator is crucial as well to optimize efficiency of total HPM system. In this study, it is aimed to estimate input Page 67

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impedance of a cylindrical axial vircator. For this purpose, different parametric studies, which are variation of the applied voltage difference, the anode-cathode distance, radius of the cathode area and the diode housing, have been performed in MAGIC simulation environment. Thus, a modified version of the classical one-dimensional (1D) space charge limiting current has been introduced to extend it to the two dimensions (2D). Moreover, by inserting a non-emitting region called “cathode ring” to the exterior surface of an emitting cathode, its effect into the emitting current has been studied. 11:00 O8-3 [A2683] A high‐efficiency L‐band relativistic backward wave oscillator with double‐ripple three‐period slow‐wave structures GE Xingjun, ZHANG Peng, ZHAO Chenyu, CHEN Siyao, ZHANG Qiang, YANG Hanwu, ZHANG Jun ( National University of Defense Technology, Changsha, China) Abstract: High power microwaves (HPMs) at low bands (L- and P-bands) have very important applications prospects. Relativistic backward wave oscillators (RBWOs) are one type of devices that are promising for producing HPMs and are extensively investigated because, for example, they have compact structure, high efficiency, and good stability. The main challenges encountered in the low-band RBWOs are miniaturization and high efficiency, which is of great interest to the HPM field. This paper presents the mechanism and realization of a high-efficiency L-band RBWO with double-ripple three-period slow-wave structures (SWSs). To reduce the radial size of the device, the coaxial SWSs are introduced to excite the quasi transverse electromagnetic (quasi-TEM) mode, which has no cut-off frequency. To reduce the axial length of the device, a coaxial extractor is designed to achieve the longitudinal mode selection and reduce the period number of the SWSs to three, which can restrain the longitudinal modes competition and enhance the beam-wave conversion efficiency. In addition, the double-ripple SWSs, possessing high coupling impedance, are chosen in the device to improve the efficiency. In simulation, microwaves centered at 1.53 GHz are generated, with power of 3.4 GW, and beam-wave conversion efficiency of 40%. In the primary experiment, microwaves centered at 1.52 GHz are generated, with power of 3 GW, beam-wave conversion efficiency of 33% and pulse duration of 40 ns, which proves that this technical route is feasible. Undoubtedly, the technical route can provide a guide to design other types of HPM sources at low bands and benefit the practical application of the compact HPM systems.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 11:15 O8-4 [A2746] A novel powerful extractor in Ku‐band relativistic transit‐time oscillator LING Junpu, HE Juntao, ZHANG Jiande, SONG Lili, DENG Bingfang (National University of Defense Technology, Changsha, China) Abstract: A novel powerful extractor in Ku-band relativistic transit-time oscillator (TTO) is proposed. Compared with most of the extractors used in relativistic TTO, this improved one has two main features. One is that this novel extractor employs the trapezoidal section plane instead of the traditional rectangular one, and the other is that it introduces the hybrid operation modes. The trapezoidal section plane can effectively decrease the localized electric-field convergence and improve good electrostatic insulation, and thus this proposed extractor has higher power capacity. Meanwhile, operating in hybrid modes makes the extractor have larger beam-wave interaction volume than that only operating in TM01 mode, and consequently, this can further increase the power capacity of the novel extractor. To verify the function of the proposed extractor, a comparative experimental study is carried on. With the same output power of 2GW, the Ku-band TTO with this novel extractor has 4ns wider pulse duration and less surface damage than that with the traditional extractor. 11:30 O8-5 [A2945] Investigation of beam modulation on the double gap vircator KUCUK Ibrahim Semih, TIMUR Busra, DEMIR Simsek (Middle East Technical University,Turkey) Abstract: In this study, double gap vircator with coupling window is examined in the MAGIC simulation environment. Due to coupling window, generated fields in the output waveguide region is coupled to modulating cavity and modulate the electron beam. This results in enhancing oscillations and rise in the efficiency. In the present work, double gap vircator is examined under external signal application. External signal is injected to modulating cavity of the double gap vircator before the pulse voltage waveform. By this way, externally applied fields mimic the coupled fields of the vircator in the region of modulating cavity. Enhancing efficiency, earlier start time and frequency locking are observed under the influence of the external signal. Besides, vircator tuning procedure is developed and tested for different AK gap distance and pulse voltage peak values. This tuning procedure includes adjustments of AK gap distance, plunge positions and length of the coupling window. After applying this procedure, significant increase in the microwave output level is observed. For voltage level of 600kV, efficiency is increased to Page 69

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6.06% from 4.92% when tuning procedure is followed.

11:45 O8-6 [A1321] Prospect of powerful cyclotron autoresonance masers based on advanced Bragg structures at submillimeter wavelengths ZASLAVSKY Vladislav, GINZBURG Naum, PESKOV Nikolai, SERGEEV Alexander, MALKIN Andrey (IAP RAS, Nizhny Novgorod, Russia) Abstract: Possibility to use advanced Bragg structures based on coupling of travelling and quasi-cutoff feedback waves in cyclotron autoresonance masers have been studied. High electrodynamic selectivity of the proposed reflectors for the diameter up to 10 wavelengths was found and effectiveness of their application in powerful CARM-oscillators up to sub-mm wavelength bands was demonstrated. “Cold” tests of the novel Bragg structures having oversize parameter (diameter to wavelength) about 7 were carried out at the frequency band near 250 GHz proved result of the theoretical analysis. Different resonator schemes were simulated including hybrid two-mirror cavities formed by advanced and conventional Bragg reflectors. It is shown that stable regime of narrow-band oscillation with a multimegawatt power level can be achieved at a frequency of about 250 - 300 GHz in the described scheme of CARM driven by axis-encircling moderately relativistic electron beam 500 kV / 10 A, where the transverse size (diameter) of the interaction space is about 5 - 7 wavelengths and guide magnetic field is about 5 T. For suppression of the gyrotron self-excitation mechanism at spurious low-frequency quasi-cutoff modes, possibility of usage of wide azimuthal cuts in the regular section of the cavity is studied. 12:00 O8-7 [A1766] Design of radial sheet beam terahertz source based on radial pseudospark discharge plasma electron gun ZHANG Dian, ZHANG Jun, LI Song, ZHONG Huihuang (National University of Defense Technology, Changsha, China) Abstract: To satisfy the demands of compact, inexpensive terahertz (THz) sources with power of hundreds of watts in some applications of THz technology, a kind of radial sheet beam THz source without external magnetic field driven by radial pseudospark discharge is proposed. Compared to the latest reported axial quasi-rectangular sheet beam THz sources driven by axial pseudo-spark discharge, where sheet beam is shaped from cutting the pencil beam, sheet beam will be directly generated in radial pseudospark discharge Page 70

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process. Larger beam current, larger beam-wave interaction area together with higher potential output THz power and lower fabrication difficulty can be obtained in the radial device. Theoretical analysis and particle-in-cell simulation are employed in the design of radial sheet beam THz source. Effects of pulsed electric waveform and reported experimental energy distribution of the pseudospark-sourced electron beam are all considered in the design. To lower down the fabrication difficulty, one sided corrugations and large cylindrical power output structure are utilized in the radial sheet beam terahertz source.

Oral Session 9 - Electromagnetic, Plasma, Beam and Laser Applications; Electromagnetic Launchers; Theory and Simulation - Session Chair: YAN Ping

(BALL ROOM 3#）[10:30-12:55] 10:30 O9-1(Invited) [A1830] Light from the pulse power LI Zhenghong (Institute of Applied Electronics, CAEP, Mianyang, China) Abstract: A new type of light sources is established based on the current pulse power technology. The intense beam is produced by field emission cathode driven by the pulse power. And the beam quality is supported by the strong guiding magnetic field (B=5T). So the GW tunable THz radiation can be generated with the electric wiggler put in the strong guiding magnetic field, and the intense X-ray can be produced like that in the XFEL when the laser ray is used to replace the conventional wiggler. So both the intense tunable THz radiation and X ray can be produced from the pulse power with the aid of the superconducting magnet. 10:55 O9-2 [A0273] Researching on the decoupling at IFP’s dielectric wall accelerator YE Mao, YI Shen, XIA Liansheng, ZHANG Huang (Institute of fluid physics, CAEP, Mianyang, China) Abstract: The Dielectric Wall Linear Accelerator is a new kind of accelerator based on pulsed power technology. As it has significant characteristics, such as high accelerating gradient, miniaturized size, simple structure and low cost, it is widely promising to be used in medical heavy ion therapy area. The Institute of Fluid Physics, Chinese Academy of Engineering Physics (IFP, CAEP) began the investigation on dielectric wall accelerator in 2011, and have built a sample dielectric wall linear proton accelerator. In the recent experiments, the proton energy reached 400keV within 60mm

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accelerating structure. However, during the debugging process of dielectric wall proton linear accelerator, it is found that the circuit coupling among pulsed power source will cause dramatic decline of electric field in the accelerating cavity, and the result is the energy gain for proton is much smaller than expectation. Based on this phenomenon, this paper proposes a new structure which divides the joint accelerating electrode among primary power source into two parts in axial direction and adds a thin dielectric film between the two parts. Besides, the electric field distribution in the accelerating cavity is simulated by numerical simulation method. The simulation results show that the structure with diaphragm blocks the charging and discharging channels among pulsed power source in circuit and suppresses the circuit coupling among power source effectively. Meanwhile, the decelerating electric field intensity formed in the diaphragm is limited, so the proton is still able to realize effective acceleration after passing through such an accelerating structure. Experiment result indicates that the simulation result satisfying quite well. 11:10 O9-3 [A0989] Lithium ion battery based compact capacitor charging power supply for HEMP application CHO Chan-Gi1, JIA Ziyi1, SHIN Jinho2, RYOO Hongje1 (1. Chung-Ang University, Korea; 2. Replex Co., Ltd) Abstract: In this paper, a compact capacitor charging power supply using lithium ion battery as an input voltage source is suggested for applying High Altitude Electromagnetic Pulse (HEMP) field. The proposed pulse power supply system consists of 6 kW charger using three phase transformers and a secondary resonant circuit which located at the after of output diode rectifiers. The secondary resonant circuit produces the targeted output voltage from the output capacitor of 6 kW charger as a voltage source. The performance of the proposed system is verified by simulation and resistive load tests and, at last, the equivalent circuit of HEMP is connected to the load to demonstrate the feasibility of the proposed system. 11:25 O9-4 [A2016] Investigation and application of a portable flash X‐ray generator based on EDFEG and EEOS WU Youcheng1, DENG Jianjun1, HE Hongliang2, LIU Gaomin2, DAI Wenfeng1, FU Jiabin1 (1. Key Laboratory of Pulsed Power, Institute of Fluid Physics, CAEP, China; 2. Laboratory for Shock Wave and Detonation Physics Research, CAEP, China) Abstract: As a compact pulsed power supply, the explosive-driven ferroelectric generator (EDFEG) has high energy density and can autonomously produce more than a peak voltage of 100 kV with a pulse width of a few microseconds, but its rise time is on the order of Page 72

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100 ns. In order to develop a portable flash X-ray generator, a novel compact explosive pulsed power is proposed in present paper. An EDFEG is used as primary power to charge a pulse capacitor, then the capacitor outputs high current through an inductor and an electrical exploding opening switch (EEOS). Finally, a fast high voltage pulse is generated on an X-ray diode. Complete FE-AFE transition of poled PZT95/5 ferroelectric will happen at shock stresses of 3.5 GPa. A circuit model was built to investigate this portable X-ray generator. In simulation EDFEG must output more than 1300 μC charge into pulse capacitor with charging voltage of about 80 kV. And a pulse with high voltage of 230 kV and pulse width of 20 ns can be generated on an X-ray diode with equivalent impedance of 50 Ω after metal wires electrical explosion happens. The principle prototype’s experiments of the X-ray generator were conducted, whose weight is about 15 kg. EDFEG of PZT95/5 ferroelectric output the peak current of 350 A with pulse width of 3.9 μs. After discharging switch was triggered the capacitor began to discharge and produced a peak current of 15.3 kA through an inductor and an EEOS. A peak voltage of about 200 kV was generated and delivered into the diode with rise time of 3.0 ns and pulse width of 30 ns (FWHM). After a delay time a peak current of 3.0 kA arose and an X-ray pulse of 19 ns width (FWHM) with a dose of about 2 mR at 1 m was obtained. The size of X-ray source measured is less than 1.0 mm, and its space resolution is 0.05mm. A flash photography experiment for research on Richtmyer-Meshkov (RM) instability of Sn metal’s free boundary was conducted by the use of this portable X-ray principle prototype. A distinct dynamic image of the development of RM instability of Sn metal’s free boundary was gained for the first time. 11:40 O9-5 [A3309] Experimental registration of tubular parts collision under magnetic pulse acceleration KRUTIKOV Vasiliy, SPIRIN Alexey, PARANIN Sergey (Institute of Electrophysics of the Ural Branch of the Russian Academy of Sciences, Yekaterinburg, Russia) Abstract: Magnetic pulse welding (MPW) is a solid-state impact welding technique, in which colliding parts are accelerated by pulsed magnetic field. MPW is favorable for joining hard-to-weld ferritic-martensitic and oxide-dispersion strengthened steels or coated steels. The movable part is called the flyer, other one is called the target. The key parameters of MPW are impact velocity and contact front velocity. The present work was aimed to determine the contact front velocity and to reveal flyer inner wall profile before the collision for a telescopic steel tube pair. The measurement was conducted by registration of electrical contact between the parts. The measured contact front velocity ranged from 5 to 300 km/s Page 73

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depending on the target shape. The flyer inner wall moves almost parallel to the axis. Contrary to the hypothesis that the flyer tube end would firstly meet the target, it came last. The paper will discuss the influence of the acceleration gap and tubes position in the coil on the contact front velocity and the flyer profile before the impact. This work was performed within the state task No. 0389-2015-0025, partly financed by RFBR grant No.16-08-00919, and research project of RAS program No.18-2-2-8. 11:55 O9-6 [A2051] Research on optimizing discharge parameter of distributed energy storage railgun ZHU Qi, DAI Ling, MIAO Jianhua, WANG Shaojie, LIN Fuchang (State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science & Technology, Wuhan, China) Abstract: Distributed energy storage (DES) railgun is a research hotspot in the field of Electromagnetic Launch (EML). It has higher efficiency over the breech-fed railgun, due to less inductive energy remaining in the rail and lower rail resistive loses. An optimization method is presented in this paper for the power module configuration, discharge sequence and current input points of DES railgun. Based on Matlab platform, discretization method is used to write the code calculation procedure of mathematical model of DES railgun. The accuracy of the calculation procedure is confirmed by comparing with results of Pspice simulation. In addition, main parameters that affect the system performance are optimized, including launch velocity, launch efficiency, maximum total rail current and pulsation amplitude. Finally, a set optimal parameter of power module, the discharge sequence and the current input points are obtained. Taking a DES electromagnetic launch system consisted of 24MJ pulsed power supply and 10m railgun as an example, the power discharge parameters are optimized by the method. Results show that launch efficiency is 27%. Compared with the actual measured value (about 15%) of the 24MJ breech-fed electromagnetic launch system, the launch efficiency is improved by 12%. The validity of the optimization method is demonstrated. 12:10 O9-7 [A2422] Study on power supply for space vehicle electromagnetic launch WANG Shaojie, DAI Ling, MIAO Jianhua, ZHU Qi, LIN Fuchang, ZHOU You (State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science & Technology, Wuhan, China) Abstract: The use of a linear motor to drive the space vehicle in a levitation control track can achieve track reuse and reduce costs. Page 74

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The speed of the vehicle varies greatly, thus a power supply with the frequency adjustable and a high current of several hundred kA is required. So two power supply schemes were proposed based on high-current pulsed power supplies. The running parameters of the linear motor were calculated by ANSYS. Then based on the MATLAB platform, two power supply simulation models were built, according to the operation parameters. One was thousands of capacitor pulse discharge units (CPDU) with distributed discharge, and the other was hundreds of pulsed alternators with pulse width modulation (PA-PWM). By combining the two power supply models and the linear motor model respectively, two sets of integrated dynamics simulation models were established. The results of the simulation showed that the two schemes could accelerate dozens of tons of vehicles to hundreds of meters per second. The CPDU was simple. But the PA-PWM could achieve continuous adjustment of the frequency, and its acceleration pulsation was smaller. Meanwhile, the number of devices was greatly reduced, which was conducive to precise control of the launch process. 12:25 O9-8 [A1468] Evaluated collision cross sections for particle modeling in copper vapor vacuum arcs YANG Wei, ZHOU Qianhong, YANG Wenyuan, DONG Zhiwei (Institute of Applied Physics and Computational Mathematics, Beijing, China) Abstract: Direct-simulation Monte Carlo and particle-in-cell (DSMC-PIC) method is a powerful tool in studying metal vapor vacuum arcs (VA). However, the collision cross sections (Xs) for metal atoms/ions are not evaluated yet, compared to the already developed database for gas discharges. In this paper, the common electrode material copper (Cu) is taken as an example for survey of Xs. Various experimental data, theoretical calculation and analytical fitting formula are reviewed. The electron-impact Cu elastic, excitation and ionization Xs are found to have an overall accuracy within 15%. The Cu-Cu+ resonant charge-exchange Xs is not as accurate as that of e-Cu collision. The Cu-Cu interaction Xs by variable hard sphere model requires further validation. Based on the evaluated Xs, the mean free path and collision frequency are derived in copper VA plasmas, and compared to the Debye length and plasma oscillation frequency, respectively. The influences of those spatial and temporal scales are discussed in developing DSMC-PIC codes for modeling of copper VA.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 12:40 O9-9 [A2597] Research on the relationship between liquid pulsed discharge energy and cavity expansion characteristics LIU Yi, REN Yijia, LIU Yang, LIN Fuchang (State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science ＆ Technology, Wuhan, Hubei Province, China) Abstract: Obtaining the relationship between the liquid pulsed discharge energy and the cavity expansion characteristics can reasonably improve the conversion efficiency of the liquid pulsed discharge energy, and increase the intensity of the shock wave when the same electric energy is injected. An impulse high voltage is applied across the needle-needle electrodes immersed in the liquid. When the breakdown voltage is reached, the gap will breakdown and an arc connecting the electrodes will be formed in the gap, so that a large current will flow through the gap. Due to the Joule heating effect of the current, the ambient liquid will evaporate and form a cavity. The electric energy, which continuously injects into the arc, will be converted into the internal energy stored in the cavity and the mechanical energy of the expansion of the cavity. The periodic motion of the expansion and contraction of the cavity form a shock wave that propagates in the liquid. With the increase of injected energy, the maximum diameter of the cavity and the period of cavity vibration will increase. The energy of the shock wave generated by discharge is closely related to the characteristics of cavity vibration. In order to describe the relationship between injected energy and the characteristic of the cavity motion in more detail, a high-speed camera is used to record the image of gap expansion at different moments during the period of the gap breakdown. The voltage and current of the arc are measured using a voltage probe and a current probe. A pressure probe is used to measure the intensity of the shock wave formed by the discharge at the same time. Using the dimensionless model to simulate the discharge under experimental parameters. According to the comparative analysis of experimental measurement waveform, simulation waveform and cavity expansion images, the numerical relationship between injected energy and cavity expansion characteristics can be given. Based on the proposed model, the effect of cavity expansion characteristics on the shock wave intensity can be studied..

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Poster Session IV - Pulsed Power Technology, Systems and Components - Session Chair: CHEN Dongqun (BALL ROOM 2#)[13:30-15:00] P4-1 [A0163] Optimizing design of convolute of PTS CHEN Jingping, REN Ji, DING Yu, LI Yong (Institute of Fluid Physics,CAEP, Mianyang, China) Abstract: The majority of PTS experiments experience some losses on order of multi-MA attributed to the convolute, the reasons why convolute appear breakdown phynomena are analyzed. In order to optimize convolute of PTS, the shortage of convolute is pointed out, successful experience of convolute of Saturn and ZR are reviewed. The technical approach and methods of optimizing design of convolute of PTS are put forward. The optimization results will await for future experiments. P4-2 [A0399] Solid‐state SOS+NLTL approach for multi‐gigawatt short pulse generation RUKIN Sergei, GUSEV Anton, LYUBUTIN Sergei, PEDOS Maxim, PONOMAREV Andrey, SLOVIKOVSKY Boris, TIMOSHENKOV Sergeri (Institute of Electrophysics UB RAS, Russia) Abstract: Gyromagnetic nonlinear transmission lines (NLTLs) are widely used to convert an input video pulse into an output radio-frequency (RF) pulse. At such an operating regime, the duration of the input pulse significantly exceeds the period of the oscillations generated by the NLTL. In this work experiments were made in which the duration of the input pulse was close to the period of generated oscillations. In this approach, NLTL does not operate as a generator of a train of radio-frequency oscillations, but as a wave magnetic compressor of the input pulse, because the main part of the input pulse energy is transmitted only to the first peak of the oscillations. Power amplification is achieved due to the voltage amplitude of the first peak across NLTL output exceeds the voltage amplitude of the input pulse. As a source of input pulses a solid-state SOS generator was used which eventually allowed to create a completely solid-state pulsed power system capable of operating at high pulse repetition frequency. A special feature of the SOS+NLTL approach consists in that the pulse power amplification is achieved without the use of any additional closing or opening switches. Gyromagnetic NLTL combines the functions of the switch, compressor, and former of the output pulse. The total pulsed power system can involve several sequential stages of energy compression when the pulse compressed by the first NLTL is applied to the next NLTL with higher oscillation frequency. As a source of input pulses a solid-state SOS generator of S-500

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type was used in the experiments. It provided 6-GW pulses (500 kV across 40 Ω load) with FWHM of 7 ns. In the experiments, one-, two- and three-stage magnetic compressors were used based on NLTLs with different diameters. At the output, pulses with subnanosecond duration with a record high peak power exceeding 30 GW were obtained. The solid state SOS+NLTL approach allowed carrying out experiments at pulse repetition frequency up to 1 kHz in burst mode of operation. P4-3 [A0461] High‐voltage subnanosecond multistage converter of a pulse form based on nonlinear transmission lines ULMASKULOV Marat, SHUNAILOV Sergei, SHARYPOV Konstantin, YALANDIN Michael, SHPAK Valery, PEDOS Maxim, RUKIN Sergei (Institute of Electrophysics UB RAS, Ekaterinburg, Russia) Abstract: The variants of multistage converters (MSC) of nanosecond pulse form of a high-voltage driving pulser giving both an increase in voltage amplitude and pulse risetime sharpening was designed and tested. The solid-state modulator S-5 was used as a driving generator, forming high-voltage unidirectional pulse with duration ~5 ns (FWHM) and amplitude 500kV across a load 50 Ohm. The MSC was based on 3 serial connected coaxial nonlinear transmission lines (NLTL) with oil insulation under pressure, when packages of ferrite rings with a decreasing cross-section were utilized. The NLTLs had an independent longitudinal external magnetic field providing controllable saturation of the ferrite cores. An autonomy of each block allowed the implementation of converters with different combination of the NLTLs. Due to sequential transformation of the driver pulse, either single pulse with maximum amplitude and a shortest risetime or a sequence of subnanosecond pulses with a large modulation depth could be obtained. The gyromagnetic NLTLs excite rapidly damped oscillations. Usually only first two or three leading peaks have high values of the amplitude and modulation depth. Therefore, for feeding the NLTL, it is advisable forming of pulses with duration sufficient to form the first few peaks. In this work the method of transformation of a pulse shape (STS) is implemented, when each NLTL forms a sequence of the peaks of pulses with durations which are optimal for next stage NLTL. Thus, the first NLTL was used for increasing of voltage amplitude of a driver pulse. The increase of the number of modulation cycle took place in the next two stages with increase in modulation depth to ~70%-80% when leading peak amplitude was up to ~700 kV. When utilizing ferrite rings with small diameter (several mm) another MCS operation mode was implemented, which provided sequential increase in the voltage amplitude of a single peak pulse due to the shortening of the duration and maximum sharpening of a risetime. As a result, the pulse with voltage amplitude of ~785 kV with risetime of 58 ps (45 ps, taking into account reduction of measuring cable path) and pulse duration shorter 150 ps. The work was fulfilled in the frame of the IEP state task No.

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0389-2015-0026, and by the RAS Program No.10. P4-4 [A1274] Design and the first test results of ten 1 MA‐LTD stages stacked in series CHEN Lin, ZOU Wenkang, ZHOU Linagji, JIANG Jihao, WEI Bing, HE An, WANG Meng, XIE Weiping, WANG Jie, ZHANG Yuanjun (Key Laboratory of Pulsed Power, Institute of Fluid Physics, CAEP, Mianyang, China) Abstract: The ten 1 MA-LTD stages stacked in series was designed with a magnetically insulated transmission line (MITL) to couple with low impedance diode based on the 1 MA-LTD stage prototype which had been constructed and tested successfully. There are 320 multi-gap switches (200 kV/40 kA) and 640 storage capacitors (100 kV/100 nF) with stored energy of nominal 320 kJ in the generator. The MITL in which the inner conductor with radius of 584 mm serves as the cathode, transfers electrical energy from the capacitor to the e-beam diode load. The generator has an outer diameter of 3 m and an overall length of 3.5 m. According to electrical circuit simulation, it can deliver 1 MA fast pulse in about 150 ns into a 0.9 ohm load. After having finished assembly of the ten LTD stages and sub-systems conditioning, we conducted the high voltage tests. In order to reduce the electron sheath current, the new inner conductor with radius of 563 mm also has been tested in experiments. In the presentation, the results for the two MITLs will be discussed. P4-5 [A0236] Design and implementation of a xenon flash lamp trigger circuit based on modified flyback circuit SONG Seung-Ho, CHO Chan-Gi, PARK Su-Mi, PARK Hyun-Il, RYOO Hong-Je (Chung-Ang University, Korea) Abstract: This paper presents design and implementation of the pulse trigger circuit for xenon flash lamp drivers. Output specifications of the proposed trigger circuit are as follows: output pulse voltage 32kV; sinusoidal pulse width 0.9s and pulse energy 0.25J/pulse. The trigger circuit is based on a modified flyback circuit in discontinuous conduction mode to take advantage of both the high boost ratio from the resonance with output capacitor and series connecting with main pulse circuit using the flyback transformer which is designed to deliver high current. Additionally, the unique high voltage flyback transformer with high turn ratio with minimizing leakage inductance is designed. The detailed design procedure for the pulse trigger circuit is described. To verify the proposed design, PSpice modeling was performed. Finally, experimental results proved the effectiveness of the xenon lamps triggering operation.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 P4-6 [A0400] Adjustable precise synchronization of two nanosecond high voltage generators SHUNAILOV Sergei, ULMASKULOV Marat, SHARYPOV Konstantin, SADYKOVA Anna, SHPAK Valerii (Institute of Electrophysics UB RAS) Abstract: In the experiments on high-power microwave generation two-channel setups based on synchronized nanosecond high-current accelerators RADAN-303 (voltage ~ 200 kV, front ~ 2 ns, FWHM ~ 5 ns) are used. Such generators design represents the double forming lines construction with a nitrogen high-pressure spark gap one electrode of which is grounded. As a result, it is convenient to control the spark gap by a short HV sync pulse. Usually, it is necessary to synchronize the channels with time spread much less than the high-voltage generator pulse duration. In perspective experiments, there is also a need to vary the delay between channels with sub-nanosecond accuracy. Thus, the triggering pulses ~ -100 kV allowing a precision offset are required. In the paper, the solution of this task is demonstrated by splitting the output high voltage pulse of the third (master) RADAN generator. Meanwhile, a coaxial ferrite spiral lines (FSL) with an external bias field created by a DC solenoid are installed in both synchronized channels. FSL is a coaxial line with an oil insulation whose central electrode is made of a spiral with a cylindrical ferrite core on the axis. These FSLs sharpen the rise time of a split pulses up to 1 ns. In addition, changing the bias field magnitude and direction one can change the duration of the output pulse in a wide range without essential losses in the amplitude. Adjustment of the bias field, not only sharpens the pulse, but also varies the delay of the trigger pulse front and, respectively, the start of the driven generators. The maximum delay of one channel relative to the other was 1.5 ns. The standard time deviation, the minimum relative jitter of two nanosecond high voltage generators was determined at the level of 55 ps. This work was supported by RFFI Grant No. 16-08-00230. P4-7 [A1601] Flyback based high voltage pulsed power generator for triggered vacuum switch KIM Shin1, BAE Jung-Soo1, KIM HYoung-Suk2, YU Chan-Hun2, 3 3 2 LEE Byung-Joon , AHN Suk-Ho , JANG Sung-Roc (1. University of Science&Technology, Daejeon, Korea; 2. Korea Electrotechnology Research Institute; 3. Pohang Accelerator Laboratory) Abstract: This paper describes the design of the high-voltage pulsed power generator for triggering TVS (Triggered Vacuum Switch). Based on the basic operating principle of Flyback converter that store the energy on the magnetizing inductance and transfer it to the secondary of the transformer, a compact trigger circuit is design to achieve 830 V/V of high step-up ratio (output pulse voltage/input dc voltage). The proposed trigger circuit consists of

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two stages that include the boost converter stage for boosting the voltage from 24Vdc to 100Vdc and the flyback stage for generating 20kVpulse from 100Vdc. In particular, the proposed structure of high-voltage transformer has the advantages from the point of view of minimizing leakage inductance and providing insulation. The detailed design of the proposed trigger circuit and experimental results with TVS is discussed in following paper. P4-8 [A1611] Design and testing of bipolar pulsed power supply with high efficiency and power density for strategic mineral exploration BAE Jung-Soo1, KIM Jong-Soo2, KIM Hyoung-Suk2, YU 2 1 2 Chan-Hun , KIM Shin , JANG Sung-Roc (1. University of Science&Technology, Deajeon, Korea; 2. Korea Electrotechnology Research Institute, Korea) Abstract: This paper describes a 25kW bipolar pulsed power supply for strategic mineral exploration. A 500V, 12.5A unit module consisting of a highly efficient LCC resonant converter and a full bridge-based bipolar pulse switching unit is designed. The LCC resonant converter has a trapezoidal-shaped resonant current for reduced conduction loss. For achieving the high power density, the leakage inductance of the transformer is used as resonant inductance without an external inductor. Moreover, the designed gate drive circuit-based the repetitive short pulse is proposed to operate the frequency range from DC to 8 kHz and reduce the gate transformer. Four modules are connected in series and parallel in order to operate the power supply in either loop mode or grounded dipole mode. Depending on the load condition, the pulse power source capable of delivering the required high voltage and low current (2kV, 12.5A) or low voltage and high current (500V, 50A) is operated either grounded dipole mode or loop mode respectively. In order to satisfy the output voltage balancing of the four modules, the third wire is wound to compensate the transformer of LCC resonant converter. The design of the bipolar pulsed power supply and experimental results will be discussed in following paper. P4-9 [A2753] Precise stability control system for pulse modulator power supply LIU Yongfang, YUAN Qibing, GU Ming (Shanghai Institute of Applied Physics, China) Abstract: Shanghai Soft X-ray Free Electron Laser (SXFEL) facility is under testing at Shanghai Institute of Applied Physics (SINAP), Chinese Academy of Sciences. The stability of RF system is one of the major factors to get great beam performance. It is mainly determined by klystron modulators power supply. The beam voltage of the LINAC klystron modulator, which is the pulsed power source of the RF amplifier, is directly affecting the RF amplitude and phase. This paper shows the suitable upgrade scheme of the modulator power supply and design considerations for the stability improvement of modulator power supply for Shanghai SXFEL. We present a real time feedback control Page 81

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system of LINAC pulse modulator to improve pulse to pulse amplitude stability. The feedback control system is based on the principle of embedded FPGA techniques. The control system consists of an embedded NIOS II processor, a high resolution ADC and an upper computer. The NIOS II processor manages on chip FIFO, ADC, IRQ, and Ethernet. The relevant experiments indicate that the feedback control strategy reaches required function. It is useful to improve the stability of existing modulator power supply. P4-10 [A2963] Research on repetitive charging control technology of parallel running high power CCPS LIU Kun, XU Xuzhe, GAO Yinghui, SUN Yinghui, SUN Yaohong, YAN Ping (Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China) Abstract: With the development of pulsed power technology, the high voltage large current discharge pulse power supply need more and more energy for the high frequency repetitive discharging, so that the primary energy should be with high power and high accuracy. The high-frequency high-voltage capacitor charging power supply (CCPS) is widely used as the primary energy in the field of pulsed power because of its simple structure, mature technology and high stability, but restricted by the power density and charging speed, it has not been widely used in the high frequency repetitive large current discharging. In order to enhance the out power, there are 12 CCPS parallel connected at the output end, which are unified controlled by the upper computer software, so that the 12 CCPS can finish the rapid charging for the large capacitor load. At the same time, the voltage feedback and timing function of the upper computer software are used to control the repetitive charging frequency of the 12 CCPS, so that the charging precision and charging rate can be controlled accurately. P4-11 [A2985] Development of ignitor power supply with fast rising output voltage using 13kV SiC MOSFETs 1 1 2 MORI Hitoshi , TOKUCHI Akira , FUKUKA Kenji (1. Pulsed Power Japan Laboratory Ltd., Japan; 2. National Institute of Advanced Industrial Science And Technology Advanced power Electronics Research Center, Japan) Abstract: In order to improve ignition process of fossil fuel engines, fast rising voltage on igniting electrode is studied. We developed an ignitor power supply with output voltage of 45kVp, rising time ~100ns (10%-90%) and repetition rate 1,000 pps. The power supply is equipped with SiC FETs of 13kV withstanding voltage and step-up transformer. A part of this work has been implemented under a joint research project of Tsukuba Power Electronics Constellations (TPEC).

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 P4-12 [A0076] Development of compact repetitive Marx generator powered by batteries 1 2 2 1 KUK J. H. , HWANG S.M. , LIM T.H. , CHOI J.S. (1. Agency for Defense Development, Korea; 2. Hanwha Corporation, Korea) Abstract: In order to repetitively supply high voltage pulses to an UWB source, the compact repetitive Marx generator powered by batteries has been developed and tested. It consists of an initial power supply with battery pack and a self-triggered Marx generator. The battery pack composed of rechargeable batteries supplies electric power to the initial power supply. The battery pack can be detached from the initial power supply for convenience. The initial power supply using CCPS can repetitively charge the Marx generator up to 50 kV at more than 100 Hz. The initial power supply is controlled by an optical pulse trigger pendant to be operated at a long distance. Total 18 stages in two lines are assembled in the Marx generator for compact size and circuit simplification. Each stage of the Marx generator has a ceramic capacitor of 50 kV and 400 pF. The parameters of the circuit components constituting the Marx generator are determined by the circuit simulations. This paper describes the design, the fabrication, and the test results obtained from this study. P4-13 [A0257] Simulation research on the building process of hundreds of kJ Marx generator JIA Wei1, YAO Weibo1, CHEN Zhiqiang1, GUO Fan1, ZENG 2 1 Jiangtao , QIU Aici (1. State Key Laboratory of Intense Pulse Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, China; 2. State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University Xi’an, China) Abstract: Based on the hundreds of KJ Marx generator used in the “Shanguang II” simulator, a whole-circuit model is designed to study the generator`s building process. The key parameters related with the arising of the overvoltage on the internal switches of Marx and a switch circuit-model with the information of the switching delay time and jitter are included in this model. With these switches on one by one in the Marx, simulation is done step by step to understand the generation, transmission and distribution of the overvoltage on these switches, and to research the interaction relationships of the overvoltage, circuit parameters and switch characteristics. Simulation results indicate that the Marx generator`s building time and jitter both mainly come from its the first two rows. The first row`s building time and jitter mostly result from the external trigger condition and switch-on characteristics of its switches. The second row’s building time and jitter mainly decided by the circuit structure and its parameters related with the generation of the overvoltage on its switches. The building time from the first two rows ratios the Marx`s building time greater than 70%, when there are auxiliary trigger resistors in the Marx. Without these trigger resistors, the ratio is about more than 60%. These simulation Page 83

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conclusions are in accordance with previous experimental results. P4-14 [A0730] Energy efficiency improvement of nanosecond pulsed discharge plasma processing IIDA Shuhei1, IKOMA Daichi1, SASAKI Kanji1, WANG Douyan2, 2 NAMHIRIA Takao (1. Graduate School of Science and Technology, Kumamoto University - Japan; 2. Institute of PulsedPower Science, Kumamoto University - Japan) Abstract: The development of a short pulse generator is of paramount importance for the energy efficiency improvement of various applications. Recently, the nanoseconds pulsed power generators, which can generate a pulsed voltage with 5 ns duration and 2 ns rise and fall times, have been developed. As the result, the nanoseconds (ns) pulsed discharge leads to higher energy efficiency of plasma processing, including the ozone generation and the polluted gas treatment. In the previous works, the ns pulsed discharge was employed to generate ozone and treat nitric oxide, energy efficiencies were high. In these works, the parameters of the applied ns pulsed power such as the peak, the polarity and the repetition ratio of the applied voltage and the parameters of the coaxial discharge reactor such as the inner and the outer electrode diameters and the electrode length were changed to obtain the characteristics of the plasma processing by the ns pulsed discharge. For further improvement of the energy efficiency of the plasma processing, in the study, the nanoseconds pulsed power generator has been modified to deliver the shorter voltage rise and fall times. In the presentation, the characteristic of the modified nanoseconds pulsed discharge processing would be indicated. P4-15 [A0944] Construction of a solid‐state pulse modulator for a 2.5 MW magnetron used in the 9 MeV electron accelerator LIM Heuijin1, JEONG Dong Hyeok1, LEE Manwoo1, SHIN Sang 1 1 2 Woong , YI Jungyu , RO Sung Chae (1. Dongnam Institute of Radiological & Medical Sciences, Korea; 2. Dong-A HiTECH, Korea) Abstract: We are developing the 6 MeV and 9 MeV C-band standing-wave accelerators for the radiotherapy machine in Dongnam Institute of Radiological & Medical Sciences, Busan, Korea. The first pulse modulator was constructed with the thyratron-switched pulse-forming network and is currently operating with the 6 MeV electron accelerator. In the next step, with the help of high power semiconductors, the solid-state pulse modulator was proposed and designed based on the Marx generator. The 6 MW pulse modulator was developed for the RF power source operation and includes a capacitor charging power supply, a Marx pulse generator consisting of 40 storage-switch stages, a high voltage pulse transformer, a heater isolated transformer, and a heater controller. It produces the pulse of 50 kV and 120 A and the heating power of 12.5 VAC required by the magnetron in the 9 MeV electron accelerator. Each storage-switch stage is designed to switch the current and Page 84

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voltage rate of 280 A and 720 V, and to use the capacitor of 25 μF which is chosen for the voltage droop of 10 % with the pulse width of 5 μs. Since the prototype Marx pulse generator including 8 storage-switch stages was successfully tested, the full Marx pulse generator including 40 storage-switch stages and sub-systems were constructed, integrated and tested with the load system and with the 2.5 MW magnetron used in the accelerator. In this paper, we present and discuss the design and construction of the modulator and the test results. (This work was supported by the Dongnam Institute of Radiological & Medical Sciences (DIRAMS) grant funded by the Korea government (MSIT) under Grant 50495-2018.) P4-16 [A2191] A high voltage pulse generator based on PFN and varistors WU Qilin, CUI Yancheng, GAO Jingming, YANG Hanwu (College of Advanced Interdisciplinary Studies, National University of Defense Technology, China) Abstract: This paper puts forward a novel high voltage pulse generator, which can output a near square waveform across the load. The generator is composed of a conventional Marx generator, an LC filter and a metal-oxide varistor (MOV) in parallel with the load. The Marx and the filter form a two-section type-A Guillemin pulse forming network (PFN). The PFN outputs a near square waveform and the MOV further stabilizes the voltage because of the MOV's nonlinear resistivity. Circuit simulation verifies the working principle. Design parameters for the conventional PFN are derived. Considering the stray inductance of the filter, a more realistic PFN circuit is proposed and its parameters are derived. Preliminary experiments are conducted and typical output waveforms have 50 ns rise time, ~1000 ns pulse width and 6 kV peak voltage. This generator is suitable to be used as a compact, long-pulse high power microwave modulator as it has a simple design, a well-defined flat top and it can output near constant voltage even if the load's impedance varies. P4-17 [A2543] The pulsed power system for Dragon‐II LI Yuan (Institute of Fluid Physics, Mianyang, China) Abstract: The Dragon-II is an accelerator with capability of providing 3 pulsed electron beams under MHz repetition rate. Therefore, its pulsed power system need to generate 3 pulses, a couple of hundred kilo-volt each, to accelerating the beams with highly accurate synchronization. Since no high power switch can work under MHz repetition yet, a scheme, which uses parallel sub pulsed power system and isolating component, has been developed, constructed and tested. By now, the system can provide 3 pulses with 300 kV (maximum) and 300 ns time interval (minimum) to 92 inductive cells with a jitter less than 5 ns.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 P4-18 [A2704] A compact repetitive PFN‐Marx generator LI Zhiqiang, YIN Yi, LI Wei, WANG Yuwei, HONG Zhiqiang, LI Da (National University of Defense Technology, Changsha 410073, China) Abstract: A compact repetitive PFN-Marx generator was constructed for the application of generating electron beams. This generator has nineteen stages with inductive isolation. Every stage consisted of four mica capacitors which may be charged the maximal voltage of 50kV by a pulse transformer in the time of 40s. A compact Marx trigger with the integrated design of a pulse transformer and a magnetic switch which have a common magnetic core was also fabricated. This generator can operate at 50Hz rep-rate with the output power of 4GW, the impedance of 35W and the pulse width of 120ns. This paper will discuss the operating characteristics of this generator.

P4-19 [A2190] Preliminary study on pulse width adjustable pulse generator based on the magnetic switch and metal‐oxide varistor CUI Yancheng, YANG Hanwu, GAO Jingming, LI Song, SHI Chengyu, WU Qilin (National University of Defense Technology) Abstract: The pulsed power technology has been applied to many defense and industrial fields. Different applications have different demands on the parameters of the pulsed power system. However, the parameters of the current pulsed power systems are usually fixed and can be changed easily. As a special nonlinear device, metal-oxide varistor was considered to be applied for generating square pulses which has been verified in experiment. Moreover, the magnetic switches are widely used in the field of the pulsed power technology due to the special switching characteristic. This paper proposes a high voltage pulse generator with pulse width adjustable based on the magnetic switch and metal-oxide varistor. It uses the combination of the pulse forming network and metal-oxide varistor to generate quasi-square pulses, with the magnetic switch as a crowbar switch to sharpen the falling edge and by changing the reset current to adjust the pulse width. The paper presents theoretical analysis as well as simulation study, and preliminary experiment based on the simulation results. In the preliminary experiment, the falling edge of the voltage waveforms obtained on a dummy water load is less than 50 ns, the flat-top is about 7 kV and with the pulse width adjustable within 200 ns-900 ns. This kind of pulse generator with pulse width adjustable can be applied to many fields such as corona plasma generation, industrial dedusting and medical disinfection.

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Poster Session V - High Power Microwaves and RF Sources - Session Chair: YUAN Chengwei (BALL ROOM 2#) [13:30-15:00] P5-1 [A1652] Investigation of promising schemes of millimeter‐wave high‐power BWT and TWT on spirally curved rectangular waveguide BADARIN Artem1, KURAYEV Alexander1, RAK Alexey2, KURKIN 3 2 3 Semen , KORONOVSKII Alexey , HRAMOV Alexander (1. Belarusian State University of Informatics and Radioelectronics, Russia; 2. Saratov State University, Russia; 3. Yuri Gagarin State Technical University of Saratov, Russia) Abstract: The designs of BWT and TWT of a millimeter range with two wide band electronic beams are proposed and investigated. As an electrodynamic structure of the tubes, it is proposed to use a spirally curved waveguide in the basic H10 mode. Unlike existing designs on an undulating bent waveguide, the proposed schemes allow to significantly increase the current of electron optics, which significantly improves the output characteristics. Analytical analysis has shown the possibility of effective interaction of the electron beam with both direct and reverse electromagnetic waves for certain values of the control parameters of the systems. We have carried out three-dimensional numerical simulation of the proposed schemes. The results obtained make it possible to consider the designs of the proposed lamps promising. The work has been supported by the Russian Foundation for Basic Research (Project 17-52-04097) and the Ministry of Education and Science of the Russian Federation (Project 3.859.2017/4.6). P5-2 [A3116] Improved design and experiment of a high power Ku‐band gyro‐TWT XU Yong, SUN Miao, PENG Tinghui, WANG Jianxun, LUO Yong, PU Youlei, WANG Li, YAN Ran, JIANG Wei, LIU Guo (University of Electronic Science and Technology of China) Abstract: Improved design and experiment of a high power Ku-band gyrotron traveling wave tube amplifier (gyro-TWT) operating in the TE01 mode are presented in this paper. In design, a broadband multi-channel TE01 mode input coupler and a three-disk berillia ceramics output window are adopted. In order to suppress the potential gyro-backward wave oscillator interactions, a new type BeO-SiC composite lossy ceramic rings and pieces hybrid loaded high frequency structure is also adopted. The designed gyro-TWT is driven by a 70 kV, 23 A gyrating electron beams with velocity ratio 1.2. The preliminary hot test experiment shows that the maximum output average power of the designed gyro-TWT is ~21.6 kW at 16.2 GHz, corresponding to 432 kW saturated pulse power (5% duty ratio), 26.8% efficiency, 40.1 -dB saturated Page 87

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gain and -3 dB bandwidth of 2 GHz. P5-3 [A3208] An ultra‐compact 600 kV pulsed transformer DE FERRON Antoine S.1, PECASTING Laurent1, RIVALETTO 1 2 3 Marc , PECQUOIS Romain , NOVAC Bucur (1. Université de Pau et des Pays de l’Adour, France; 2. HI PULSE, France; 3. Loughborough University, UK) Abstract: The paper describes an ultra-compact multi-primary winding, magnetic core pulsed transformer that can generate voltage impulses of 600 kV, with a rise time of less than 270 ns. Details of the design is provided and the experimental data are compared with those of numerical modeling. P5-4 [A3251] Experimental demonstration of L‐band relativistic magnetron with multichannel radial output of the microwave power HE Chaoxiong, LI Tianming, HU Biao, FENG Yifu, LI Jiayin (University of Electronic Science and Technology of China) Abstract: A previous computational study of an L-band relativistic magnetron with multichannel radial output using the particle-in-cell code have been analyzed. The research described in this paper aimed to achieve an experimental verification of two outputs configuration. The magnetron was driven by a linear induction accelerator (~600 kV, and 70 ns). The experimental results of the L-band magnetron operation with a six-vane anode block and multichannel radial outputs for microwave power extraction are presented. Both solid as well as transparent cathodes have been tried in the study so as to know the maximum power, cathode current and RF startup delay time. The maximum power and frequency are 1.21 GW and 0.96 GHz respectively with the transparent cathode. The maximum output power is obtained at a magnetic field of B=0.40T. P5-5 [A3302] Asymmetric mode competition in a relativistic backward wave oscillator SONG Zhimin, SUN Jun, CAO Yibing, FAN Zhiqiang, ZHANG Guangshuai, WU Ping (Northwest Institute of Nuclear Technology ,China) Abstract: Relativistic backward wave oscillator (RBWO) is one of the most important high power microwave (HPM) generator. Its stability and reliability must be further improved in order to satisfy the application. The factors to limit the performance are varied, including intense field breakdown, beam breakup, mode competition and so on. Based on a C-band RBWO, the mode competition is carefully analyzed and the correlated effects on RBWO are further revealed. As shown in the studies, for an axisymmetric system, asymmetric mode competition still probably exists. Therefore, it is very

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necessary to build the three-dimensional particle-in-cell (PIC) model in order to investigate mode competition. Mode competition probably causes field leakage toward diode and eventually results in impedance collapse. Also, mode competition can destroy the energy coupling between the operation mode and the electron beam and leads to pulse shortening. Some positions of the electrodynamics structure even occur field breakdown more intensely when mode competition exists. In order to improve the performances of the RBWO, it is essential to design the structure more roundly so that asymmetric mode competition can be effectively depressed. The studies can provide a good guidance for some researchers in HPM domain. P5-6 [A2938] Nonlinear Kompfner absorption in the course of interaction of a high‐current relativistic beam with the fundamental decelerated mode of a waveguide with a shallow corrugation ZASLAVSKY Vladislav, ABUBAKIROV Edward, VIKOV Mikhail, GINZBURG Naum, ZHELEZNOV Ilya, ROSENTHAL Roman (IAP RAS, Nizhny Novgorod, Russia) Abstract: Recently, much progress was made in generation of high-power ultra-short electromagnetic pulses based on the superradiance (SR) effects. Peak power in such pulses can exceed the power of the electron beam. However, the SR pulses repetition frequency does not exceed 1 kHz which limits the number of possible applications. As was shown earlier, equally high peak power at the repetition frequency of up to 100 MHz can be reached in the oscillator based on the passive mode synchronization effects. Alongside the amplification element (either relativistic TWT or relativistic BWO), the key element in such an oscillator is a nonlinear absorber in the feedback loop. This absorber should absorb the small amplitude signals almost entirely and be transparent for large amplitude signals. In the present paper we show that an element where a rectilinear high-current electron beam interacts with the fundamental decelerated mode of a waveguide with a shallow corrugation can be used as an absorber. For realization of Kompfner suppression effect, the phase velocity of the wave should be somewhat larger than the translational velocity of electrons. Results of the theoretical analysis based on the averaged model were confirmed by PIC simulations within the KARAT software package. P5-7 [A0131] Variation and saturated phenomena of polypropylene film flashover voltage under different SF6 pressure 1 2 2 2 1 CHEN Zhiqiang , JIA Wei , GUO Fan , LI Junna , JI Shengchang (1. Xi’an Jiaotong University, Xi’an, China; 2. Northwest Institute of Nuclear Technology) Abstract: In practical operation of EMP simulators, the flashover phenomenon on the edge of polypropylene dielectrics dominates the insulation failure mode of peaking capacitor. In order to analyze the characteristic of polypropylene film flashover voltage under high-pressure SF6, an experimental platform is established, and the rise-time of the applied pulse voltage is about 27ns. Page 89

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Experiments were performed on finger electrodes, and the pressure of SF6 was set from 0.1MPa to 1.0MPa. The experimental results show that the relationship of flashover voltage and gas pressure could be divided in to two areas: in low pressure area, the flashover voltage increases as the gas pressure linearly; in the high pressure area, the growth of flashover voltage gradually slows down and approaches to a saturation value. As the increase of gap distance, the saturation point of gas pressure become lower and lower, and even close to 0.4MPa with the 9mm gap distance. When high surface resistivity and the charge traps distribution on the polypropylene film are taken into account, the accumulation and emission of surface charge on the film is recognized as the primary reason for the saturated phenomena. The study is of significance in guiding the insulation design of the peaking capacitor in EMP simulators. P5-8 [A0445] Multichannel nonlinear transmission line generator with effective frequency of microwave modulation 8 GHz ULMASKULOV Marat, SHUNAILOV Sergei, SHARYPOV Konstantin, YALANDIN Michael, SHPAK Valery, PEDOS Maxim, RUKIN Sergei (Institute of Electrophysics UB RAS, Ekaterinburg, Russia) Abstract: The results of testing of high-voltage four-channel system of rf-generators based on the coaxial gyromagnetic ferrite nonlinear transmission lines (NLTL) with external biasing and frequency of rf-modulation of high-voltage pulse envelope of ~8 GHz are presented. Such an increase in the modulation frequency in comparison with what was achieved earlier was provided by both higher rate of voltage rise of an input pulse (dU/dt ~ 0.4 MV/ns) and small sizes of the ferrite rings (dia of several mm). The solid-state modulator S-5 was used as a driving generator, forming high-voltage unidirectional pulse with duration ~5 ns (FWHM) and amplitude -500kV across a load of 50 . The pulse was split in 4 channels with individual NLTL. As insulation of the lines, transformer oil under pressure to 10 atm. was used. Input pulse voltage at each single channel was ~-200 kV (at 50 Ohm). The pulses with fast damped rf-modulation were formed at the NLTL output while maximum modulation depth was more than 50%. The minimum period between peaks corresponds to modulation frequency ~8 GHz. The additional coaxial spiral line with a central ferrite core and the external magnetic field were installed into each channel, which provided independent control of delay of the channel. While total spread in amplitude of initial pulse was 10%, the maximum relative jitter of 4 channels was estimated at 20-25 ps, which is much shorter than period of microwave oscillations. Possibility of a coherent far-field summation of the rf-emmision fields radiated by the 4 channel system of conical antennas was demonstrated. This work was supported by grant of RFFI №16-08-00058.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 P5-9 [A1327] Excitation of microwave oscillations based on the interaction between squeezed state of electron beam and photonic crystal modes FROLOV Nikita, KURKIN Semen (Saratov State University, Saratov, Russia) Abstract: In this paper we propose the application of photonic crystal structure for amplification of microwave oscillations in relativistic electron beam induced by the beam-plasma instability in the absence of ions. Previously, it has been shown that interaction between the electron beam and charged high-dense electron plasma represents a mechanism for microwaves generation in the range of 18-40 GHz depending on beam current and energy. From the viewpoint of application of photonic crystal as an output electrodynamical structure seems to be a prospective way to gain the amplitude of longitudinal space-charge waves in the electron beam. So, this study aims at the model development and numerical particle-in-cell simulation of the described microwave system to consider its efficiency gain by means of photonic crystal. The work has been supported by the Russian Foundation for Basic Research (Project 16-32-60107) and the grant from the President’s program (Project MK-1163.2017.2). P5-10 [A1531] Effective suppression of field attenuation for the solenoid with rapid pulse discharge SONG Zhimin1, SUN Jun1, ZHANG Guangshuai1, CAO Yibing1, 1 2 FAN Zhiqiang , DING Zhenjie (1. Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi’an, China; 2. Key Laboratory of Physical Electronics and Devices of the Ministry of Education Xi’an Jiaotong University, Xi’an, China) Abstract: Solenoid is commonly an important part of the high power microwave (HPM) system. It can provide the guiding magnetic field for the intense relativistic electron beam (IREB) to stimulate HPM. The solenoid usually consists of several coils and is driven by the charging capacitors. In HPM domain, the discharge period of the designed solenoid is generally several tens milliseconds, which is far beyond the IREB duration. Consequently, most of the pulse energy is wasted and the efficiency of the solenoid system is very low. Decreasing the discharge period of the solenoid system is an effective method to enhance the energy efficiency. However, the eddy-current loss in the metal wall would inevitably increase as the discharge period decreases, which can result in the magnetic field attenuation and delay. Slot structure is proposed to suppress the eddy-current loss caused by the rapid discharge in the article. The effects of the slot parameters on the field attenuation are numerically investigated. The elementary results demonstrate its feasibility. Such a solution is also easy to put into practice.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 P5-11 [A1755] Theoretical design and numerical simulation of an X‐band SES pulse compression system JIANG Tao, YANG Meng, JIANG Zili, XIONG Zhengfeng, NING Hui, YAN Feng (Northwest Institute of Nuclear Technology) Abstract: An X-band Switched Energy Storage (SES) microwave pulse compression system is presented and its theoretical analysis and numerical simulation are carried out. Detailed dimensions of the resonant cavity are theoretically calculated and numerically optimized. The optimized length of the resonant cavity is 1178.2mm, among which the length from the input coupling iris to the midline of the H-T outlet is 1066mm and the length from the midline of the H-T outlet to the right short side is 112.2mm under the resonant frequency of 9.3 GHz and output pulse width of 10ns. The corresponding resonant mode is TE1,0,52 with the quality of 5397. Further, the input coupling iris is designed and optimized by simulation. When the width of the rectangular coupling iris is 11mm, the coupling coefficient is 1.05, which is beneficial for high energy storage efficiency. The output power gain is theoretically calculated as 11.7. At last, the position of the fast switch is optimized. When the fast switch is set 77 mm away from the midline of the H-T outlet, the transmission coefficient of the H-T outlet is 96.6%, corresponding to the energy transmission efficiency of 93.3%.This SES microwave pulse compression system is expected to compress a 100kW pulse to 1MW level. P5-12 [A3344] Research and development of compact Marx generator for driving high power microwave GAO Huailin (Institute of Electronics, Chinese Academy of Sciences, Beijing, China) Abstract: A 14-stage 700kV, 240J Marx generator is designed and developed to drive high power microwave generation. Each stage of the Marx generator consists of 8 capacitors connected in parallel, arrayed around an annular switch electrode, and charged and isolated by 500kW/30kV resistors and 19mH/100kV inductors respectively for applications in pulse mode or repetitive-rate mode respectively. The discharge plasma switch of the Marx generator is designed in the form of annular rail gap to reduce the switch inductance, and has the diameter of 100mm and spark gap of 2.5mm. The system is placed in a pressure vessel filled with N2 gas from 7atm to 15atm. The maximum 329kV pulse voltage from pulse forming line has been applied to drive the high-power microwave generator, and GWs microwave radiation from 200MHz to 600MHz has been generated for the effect test of high field microwave interaction with matter. The detail design and experimental results will be given in this progress report.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 P5-13 [A0074] A novel low‐voltage overmoded coaxial sub‐terahertz oscillator with resonant reflector and extraction cavity CHEN Zaigao (Northwest Institute of Nuclear Technology) Abstract: In terahertz band, overmoded coaxial slow wave structures (SWSs) can make the fabrication and assembly of low-voltage backward wave oscillator (BWO) easily done. However, it also brings about deleterious effects, such as mode competition and large current density, et al. To solve these problems, the overmoded coaxial BWO with resonant reflector and energy extraction cavity are proposed in this paper, the cold testing results indicate that the proposed resonant reflector can reflect the electromagnetic wave in a wide frequency range. Furthermore, the three-dimensional particle simulation results illustrate that when the operation voltage and current density are 7 kV 2 and 17.6 A/cm , respectively, the quasi-TE11 can be suppressed, and the new proposed coaxial BWO can successfully generate the terahertz wave with the output power of 1.15 W at the frequency of 0.34 THz. Although the overmoded ratio of proposed BWO reaches 8.0, the resulting dispersion curve of quasi-TEM mode almost overlaps with the dispersion curve of high-order quasi-TE11 mode, the frequency spectrum of the generated signal is very pure. The field distributions in the transverse section of coaxial SWSs also demonstrate that there is no asymmetric mode excited in the device. P5-14 [A1477] Design of high‐order terahertz EIO with two beams LI Shuang, WANG Dongyang, TENG Yan, WANG Guangqiang (Northwest Institute of Nuclear Technology) Abstract: EIO operating at high-order mode, such as TM31, shows the advantages in offering improved power capability and mitigating the difficulties in micro-fabrication because of the enlarged inner surface. Increasing the working current is useful in improving the EIO’s output power. However, such e-gun is not fully developed nowadays. So the method of applying two beams in EIO is proposed based on the distributions of Ez in high-order EIO. In the optimized two-tunnel structure, the output power is obviously enhanced. When the beam’s voltage is 15kV and the current for each e-gun is 80mA, the output power reaches about 75W, nearly double of that in the structure with only one tunnel. P5-15 [A1573] Theoretical analysis of high‐ efficiency terahertz folded‐waveguide slow‐wave‐structure with sectional parameters ZHANG Fang, DONG Zhiwei, YANG Wenyuan, SHU Xiaojian, YANG Wei (Institute of Applied Physics and Computational Mathematics) Abstract: A novel high-efficiency folded-waveguide slow-wave-structure, designed with variable parameters in sections to match beam’s energy Page 93

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changes in its modulation with electromagnetic wave, is analyzed. Small signal theory and three-dimensional PIC code are used to analyze beam-wave interaction. Method for designing this new slow-wave-structure is summarized. A 0.345THz two-stage folded-waveguide slow-wave-structure is achieved to test this idea. By comparing with conventional parameter-homogeneous slow-wave-structure, two-stage structure’s output power and electron-wave conversion efficiency are both increased by 94%. This idea can also be applied to multi stages, while the energy of trapped electrons are reduced step by step, then electronic efficiency and device’s output power will be improved higher and higher. The new type SWS has compact structure, few parameter changes and simple connection between different sections, and easy to realize integrated processing. P5-16 [A2448] Investigations on TE01 circular waveguide bend for high power microwave applications ZHANG Qiang, YUAN Chengwei, HAO Dongqing (Institute of High Power Microwave Technology, NATIONAL UNIVERSITY OF DEFENSE TECHNOLOGY, Changsha, China) Abstract: The design methodologies, numerical and experimental results for TE01 circular waveguide bend were reported. It is shown that, some special structures can realize mode conversion between TE01 circular waveguide mode and TE20 rectangular waveguide mode. Furthermore, circular waveguide bend for transmitting TE01 mode can realize high transmission efficiency in a small structure. The optimized bend has a transmission efficiency of over 99.9% at 9.45GHz, and exceeds 99.6% in the range of 9.21GHz ~ 9.57GHz. Different surface material were utilized to analyze the bend, and stainless steel was used for manufacture, its curvature radius was less than 200mm. Experimental results show that the bend has high power handling capacity, and TE01 mode transmission efficiency has exceeded 97%. P5-17 [A2552] A high‐power X‐Band diplexer based on corrugated coaxial waveguide filters ZHAO Xuhao, YUAN Chengwei, ZHANG Jiande, ZHANG Qiang (Institute of High Power Microwave Technology, National University of Defense Technology, Changsha, China) Abstract: Through mode matching analysis, an X-band diplexer based on overmoded coaxial waveguide filters is proposed in this paper. The diplexer is composed of two radial waveguide structures connected by six rectangular waveguides. The former radial waveguide is used to extract the filtered microwave, the latter can combine the microwave output from the rectangular waveguides. As the key part of the diplexer, two corrugated coaxial waveguide filters operating at TEM mode are designed with the central frequency of 9.3GHz and 9.7GHz, respectively. The bandwidth of both filters is 300MHz, which is broad enough for narrow-band high-power microwave (HPM) sources. Simulation results show that the transmission efficiency of the diplexer is over Page 94

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99% within passband and the power handling capacity exceeds 5 GW. The filter with central frequency of 9.3GHz was fabricated and tested under high-power microwaves (HPMs) with power of GW level and pulse duration of 100ns. The waveforms obtained from the experiments verify the feasibility and high power handling capacity of the corrugated coaxial waveguide filter and diplexer. P5-18 [A2658] A high‐power and high efficiency bend over‐mode coaxial waveguide ZHANG Jianqiong, WANG Qingfeng, LIU Qingxiang, LI Xiangqiang, LIANG Yuan (School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, China) Abstract: A bend over-mode coaxial waveguide with advantages of high efficiency and high power handling-capacity is investigated. The principle of the proposed waveguide is as follows: the TEM mode in coaxial waveguide is converted to TE11 modes of two 180° sector waveguides, and then the sector waveguide bends with a demanded turning angle, afterwards the TE11 modes in the two sector waveguides are merged into the TEM mode of the coaxial waveguide. A C-band waveguide prototype with a center frequency of 4.0 GHz and a turning angle of 45° is designed and fabricated. The experiment results show that: the transmission loss of the fundamental mode at the center frequency is 0.2 dB, and the VSRW is 1.1；When the frequency ranges from 3.8 to 4.2 GHz, the transmission loss of the fundamental mode is less than 0.4 dB and the VSWR is less than 1.5. The field distributions of this waveguide are analyzed through simulation, which prove its advantage of high power-handling capacity. P5-19 [A2867] Transient far‐field analysis of HPM on reflector antenna with TDPO WANG Lulu, HUANG Wenhua, LI Ping, WANG Haibo, ZHANG Yonghua, FANG Wenrao (Northwest institute of Nuclear technology, Xi’an, China) Abstract: Physical optics method is often used in the far-field analysis of large diameter reflector antenna which is applied to the high power microwave system. But when reflector antenna is used in an ultra-wideband (UWB) HPM source system, the calculation results in frequency domain depends on the number of sampling points, which leads to low computational efficiency and large memory. Therefore, the time-domain physical optics method is used to analyze the transient far-field characteristics of the HPM of a large-diameter reflector antenna, and the wide-band result characteristics can be obtained through a calculation process analysis. The physical optics method is extended to the time domain, and the expression of TDPO is derived with Stratton-Chu integral equation using inverse Fourier transform. For the large diameter

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reflector antenna, HPM short pulse response of short pulse and continuous wave is analyzed. The short pulse response of different direction in the far-field with the feed at the focal point of antenna is calculated and the effect of the pulse response in different direction when the feed’s horizontal offset is analyzed P5-20 [A3144] A tri‐band serpentine mode converter WANG Keqiang, LI Hao, CAI Chen, LI Tianming, WANG Haiyang, HU Biao, ZHOU Yihong (University of Electronic Science and Technology of China, Chengdu) Abstract: The mode converter is a key component in the high-power transmission systems. In this paper, a tri-band serpentine coaxial waveguide embedding circular waveguide mode converter is achieved with a structure length of 1300mm. In this design, the coaxial mode converter has the same curvature distribution along longitudinal propagation axis with the inner embedded circular mode converter. The coaxial TEM mode (Coa.TEM) and circular TM01 modes (Cir.TM01) can be transformed simultaneously into coaxial and circular TE11 modes (Coa.TE11 and Cir.TE11) through coaxial mode converter and circular mode converter, respectively. Moreover, the outer coaxial mode converter operates at 8.5GHz (X band) and 15GHz (Ku band), and the center frequency of the circular mode converter is 35GHz (Ka band). The maximum conversion efficiencies of the synthesized tri-band mode converter at these three frequencies are all over 97.5%, and the bandwidths (conversion efficiency is over 90%) are 300MHz, 600MHz, and 800MHz, respectively. Overall, this design realizes transforming the Coa.TEM mode into the Coa.TE11 mode at X band and Ku band, and transforming the Cir.TM01 mode into the Cir.TE11 mode at Ka band with a compact structure, and it has a symmetry and reciprocity transmission system. P5-21 [A2659] The influence of the state of plasma opening switch (POS) on the characteristic of high current cathode emission CAI Dan, SUN Jianfeng, REN Zeping (State Key Laboratory of Intense Pulsed Radiation Simulation and Effect (Northwest Institute of Nuclear Technology), Xi’an, China) Abstract: High power POS could sharp the frontier of voltage waveform and multiply the amplitude of voltage and transmission power. Thus, it has been widely applied in the large-scale radiation simulation equipment in order to enhance the dose rate of γ-rays produced by bremsstrahlung diode. The previously simulation results have shown that the space distribution of voltage waveform after POS could influence the electron beam distribution on the anode target of high impendence bremsstrahlung diode, and then affect the field distribution of γ-rays. However, the influence of the state of POS on the space distribution of voltage waveform after POS has not been reported until now. In this paper, three dimension fully electromagnetic particle-in-cell simulation has been carried out for this interesting issue. Page 96

EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 P5-22 [A2874] Particle‐in‐cell simulation of anode plasma dynamics in the self‐magnetic‐pinch diode LI Yongdong, LUO Wei, WANG Hongguang, ZHANG Pengfei (1. Key Laboratory for Physical Electronics and Devices of Ministry of Education, Xi'an, ShaanXi, China; 2. State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China) Abstract: The self-magnetic-pinch diode (SMPD) produces an intense electron beam source pulsed power-driven X-ray radiography. It has long been understood that the electrode plasma formation and expansion of the diode can cause rapid impedance collapse. It is assumed that the rapid reduction of diode impedance may be resulted by the anomalous behavior of anode plasma. Particle-in-cell (PIC) simulation of a typical SMPD is implemented with PIC code-UNIPIC. The simulation results indicate that the anomalous behavior of anode plasma is caused by the instability of plasma. Various anode-to-cathode gaps of diode are used to investigate the influence of the impedance machining between the diode and the magnetically insulated transmission line on the anode plasma behavior. And the change of input voltage of the SMPD in simulation shows how the voltage amplitude and the waveforms affect the anode plasma dynamics of the diode. The results indicate that the less impedance machining between the MITL and the diode caused the higher growth rate of instabilities of the anode plasma, which means more rapid reduction of diode impedance. P5-23 [A1224] Analysis on temperature rise characteristics of laser‐removed transmission line winding foreign bodies LI Jing, FANG Chunhua, LIU Haochun, FANG Yu (College of Electrical Engineering and New Energy, China Three Gorges University, China) Abstract: Using continuous laser to ablate winding foreign bodies of the overhead transmission line, the foreign bodies melt from the line by absorbing heat. In order to study the temperature rise characteristics of foreign bodies and transmission line in the process of ablation of foreign bodies by laser and determine ablation time at specific power to avoid damage to transmission line. This paper uses finite element method to simulate the ablation process of foreign bodies by ANSYS software. The laser ablation experiments were carried out using different kinds of foreign bodies. The experimental results have some reference value to further standardize and popularize the use of laser to remove foreign bodies from the power grid.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 P5-24 [A2173] Influence of pulse laser spot speed on the surface cleaning effect of porcelain insulators FANG Yu, FANG Chunhua (China Three Gorges University, Yichang, China) Abstract: At present, the cleaning methods of porcelain insulators are charged with water, with electrochemical cleaning, etc. These methods still have some deficiencies in varying degrees. The pulsed laser cleaning porcelain insulator has the advantages of low running cost and strong operability, but the laser cleaning efficiency is affected by the spot speed. In order to study the effect of the pulse laser on the surface damage of the porcelain insulator surface, the ANSYS simulation software is used to simulate the process of cleaning the surface of porcelain insulators by different laser point speed of the pulse laser, and then the temperature field and the stress field on the porcelain insulator surface are analyzed. In the experiment, the porcelain insulator is cleaned by pulsed fiber laser with a single pulse energy of 1.48mJ. It is found that the cleaning efficiency is the highest when the laser spot speed is 1000mm/s. Through theoretical and experimental analysis, we get the best laser spot speed, which can be applied to improve the efficiency of industrial pulsed laser cleaning insulator.

Poster Session VI - Particle Beam Technology - Session Chair : ZHANG Zicheng (BALL ROOM 2#) [13:30-15:00] P6-1 [A1455] Robotic development for the visual inspection and the clean out of a vacuum coaxial line CARON Michel1, HOURDIN Laurent1, TOURY Martial1, AURIEL Gerard1, DUCASSE Fabrice1, MAGNAN Jerome1, HEBERT 2 Guillaume (1. CEA, France; 2. IRELEC) Abstract: Radiographic diodes for most of the X-ray flash pulsed power drivers have to be refurbished after each single shot. In operation, cathode and anode material are damaged due to the high energy deposited by the electron beam over a very short surface area (<

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development process from the concept design to the manufacture of the prototype. The results of the operational tests carried out in the Technology Development Centre at AWE are presented and a conclusion on TRL level achieved is drawn. P6-2 [A0524] Development of diagnostic neutral beam injection system using PIG ion source in VEST LEE Kihyun, CHOI Jaeyoung, LEE Soonghyeong, CHUNG K.J., HWANG Y.S. (Seoul National University, Seoul, Korea) Abstract: A diagnostic neutral beam (DNB) injection system in VEST has been developed for charge exchange spectroscopy (CES) diagnostic. A hydrogen ion beam with beam energy of 30keV and beam current of 0.3 A is extracted from PIG ion source. A high density hydrogen plasma of ~1x1018 m-3 is produced by pulsed arc power, which is sufficient to achieve 300 mA with an extraction aperture of 10 mm in diameter. The maximum ion beam current density is as high as 0.6 A/cm2 which is suitable for obtaining CES signals with high spatial resolution. Pulse-modulated high voltage of ~30kV for beam extraction is supplied from all solid-state Marx generator. Neutral beam of ~150mA is injected to VEST through neutralizer with 50% efficiency. In this paper, the pulsed ion beam characteristics as well as the detailed design of DNB system including PIG ion source and neutralizer are presented P6-3 [A0739] Multipoint vacuum arc as cathode plasma source for sub‐millisecond operation of GESA‐facilities. AN Wladimir, FETZER Renate, WEISENBURGER Alfons, MUELLER Georg (Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz, 1, Eggenstein-Leopoldshafen, Germany) Abstract: The extension of the field of application of GESA facilities to non-adiabatic material treatment with sub-millisecond high-energy electron beams required a comprehensive modification of the cathode. In the new cathode design, the plasma generated by vacuum arc discharges at the tips of several carbon fibers serves as electron source. Here, results of the emission behavior of the new cathode are presented. At a maximum allowed load of the individual fibers of 1 A, it is possible to achieve emission current densities up to 0.5 A/cm². For a typical beam compression of K=10-16, this results in power densities at the target of up to 0.7 MW/cm² over pulse durations up to ~450 µs. The GESA concept with relatively low current density at the cathode and strong beam compression has the advantage that the cathode can be operated at relatively low plasma density. Thus, the formation of cathode spots at the metal surfaces that are in contact with the plasma can be controlled more easily. Using optical diagnostics, the ignition behavior of the vacuum arcs and the dynamics of the plasma was investigated. The findings enabled an

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optimization of the electrode geometry and potential distribution in order to generate a homogeneous cathode plasma. P6-4 [A0823] An application of vacuum arc discharge for an injector of high‐intensity pulsed accelerator YANG Zhen, DONG Pan, LI Jie, ZHENG Le, WANG Tao, LONG Jidong (Institute of Fluid Physics, CAEP, Mianyang, China) Abstract: Vacuum arc discharge plasma sources can produce high-intensity, multi-component, and short-pulse-width ion beams, which make them widely used in many areas, such as nation security, aerospace, scientific research and geologic prospecting. A vacuum arc ion source with hydride electrodes has been developed by Institute of Fluid Physics (IFP) to provide high-intensity, short-width hydrogen beam for a particle accelerator injection. Here we summarize some recent developments in the vacuum arc ion source. Some technical issues and future work are also introduced and discussed in the text. P6-5 [A0896] Formation of streamers in a point‐to‐plane gap filled with different gases at both polarities in threshold and overvoltage conditions BELOPLOTOV Dmitry, LOMAEV Mikhail, TARASENKO Victor, SOROKIN Dmitry (Institute of High Current Electronics, Tomsk, Russia) Abstract: The formation of streamers in different gases is actively studied. There are different factors which determine parameters of streamers. The main ones are the electric field strength and the overvoltage level. The question of the mechanism of preliminary ionization of the gas ahead the streamer is open. Photoionization mechanism is well developed for air. However, there are difficulties in describing the formation of streamers in pure atomic and molecular gases. Aim of present work is to compare the streamer formation dynamics in nitrogen, air, and neon in threshold and overvoltage conditions. The formation of streamers in a point-to-plane gap filled with air, nitrogen, and neon under threshold and overvoltage conditions was experimentally investigated with four-channel ICCD camera. Waveforms of voltage and current pulses were registered simultaneously with shooting. Under threshold conditions, branching of streamer in nitrogen was observed. At same conditions a single large streamer was observed in air and neon. At high overvoltage, only one large streamer was observed in nitrogen, air, and neon. It was assumed that the characteristic X-ray radiation produced by runaway electrons pre-ionizes a gas ahead a streamer at high overvoltage and positive polarity. Runaway electrons pre-ionize a gas at negative one.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 P6-6 [A0951] Performance of electron cyclotron resonance ion source depending on resonance position and magnetic field configuration HAM Seunggi, LEE Yuna, CHUNG Kyoung-Jae, HWANG Y.S. (Dept. of Nuclear Engineering, Seoul National University, Korea) Abstract: Focused ion beam (FIB) is utilized for various fields which require high resolution and yield. As an ion beam source of FIB system, a plasma ion source has an advantage over conventional liquid metal ion source (LMIS) in terms of high beam current, long lifetime and utilization of various gases. Among various plasma sources, electron cyclotron resonance ion source (ECRIS) is attractive due to its capability of high-density plasma generation at low pressure. In this work, we have developed a compact ECRIS operating at frequency of 2.45 GHz. An antenna is inserted in the middle of a discharge tube made of quartz and an array of ring-shape permanent magnets is mounted outside the discharge tube for the formation of appropriate magnetic field. In this paper, we present the performance of ECRIS depending on the operating conditions, especially the position of resonance zone and magnetic field configuration near the extraction aperture. Based on the experimental results, we also discuss the optimum conditions for maximizing the amount of extracted ion beam. P6-7 [A1243] Optimization of operation parameters for a vacuum electron diode with a multicapillary carbon‐epoxy cathode. POLOSKOV Artyom, EGOROV Ivan, SEREBRENNIKOV Maksim (Tomsk Polytechnic University, Tomsk, Russia) Abstract: Procedure of a vacuum electron diode configuring is described for ASTRA-M pulsed accelerator (up to 450 kV of accelerating voltage, up to 0.5 kA of beam current, 150 ns of beam pulse duration at FWHM). The vacuum electron diode utilizes multicapillary carbon-epoxy cathode surrounded by shielding electrode. The following aspects were taken into account for optimization: spectrum of electron kinetic energies (voltage and current detectors); an energy release of the beam in the diode (calorimeter); distribution of the electron beam energy in the cross section of the beam (sectioned calorimeter); light characteristics for selected points of emission (optical system for cathode surface capture). The procedure described provides accurate tuning of the pulsed electron beam parameters for conditions of research and practical applications. P6-8 [A1816] Design of compact accelerator module of the induction synchrotron HUANG Ziping, WANG Wei (Institute of Fluid Physics, CAEP, Mianyang, China) Abstract: Induction synchrotron (IS) has been a focus of improving the intensity of high ion beams. But IS has a serious beam loss problem at the beginning of Page 101

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the acceleration caused by the mismatch of the magnetic deflection field and accelerated electric field, because the pulse voltage of the induction accelerating cavity cannot adjust quickly. The simulation of beams longitude dynamics proves that increasing the number of accelerating cavities can effectively reduce beam loss. In this paper, a compact induction accelerator module is introduced. Compared with the existing induction accelerator module of KEK, the new design can increase the number of accelerating cavities to more than 5 times in the same installation space, and the voltage top drop of the acceleration pulse has also been improved. P6-9 [A2333] Influence of background gas on ion charge, ion counts and ion velocities in pulsed cathodic vacuum arcs based on surface flashover WAN Xiang, XU Ao, CHEN Lei, JIN Dazhi (Institute of Electronic Engineering, CAEP, Mianyang, China) Abstract: Cathodic vacuum arcs have been used to provide high current ion beams for film deposition and material modification. Plasma ejects from the cathode spots into the interelectrode region. There are high energetic and multiply-charged ions in the flux. An important feature of film deposition is the relatively high kinetic energies of the generated particles by vacuum arc compared with other deposition methods as sputtering and evaporation. The bombardment of a growing film by energetic particles strongly influences the growth mechanisms and the quality of the film. In many practical cases, the discharge chamber is filled with background gas with the purpose of producing compound thin films of the cathode material and the gas species. In the paper the interelectrode plasma-gas interaction is studied in a pulsed cathodic arc with an aluminium cathode and nitrogen, argon and helium as filling gases. The ion velocity distribution and the ion charge distribution for different pressure values (a range of 10-5~10-1Pa) are obtained, using a dual energy analyzer/mass spectrometer. According to the calculation of ion mean free path, the Plasma probe is placed approximately 40mm away from the cathode spots, avoiding or reducing ion collision with ambient gas in ion expansion, and concentrating on the research of the interelectrode plasma-gas interaction. The energy distributions of ambient gas ions, whose generation is concerned to background gas pressure, are introduced. The result indicates that the interelectrode plasma is affected by the presence of ambient gas. P6-10 [A3075] Light spot of pulsed vacuum arc discharge with hydrogenated cathode CHEN Debiao, DONG Pan (Institute of Fluid Physics,CAEP, Mianyang, China) Abstract: Vacuum arc discharge with hydrogenated cathode has been used in many subjects, such as material surface modification, oil logging, and accelerator. Unlike pure metallic cathode, there is gas release during vacuum

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arc discharge with hydrogenated cathode. Obviously, there are some new phenomena comparing with pure metallic cathode. So we used magnifier lens and ICCD camera to observe the light spots of pulsed vacuum arc discharge with hydrogenated cathode. The resolution of the measurement system was about 5 m. The discharge duration was about 1 s, and the current waveform was sinusoidal. Just as hypothesis, the light spot was assembled together as a large one, unlike small ones distributing randomly in the pure metal situation. This phenomenon was caused by gas pressure at cathode spots. The gas release caused high pressure at cathode spots and made the new cathode spots stay near the old ones. So the cathode spots were continuous and the plasma was assembled, which caused an integrated light spot. Occasionally, there were two or more light spots in a single discharge, which was caused by metallic droplet. The light spot’s shapes were not affected by arc current except area. The results show that the cathode spots are continuous when the cathode is hydrogenated. P6-11 [A3100] Thermionic cathode gun for a new generation of X‐ray tubes QIN Zhen, PING Liu, CHEN Dandan, PENG Yufei, LI Jianbei, ZHAO Wei, LONG Jidong (Institute of Fluid Physics, CAEP, Mianyang, China) Abstract: The new generation of X-ray systems require multiple electron sources to replace the original mechanical structure. This article describes the physical design, manufacturing, and performance testing of a thermionic cathode gun for such use. The emission current is designed to be higher than 100mA with a pulse width of 100μs and a repetition frequency of 100Hz. The test uses a DC power supply that can provide 1.8kV anode voltage and a grid power supply with adjustable range of -60V to 200V. Computational simulation and optimization have been carried out at the design stage, including electron gun structural design and thermal design. This paper introduces the emission test results and operating conditions of the electron gun. In the test, the emission current density of thermionic cathode is higher than 11.59A/cm2 and the emission current of electron gun is higher than 553mA. The basic test results show that the electron gun in the design, manufacture and operation of all the major indicators fully meets the requirements. P6-12 [A3132] The spatial distribution of ions in a pulse vacuum arc plasma with a metal deuteride electrode ZHENG Le, DONG Pan, LIU Feixiang, LAN Chaohui, LONG Jidong (Institute of Fluid Physics, CAEP, Mianyang, China) Abstract: Vacuum arc discharge plasma is rich in ionic components, and the ions also have different spatial distributions. To study the spatial distribution of ions in a pulse vacuum arc plasma with a metal deuteride electrode, a compact magnetic mass spectrometer is designed. The experimental results show that,

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while the ion source operates at 60A-120A, metal ions mainly concentrated on the axis, but the distribution of deuterium ions is relatively more isotropic along the radial direction. The fraction of deuterium ions at the edges is greater than that on the axis. While the ion source works at higher arc current, the distribution of the ions is more isotropic. Deuterium ions are easier to reach isotropic than metal ions by increasing the arc current. P6-13 [A3348] Time‐and‐space resolved characteristics of the cathode and anode plasma evolutions in a long pulsed magnetically insulated coaxial diode ZHU Danni1, ZHANG Jun2, MENG Jin1 (1 National Key Laboratory of Science and Technology on Vessel Integrated Power System, Naval University of Engineering, China; 2. College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, China) Abstract: Time-and-space resolved characteristics of the cathode and anode plasma evolutions in a long pulsed (260 ns) magnetically insulated coaxial diode with an edged graphite cathode and a stainless steel anode are investigated. The evolution of the cathode and collector plasmas in magnetically insulated coaxial diode was firstly visible on the front view at the same time through a fast framing camera. The average radial expansion velocity of the cathode plasma was about 1~4 cm/us in this diode under an axial guiding magnetic field. The outward velocity of the cathode plasma was close to the inward one. Due to the suppression of the axial magnetic field, the radial velocity becomes smaller in stronger magnetic field. The anode plasma inside the collector axially expanded much faster in the outward directions than in the inward directions, a very distinct and experimentally observable phenomenon described in this article. P6-14 [A0187] The energy loss for an energetic ion beam around Bragg peak in plasmas WANG Guiqiu, LI Yujiao, YI He, WANG Yaochuan, LIU Dajun (Dalian Maritime University, China) Abstract: Energy loss of ions propagating in plasmas has been a subject of research for several decades because it has lots of applications in many different fields of science such as inertial confinement fusion, plasma diagnostics, and medical applications. Using intense particle beams to heat plasma has become a very important method in fusion research due to their advantages of high-energy concentrations and fast repetition rates. We will study the energy loss for an energetic ion beam in plasma by molecular dynamic simulation methods, and pay the emphasis on the influences of plasma parameters on the stopping power of an energetic ion beam for different projectile energy. Energy loss will be studied especially for the energy region around Bragg Peak.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 P6-15 [A1214] Distribution of electrons with a kinetic energy of 150‐400 keV in a cross section of a pulsed beam. POLOSKOV Artyom, EGOROV Ivan, ISEMBERLINOVA, Asemgul, SEREBRENNIKOV Maksim (Tomsk Polytechnic University, Tomsk, Russia) Abstract: Study of spatial distribution for electrons of various kinetic energies is presented. Electron beam pulse is generated by ASTRA-M accelerator (up to 450 kV of accelerating voltage, up to 0.5 kA of beam current, 150 ns of beam pulse duration at FWHM). It is shown that the diameter of the electron beam imprints captured by dosimetric film and sectioned calorimeter reduces with an increase in average energy of electrons. Electric field analysis of accelerating gap is presented as a hypothesis for explanation. The aspect described is important for practical applications of pulsed electron beams. P6-16 [A1325] The fast‐pulse repetitive frequency emission characteristic of high current carbon nanotubes cathode XIANG Fei (Science and Technology on High Power Laboratory, Mianyang, China) Abstract: With the development of high power microwave technology, the demand electron beam repetition frequency, current density, response time and emission uniformity is higher and higher. Carbon nanotubes (CNts) cathode was widely studied because of their special structures and excellent field emission characteristics. In fact, the CNts cathode is regarded as thin film cathode, the interface bonding will affect vacuum performance, stability, lifetime and repeat ability. The direct growth of CNTs may be a simple and effective means for preparing cathode. High current electron beam can be obtained for CNTs cathode by plasma emission. Graphitizing CNTs films were synthesized on the surface of Cu substrate by pyrolysis of iron phthalocyanine. The tubes’ length was about 10~20μm, the tubes’ diameter was about 20 ~ 50nm.If electron energy was up to 1MeV and the pulse upward gradient was about 60kV/ns, for CNTs cathode the emission beam intensity was up to 15kA and the peak bundle density was about to 1kA/cm2, the emission stability repetitive frequency was up to 50Hz, SEM images before and after the cathode emission indicated that the emission mechanism was flashover plasma and the repeated emission lifetime was far more than 1000 shots, because the Cathode surface morphology was complete and no desorption occurred. The plasma speed was 3.9cm/µs in proximity. P6-17 [A1376] Study of the intense relativistic multi‐beam WANG Ganping1, LI Chunxia2, LI Fei2, JIN Xiao2, HUANG Hua2, 2 LIU Zhenbang (1. Graduate School, CAEP, Beijing, China; 2. Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics, CAEP, Mianyang, China) Page 105

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Abstract: Relativistic multi-beam klystron is an effective microwave device for its low space charge effect with high current. With high current multi electron beams, the output power can be up to the order of gigawatt. In this paper, the development progress of the intense relativistic multi-beam is introduced. In addition, taking into account the effect of the mirror-image beams, an analytical theory for the drift of multi-beam in the annular waveguide is presented, which can make quantitative predictions for the angular drift displacement of the multi-beam. To decrease the current loss, a new guiding system named composited magnetic system is proposed. Numerical analyses show that the transmission efficiency is higher than the previous case due to the vanishing electron emission from cathode stick and rod. At present, the feasibility of composited magnetic guiding annular relativistic electron beam has been proved by experiments, and the study of multi-beam is in progress. P6-18 [A1659] Electron‐optical systems for planar gyrotrons ZASLAVSKY Vladislav, GLYAVIN Mikhail, KUFTIN Andrey, MANUILOV Vladimir (1. IAP RAS, Nizhny Novgorod, Russia; 2. Nizhny Novgorod State University, Russia) Abstract: The methodology of designing an electron-optical system (EOS) that forms ribbon helical electron beams (HEBs) for high-power high selectivity gyrotrons is developed. As an example, we considered the EOS for a 140-GHz gyrotron operating at the first harmonic of the cyclotron frequency with an accelerating voltage of 50 kV, a beam current of 30 A, and a magnetic field compression of 36. A planar geometry of the magnetron-injection gun (MIG) is suggested. The adiabatic theory of MIGs modified for the case of planar geometry of EOS is used for preliminary estimations of MIG parameters. 3D numerical simulation of the HEB properties based on the CST STUDIO SUITE code is performed to find the optimal configuration of a planar MIG. The main factors that affect the HEB quality are considered. It is shown that a ribbon HEB with a pitch-factor of 1.3 and velocity spread not exceeding 25%–30% can be formed. Calculation of the beam-wave interaction with the obtained HEB parameters proved that a high output power with a sufficiently good efficiency of about 20% can be reached. Simulations show the feasibility of the experimental implementation of a novel planar EOS and its use in short-wave planar gyrotrons. P6-19 [A1847] High energy X‐rays and its shielding design on 3MV intense pulsed electron beam diode YANG Hailiang (Northwest Institute of nuclear technology, Xi’an, China) Abstract: The high energy X-rays has undergone a transformation in recent years with the developing of interest in compact, high intensity pulsed power driven electron beam sources. The X-rays requirements and the choice of a consistent driver source determine the accelerator parameters, which can be met by demonstrated fast linear transformer driver (FLTD). The structure of Page 106

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3MV intense pulsed electron diode driving by FLTD was designed. The optimization parameters of tantalum and tungsten anode targets were calculated. The energy spectrum, angle distribution and dose of X-rays producing by diode with different structures and materials were given. The escape electron energy spectrum and angle distribution were also reported. For the 3-MV diode voltage, 1-MA electron beam current, 120ns time width，the dose of high energy X-rays at 1m was ~3000rad in the forward direction(0°). The shielding structure and parameter of X-ray producing by intense pulsed electron beam diode were proposed. P6-20 [A1922] The characteristics of anode plasma expansion in rod‐pinch diode GENG Lidong, XIE Weiping, YUAN Jianqiang, WANG Minhua, CAO Longbo, JIANG Jihao, HE Yang, MA Xun (Institute of Fluid Physics, CAEP, Mianyang, China) Abstract: The rod-pinch diode is a cylindrical pinched beam diode that generates an intense pulsed small diameter bremsstrahlung source for flash radiography. The intense electron beam is generated from cathode by explosive electron emission. In this process, the plasma is formed on the cathode surface due to the supply of the high voltage pulse. The anode plasma is produced when the intense electron beam bombards the anode, and the energy deposited by electrons is large enough to heat the surface temperature to a few hundred degrees. The radial expansion of electrode plasma shortens the gap between the cathode and anode. To understand the gap closure mechanism and study the plasma expansion velocity in the ML phase, we discuss a series of rod pinch diode experiments with various ratios of cathode and anode diameters to predict the plasma expansion velocity of anode. In this work, the diode consists of a 1.5 mm diameter tungsten anode rod that extends through the annular cathode 10mm. Four ratios of cathode and anode diameter are studied using the experiment and theory. We compared the diode current obtained in the experiment with critical current of ML phase for different ratio of cathode and anode diameters, and concluded the plasma expansion velocity. The experimental results indicate that the ratio is more than three times at end of the ML phase. This behavior is attributed to the closure of the gap during the expanding electrode plasmas. The results reveal the dynamic characteristic of the anode plasma velocity. For shot 10829, the anode plasma velocity is more than ~2.5cm/μs at the beginning of the ML phase, but this velocity slows down to ~0.5cm/μs at the end.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 P6-21 [A2702] Energy evaluation of pulsed heavy ion beam in bipolar pulse accelerator TERADA Satoshi, HONOKI Tarou, YAMAMOTO Kouhei, ITO Hiroaki (University of Toyama, Japan) Abstract: We have developed a new type of pulsed ion beam accelerator named “bipolar pulse accelerator” for improvement of the purity of the intense pulsed ion beam. In order to confirm the principle of the accelerator, a double coaxial type bipolar pulse generator and a prototype of the experimental system were developed. The bipolar pulse generator consists of a Marx generator and a pulse forming line (PFL) with a rail gap switch on its end. The system utilized a magnetically insulated acceleration gap and operated with the bipolar pulse. A coaxial gas puff plasma gun was used as an ion source, which was placed inside of the grounded anode. Source plasma was injected into the acceleration gap. When the bipolar pulse was applied to the drift tube, the ions were successfully accelerated from the grounded anode to the drift tube in the 1st gap by the negative pulse of the bipolar pulse. The ion energy was in reasonable good agreement with the acceleration voltage, i.e., 1st pulse (negative pulse) voltage of the bipolar pulse. We are doing experiments on the two-stage acceleration of pulsed ion beam with the bipolar pulse accelerator. P6-22 [A2082] A study on ultra‐fast optical diagnostics of IREBs explode emission process WANG Tengfang1, PENG Shuming1, JIN Xiao2, HUANG Hua2, LIU Zhenbang2, HE Hu2, GE Yi2, DENG Derong2, WANG Ganping2 (1. Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Fudan University. Shanghai, China; 2. Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics, CAEP, Mianyang, China) Abstract: The intense relativistic electrons beam cathode is one of the important components of the high power microwave system. Its performance has always been a focus of research. The commonly used intense cathodes are explosive emission cathodes, the electrons are obtained from the plasma formed on the surface of the cathode. Therefore, the study of cathode plasma properties has always been an important part of the intense cathode research. This article uses an ultra-fast camera to perform optical diagnostics of conventional graphite cathodes and carbon/carbon composite cathode plasmas. The camera has a minimum exposure time of 5 ns and 12 channels. The delay time between each channel can be set arbitrarily. The images of the formation, expansion, and attenuation of the plasma during the entire explosion of the cathode can be obtained, with a very high time resolution. In the experiment, photos were taken on the front and side of the cathode respectively, and set the delay time for each channel to obtain 12 plasma emission images at different time. Uniformity of the intense electrons beam can be obtained by analyzing the spatial distribution of plasma luminescence. This Page 108

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result combined with the microscopic appearance of the cathode surface can be used to analyze the intense electrons emission characteristics of the cathode. The plasma expansion rate and attenuation rate can be calculated through image processing means by analyzing the edges of the plasma at different time, which relates to beam width and cathode re-frequency characteristics. Compared with the plasma expansion rate which is obtained by theoretically calculating the diode diversion coefficient, the result of the plasma expansion rate calculated by the optical diagnostic method is consistent with the actual situation. This research establishes an important experimental foundation for further in-depth study of the mechanism of intense cathode electron emission.

Oral Session 10 - Compact and Repetitive Pulsed Power Systems - Session Chair: MANKOWSKI John (BALL ROOM 1#)[15:00-17:30] 15:00 O10-1(Invited) [A0704] Design of the magnetically insulated inductive adder for 50‐stage LTD module ZOU Wenkang1, CHEN Lin1, WANG Meng1, ZHOU Liangji2, LIU Laqun1, GUO Fan1, DENG Mingmeng3, ZHU 3 1 1 Jianping , XIE Weiping , DENG Jianjun (1. Institute of Fluid Physics, CAEP, Mianyang, China; 2. University of Electronic Science and Technology of China; 3. Institute of Mechanical Manufacturing Technology, CAEP) Abstract: The linear transformer driver (LTD) is one of the most promising technologies for developing pulsed power facility for fusion or other high energy density physics research. LTD uses low capacitance, low inductance components, therefore, the current rise time of output pulse from the basic discharging unit is as fast as 100 ns or even smaller. However, due to low outputting voltage of a single stage, inductive voltage adder (IVA) technology is necessary to sum the stage voltage up and restrict the high voltage inside. In CAEP, an LTD module for fusion scale facility is being developed, in which 50 identical MA LTD stages are connected in series to achieve 4.5 MV/1 MA output on a matched load. The IVA of the module is magnetically insulated to minimize the inductance in transmission line. The module, which is presently named M-50, is the first full scale module for a fusion accelerator of the world. Now it is in step-by-step testing. In this presentation, the physical and engineering design for the 19.2-m IVA system will be presented.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 15:25 O10-2 [A0307] Study of thermal effects in high magnetic field massive coils with modified surface conductivity and new experimental approach SPIRIN Alexey V., KRUIKOV Vasiliy I., BOLTACHEV Grey Sh., PARANIN Sergey N., KOLEUKH Dianna S., RUSSKIKH Pavel A. (Institute of Electrophysics UB of RAS, Yekaterinburg, Russia) Abstract: The work concerns realization of a conductor with monotonically changed conductivity with deep and theoretical description of magnetic and thermal effects in such systems under high magnetic fields. It is important for developing tool coils (inductors) exploited in magnetic pulsed technologies, e.g., hard metals welding. Magnetic field diffusion, taking thermal effects into account, inside an inductor material with an inhomogeneous initial electrical conductivity and associated thermomechanical stresses was analyzed by numerical solution of the problem. Thick-walled cylindrical single-turn coils of steel were used as model inductors for theoretical analysis and experimental testing. Steel is considered to be a perspective inductor material due to its low cost, high strength, and applicability to surface modification. Monotonically changed specific resistance of steel was realized by saturating the steel surface with dopant chromium atoms (pack chromizing technique). But specific application of steel for inductor production leaves open the questions on its electrical properties and inductor durability. The study of electrical properties, mechanical and microstructural characteristics of structural steels with modified surface layer changing with depth are the integral parts of the study. The detailed results will be highlighted in extended paper. Financial support: State task, RFBR, and RAS program projects (No. 0389-2015-0025, 16-08-00919, 18-2-2-8). 15:40 O10-3 [A0625] Developing compact and repetitive pulsed power sources based on inductive pulse forming lines YU Liang, SUGAI Taichi, TOKUCHI Akira, JIANG Weihua (Nagaoka University of Technology, Japan) Abstract: Some new voltage adding schemes using inductively charged transmission lines have been proposed and experimentally demonstrated. These methods use current charging to replace traditional voltage, which means energy storage unit is inductor of transmission line instead of capacitor. In addition, the closing switch is replaced by an opening switch as the main control switch, in these methods. These new circuit topologies can be called Inductive pulse forming lines (Inductive PFLs). In this paper, first of all, three different circuit topologies are discussed, which are type A inductive-PFL, type Page 110

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B inductive-PFL, and inductive Blumlein line. The experimental results show that these methods can output rectangular waves, unlike pure inductor energy storage, which only output exponential wave. Secondly，these new inductive energy storage methods can get higher voltage output through voltage adding. The type A used time isolation as transmission-line-transformer (TLT) to get output voltage adding with multiple PFLs, while the type B combined the functions of PFL and TLT into one set of transmission lines by magnetic core isolation. The inductive Blumlein line is used to achieve the output voltage adding by simple stacking PFLs and switch series isolation. These methods have advantages and disadvantages, which are believed to have certain significance in nanosecond compact and repetitive pulsed power generation. 15:55 O10-4 [A1026] Simulation and experimental research on pulse forming networks based on MLCC WANG Limin1, LIU Qingxiang1, HUANG Wenhua2, ZHU 1 1 Yahui , WANG Qingfeng (1. School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, China; 2. Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi¡’an, China) Abstract: Pulse forming networks based on MLCC were studied. The pressure and discharge efficiency of MLCC were tested. Four PCB pulse forming networks based on MLCC were designed. The circuit simulation of pulse forming network was carried out using PSpice software considering the distribution inductance and resistance. The results show that, the distribution resistance will cause the top drop on the output waveform of pulse forming network. Three-dimensional modeling and numerical simulation of pulse forming networks in four different structures were performed by the method of transient field simulation. Finally, a discharge experiment was conducted on pulse forming networks in four different structures; the new fast thyristor was used as the discharge switch. With charging voltage 4kV, the simulation results were verified by comparison. 16:10 O10-5 [A1056] New design and development for an ultrahigh‐voltage short pulse switch power supply TAKAYANAGI Tomohiro, UENO Tomoaki, HORINO Koki (J-PARC/JAEA, Tokyo, Japan) Abstract: An ultrahigh-voltage short pulse switch instead of a thyratron switch using SiC-MOSFET of operating at high withstand voltage, low loss, high frequency and high temperature has been designed and developed. This switch has a radially symmetric type of a module switch which does not cause level fluctuation due to the timing jitter by equalizing the circuit length independently of the Page 111

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number of semiconductor switches. By connecting these modules hierarchically in series, it is possible to cope with high voltage and current output of 40kV/2kA or more. The design and preliminary test results are presented here. 16:25 O10-6 [A1217] Design and experimental study of compact pulse power driver WANG Peng, TAN Jie, LUO Min (Institute of Applied Electronics, CAEP, Mianyang, China) Abstract: The annular pulse forming line which uses BaTiO3 material is developed. Material characteristics and the influence on the electric field when the manner of the electrode silver plated of the pulse forming line were analyzed and researched, and the electric field of the pulse forming line has been advanced via epoxy resin sealing simultaneity. A 37-stage compact Marx generator is designed based on the pulse forming line. The electric field intensity distributions of the configuration with the system were simulated. According to the results of the simulation, the electric field of the configuration equals that of the coaxial design, which gives an optimized contour dimension. In experiment, when the PFL is charged at ±20 kV, the output voltage is more than 680kV and the pulse width is about 65 ns on the matching load. 16:40 O10-7 [A1247] Development of solid‐state LTD using silicon carbide MOSFETs FENG Yu, TSUKINOSUKI Ikemoto, TAICHI Sugai, AKIRA Tokuchi, JIANG Weihua (Extreme Energy-Density Research Institute, Nagaoka University of Technology, Japan) Abstract: Solid-state LTDs are being developed for industrial applications. Switching device is one of the most important components of an LTD. It directly affects the LTD performance including the output voltage, current, rise-time, and repetition rate. In this research, we are studying the characteristics of silicon carbide MOSFETs for applications to solid-state LTDs. Samples of different models of commercially available SiC-MOSFETs have been compared with the Si-MOSFETs that we have used so far on LTD. Furthermore, prototype of LTD modules based on SiC MOSFETs has been tested and evaluated. The trade-off between the system performance and the components cost is the key development issue in this study. The experimental results will be reported in detail at the conference.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 16:55 O10-8 [A1350] A novel compact high power Marx generator system with hundreds‐nanosecond quasi‐squared output pulse and tens of nanoseconds low output jitter in rep‐rate LI Fei1, SONG Falun1, ZHU Mingdong2, JIN Xiao1, GAN 1 1 Yanqing , GONG Haitao (1. Institute of Applied Electronics，CAEP，Mianyang China; 2. China State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin, China) Abstract: A high power Marx-type generator system is developed based on newly designed pulse forming module 2-branch pulse forming circuit and circular-electrode-mounted rep-rate gas switch. Compared to traditional Marx generator that can only output double-exponential pulse profile, the output waveform is improved to quasi squared shape with hundreds nanosecond in width, while the size has been reduced considerably. A novel pulse forming module is designed based on Guillemin type C pulse forming network, in which the number of branches have been developed to the lowest 2 to reach a more compact design. The pulse forming module can generate 180 ns quasi-squared waveform directly via careful circuit parameters adjustment. Cylindric gas switch that composed of planar trigger electrode, circular discharging electrode, and plexiglass support whose inner surface shows periodic uneven topography, is developed to reach low jitter and high working stability. The as-designed pulse forming modules and gas switches are mounted into a special container in turns to construct a 20 stage Marx-type high voltage pulse generate unit, which is the most important part of the Marx generator system. The pulse generating unit shows high output energy density of 3.8 kJ·m-3 with output voltage of 900 kV. The system could work at pulse repetition intervals mode continuously at 30 Hz for 300 times and 10 Hz for 1100 times, while its output pulse power keeps at 16 GW and output jitter as low as 10 ns in size not more than 1.5 m-3. The output waveform profile shows rare difference. This research has further developed the practical application of pulse forming network to the lowest 2 branches, and low output jitter of gas switch to 10 ns at rep-rate of 30 Hz, which is considerably helpful to promote the general application of pulsed power technology.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 17:10 O10-9 [A1553] 40‐kV, 300‐A, 3‐kHz high‐voltage compact solid‐state pulsed power modulators SONG Seung-Ho, CHO Chan-Gi, PARK Su-Mi, CHO Hyun-Bin, RYOO Hong-Je (Chung-Ang University, Korea) Abstract: This paper describes development of the 40-kV 300-A 3-kHz high voltage solid-state pulsed power modulator (SSPPM) for general purpose applications. The solid-state pulsed power modulator is upgraded from the power cell-based 40-kV, 150-A and 3-kHz solid state modulator proposed in 2012, and implemented in two configurations: two IGBTs in parallel and a large capacity IGBT. The basic structure and operation principle are the same. To increase the output current capacity, a total of 48 switches were replaced with high current rating IGBTs, and the gate driver was also optimized. In addition, a comparative study is presented with cells with increased current capacity by adding a discharge switch in parallel to each cell, focusing particularly on the reliability of pulse output characteristics. Finally, experimental results with resistive load and gas treatment reactor have proved the reliability of the modified solid-state pulsed power modulator.

Oral Session 11 - Antennas - Session Chair: QIAN Baoliang (INTERNATIONAL HALL) [15:00-17:30] 15:00 O11-1 [A0121] Analysis of wide angle scanning of high power microwave waveguide slot array antenna with grooves MENG Fanbao, XIE Ping, MA Hongge (Institute of the Applied Electronics, CAEP, China) Abstract: In this paper, a subwavelength choke groove structure is symmetrically loaded at both sides of each longitudinal slot of the HPM waveguide array. The choke grooves not only reduce the mutual coupling between the rectangular waveguide but also improve the capability of wide-angle scanning of array by modulation of the surface wave propagation of array. The effectiveness of the proposed surface grooves is verified by numerical simulation and experiment. It is found that the scanning angle with the gain of array decreased 3dB without choke groove structure is only 24°, and it is 37° for the array with surface groove structure. The influences of groove parameters on the mutual coupling and wide-angle scanning performance are discussed. The physical mechanism of the corrugated structure is investigated. The groove proposed in this letter does not adopt the choke mechanism, the best depth of groove Page 114

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is not λ/4 but 0.17λ. It is groove cavity resonance and coupling between grooves and slots that determine the distribution of surface electromagnetic resonance mode. Furthermore the power-handling capacity of array is also analyzed. The result of experiment shows that power-handling capacity of array antenna can reach 957 MW. 15:15 O11-2 [A0746] High power radio frequency dummy load using liquid absorber RAHIMI Ghasem1, RAHIMI Ghasem1, YOUSEFIYAN 2 Mohsen (1. Azad Univercity,Tehran, Iran; 2. Sharif Univercity ) Abstract: This paper reports on the results of design, simulation and construction of radio frequency dummy load at the operating frequencies range of S and C Band. An efficient radio frequency dummy-load structure is designed as a two-port device with an impedance that matches the characteristic impedance of a radio frequency source and a given transmission line. The other port of the dummy load is used for analysingfrequency and power absorption. This dummy load design is successful for operating with up to several hundred megawatt of RF power at about μs pulse width and several repetition rate in the S and C band frequency. Important parameters of a dummy load are its VSWR and power handling capacity. To have a wide band dummy load we designed with three-layered wide-aperture dummy load filled with water or ethanol-based working liquid. As a result of the calculations the reflection coefficient of the TE11 electromagnetic wave from the dummy load at normal incidence was obtained. Using the simulation results, the frequency dependent transmission and reflection coefficients of the dummy load were calculated for normal incidence of a monochromatic plane at the bandwidth. The results of dummy load structure simulation optimization are very useful for estimations of the optimal parameters previously obtained in the simplified two-dimensional model. Then we use the optimal parameters to construct high power radio frequency dummy load. This dummy load is designed and tested for about kilo watt average input RF power with very low input reflection coefficient (S11 ≤ -15 dB) and 8% bandwidth at center frequency of 3 GHz. 15:30 O11-3 [A0943] Validation studies for two design approaches of TM01 to TE11 mode converter for high power applications TANC Zafer, TIMUR Busra, DEMIR Simsek (Middle East Technical University, Turkey) Abstract: The aim of this study is to validate two of the optimum TM01 to TE11 mode converter designs in terms of conversion efficiency and bandwidth for the usage of high power microwave Page 115

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applications. First design changes the propagating mode by semi-circular waveguide sections; whereas, the second one provides the requirement by metallic inserts. Both of the converters are designed at a centre frequency of 2.9 GHz, they are capable of operating over 2.8-3.0 GHz band; furthermore, the simulated designs have at least 90% and 98% efficiencies along that operating band, respectively. These results will be compared to the experimental ones which will be obtained when the productions of both converters have been completed. 15:45 O11-4 [A2003] Design of a compact mode‐converting antenna for high‐power microwave applications SUN YunFei, HE Juntao, YUAN Chengwei (National University of Defense Technology, China) Abstract: A compact mode-converting antenna operating at Ku-band for high-power microwave (HPM) application is proposed in this paper. This antenna can radiate azimuthally symmetric modes such as TE01 circular waveguide mode and coaxial transverse electromagnetic (TEM) mode directly and produce a pencil beam. The antenna is composed by a conical horn and a mode conversion lens which can be also called transmit array (T-A). The proposed T-A consists of numerous elliptical-hole elements, a full transmission phase range of 360°can be achieved when the microwave passes through the T-A. An antenna with the length of 369.2mm and an aperture diameter of 340mm operating at 14.25 GHz is designed, which has a gain of 26.1 dBi and reflection loss less than -20 dB. The simulated results show that this antenna has a power handling capacity of more than 500 MW. 16:00 O11-5 [A2187] Design of a horn feed for a dual‐band radiation system YU Yuanqiang, FAN Yuwei (National University of Defense Technology, China) Abstract: In this paper, a horn feed for a dual-band radiation system is investigated numerically. The horn feed can combine the dual-band TE11 (1.775 GHz and 3.175 GHz) mode microwaves after the dual-band mode converter, then the microwaves can be radiated by the conical horn antenna into the air easily. The horn feed has high transmission efficiencies of the TE11 modes that are 99.6% at 1.775 GHz and 99.2% at 3.175 GHz, respectively. It produces the total return loss of 0.4% at 1.775 GHz and 0.6% at 3.175 GHz. The maximum electric field strength is 9.0 V/cm and 10.0 V/cm, respectively. The power handling capacity is 6.0 GW at 1.775 GHz and 4.9 GW at 3.175 GHz, respectively. It can inhibit the high order modes that are stimulated because of the structural breaks, and it Page 116

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has a great far-field radiation pattern at each band. 16:15 O11-6 [A2326] A new type of high power active phased array antenna ZHANG Muqun, YUAN Chengwei, ZHANG Qiang (National University of Defense Technology, China) Abstract: Based on actual demand, a metal high power antenna unit is designed. There is extra tightly coupled structure in each unit cell to facilitate the ability of far-field coupling between arrays. Meanwhile, a variety of feed structures are designed, so it is more easy to cooperate with different feed forms. Finally, the standing-wave ratio of antenna is lower than 2 when it works between 0.5-2GHz,.The size of the antenna unit is about 54% of the wavelength in high frequency, which has the characteristics of miniaturization. 16:30 O11-7 [A2545] All‐metal polarization conversion metamaterial lens for high power microwave applications ZHAO Xuhao, YUAN Chengwei, ZHANG Jiande, ZHANG Qiang (National University of Defense Technology, China) Abstract: A novel metamaterial lens for polarization conversion made by all-metal is presented in this paper. The proposed metamaterial lens is composed of numerous polarization conversion units consisting of a split-ring aperture and a rectangular aperture. The phase of the input microwave can be manipulated by the polarization conversion unit. Simulation results show that a full transmission phase range of 360° can be achieved for a transmission efficiency better than -99.6% at 14.25 GHz by rotating the unit. Besides, the metamaterial lens can radiate a gain-enhancing wave in the desired direction with the polarization conversion among linear, right-handed circular and left-handed circular polarization. Furthermore, the power handling capacity of the all-metal lens in this paper is over 2 GW, which can be applied in the field of high power microwave (HPM). 16:45 O11-8 [A2757] Design of a beam‐steerable array antenna for high power microwave applications YU Longzhou, YUAN Chengwei, HE Juntao, SUN Yunfei, ZHANG Qiang (National University of Defense Technology, China) Abstract: A beam-steerable array antenna has been presented in this paper. The antenna system is composed of a radial line helix array and a dielectric lens layer. A C-shaped slot is applied to the Page 117

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radial line array, which is used as the feeding source, and the radial line array realizes a circularly polarized wave (CPW) radiation and a 22 degree beam deflection. To rotate the radial line array and the dielectric lens synchronously, a beam-steerable in the range of ±45 degrees is realized. The entire arrangement of the antenna system is capable of handling high power according to the simulation results. 17:00 O11-9 [A0745] Carbon‐nanotube‐doped copper explosive emission cathode 1 1 2 2 WU Ping , SUN Jun , YANG Wenshu , WU Gaohui (1. Northwest Institute of Nuclear Technology, Xi’an, China; 2. Department of Material Science and Engineering, Harbin Institute of Technology, Harbin, China) Abstract: Explosive emission cathodes (EECs) are widely used in high power microwave (HPM) systems. Their emission properties have prominent influence on the conversion efficiency and stability of HPM generators. The carbon nanotube (CNT) cathode, due to its low emission threshold, has attracted much attention in recent years. However, under the circumstance of explosive emission, the conventional CNT cathode usually presents a short lifetime because of the shedding of CNTs from the metal substrate caused by heating. This paper describes a CNT-doped copper EEC which avoids this disadvantage. This novel cathode is manufactured with the pressure infiltration method. By doping CNTs in the copper substrate, the cathode emission uniformity can be improved in comparison to the normal copper cathode, and the cathode lifetime can be prominently lengthened relative to the conventional CNT cathode. In HPM generation experiments based on a relativistic backward wave oscillator, the CNT-doped copper cathode presents good emission properties, leading to higher conversion efficiency and larger microwave duration than the normal copper cathode, and meanwhile, its lifetime exceeds 3 × 105 pulses under the condition of voltage ~ 1 MV and current ~ 10 kA, which is much longer than that of the copper cathode.

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Oral Session 12 - Z, X-Pinches and Imploding Liners; High Power Diodes - Session Chair: XIE Weiping (BALL ROOM 3#)[15:00-17:30] 15:00 O12-1(Invited) [A0227] Initial behavior and preconditioning of wire array Z pinches WU Jian1, QIU Aici1, SUN Fengju2, LI Mo2, LU Yihan1, LI Xingwen1, SHI Huantong1 (1. Xi'an Jiaotong University, China; 2. Northwest Institute of Nuclear Technology, China) Abstract: Initial behavior of the wire array Z pinches, including the core-corona structure formation, and the inhomogeneous ablation were investigated. The plasma density distributions were measured using laser probing from both the radial and end-on directions. Various methods, including fast rising current, insulating coating, and positive electric field, were applied to precondition the initial behavior of the wire array, and their influences on the wire array were investigated. In particular, a method using a fast-rising and tailored prepulse current was proposed, and the facility “Qin-1”, which coupled a ~10 kA 20 ns tailored prepulse generator with a ~ 0.8 MA 160 ns main current generator, was setup. The tailored prepulse current could appropriately preheat various wire arrays to prevent formation of core-corona structures. And the implosion of a gasified aluminum-wire array showed no ablation phase and allowed all array mass participating in the implosion. The seeds for the MRT instability formed from the inhomogeneous ablation were suppressed. However, the magneto Rayleigh-Taylor instability during the implosion was still observed. Further researches on the generation and development of the magneto Rayleigh-Taylor instabilities of this gasified wire array are needed. 15:25 O12-2 [A0106] The suppression of core‐corona structure for aluminum wire array and its influence on the implosion dynamics under a current of mega‐ampere QIU Aici, ZHANG Jinhai, WANG Liangping, LI Mo, SUN Tieping, CONG Peitian, LI Yang, SHENG Liang, WU Hanyu (1. Department of Engineering Physics, Tsinghua University, China; 2. Northwest Institute of Nuclear Technology, China) Abstract: The core-corona structures, namely the dense wire core in atomic state surrounded by plasma with high temperature and low

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density, are widely observed in wire array Z-pinch experiments under a current of mega-ampere for the early breakdown of each metal wire. The corona plasmas are accelerated toward the array axis by the global J×B force. The wire cores, as well as the plasma streams, both exhibit a characteristic millimeter scale modulation along the axis. The wavelength of this modulation just depends on the wire material according to experiments on many different current-scale generators (~0.5mm for Al and ~0.25mm for W). These modulations are also the initial perturbations of the following array implosion, which will aggravate the development of plasma instability. In order to suppress the core-corona structure, two-stage wire array experiments has been carried out on Qiangguang-Ⅰgenerator (1.3MA,~80ns). Two-stage array consisted of two parts: the top load wire array and the lower inverse wire array. The adding inverse array was to be a shut-down switch to ensure the vaporization and uniform expansion of aluminum wires in load array during the pre-pulse current before current switch and the implosion of load array during the main pulse current after current switch. The load aluminum wires with a diameter of 15μm were completely vaporized by adjusting the parameter of two-stage array and regulating the pre-pulse of the generator. The results showed that the shutdown time of inverse array depended on wire number. The shutdown time was 40ns after the start of main current when two aluminum wires were placed in inverse array, which ensured that there were still enough time during main current for load array to implode and radiate X-rays. The vaporized wire cores expanded uniformly along the axis with a smooth boundary and the average wire diameter was 1.8~1.9mm. The vaporized wire cores were ionized rapidly after the shutdown of inverse array. The perturbations of plasma instability were firstly observed at the boundary of vaporized core and developed rapidly after the start of implosion. The average wavelength of these perturbations was 600~650μm. The precursor plasma was barely observed on the array axis in optic images. Considering the waveform of X-rays and the main current, the implosion of the vaporized load array tended to zero-shell model. Nevertheless, there were still some fractions of plasma being left down at the initial position to lead the second implosion for the fast development of plasma instability in implosion, which resulted in the double peaks of X-rays. The suppression methods of the implosion instability will be further studied and explored in future.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 15:40 O12-3 [A1085] Large‐scale instabilities and its suppression during skin electrical explosion CHAIKOVSKY Stanislav1, VANKEVICH Vladislav2, DATSKO Igor2, LABETSKAYA Natalia2, ORESHKIN 3 2 2 Evgeny , RYBKA Dmitry , SHUGUROV Vladimir (1. Institute of Electrophysics of the Ural Division of the Russian Academy of Sciences, Ekaterinburg, Russia; 2. Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia; 3. P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia) Abstract: The pulsed power MIG generator (current amplitude up to 2.5 МА and current rise time of 100 ns) was used to investigate the growth of large-scale instabilities during skin electrical explosion of metal cylinders with diameter of 1-4 mm. The plasma behavior and the instabilities arising at the conductor surface were recorded with a four-frame optical camera (frame exposure of 3 ns). Large scale plasma perturbations were registered as strata with wavelengths of 0.02–0.2 cm that arise approximately 100 ns after the current starts to flow through the conductor. Ti-coating of the copper conductors allows one to delay surface plasma formation and suppress the growth of large-scale instabilities. Experimental results will be presented and discussed. This work was supported by the Russian Science Foundation, Grant No. 16-19-10142. 15:55 O12-4 [A2679] Augumented Tokamak LI Ge (Institute of Plasma physics, Chinese Academy of Sciences, China) Abstract: An augumented tokamak is suggested here for improving the fusion performance of plasma pulse  the fusion-triple product and the discharging time in a superconducting machine, such as Experimental Advanced Superconducting Tokamak (EAST), ITER and China Fusion Engineering Test Reactor (CFETR). In-vacuum primary coils are inserted within tokamak vacuum vessel for starting up the plasma pulse to its flat-top phase to save expensive volt-seconds of existing superconducting coils, which can be used to extend the flat-top phase of the expensive plasma pulse. Additional pulse power system and compatibility with superconducting coils are further considered.

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EAPPC & BEAMS 2018 / Programme Tuesday 18 September 2018 16:10 O12-5 [A2531] A tunable terahertz Cherenkov radiation from a cylindrical dielectric‐lined subwavelength array ZHANG Ping (University of Electronic Science and Technology of China, Chengdu, China) Abstract: The subwavelength metallic array will strongly support surface wave, it is a local field and can propagate along the surface of the metallic array. We employ the dielectric medium loading, so that the surface wave can be transformed into Cherenkov radiation when the Cherenkov radiation condition is satisfied. Based on this mechanism, a tunable THz radiation source is proposed. In the structure of a dielectric rod covered by subwavelength metal rings, the surface wave is excited by electron bunch on the subwavelength metal ring array, and then transformed into Cherenkov radiation in the dielectric medium rod. The working frequency is determined by the intersection of the surface wave dispersion curve and electron beam line, and can be tuned by adjusting the beam energy. The theoretical analysis and computer simulation show that this Cherenkov radiation has a wide and continuous tuning band in the THz range. With the developing of electron acceleration and focusing, this kind of radiation will become an attractive way to generate THz radiation for spectroscopic and related applications.

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Wednesday 19 September 2018

Plenary Session 3 Plenary Speaker: WANG Xinxin - Chair: SINCLAIR Mark

(BALL ROOMS No. 1 & 2#）[08:30-09:20] 08:30 [A3337] Research on Electrical Explosion of Wire in Tsinghua University WANG Xinxin (Tsinghua University, Beijing, China) Abstract: Electrical Explosion of Wire (EEW) is performed with a pulsed current flowing through a metallic wire. As the energy deposited into the wire by Joule heating increases, the wire undergoes the rapid phase transitions (solid ® liquid ® vapor ® plasma). When the wire starts vaporization, the wire resistance dramatically rises and then one of the three discharge modes (cutting-off current, restrike, breakdown) occur, depending on the wire voltage and the density of the expanded metallic vapor along the wire surface. In the different medium (vacuum, gas, liquid, solid) surrounding the wire, EEW behaves differently and thus has different applications. In this paper, we present the experimental results of EEW obtained by Tsinghua University, including EEW in vacuum for X-pinch and Z-pinch, EEW in gases for the nanopowder production and EEW in liquid for the generation of shock waves.

Plenary Session 3 Plenary Speaker: TAKAYAMA Ken - Chair: JIANG Weihua

(BALL ROOMS No. 1 & 2#））[09:20-10:10] 09:20 [A3340] Pulsed Power Technology and Advanced Accelerators TAKAYAMA Ken (High Energy Accelerator Research Organization, Tsukuba, Japan) Abstract: Evolution of modern accelerators base on the recent development in pulsed power technology is quite remarkable. Accelerators where all pulse components are driven by solid-state devices are no longer a dream. In this context, notable activities to realize the dream are going on in Japan and Korea. They will be reviewed at the conference, where the following topics are included: (1) Alternative of Thyratorn in Klystron modulators; (2) Switching device for a chopper, electrostatic injection kickers and extraction

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kicker magnet and their performance in beam experiments; (3) Switching power supply for circular induction accelerators such as an induction synchrotron and induction microtron; (4) Acceleration of a heavy ion beam employing these pulsed power devices. Details of R&D works on original devices, novel concept, and their successful demonstration/daily-use in Japan and Korea will be described.

Oral Session 13 - Compact and Repetitive Pulsed Power Systems; High Current and High Energy Systems; Theory and Simulation - Session Chair: CHAIKOVSKY Stanislav (BALL ROOM 1#)[8:30-12:30] 10:30 O13-1 [A2786] Development of chopper type MARX unit for ILC using 3.3 kV SiC devices SAWAMURA Yo1, TOKUCHI Akira2, AKEMOTO Mitsuo3, NAKAJIMA Hiromitsu3, KAWAMURA Masato3, FUKUDA 4 Kenji (1. Pulsed Power Japan Laboratory Ltd. , Japan; 2. Pulsed Power Japan Laboratory Ltd., Kusatsu, Japan; 3. High Energy Accelerator Research Organization (KEK); 4. National Institute of Advanced Industrial Science and Technology Advanced Power Electronics Research Center) Abstract: The ILC (International Linear Collider) planned klystron power supply is called a MARX modulator and generates a pulse voltage of 120 kV, 140 A, 1.9 ms and supplies it to the cathode of the multi-beam Klystron. Small size, low cost, high reliability are strongly desired for the power supply to be mounted. The prototype power supply consists of SiC MOS-FET and SiC diode with 2.4 kV withstand voltage (2 serial withstand voltage 1.2 kV elements). To further improve reliability, we report on the development of a chopper type MARX unit equipped with a 3.3 kV withstand voltage SiC devices. A part of this work has been implemented under a joint research project of Tsukuba Power Electronics Constellations (TPEC). 10:45 O13-2 [A3080] Design of high‐voltage rectangular pulse generator based on serial switches and time‐delay driver RAO Junfeng, LIU Haotian, JIANG Song, LI Zi, TANG Zhengyu (University of Shanghai for Science and Technology) Abstract: In the application of pulse power technology, capacitive loads require that the high-voltage pulses have fast front and back edges. Using multiple semiconductor switches in series to discharge high-voltage capacitors can generate high-voltage pulses. This Page 124

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paper proposes adding a group of truncation switches to obtain fast back edges. It is pro-posed to convert one driving signal into two driving signals with a delay by adding some time-delay circuits, so that only one synchronous driving circuit can be used to both the discharge switches and the truncation switches at the same time, thereby realizing the high-voltage output with an extremely simple circuit. In terms of drive control, both the discharge switches and the truncation switches adopt a synchronous drive scheme with magnetic isolation, which ensures the synchronism of switching. A Time-delay drive circuit is added to the secondary sides of the isolation transformers to ensure that the truncation switches are turned on after the turn-off of the discharge switches, thus sim-plifying the drive circuit while realizing the fast back edges. Experiments were carried out over resistive and capacitive loads with and without truncation switches. Rectangular pulses with various voltage amplitudes, pulse widths, and frequency are obtained. The experiments verified the feasibility of delayed driving and the truncation effect of the pulse. 11:00 O13-3 [A2031] Developments of a high performance, high‐current vacuum diode for HPM applications XUN Tao, SUN Xiaoliang, YANG Hanwu, LIU Lie, ZHANG Jun, ZHANG Jiande, ZHONG Huihuang (College of Advanced Interdisciplinary Studies, National University of Defense Technology, China) Abstract: As a core part, the performance of a high-current electron beam diode is inevitably essential for HPM sources. The attractive feature of these diodes are high-electric field vacuum interface, high quality high current density electron emission, and high peak thermal load collector, which are compatible with high repetition rate operations. In this paper, the developments of a high performance vacuum diode for HPM studies are presented. First, an improved coaxial high-voltage ceramic vacuum interface applied in a repetitive pulse generator was designed and tested. Key structures such as the anode and the cathode shielding rings of the ceramic insulator have been optimized to significantly reduce E-field stresses. Aging experiments with this interface were conducted in the condition of ~600 kV, ~80 ns and 1~5 Hz pulses. Second, the large-scale, well-aligned SiC nanowires were developed. The current density was on the order of 1.2 kA/cm2 at an electric field of 90 kV/cm. By comparison with polymer velvets, the SiC nanowires showed larger current amplitude, a smaller ignition delay, more uniform surface plasmas, and constant diode impedances during the pulse flattop. At last, a novel high-current beam collector based on helix cooling channels was conducted and the device can afford a transient thermal load at the level of 1012 W/m2. Experiments show that the Page 125

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collector connected to an RBWO has a potential long lifetime at 30 Hz. The whole work of this paper makes an important contribution to the practical use of HPM systems. 11:15 O13-4 [A0693] Streamers development process in mineral oil under nanosecond pulse simulated with finite‐element software WANG Qi, YAN Ping, WANG Jue (Institute of Electrical Engineering of Chinese Academy of Sciences, China) Abstract: In this paper, streamer behavior of transformer oil under nano-second pulse voltage is investigated with both experimental observations and simulation. The breakdown characteristics of pin-to-plane electrodes oil gap were investigated using the nanosecond SOS-based pulse generator SPG200 with single pulse and repetitive pulse conditions (1, 10, 100, 500, 1000Hz). A 2D positive streamer diffusion propagation model in mineral transformer oil under nano-second pulse is carried out using a finite-element method. The experimental and simulation results reveal that the breakdown electric field of repetitive pulse is much lower than that of single pulse. The streamer development process of nanosecond discharge under repetitive pulse conditions is also discussed. 11:30 O13-5 [A2352] Studies of field emission and electrical breakdown processes across vacuum gaps between metallic electrodes YAN Shengmei (Institute of Electronic Engineering, CAEP, Miayang, China) Abstract: Suppressing an electrical breakdown of vacuum gap is one of principal factors to achieve higher performance and reliability of advanced facilities, such as particle accelerators, space crafts, vacuum interrupters, etc. In the paper, the effect of stainless steel cathode surface morphology, oxidization and gas absorbed on field electronic emission in high vacuum (10−6Pa) is studied. The influence of surface morphology, adsorbed gas and oxidization of stainless steel electrode surface on the field emission current at the initiation of high voltage vacuum breakdown is presented. Since enhanced field emission (EFE) is often observed there, we have investigated the influence of surface morphology, gas adsorbed and oxides on the EFE of stainless steel by means of a field emission vacuum system (FEVS) and the field emission current was measured. The measured results show that the oxidation of stainless steel electrode surface will lead to the increase of field emission current and the gas adsorbed will induce the decrease of field emission current. At the same time, the work function of oxidized stainless steel material is theoretically analyzed and tested. The

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experiments also have been completed under different gas pressures. The breakdown voltages of the different surface cases of stainless steel electrodes were experimentally got. The experimental results are significant to evaluate the influence of surface morphology, oxidization, gas adsorbed, low pressure atmosphere on the vacuum breakdown of metallic electrodes gap. 11:45 O13-6 [A2670] Application of inverse Jiles‐Atherton model in magnetic cores with air gap and correction of its temperature characteristics ZHANG He1, LIU Yi 2, LIN Fuchang 2 (1. Huazhong University of Science and Technology, China; 2. Key Laboratory of Pulsed Power Technology (Huazhong University of Science and Technology) , China) Abstract: J-A(Jiles-Atherton) model is widely used in the description of the magnetization characteristics in alternating magnetic field by describing the hysteresis loop. Based on the decomposition of magnetization intensity in the traditional J-A model, an inverse J-A model is established, which uses magnetic flux density as an input variable. Inductors with cores are widely used in high frequency switching power supply. In order to prevent core saturation caused by AC or DC current bias, air gap is needed in magnetic cores. Air gap greatly increases the magnetic resistance of the magnetic circuit, which makes it difficult for magnetic cores to be saturated. Hysteresis loops of magnetic cores with different lengths of air gap are measured. The inverse J-A model is used to describe magnetic characteristics of magnetic cores with air gap. As the temperature rises, the thermal motion of the metal atoms increases and the magnetic domain arrangement gradually becomes disordered, so magnetic characteristics are influenced by high temperature. The influence of temperature on characteristic parameters of J-A model is taken into consideration. The revised J-A model based on temperature is proposed. 12:00 O13-7 [A2853] 2D PIC simulation of insulator surface flashover in vacuum with gas diffusion model ZHANG JIanWei, WANG HongGuang, LI YongDong, LIN Shu, LIU ChunLiang (Key Laboratory for Physical Electronics and Devices of Ministry of Education, Xi’an Jiaotong University, Xi’an, China) Abstract: A 2D PIC code with gas diffusion is built to investigate the whole process of insulator surface flashover in vacuum. The secondary electron emission avalanche (SEEA) is simulated to obtain the curves of voltage and current. Then, the influences of the voltage, the magnetic field, the elastic scattering electron and the Page 127

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back scattering electron on the SEEA are shown. Besides, the gas diffusion in two dimension is considered. Simulation result shows the gas ionization becoming the main factor to the surface breakdown, which is in accordance with the theory. Simulation result shows that the pressure doesn’t keep same in dielectric surface when breakdown occurring. The pressure in the anode is much larger than any other position in the simulation region. At last, the influence of desorption gas type is investigated. 12:15 O13-8 [A3264] Dynamic behavior of particles in dielectric liquids under DC stress XUE Qingjiang, TIMOSHKIN Igor, GIVEN Martin, WILSON Mark, MACGREGOR Scott (High Voltage Technologies Group, Institute for Energy and Environment, Department of Electronic and Electrical Engineering, University of Strathclyde, UK) Abstract: In recent years, a number of research papers have been focused on the analysis of the breakdown properties of different dielectric fluids containing with suspended small scale (micron/sub-micron) particles. These “nano-fluids” can have tunable dielectric permittivity, higher breakdown strength and better heat conduction properties. They therefore can potentially be used as liquid dielectrics in transmission/pulsed forming lines and other components in power and pulsed power high voltage systems. However, despite a number of research publications which demonstrate that nano-fluids may provide some advantages over traditional insulating liquids, the role of the added particles in modification of their dielectric properties is still not fully understood. The present paper focuses on an investigation of the dynamic behavior of two types of particles, low conductive glass bubbles (3M types K&S S32) and TiO2 (DuPont Ti-Pure titanium dioxide) particles with significantly higher electrical conductivity and dielectric permittivity, that have been dispersed in the mineral oil, OM16, and both natural, MIDEL eN 1204, and synthetic, MIDEL 7131, ester liquids. Dynamic movement of the dispersed particles has been studied using an optical microscope and a CCD camera. Conduction currents through liquids with dispersed particles were measured to study particle charging under DC stress, whose electric field strength is up to 4 kV/cm. The obtained results show that the dynamics of the dispersed particles is mainly governed by their electrical and dielectric properties, and the hydrodynamic, electrical and dielectric properties of the host fluid. A mathematical model based on the Maxwell-Wagner relaxation and dipole-dipole interaction has been developed and implemented in MATLAB software. This dynamic model takes into account both electrical and dielectric properties of the particles and the host fluid. The predictions of this model on the interactions between the dispersed particles and the fluid when the Page 128

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system is stressed with a step voltage are reported.

Oral Session 14 - High Current Accelerators; Plasma, Ion and Electron Sources - Session Chair: CARON Michel

(INTERNATIONAL HALL）[10:30-12:40] 10:30 O14-1(Invited) [A3291] R&D of LIA for radiography in China DENG Jianjun, SHI Jinshui, ZHANG Linwen, LI Jin, CHEN Sifu, XIA Lianshen, YU Haijun, HUANG Ziping, LIXin, JING Xiaobin (Institute of Fluid Physics, CAEP, China) Abstract: The research and development status of Linear Induction Accelerator (LIA) for radiography in China are overviewed. The flash X-ray radiographic images are used to obtain information on shapes, densities, and edge locations of the fast moving materials in the thick object. LIA is the optimum flash X-ray radiography source for its unique capability to provide intense beam pulse with high energy and good beam quality. To develop the flash X-ray radiographic capability of China, three LlAs have been built in recent 30 years: the LIAXF (10 MeV, 2.3 kA, ~4mm spot size) began operation at 1983, supplying a gap for the LIA-radiography in China; the Dragon-I (20 MeV, 2.5 kA,<2mm) began operation at 2003, which reached the highest level of single-frame radiography of that time; and the Dragon-II (20 MeV, 2 kA, <2mm, 3 pulses), the first multi-pulsed LIA in MHz rep-rate at the burst mode, has been used for multi-frame radiography since 20l5. In addition, some key technologies and components of Dragon-II will be introduced in this report. 10:55 O14-2 [A0391] High‐current electron beam formation under condition of far‐ahead preinitiation of explosive‐emission cathode in a magnetically insulated coaxial diode SHUNAILOV Sergei1, YALANDIN Michael1, Ul'MASKULOV Marat1, SHARYPOV Konstantin1, SADYKOVA Anna1, ROMANCHENKO Ilya2, ROSTOV 2 Vladislav (1. Institute of Electrophysics UB RAS, Russia; 2. Institute of High-Current Electronics SB RAS, Russia) Abstract: High-current beam formation in a magnetically isolated coaxial diode (MICD) during the initiation of explosive electron emission at the cathode by a short voltage pulse passing ahead of tens to hundreds of nanoseconds with respect to the main Page 129

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accelerating pulse (-150 kV amplitude, ~1 ns duration) is analyzed. The initiating voltage pulse forms a primary tubular electron beam. Unlike the effect of double pulses with an interval of up to units of nanoseconds and prepulses, in our case, the changes of the MICD electron current were more significant. In particular, with the increase of the initiating pulse advance to a certain value, the rise of the thin-walled tubular beam current to a twice maximum vacuum current for the case of an extended anode tube is recorded behind the anode neck. The achieved value is close to the current that corresponds to the matching of MICD and the supply high-voltage generator with an impedance of 44 , while in the absence of the advanced pulse (beam) the MICD impedance is not less than 100 . The current growth in the conditions of initiation is accompanied by a drop in electron energy. For the growth of the beam current with an increase in the advance time of the cathode initiation, we associate with a combination of the following factors: (1) the flight of the explosive emission plasma along the magnetic field effectively reduces the MICD accelerating gap before the arrival of the main voltage pulse; (2) after passing the primary electron beam leaves the tubular ionized channel in the residual gas, providing e-beam charge compensation. In confirmation of the role of the second factor, we observe the sensitivity of the beam current to the residual gas pressure in MICD and to the duration of the initiating beam. In addition, with the increase of the interval between pulses greater than a certain value, the decay of the main beam current begins, which is associated with the plasma recombination in the ionized region. The work was fulfilled in the frame of IEP state task No. 0389-2015-0026, supported by the RAS Program No.10, and, in part, by RFBR Grant No. 17-08-00046. 11:10 O14-3 [A1447] In‐situ magnetic field measuring system for linear induction accelerator CARON Michel1, HOURDIN Laurent 1, TOURY Martial 1, AURIEL Gerard 1, BERNIGAUD Virgile 1, MAGNAN Jerome 1, HEBERT Guillaume 2 (1. CEA , France; 2. IRELEC) Abstract: The performances of a Linear Induction Accelerator based flash X-ray radiographic machine are strongly dependent on the quality of the magnetic fields that transport the electron beam from the cathode to the target. The first radiographic axis in the joint UK France EPURE Facility at CEA VALDUC in France contains up to 72 solenoids. In order to achieve the highest standard in radiography, the 3D magnetic field maps (Bx, By, Bz) must be known and controlled over time on each individual solenoid. In this work, the development of a new system, called SIMIS, is presented. The two main objectives Page 130

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for this new measuring system were to achieve: 1- the accuracy required for both positioning and magnetic field to make sure that field maps meet the requirements of the beam dynamics; 2- the least time-consuming control by performing in situ measurement. The concept and detailed design studies prior to manufacturing are reported. Then, the main results from the experimental validation of the prototype in the Technology Development Centre at AWE in the UK and in EPURE in France are presented and analyzed. This prototyping stage has played a key role, since all the lessons learnt have been taken into account to define the final operational system which has not been manufactured yet. Finally, some examples of recent experimental achievements on the EPURE axis 1 LIA machine are shown and the benefits for the operation team are highlighted. 11:25 O14-4 [A2912] Merlin inductive voltage adder – Commissioning and optimization at AWE SINCLAIR Mark1, THOMAS Ken 1, BEECH Paul 1, THREADGOLD James 1, GOUDE David 1, HYNES Carl 1, HUGHES Adrian 1, NESBITT Jeff 1, CSRON Michel 2 (1. AWE Aldermaston ,UK; 2. CE) Abstract: AWE has been working with L3 Applied Sciences to develop its next generation flash X-ray source, the Merlin Inductive Voltage Adder. Merlin has been built, commissioned and tested in a purpose built facility at AWE, the Martin White Technology Development Centre. Commissioning and testing of Merlin has progressed through a number of phases, inactive commissioning of all systems, and then a progressive series of active commissioning tests, starting with the Marx generator through Pulsed Power Tests with a test load (the Large Area Diode) culminating with focused X-ray diode shots with the Self Magnetic Pinch Diode. This presentation will concentrate on the active commissioning tests of Merlin, detailing the results and experiences from the Pulsed Power tests and the X-ray diode optimization. 11:40 O14-5 [A0354] Characteristics of vacuum arc discharge with hydrogenated electrode DONG Pan, LI Jie, ZHENG Le, LONG Jidong (Institute of Fluid Physics, CAEP, China) Abstract: Vacuum arc ion source has many advantages such as strong ion current, small space, so it is used in many applications like material modification, accelerator, and neutron generator. Besides pure metal, cathode could be made of hydrogenated metal, which could produce and utilize hydrogen ions. Comparing with pure metal, there is one more gas release process for hydrogenated cathode Page 131

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during discharge, which would bring some different characteristics. A Scanning Electron Microscopy (SEM) was used to survey the surface morphology after just a single discharge. The results show that the cathode spots are continuous distribution though the hydrogenated electrode had many micro cracks and the cathode surface was flocculency with many gas pores. Besides, an ICCD camera with enlarger lens was used to photograph cathode spots during discharge. Unfortunately, the cathode spots’ emission light was jumbled together due to their continuous distribution. So it could only observe a single light spot. There were two or more light spots occasionally due to nearby metal droplet’s ignition. 11:55 O14-6 [A0636] Impulse‐breakdown characteristics of high‐power gas switch based on graphene cathode WANG Gang, SU Jiancang, ZHANG Xibo, LIU Sheng, PAN Yafeng (Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an, China) Abstract: The graphene cathode has the advantage of the field emission stability and intense emission ability. The graphene cathode was developed by Chemical Vapor Deposition (CVD) on copper electrodes. A new low-jitter self-breakdown gas spark switch based on this graphene cathode was put forward. The impulse-breakdown characteristics of this switch in the even electric field were studied. In the self-breakdown experiment, the gap length and the gas pressure of the switches were various. When the gap length was 5 mm and the gas pressure was 0.8 MPa, the average breakdown voltage was almost 82.9 kV, the minimum breakdown voltage was almost 80.5 kV, the voltage jitter was only 1%. In addition, compared with the case of other cathodes, the voltage jitter was obviously lower. This graphene cathode appears to be suitable for high-power gas switch and intense emission source applications. 12:10 O14-7 [A0878] Inversion of the polarity effect in nanosecond gas discharges BELOPLOTOV Dmitry1, GENIN Dmitry 1, SHTANGOVETS Dmitry 2, TARASENKO Victor 1 (1. Institute of High Current Electronics, Tomsk, Russia; 2. National Research Tomsk State University) Abstract: Great attention has been given to study of nanosecond discharges in gaps with an inhomogeneous distribution of the electric filed strength filled with different gases. Tasks set before researches are aimed to study parameters and properties of nanosecond discharges, in particular switching characteristic. It is known that the polarity of the voltage pulse affects the value of the breakdown Page 132

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voltage of the point-to-plane gap. In case of the breakdown of the gap in quasi-static electric field the breakdown voltage at the negative pointed electrode is higher than at the positive one. This phenomenon was called the polarity effect. However, it has been experimentally established that in the case of nanosecond discharges the inversion of the polarity effect occurs: the breakdown voltage of the point-to-plane gap at the negatively pointed electrode is lower than at the positive one. Currently there is no explanation of the inversion of the polarity effect. In this work we experimentally studied the influence of polarity of nanosecond voltage pulses on breakdown parameters in different gases. Streamer velocity was measured by an optical method. The instant of streamer start was determined. Furthermore, an effect of a cathode surface state on the breakdown voltage was studied.

Oral Session 15 - Pulsed Power Diagnostics - Session Chair: LIN Fuchang (BALL ROOM 3#)[10:30-12:35] 10:30 O15-1(Invited) [A0637] Diagnosing pulsed power flow through flyer velocimetry HESS Mark, LAITY George, PETERSON Kyle, HUTSEL Brian, JENNINGS Christopher, VANDEVENDER J. P., GOMEZ Matthew, AMPLEFORD David, KNAPP Patrick, PORWITZKY Andrew (Sandia National Laboratories, US) Abstract: A critical component for the performance of experiments on the Z Pulsed Power Facility at Sandia National Laboratories is the delivery of electrical power to the target. While numerous types of diagnostics have been developed for assessing power delivery, in this talk we will focus on diagnostics that utilize the velocity response of flyers measured from Photonic Doppler Velocimetry (PDV) and/or Velocity Interferometer System for Any Reflector (VISAR) probes in the inner MITL/return can region to assess power flow. These flyers offer a non-invasive and time-dependent approach for diagnosing pulsed power flow. In particular, flyers at Sandia have been designed and tested for the following pulsed power purposes: measuring time-dependent load currents on axial surfaces in the inner MITLs/return can region, making highly accurate and high-speed peak current measurements in the inner MITL regions/return can, measuring the current on non-axial inner MITL/return can surfaces, and the detection of charged particles depositing their energy on the surfaces of inner MITLs/return can. Our talk will provide an overview of each of these velocimetry diagnostics, and will show data from Page 133

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these diagnostics which were fielded on Z Pulsed Power Facility experiments. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This work was partially supported by the LDRD program at Sandia National Laboratories, project 20-9240. 10:55 O15-2(Invited) [A1158] Recent diagnostic platform accomplishments for studying vacuum power flow physics at the Sandia Z accelerator LAITY George, DOLAN Dan, HESS Mark, HUTSEL Brian, JOHNSTON Mark, LAMPPA Derek, PATELl Sonal, PORWITZKY Andrew, VANDEVENDER Pace, WEBB Tim (Sandia National Laboratories,US) Abstract: The Sandia Z Facility routinely delivers 25-27MA current pulses to a variety of high energy density physics experiments including compact X-ray sources, inertial confinement fusion studies, dynamic materials experiments, and more. The various load configuration requirements typically span a wide range of different impedance and/or pulse shapes, resulting in a variety of coupling efficiencies with the pulsed power driver. Non-ideal current coupling between the pulsed power driver and target is typically the result of dynamic current losses in multiple areas of the vacuum magnetically insulated transmission line (MITL) architecture. These losses: (1) can be difficult to model with conventional simulation techniques; (2) can be caused by several coupled physical processes including space charge limited electron and ion flows, plasma formation in desorbed neutral layers, electrode vaporization, and negative ion transport; and (3) can potentially become even more severe for higher current, next-generation pulsed power accelerator concepts under consideration. In order to provide critical experimental data for improving predictive models of vacuum power flow, we have developed a dedicated experimental platform based on a raised extension of the radial transmission line coupling simple non-imploding Al targets to the Z vacuum convolute. This raised extension has been configured to allow for multi-dimensional, chordal lines-of-sight for new spectroscopic diagnostics in development. Over the past 18 months, our group has been successful in commissioning 12+ new diagnostics at the Z Facility across a range of capabilities including emission and absorption spectroscopy, surface velocimetry techniques, plasma interferometry, electrical-based particle diagnostics, film-based measurements, and more. We have now completed eight fully-instrumented, dedicated Page 134

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power flow experiments at the Z Facility, demonstrating more than 80+ independent measurements on each experiment. These experiments are being closely coupled with ongoing work to improve predictive code models of plasma formation in pulsed power accelerators. This paper will describe the ongoing development of this platform, examples of key diagnostics, and results from recent Z experimental campaigns dedicated to exploring vacuum power flow physics on large pulsed power accelerators. 11:20 O15-3 [A0629] Influence of nitrogen / oxygen gaseous ratio on nanosecond pulsed discharge behavior RYU Terumasa1, YAMAGUCHI Hitoshi1, WANG Douyan2, NAMIHIRA Takao2 (1. Graduate School of Science and Technology, Kumamoto University - Japan; 2. Institute of Pulsed Power Science, Kumamoto University – Japan) Abstract: Non-thermal plasma has been actively studied for industrial and environmental applications. The observation of discharge plasmas is beneficial for better understanding of the plasma physics of this growing field. It is well known that a streamer head always has the largest electric field between electrodes. Furthermore, the streamer head produces a variety of radical species according to feeding gas with high efficiency. Therefore, the feeding gas composition into the plasma reactor strongly contributes to the generation of radicals and behavior of the streamer head. In the recent study, a nanosecond pulsed power generator which can generate a pulsed voltage with 5 ns duration was developed and achieved the highest efficiency on ozone generation. However, the underlying mechanisms of these high efficiencies are not well understood. Therefore, the present study focused on obtaining an optimal gas composition ratio between nitrogen and oxygen in a coaxial reactor for the ozone generation. In the experiment, the discharge propagation process was observed using a high-speed gated ICCD camera. As the result, the gas ratio significantly affected the discharge propagation process. This can be explained due to each characteristic of nitrogen and oxygen such as UV radiation, electron attachment, and photoionization. 11:35 O15-4 [A0735] Modified laser‐induced fluorescence‐dip spectroscopy in Xenon for measuring a weak electric field distribution at the edge of electron emission plasma WANG Zhen, AN Wladimir, MUELLER Georg (Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz, 1, Eggenstein-Leopoldshafen, Germany) Abstract: A non-invasive optical method, LIF-DIP spectroscopy, for measuring the weak electric field distribution at the edge of the Page 135

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cathode plasma in a pulsed electron accelerator will be presented. The diagnostics was adapted to obtain the entire field distribution within one measurement. The main difference to already described LIF-DIP spectroscopy is the usage of a tunable dye laser with a bandwidth of about 1 nm, which is used for resonant excitation of the Rydberg levels. The brought bandwidth of 1 nm allows for simultaneous measurement of the electric field within a certain interval. The spectral width of the laser covers the variation of the electric field from a few hundred V/cm up to a few kV/cm. The calibration of the diagnostics was performed at a test stand with quasi-static electric field. The results agree with the calculations of the Stark splitting of Xe ns and nd levels. An electric field resolution of 50 V/cm is achieved in the measurement range 300-1000 V/cm and 300 V/cm is obtained for 1000-4000 V/cm. In the next step, these diagnostics will be adapted to the pulsed electron beam accelerator GESA. 11:50 O15-5 [A0809] Simulation and construction of ultrafast capacitor divider for voltage measurement of pulsed power source RAHIMI Ghasem1, HOSEIMI seyed najomdin2, ZADEH amin tarverdi2 (1. Azad Univercity,Tehran, Iran; 2. Sharif University) Abstract: Capacitive high voltage divider probes (CHVD) developed for very wide bandwidth and fast rise time voltage measurements in many pulsed power applications. We describe here the design and electrical model, construction, calibration and testing of a fast rise time capacitive high voltage probe. Physically, the compact probe consists of two stages. The first stage is the capacitor portion which is responsible for the majority of the division ratio. The second stage of the divider composed of discrete high frequency resistors in a small, electrically shielded box which enables measuring a pulse width of less than 5 microseconds without the need for integration reveal. The divider smoothly transitions from a capacitive topology at high frequencies, giving it a very flat attenuation curve at a 3dB point up to 1.9 GHz. The probe is calibrated in time-domain and frequency domain precisely. The frequency response of the probe was extracted by a network analyzer using a novel technique. The time domain calibration is done by using two source homemade 40 kV/500 ns sinusoidal and 10KV/ 0.35 ns pulser with a standard Pintek HV-39pro (40 kV/220 MHz) probe and liquid resistivity probe. The voltage divider has a 5000X voltage ratio with output to 50  termination for sampling oscilloscope without any distortion or high voltage problem. This capacitive probe can easily capture a 200 kV Impulse voltage generated by any pulsed power source such as Marx generator or Pulse Forming Network (PFN) through a dummy load .

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EAPPC & BEAMS 2018 / Programme Wednesday 19 September 2018 12:05 O15-6 [A1476] Pulse measurement analyses on Rogowski coil PAN Yafeng, LIU Sheng, ZHANG Xibo (Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: The current measurement of the coaxial output line with slotted Rogowski coil is introduced in this paper. Such Rogowski coil can be clarified by the working principle of the transformer, the primary is open-loop shielding slot, the secondary is solenoid. The influence of circuit parameters on measurement is analyzed. Based on the finite element electromagnetic field software, a local simulation model is established to verify the transformer working principle of the Rogowski coil. The local model can be effectively extended to the actual full size. The simulation results show that the size of the wire diameter and the cross-sectional area of the solenoid have no effect on the measurement, and the reduction of the gap between the adjacent turns can improve the flat-top quality of the pulse waveform. The experiment measurement of a high-power hundred-ns level pulse sign is carried out, and by increasing the coil turns, namely reducing turn gap, the problem of the original measuring pulse flat top is solved, the experimental results are consistent with the simulation. The research shows that the transformer circuit analysis method and the local model electromagnetic field simulation method are feasible. 12:20 O15-7 [A3196] When a D‐dot operates like a V‐dot? NOVAC B. M.1, SENIOR Peter1, XIAO Renzhen2, HUISKAMP Tom3, PEMEN A. J. M.3, PECASTAING Laurent4, de FERRON Antoine S.4, RIVALETTO Marc4, 5 WANG Meng (1. Loughborough University, UK ; 2. Northwest Institute of Nuclear Technology ; 3. Eindhoven University of Technology, The Netherlands ; 4. Université de Pau et des Pays de l’Adour, France ; 5. Institute of Electrical Engineering, CAS, China) Abstract: The paper highlights an important challenging phenomenon that appears whenever an attempt is made to measure fast voltage impulses, with the differentiating probe positioned too close to the closing switch of a pulse forming line generator.

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Poster Session VII - Pulsed Power Technology, Systems and Components - Session Chair: JIN Xiao (BALL ROOM 2#) [13:30-15:00] P7-1 [A0132] Modeling and fault analyzing for power conditioning system of solid‐state laser facility SHEN Hao, ZHANG Xiongjun, CHEN Dehuai, LAI Guiyou, TANG Haibo (Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, China) Abstract: The power conditioning system (PCS) which provides matched pulse energy for amplifier is a subsystem of a solid-state laser facility. Some of catastrophic faults such as capacitor internal short-circuit, bus bar breakdown to ground or high voltage cable short, may occur in the PCS due to the process of charging and discharging which involve high voltage and huge current. To analyze these cases, firstly, the model of the PCS and three main faults was proposed. Secondly, the structure of PCS was designed, the nonlinear effect of xenon lamp for system model was analyzed based on simulation results and a fixed model with compensation parameter was presented, the experiment results verified the effectiveness of the fixed model. At last, the tolerance and safety of key components such as damping elements, capacitors, ballast inductors, is analyzed when faults happened. As a result, the proposed model provides some support for parameter design and fault protect of PCS. P7-2 [A0155] A 15 GW, 150 ns pulse width, 30 Hz, compact rep‐rate pulse generator based on a Tesla transformer and a mixed PFL LI Rui, SU Jiancang, WU Xiaolong, ZENG Bo, ZHENG Lei, YU Binxiong, ZHAO Liang, CHENG Jie, QIU Xudong (Northwest Institute of Nuclear Technology, China) Abstract: A pulse generator is fabricated to generate intense electron beams for the purpose of high power microwave (HPM) generation. The generator mainly consists of a mixed pulse forming line (PFL), a Tesla transformer, a bruce dual-electrode gas switch, a short transmission line and a load. The mixed PFL is composed of a series 29-stage ceramic capacitor-loaded annular pulse forming network (PFN) and a coaxial PFL. A single stage composed of an inner conductor, an outer conductor and several capacitors is designed, with a characteristic impedance of 1.17 Ω, an electrical length of 65 ns and a sustaining voltage of 52.4 kV. The improved Tesla transformer is used to charge the mixed PFL to the voltage of 1.5MV. The generator can output electrical pulses with a width as long as 150 ns at a level of 15 GW and a repetition rate of 30 Hz when the main switch closes. The overall structure of the system is compact with a diameter of 1.2 m, a length of 6.7 m, a weight Page 138

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about 11 ton. Compared with the generator “TPG700L”, the output power of this generator is nearly doubled, while the volume is reduced by about 50%. P7-3 [A0581] Development and application of a solid‐state Marx generator REN Xiaojing, OKADA Yuji, SUGAI Taichi, TOKUCHI Akira,JIANG Weihua (Extreme Energy-Density Research Institute, Nagaoka University of Technology Nagaoka, Niigata 940-2188, Japan) Abstract: Pulsed power generators are being used in more and more industrial areas. Among various solid-state pulsed power sources, Marx generators are relatively popular because of their characteristics in modularity and voltage multiplication. We are developing a Marx circuit switched by MOSFETs for applications to ozonizer. It consists of 12 modules and is rated for maximum output voltage of 12 kV. Each module has two switching units for charging and discharging respectively in order to achieve repetition rate and operation efficiency. The modules are controlled by optical fibers and powered by isolation transformers. Rise-time and pulse-width are key development issues in this study. The experimental results will be reported in detail at the conference. P7-4 [A0729] Preliminary investigation of comb‐type pulse forming line with low impedance LIU Shifei, ZHANG Zicheng, LI Song (College of Opto-Electronic Science and Engineering, National University of Defense Technology, Changsha, China) Abstract: Development of pulsed power technology is towards high power, longer duration and more compact structures. Compact coaxial propylene carbonate pulse forming lines are widely used in the application of pulsed power systems. In order to further lengthen the duration and decrease the geometrical sizes of pulsed power systems, a comb-type pulse forming line is adopted. It is a slow-wave structure with comb-type inner electrode. In this paper, the operation principle, numerical simulation and experimental investigation of the comb-type forming line are carried out, respectively. Firstly, the operation principle is briefly introduced. The principle to increase the duration is explained. Secondly, the PSpice model is built by the L-C network. Based on the calculated parameters, the electrical circuit is simulated. Finally, the comb-type pulse forming line is experimentally tested and verified. For the comb-type propylene carbonate forming line with a 67 cm length to replace the traditional coaxial one, it has an impedance of 10  and a doubled duration of 70 ns. Experimental data on its test results are given. The experimental results are in accordance with the numerical simulations. The preliminary investigation approved the comb-type pulse forming line feasible and set a solid foundation for its application in the pulsed power system.

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EAPPC & BEAMS 2018 / Programme Wednesday 19 September 2018 P7-5 [A0836] A kind of solid state rectangular pulse Marx generator with adjustable output pulse width FAN Xuliang, LIU Sheng, WANG Junjie, PAN Yafeng, SUN Xu, WAG Gang (Northwest Institute of Nuclear Technology, Xi,an, China) Abstract: The Marx generator which can output rectangular pulse has been widely used in these years. Many types of Marx generator have been researched. However, the gas gap switches which are widely employed in these systems always result in high possibility of uncertainty. A kind of solid state rectangular pulse Marx generator based on magnetic switch is proposed in this paper, and the trigger system which are always necessary in the other types of Marx generator is discarded in the proposed generator. Furthermore, in order to satisfy a wider range of application requirements, a kind of technical solution of solid state rectangular pulse Marx generator with output pulse width adjustable is proposed, and the working process is simulated. The results show that the Marx generator has the capability of outputting rectangular pulse which width is adjustable from 50ns to 100ns. P7-6 [A1272] Research on the compact pulsed power source based on PCSS LUAN Chongbiao, LI Hongtao, XIAO Jinshui, MA Xun (Institute of Fluid Physics, China Academy of Engineering Physics, China) Abstract: Si PCSS with reflective cavity structure and the solid-state pulse forming line based on the PbO-SrO-Na2O- Nb2O5-SiO2 (PSNNS) glass-ceramics material have been manufactured. Then, a compact pulsed power source based on PFL-Marx structure has been prepared, and the lifetime of the prepared pulse power source, which works at output voltage 17kV, output current 1.1kA, pulse width 55ns, rise time 14ns and repetition frequency 1kHz, reaches 1106 shots. P7-7 [A2376] Development of an all solid state nanosecond pulse generator and its desaturation protection experiment research MA Jianhao, DONG Shoulong, TAN Jianwen, YAO Chenguo (State Key Laboratory of Power Transmission Equipment &System Security and New Technology, Chongqing University, Chongqing, China) Abstract: All-solid-state high voltage nanosecond pulse generator can be used effectively in tumor ablation, plasma, food processing and the like. The all-solid-state nanosecond pulse generator, which based on the principle of traditional Marx circuit and SiC MOSFET, merely achieves 50-80ns both rising and falling edges even with the chopping switch. In this paper, the design with a new dual-driver circuit optimizes the design of circuit parameters, which has greatly sharpened the rising edge and falling edge than the original topology. Moreover, since the instantaneous output of the pulse, it is hard to turn-off Page 140

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quickly in the case of abnormal operations. There is also always no self-test function before power on in many pulse generators. The experimental results show that the proposed generator in this paper can output voltage amplitude 0-8kV, pulse duration 180-900ns, rising/falling edges both within 25ns. At the same time, this paper also carried out under-saturation protection experiment to analyze the feasibility of desaturation protection of nanosecond pulse generator. In addition, due to the characteristics of the Marx topology, the effective adjustment of rise time can be achieved by controlling the precise delay of the FPGA phase-locked loop, but there is a certain range. P7-8 [A2962] High voltage switch using 13 kV SiC‐MOSFETs LIM Soowon1, TOKUCHI Akira1, OKAMURA Katsuya2, FUKUDA Kenji3 (1. Pulsed Power Japan Laboratory Ltd., Japan; 2. High Energy Accelerator Research Organization (KEK); 3. National Institute of Advanced Industrial Science and Technology Advanced Power Electronics Research Center) Abstract: Silicon carbide (SiC) MOSFETs have superior characteristics such as lower switching losses, higher breakdown voltage, higher band-gap energy and lower on-sate resistance compared to silicon (Si) MOSFETs and Si-IGBTs. In this study, we developed a high voltage solid-state switch using 13 kV SiC-MOSFETs. The switch consists of two series circuit boards and there are 12 SiC-MOSFETs in parallel on each circuit board. The SiC-MOSFETs were arranged in a circle for the uniform current distribution on each switch. It is possible to increase the maximum voltage ratings of the switch by adding additional circuit boards. This switch will be used for the power supply of the kicker in the KEK digital accelerator (KEK-DA). P7-9 [A3019] Design of a compact pulsed power system for multi‐barrel parallel railgun HE Yong (Institute of Fluid Physics, Mianyang, China) Abstract: A compact pulsed power system for multi-barrel parallel railgun is designed. The pulsed power system mainly consists of metallized film capacitor-based pulsed power supply (PPS) and high-rate discharge lithium iron phosphate battery-based fast charging power supply. The pulsed power supply consists of sixty-four 270-kJ pulsed forming networks (PFNs). Each PFN is composed of a 270-kJ capacitor (15 mF/6 kV), a thyristor stack as main switch, a diode stack as crowbar, a specific pulse-shaping inductor (10 μH/ 2 mΩ), and a coaxial cable. The PFN has an energy density of 1.25 MJ/m3. As the PFN discharging to the multi-barrel parallel railgun, the peak value of the output current of one PFN is 125 kA with a peak time of 700 μs. The fast charging power supply has two 2.5-MW charging units with power density of 1.3 kW/kg. Each charging unit has twenty 400-V lithium battery modules. The twenty modules are charged in parallel by an AC-DC station connecting to grid and discharge to 32 PFNs in series with a voltage of 6-8 kV and power of Page 141

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2-2.5MW. The design principles of the PPS and fast charging power supply are interpreted. The feasibility of the design is also illustrated by simulations. P7-10 [A2503] Experiments on multi‐stage continuous acceleration of proton beam in dielectric wall accelerator WANG Wei (Institute of Fluid Physics, CAEP, China) Abstract: A new type of compact linear accelerator, dielectric wall accelerator (DWA), is under development at the Institute of Fluid Physics (IFP). The machine, aiming at proton therapy for cancer, promises to increase the average accelerating gradient by at least an order of magnitude over that of existing linear induction accelerators. The key technologies of DWA have been researched in the past few years, including high gain gallium arsenide photoconductive semiconductor switch (GaAs PCSS), composite ceramic plate transmission line (PTL), and high gradient insulator (HGI). Recently, 5-stage continuous acceleration of proton beam has been achieved, and the total energy gain is approximately 296 keV, which is the highest energy gain of proton beam with the same accelerating theory for now. P7-11 [A0077] A fault‐tolerance method of massive capacitors charge in linear transformer driver ZHAO Yue, ZHOU Liangji, CHEN Lin, WANG Meng, XIE Weiping (Institute of Fluid Physics, CAEP, China) Abstract: The Linear Transformer Driver (LTD) can deliver very fast high power without compressing stage by stage. Compared to traditional pulsed power accelerator, the LTD can be fabricated very compact due to it does not require large oil and de-ionized water tanks. This makes it ideally fit for building petawatt-class pulsed power accelerators. Most importantly, the LTD can operate repetitively and this advantage satisfies requirement of Inertial Confinement Fusion. The 300-TW and 800-TW pulsed power accelerator are conceptually designed by SNL. The principle of LTD is that a number of capacitors, which are separated by switches, are charged or discharged in parallel. Therefore the higher voltage it outputs, the more capacitors and switches it needs. The 300-TW accelerator comprises 59400 gas switches and 118800 capacitors. And the numbers of that in 800-TW accelerator are even as high as 162000 and 324000. The capacitor charge failure will occur on condition that any one of all capacitors insulation failure as well as any one of all switches self breakdown happens. The risk of capacitor charge failure cannot be neglected because the cardinal number of elements is very large. In order to resolve the capacitor charge failure that causes capacitor insulation failure and gas switch self breakdown, a fault-tolerance system, mainly consist of isolated resistances and constant current high voltage generator of massive capacitor charge is introduced that the rest capacitors can be charged up to 97% rated voltage in case that any one of element faults happens. The circuit formula is deduced in fault mode. And the feasibility is proved by theoretical Page 142

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analysis and numerical simulation. The relationship between isolated resistance and charge coefficient (The quotient of the final voltage in faults mode divided by rated charge voltage) is discussed. The requirement of charge power and heat power of isolated resistance is calculated lastly. P7-12 [A1851] Design of a low inductance primary discharge unit for FLTD ZHANG Tianyang, CONG Peitian, HUANG Tao, ZHAI Rongxiao, YIN Jiahui, DENG Haojie, JIANG Hongyu (Northwest Institute of Nuclear Technology, China) Abstract: Primary discharge circuit composed by switch and capacitors, which is called a brick, is a basic unit of Fast Linear Transformer Driver (FLTD). Since the inductance of the brick plays a significant role in limiting the rise time and peak current of the FLTD, the inductance needs to be as low as possible. In this paper, a brick with coaxial structure is introduced. The inductance characteristic of the brick was deeply analyzed by the methods of theoretical calculation and analog simulation. The experimental results show that the brick can be operated steadily and reliably at ±100 kV when the capacitance of the capacitor was 40 nF. The inductance of the brick was only 100 nH or so. P7-13 [A2141] Study of operating characteristics of Fe‐based amorphous cores under fast pulsed voltage WANG Zhiguo, LIANG Tianxue, SUN Fengju, CONG Peitian, WEI Hao, YIN Jiahui, JIANG Xiaofeng,JIANG Hongyu, HUANG Tao, LUO Weixi (Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: Magnetic core is a crucial part of Inductive Voltage Adder. The magnetization properties of the cores at the voltage pulse with fast rise time directly influence the co-coupling effect between the primary and secondary. A characteristic parameter α, the gradient of the voltage pulse applied to per unit area core, is proposed in this paper to describe the exciting condition applied on magnetic cores. The change of equivalent resistance of eddy current loss Rc with the skin depth δ has been studied. The test platform is developed to generate exciting pulsed voltage with the rise time less than 40 ns, and the magnetizing characteristics of magnetic cores with a diameter of 970 mm have been tested under the fast pulsed voltage. P7-14 [A2468] Crow bar fast protection system for the power source of klystron WANG Bo, ZHOU Wenzhong, WAN Maliang, MU Zhencheng, LIU Meifei, RONG Linyan, XIE Zhexin, LIJian, XU Xinan, ZHANG Zonghua (Institute of High Energy Physics Chinese Academy of Sciences, Dong Guan, China) Abstract: The power source of klystron is an important part of China Spallation Page 143

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Neutron Source（CSNS）Proton Linac. Klystron may be arcing and short circuit when it works at high voltage(0-120kV), so we need crow bar fast protection system to release the power of high voltage capacitor quickly .Ignitrons is the core equipment of crow bar, it provides timely and effective protection to the klystron by short circuit ground. Based on experiment, this paper introduces the work principle and technological of crow bar fast protection system. The experimental results show that the crow bar fast protection system can provide effective discharge protection in 6 μs. P7-15 [A0302] A nanosecond pulsed rectangle calibration source for fast pulsed electrical sensors YAO Weibo1, ZHANG Yongmin2, TANG Junping2, XU Qifu2, HU 2 2 1 Yixiang , CONG Peitian , QIU Aici (1. State Key Laboratory of School of Electrical and Engineering, Xi’an Jiaotong University, China; 2. State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, China) Abstract: Fast pulsed electrical sensors are critical to large pulsed power facilities working safely and stably. It is very significant to these sensors that studying the method of calibration can help us to get the accurate working parameters for the pulsed power facilities. Based on the pulsed rectangle theory of coaxial line, a nanosecond pulsed rectangle calibration source is developed for fast pulsed electrical sensors, such as Rogowski and low resistance shunt which are not affected to stray parameters seriously and suitable for the off-line calibration method. The pulsed rectangle current amplitude of calibration source is 10.3 kA, the width of pulsed rectangle is 100.5ns, and the rise-time of pulsed rectangle is 8.3ns. Furthermore, the composition structure and the design method of critical units are introduced. Based on the schematic of coaxial matched load for pulsed rectangle measuring, the uncertainty factors of the pulsed rectangle parameters affected for calibration source are analyzed and the method of uncertainty analysis is discussed. Then the uncertainty of pulsed rectangle current of calibration source which has traceability to the International System of Units (SI) is 3.5%. Using the nanosecond pulsed rectangle calibration source, a self-producing Rogowski is calibrated. And the uncertainty of the self- producing Rogowski is 4.1%. The bandwidth is 0~3.2MHz. Finally, the results of the paper will have important value for fast pulsed electrical sensors to form a normalization method of calibration.

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EAPPC & BEAMS 2018 / Programme Wednesday 19 September 2018 P7-16 [A1144] La–Sr–Mn–Co–O films for high pulsed magnetic field measurements at cryogenic temperatures VAKARIS Rudokas1, ZURAUSKIENE Nerija2, SKIRMANTAS Kersulis1, VOITECH Stankevic2, VALENTINA Plausinaitiene3, 4 1 2 STEVAN Arsenijevic , RASUOLE Lukose , SAULIUS Balevicius (1. Center for Physical Sciences and Technology, Vilnius, Lithuania ; 2. Center for Physical Sciences and Technology, Vilnius Gediminas Technical University, Lithuania ; 3. Center for Physical Sciences and Technology, University, Lithuania; 4. Dresden High Magnetic Field Laboratory, Helmholtz-Zentrum Dresden-Rossendorf, Germany) Abstract: It has been demonstrated that colossal magnetoresistance (CMR) phenomenon in nanostructured La-Sr-Mn-O manganite films can be successfully used for the development of CMR-B-scalar sensors, which are capable to measure the magnitude of pulsed magnetic fields in very small volumes. Such sensors have been used at room temperatures to measure the distribution of magnetic fields in railguns and non-destructive pulsed-field magnets. However, for the applications in plasma science or condensed matter physics sensors operating at cryogenic temperatures and measuring high magnetic fields are required. It was found that substitution of Co for Mn in La-Sr-Mn-O films decreases the paramagnetic-ferromagnetic phase transition temperature and increases the resistivity, therefore, it could result in increase of low temperature magnetoresistance. For nanostructured films consisting of high quality crystallites separated by disordered grain boundaries, the origin of these effects is not enough understood, thus their investigations are of great importance. In this study, the magnetoresistance of nanostructured La-Sr-Mn-Co-O films was investigated at temperatures 4-100 K in pulsed magnetic fields up to 60 T. It was obtained that magnetoresistance has a minimum at 50 K and increases with decrease of temperature. The possibility to use these films for magnetic field measurements at cryogenic temperatures is discussed. P7-17 [A0094] Analysis of gap closure in parallel plate MITL using the collisional flow ions WU Hanyu, ZENG Zhengzhong, QIU Mengtong, CONG Peitian, HU Yixiang, WEI Hao, SUN Tieping, ZHANG Jinghai (Northwest Institute of Nuclear Technology, China) Abstract: Magnetically insulated transmission lines (MITLs) are used to connect high power pulse drivers with the load. Although MITLs have been used in huge pulse power generators, gap closure which results in a MITL current loss is still a challenging problem for researchers. A fluid model of the flow-ion plasma in a steady-state one dimensional MITL is developed to explore the principle of the gap closure of MITL. The model assumes the ions inside an MITL encounter effective collision with disturbed electromagnetic field and drift toward the anode. The idea is from the effective collisions between the electrons and electrostatic- and electromagnetic-field fluctuation. The model Page 145

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gives the relation between the anode-cathode (AK) gap closing speed of MITLs, voltage, electron effective coefficient, ion mass, current, and MITLs vacuum impedance. P7-18 [A0481] Calculation of 3‐D electric fields between four types of electrode profiles using the finite element method WANG Yu, LIU Qiaojue, YAO Weibo, ZHANG Yongmin, TANG Junping, QIU Aici (State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China) Abstract: In the field of high voltage discharge device and pulse gas laser, electrode profiles, in the determination of the polar electric field, have a direct impact on the quality of the product. In order to obtain big volume uniform glow discharge and improve output stability, in this paper, we selected the ball electrode, flat bulb electrode, Chang and Bruce, four different types of profiles, whose electric fields were calculated in three-dimensional space using the finite element method. Results implied the concrete locations with maximum departure from expected uniformity in the two-dimensional cross section of each electrode. Moreover, we set electrode radius 13mm and the distances between two electrodes were set to be 7, 7.5, 8, 8.5, 9, 9.5 and 10 mm respectively, and constructed four electrode profiles and fit the electrical potential difference 30kV. The d-f curves of four kinds of profiles were calculated to determine the best electrode profile at different distances which provides guidance for engineering practice. Finally, in the center of the ball and Bruce electrode, we set 10 um hemispherical bulge, changed the bump material, and calculated the clearance rate of the electric field distortion from the impurities and erosion jet. P7-19 [A1427] Research on the design and construction of pulse trigger source based on DSRD ZHANG Qi (China Academy of Engineering Physics, Mianyang, China) Abstract: The physics characteristic and work theory of drift step recovery diode(DSRD)are introduces briefly. The related pulse power source is simulated, and the optimal circuit of pulse power trigger source is obtained. Then, we set up the trigger source, get the experimental results and compare with the simulation results. After that, we will trigger the source circuit to build the FID system, and discuss the technical problems found in the process of building.

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EAPPC & BEAMS 2018 / Programme Wednesday 19 September 2018 P7-20 [A2790] PIC simulation of the vacuum power flow for a recyclable transmission line LIU Laqun1, GUO Fan2, ZHOU Liangji2, LIU Dagang1, ZOU 2 2 1 Wenkang , CHEN Lin , WANG Huihui (1. University of Electronic Science and Technology of China, Chengdu 610054, China; 2. Key Laboratory of Pulsed Power, Institute of Fluid Physics, CAEP, P.O. Box 919-108, Mianyang 621999, China) Abstract: In this paper, the method of particle-in-cell (PIC) simulation is used to study the recyclable transmission line (RTL) in the inertial-confinement fusion energy (IFE) system which is driven by Z-pinch. In the system, the initial mass of the wire array load is 50mg, and the peak current of RTL that delivers to the load is 60MA. The explosive emission model is used to simulate the electron emission of the cathode surface, and the 0-dimensional implosion model is used to simulate the implosion process of the wire array load. The effect of vacuum impedance and pulse width on the transmission efficiency of RTL is contrasted and analyzed. P7-21 [A2888] Analysis of the mechanical effect of high current impulse discharge arc XIONG Jiaming, LI Lee, DAI Hongyu, WU Haibo, YU Bin (Huazhong University of Science & Technology, China) Abstract: The high current impulse discharge arc has strong mechanical effect on the electrode and the adjacent object. This paper uses high power, high current gas switch as an example to discuss current Lorentz force, studies the gas thermal expansion force and shock wave overpressure induced by impulse discharge arc on the switch electrode, and gives the theoretical calculation expression for the maximum electromagnetic force and shock wave overpressure that the electrode may withstand. Analysis and calculation show that the maximum shock wave overpressure caused by the impulse discharge arc occurs at the initial expansion stage of the arc channel. The maximum electromagnetic pressure of the impulse discharge arc to electrode occurs at the moment when the arc current reaches its peak, and the shock wave overpressure caused by the arc expansion of impulse discharge arc is much larger than the electromagnetic Lorentz force. Under the condition of constant discharge current, by adjusting the gap distance and pressure of the gas switch, the arc shock wave overpressure caused by the arc expansion on the electrode can be reduced. P7-22 [A3191] Optimal design of square pulse forming network WANG Chuanwei, LI Hongtao , LUAN Chongbiao , XIAO Jinshui (Key Laboratory of Pulsed Power, Institute of Fluid Physics, CAEP, Mianyang, China) Abstract: The LC ladder pulse forming networks (PFNs) have long been used to produce wide flat-top pulses in the pulse generators. The actual pulse Page 147

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produced by the uniform LC ladder PFNs has ringing overshoots on the leading edge and high-ripple on the flat-top of output pulse. Although the exact equations describing the transient behavior of finite LC ladder PFNs can be derived, the optimization of LC ladder PFNs for producing low-ripple square pulse is proved to be extremely difficult. In this paper, we propose a complete algorithm to optimize the parameters of inductors to obtain low-ripple square pulse. The solution has been split into two steps. First, the differential equations that describe the transient performance of the LC ladder PFNs from the Kirchhoff Laws are solved with the numerical Runge-Kutta method. The produced waveform when a finite LC ladder networks discharged into a resistive load is analyzed, and the influence of inductors on the turn-on time is discussed in detail. Then, the values of inductors are modified by the simplex method to reduce the overshoot and ripple of output pulse. Simulation results indicate that the proposed methods can be used to design new LC ladder PFNs to generate low-ripple square pulse.

Poster Session VIII - Radiation Sources - Session Chair: SINARS Daniel (BALL ROOM 2#)[13:30-15:00] P8-1 [A1096] Study of the absorption and transmission of microwaves by the nonuniform plasma route way YAN Eryan (Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics. CAEP, China) Abstract: The research is developed in HPM (S band) ideal rectangular wave state in conditions of free electron going to appear. The vacuum reaction chamber is of column-shape with length of 270cm and diameter of 150cm. The central frequency of the microwave field is f0=2.92GHz. At this frequency, microwave can emit pulses with a duration of up to tpul = 20μs and an average power of P=10kW; i.e., the maximum total microwave power is Pgen≈1MW. The S band 2.92GHz microwave of electric field (E direction) in vertical line polarization is used to produce plasmas via focusing. In horizontal panel (H direction), the continuous wave (CW) is used for microwave cutoff method. Microwave cutoff method is adopted to diagnose the evolution of electron density in conditions of different microwave parameters (pulse width, 100ns, repetition frequency, 1000Hz, and so on). The pressure of chamber remains 300Pa. Under this condition，reflection coefficient is about 0 when frequency is 9GHz, reflection coefficient is about 0.1 when frequency is 15GHz, and reflection coefficient is about 0.8 when frequency is 36GHz. The maximum plasma density is about 1017m-3~1018m-3 by the Epstein profile model in the period of pulsed irradiation.

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EAPPC & BEAMS 2018 / Programme Wednesday 19 September 2018 P8-2 [A1951] Analysis of the various uncertainty contribution to the injection probe into transmission line ZHONG Longquan (Institute of Applied Electronics of CAEP, Mianyang, China) Abstract: For proving the reliability of computational solvers, external references based on measurement was a very valuable way for simulation validation. But the uncertainty of measurement needs to be evaluated before the comparison. This paper describes a benchmark test configuration for line injection into transmission line. Firstly an uncertainty mathematical model is developed for the measurement of current. Then various uncertainty contribution related to experimental equipment and test setup is analyzed in detail, an experimental verification based on line-injection method is offered. Lastly validation of computational model from a measurement setup is discussed. P8-3 [A2506] Damage experiments of the low noise amplifier induced by repetitive combined types of intense electromagnetic pulses YANG Meng, ZHANG Zhixiang, CAO Rui, LIi Huilai (Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, China) Abstract: The damage power of the low noise amplifier (LNA) for a receiver under typical combined types of repetitive intense electromagnetic pulses is investigated. Results of the experiments which induced by repetitive intense electromagnetic pulses with different pulse duration show that the minimum damage power of the LNA with 100 ns is 2 dB lower than with 30 ns, while 4.5 dB higher than with 500 ns. The experiments induced by combined pulses when the repetitive frequency of original pulses is both at 1 kHz are conducted, the results show as follows:(1) minimum damage power of the LNA is not changed when there is a long interval of combined pulses (longer than 5 s);(2)the decrease of minimum damage power of the LNA is about 2 dB when combined pulses borders no matter which one is in the front of original pulses; (3) minimum damage power of coincided pulses, which may be higher or lower than single type pulses, is determined by original repetitive pulses. The decrease of minimum damage power is about 2 dB when pulses with 100 ns duration coincide optimally with pulses with 30 ns duration which is 2 dB higher than the 100 ns ones.The experiment results accord well with the theoretical analysis. P8-4 [A2933] The research of the wake paths analysis of EM and protection method in the electronic systems LIN Jiangchuan, ZHAO Gang, ZHONG Longquan, CAI Jinliang (Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics, CAEP; Complicated Electromagnetic Environment Laboratory of CAEP, China) Page 149

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Abstract: The electromagnetic environment of modern battlefield is increasingly complex, and the EMC problem of electronic systems is more prominent. For determining the wake paths of electronic systems in complex electromagnetic environment and choosing appropriate protection method, a method for determining EM coupling paths and optimal protection method is presented. Based on the “Electromagnetic Topology Graph Theory”, the EM coupling paths of electronic systems is converted into digraph and assigned values. Based on the improved shortest path analysis method, the weakest link and the paths that cannot meet the shield requirements of system and any subsystems can be fast determined, which has positive edge, negative edge, loops and is under the multiple sources of interference. By introducing “unit shielding cost-effectiveness” to solve practical engineering problems, this paper proposes an “economic targets programing model” and “protection targets programing model”. On the basis of verification in a typical system, this proposed method is able to improve the efficiency of wake paths analysis and reduce the economic cost. There is a strong practical value. P8-5 [A0128] Design, simulation and construction of high power microwave windows 1 2 RAHIMI Ghasem , KHANZADE Mohhamad Hosein (1. Azad University, Tehran, Iran ; 2. Yazd University) Abstract: This paper reports on the results of design,simulation and construction of disk-shaped microwave windows at the operating frequencies range of 1.5~6GHz (L, S and C Bands). The reflection coefficient of microwaves from the window is less -15dB. We consider uniform plane waves incident normally on material interfaces and used the finite difference in time domain method (FDTD) to analyze the wide aperture microwave window. As a result of the calculations the reflection coefficient of the TE11 electromagnetic wave from the Window at normal incidence was obtained. Using the simulation results, the frequency dependent transmission and reflection coefficients of the window were calculated for normal incidence of a monochromatic plane at the bandwidth. Also, we will compare the characteristics of the input window made of the most suitable material - high-density polyethylene (HDPE), polyamide and Alumina. The results of Window structure simulation optimization are very useful for estimations of the optimal parameters previously obtained in the simplified two-dimensional model. Then we used the optimal parameters to construct high power microwave windows. P8-6 [A0387] Complex regimes of intense relativistic electron beam dynamics with coexisting instabilities 1 1 2 KURKIN Semen , BADARIN Artem , HRAMOV Alexander (1. Saratov State University, Saratov, Russia ; 2. Yuri Gagarin State Technical University of Saratov) Abstract: Relativistic electron beams (REBs) are of considerable interest for modern high-power electronics. Propagating in the drift space, REBs often Page 150

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demonstrate complex dynamics of space charge, resulting in the formation of electron structures. Under certain conditions, various types of instabilities (diocotron, slipping, Pierce, Bursian, and others) can develop in REB. The problem of the interaction and coexistence of Bursian and diocotron instabilities that can simultaneously develop in REB has been actively investigated over the past few years. The present work provides an overview of the most important recent results obtained in this area by our scientific group. Special attention is paid to the effect of the annular beam wall thickness on the dynamics of the system. We have found out that the interaction of instabilities results in the formation of a virtual cathode with a complicated rotating helical (vortex) structure and several reflection regions (electron bunches) in azimuthal direction. We have shown that the number of electron bunches in the azimuthal direction depends on the system parameters. We have discovered the connection between the number of bunches and the generation frequency in vircator. The work has been supported by the Ministry of Education and Science of the Russian Federation (Project 3.859.2017/4.6). P8-7 [A0935] Analysis of synthesis of wideband electromagnetic pulse based on gas discharge ZHANG Fan (Electronic Engineering Research Institute, China) Abstract: Time-domain synthesis is an important way to improve the intensity of radiated electromagnetic pulse. A radiation element model based on the breakdown of gas switches to generate wideband electromagnetic pulses is established. The simulation calculation and analysis of the electromagnetic pulse synthesis efficiency of two-element arrays are performed. Three typical synthetic results were obtained through the influence of breakdown time delay, and the feasibility of the wide-band electromagnetic pulse time-domain synthesis was verified by experiments. P8-8 [A1496] Numerical study on electron energy distribution function (EEDF) in microwave air breakdown ZHOU Qianhong, YANG Wei, DONG Zhiwei (Institute of Applied Physics and Computational Mathematics, Beijing, China) Abstract: The electron energy distribution function (EEDF) in microwave air breakdown is investigated by solving Boltzmann Equation (BE) and particle-in-cell-Monte Carlo (PIC-MCC) method. To solve the BE by two-term approximation, we need to make some assumptions, which may not be suitable for microwave air breakdown. The PIC-MCC method is used to investigate the time-variation of EEDF in microwave air breakdown. The EEDF is compared with that calculated by BE. It is found that the EEDF varies considerably over one field cycle. In the range of 2-3 eV, there is a large amount of energy loss due to large electron-nitrogen vibrational excitation cross section, so the EEDF concaves in that range when the field decreases. Page 151

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The variation of EEDF will influence the plasma parameters and the results of fluid model. P8-9 [A1508] Effects of secondary electrons from the beam collector in high power microwave sources CAO Yibing1, SUN Jun1, WANG Hongguang2, LI Yongdong2, SONG Zhimin1, FAN Zhiqiang3, ZHANG Guangshuai1, TENG Yan1 (1. Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi’an, China; 2. Key Laboratory of Physical Electronics and Devices of the Ministry of Education Xi’an Jiaotong University, Xi’an, China ; 3. Department of Engineering Physics, Tsinghua University, Beijing, China) Abstract: Taking a relativistic backward wave oscillator (RBWO) and a transit time oscillator (TTO) as examples, the article mainly analyzes the effects of secondary electrons from the beam collector on the high power microwave (HPM) generation. The results show that the secondary electrons can return back into the beam-wave interaction area and absorb the RF power. In some case, the secondary electrons could even stimulate unexpected mode and thus result in pulse shortening. The increased secondary electron yield would strengthen these effects. Simultaneously, the energy of secondary electrons mainly influences the synchronization between the electrons and the fields. Mode competition probably predominates for the high-energy electrons (ve>vp) and power absorption for the low-energy electrons (ve

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encourages further studies of this mechanism for THz-band generation using additional surface-wave Bragg reflectors. P8-11 [A1954] Simulation research of RF breakdown in “cold” slow wave structures operating at π‐like mode of TM01 YUAN Yuzhang, ZHANG Jun, ZHONG Huihuang (College of Advanced Interdisciplinary Studies, National University of Defense Technology, China) Abstract: RF breakdown simulations in “cold” slow wave structures (SWSs) are executed. All the SWSs are operating at π-like mode of TM01 wave. The simulation conditions are coincident with the experiments setup to be carried out. Explosive emissions of electrons in the rounded corner of SWSs together with the ionization of gas layer close to it supply the breakdown plasma. The gas layer consists of water vapor and hydrogen gas and has a pressure of 1Pa. Different kinds of circumstance of SWSs are simulated. We mainly concern about the characteristic of the plasma and its influence to microwave power. Comprehensive simulation results are obtained. The simulation results indicate that the input microwave energy is mainly absorbed, not reflected by the RF breakdown process in π-like mode SWSs. Both larger magnitude of Es-max and more numbers of periods of SWSs aggravate the microwave absorption in the breakdown process and bring about shorter transmission pulse width. The results are helpful for the design of microwave sources as well as the explanation of the RF breakdown phenomenon physically. P8-12 [A2309] Gyrotron radiation frequency tuning in the regime of Raman backscattering on an intense electron beam MALKIN Andrey, GINZBURG Naum, YUROVSKY Lev, ZOTOVA Irina (Institute of Applied Physics RAS, Russia) Abstract: For a number of applications, the opportunity of tuning of gyrotron output radiation frequency is of considerable interest. To that effect, in this presentation, we propose to use stimulated Raman scattering regime with frequency downshifting on an additional electronic beam. In the suggested scheme, the pumping wave generated in the gyrotron travels in the same direction with the electron beam while the low-frequency scattered radiation travels in the opposite direction. Under these conditions, an absolute instability can develop and the system self-excitation would take place in the absence of external resonators. This would provide a possibility of adjustment of the scattered radiation by varying the energy of the electron beam. The analysis of the proposed scheme was conducted in the framework of three-wave approximation which includes the equations for amplitudes of high-frequency pump wave, low-frequency scattered wave and the fast spatial charge wave. Based on this model, threshold conditions for generation development were determined and the dependence of the quantum output via the scattering distance. Estimations show the potential of the scheme under investigation for Page 153

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MW-level gyrotrons frequency tuning of about 20 to 40 %. P8-13 [A2703] Particle‐in‐cell(PIC) simulation study on output characteristics of relativistic magnetron LU Wei, LIU Dagang, LI Baoshan, LIU Laqun, WANG Huihui (University of Electronic Science and Technology of China, Chengdu 610054, China) Abstract: In relativistic magnetron, the external magnetic field and the input voltage have some degree of inhomogeneity, which will affect the performance of the device. In this paper, particle-in-cell (PIC) simulation is used to simulate the effect of the above two conditions on the working condition of A6 relativistic magnetron. The simulation results show that with the increase of the magnetic field irregularity, the mode competition in the magnetron is intensified, and the output power will become more and more unstable. In addition, the voltage pulse width of pulse voltage waveform, prepulse length, and flat-top disturbance will have a great influence on the mode competition and vibration time of the magnetron. P8-14 [A2705] Particle‐in‐cell(PIC) simulation research for C‐band high‐power single‐beam klystron CHEN Yanan, LIU Dagang, MA Yubin, LIU Laqun, WANG Huihui (University of Electronic Science and Technology of China, Chengdu 610054, China) Abstract: In this paper, the particle-in-cell (PIC) simulation method was used to optimize the electron gun and resonator cavity of a C-band TM010 single-beam klystron. The results were got after optimization. When the input voltage is 42kV, the output electric current of the electron gun is 18A, the conductivity coefficient is 2.2μp; When the input power is 32W, the output peak power of the klystron is 300kW, the output average power of the klystron is 150kW, the efficiency is 39.8%, the gain is about 40dB and the bandwidth is about 50MHz. P8-15 [A2899] Effects of hybrid collector plasma in the relativistic backward wave oscillator MIAO Tianze (Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, China) Abstract: The effects of hybrid collector plasma in a relativistic backward wave oscillator are investigated using numerical simulation. Here, the hybrid collector plasma refers to plasmas mixture containing two types of positive ions or a positive and a negative type of ions each. Analysis of the plasma diffusion process shows that, compared with the case of a single type of ions, two types of positive ion mixture may promote the diffusion of plasma electrons, even cause an earlier pulse shortening. In contrast, negative ions will promote plasma electron wall collision frequency to reduce the density of plasma electrons, inhibit plasma diffusion, and finally suppress the pulse shortening. Page 154

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This paper reveals the mechanism of the effects of hybrid collector plasma, which is an important step to study the role of complex plasma in practical conditions. And based on this research, a gas displacement method is suggested to be easily used in conjunction with other methods to suppress the effects of collector plasma. P8-16 [A2957] Linear analysis of a 0.34 THz confocal gyro‐TWT AN Chenxiang, ZHANG Dian, ZHANG Jun, ZHONG Huihuang (National University of Defense Technology, China) Abstract: Confocal gyrotron traveling wave tube (gyro-TWT) is a novel gyrotron amplifier capable of operating in higher order modes while generating high power at the same time. In this paper, the coupling coefficient, lossy quality factors, gain, bandwidth and dispersion characteristic of a center frequency of a 0.34 THz HE06 mode confocal gyro-TWT are studied based on the linear theory. Theoretical investigation predicts that, a saturated max gain of 17.5 dB, 3dB bandwidth of over 16 GHz are achieved at beam voltage of 60 kV, beam current of 5 A, pitch factor of 1.2 and operating magnetic field of 12.73 T. The results provide guidance for PIC simulation and experiment. P8-17 [A3313] A PIC simulation investigation on metal‐graphite explosive emission cathode GU Yu, LUO Wei, LI Yongdong (Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xian Jiaotong University, China) Abstract: The high power diode performance mostly depends on the explosive emission cathode (EEC) property. This paper focus on the metal-graphite material to improve the emission property of cathode. A parallel plate diode model is built based on the 2D PIC simulation software UNIPIC to simulate the emission process. The explosive emission process variance is investigated through changing the metrical components of cathode surface. Then, an empirical relationship between the metal adulteration and the plasma density of the cathode is found. P8-18 [A0670] Magneto‐Rayleigh‐Taylor instability driven by a rotating magnetic field: Cylindrical liner configuration DUAN Shuchao, YANG Long, XIAO Bo, KAN Mingxian, WANG Ganghua, XIE Weiping (Institute of Fluid Physics, CAEP, Mianyang, China) Abstract: Using the equilibrium Z-pinch as a magnetic-confinement fusion system was previously found to be difficult because of an unavoidable exchange or quasi-exchange mode instability. However, the development of pulsed-power technology and the dynamic Z-pinch has led to renewed interest in the Z-pinch for fusion applications. In a dynamic Z-pinch system, magneto-Rayleigh-Taylor (MRT) instability is inevitable from implosions of the Page 155

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plasma driven by magnetic pressure. While developing along with other modes of instability, the MRT instability grows much faster and by undermining the pinch symmetry is the most dangerous. We propose using a directional time-varying (rotating) driving magnetic field to suppress MRT instability in the dynamic Z-pinch. A finitely thick cylindrical liner configuration was studied. A rotational drive magnetic field is equivalent to two magnetic field components, Θ and Z, which alternate with time, referred to as an alternate theta-Z-pinch configuration. The maximum e-folding number at stagnation of the dominant mode of an optimized alternate theta-Z-pinch is significantly lower than that of the standard theta- or Z-pinch. The directional rotation of the magnetic field is independent of finite thickness; these parameters cooperate and enhance the suppressing effect. The finite thickness effect appears only when the orientation of the magnetic field varies in time and there is no reflection in the standard theta- or Z-pinch. Because the MRT instability can be well suppressed in this way, the alternate theta-Z-pinch configuration has potential applications in liner inertial fusion. This work is supported by the National Natural Science Foundation of China (Grant Nos. 11405167, 51407171, 11571293, 11605188, and 11605189) and the Foundation of the China Academy of Engineering Physics (Grant No. 2015 B0201023). P8-19 [A1838] Estimation of the neutron generation from gas puff Z‐pinch on Qiangguang facility WANG Liangping, CONG Peitian, ZHANG Xinjun, ZHANG Jinhai, LI Mo (Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: Z-pinch using a deuterium gas-puff load has been validated as a plasma neutron source (PNS) on many accelerators such as Saturn, Z, Angara-5 and S-300. The experimental results on these accelerators show that the production of the neutron can be scaled as the forth power of the peak current of the accelerator, no matter what mechanism is eventually determined to be responsible for generating fusion neutrons. The neutron production on Qiangguang generator (1.5MA,100ns) is analytically estimated that approximately 4×1010 D-D neutrons would be produced, among which the thermonuclear neutrons is only 7×107. The gas puff construction used on Qiangguang is introduced and the optimum line mass of the D2 gas is given. The results show that the optimum line mass is approximately 50μg/cm for Qiangguang's driving current. The mass density distribution obtained with the classical ballistic-transport model demonstrates that the gas puff forms a hollow gas shell with the length of 2cm. For D2 to produce a gas flow with the line mass is 50μg/cm the firing time of Qiangguang changes to 250μs and the absolute pressure of the chamber is increased to 4.2atm

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EAPPC & BEAMS 2018 / Programme Wednesday 19 September 2018 P8-20 [A2308] Characterisation of X‐pinches as flash radiographic sources for imaging shock ejecta CAMPBELL Calum1, SHEPHERD David 1, BLAND Simon 2, JONES Aled 1, SINCLAIR Mark 1 (1. AWE plc., Aldermaston, United Kingdom ; 2. Imperial College, London, United Kingdom) Abstract: AWE is currently interested in using the X-pinch as a tool for X-ray radiography of small, fast moving, objects in collaboration with Imperial College London (IC). An X-pinch is comprised of two or more micron scale wires crossed at a single point under vacuum. Passing a fast rising current, approximately 1 kA/ns, results in the breakdown of the wires at the contact point and produces X-rays, of the order 10 keV. Previous work by IC has shown that the combination of four wires crossed at a single point produces more consistent X-rays compared to previous methods, such as two crossed wires or the Z-pinch. The ‘Nene’ and ‘dry pinch’ machines at IC provide sufficient power, current and rise time for producing X-rays, while being compact and simple to operate. Our aim is to use tools such as step wedges, photo-diodes and pinholes to characterise both systems. Fulfillment of this will allow us to determine the suitability of the X-pinch for imaging material ejecta. AWE has refined the firing process of ‘Nene’ with the previously mentioned diagnostics. This has resulted in a high shot reproducibility, prior to commencing the second phase of our experiments, imaging exploding wires including imaging simultaneous X-pinches. P8-21 [A1810] Research on X‐ray backlightings of X‐pinch on Light II‐B Device ZOU Jian, ZENG Nai-Gong, WANG Chuan, ZHANG Tian-Jue, JIANG Xing-Dong (China Institute of Atomic Energy, China) Abstract: The experiments were carried out on the pulsed power generator Light II-B （~ 250 kA，50ns）developed by China Institute of Atomic Energy. The wire load X-pinch was installed on the cathode and anode of the Light II-B device and the current-return rod. Light II-B was used to drive the wire load X-pinch. With a series of backlighting images taken at different moment during wire X-pinch discharge can be clearly seen. The plasma explosion and implosion near the cross point of the X-shaped wires could be seen, especially the early behavior of the plasma formation in X-pinch. The research can provide a better understanding of the physics plasma formation. P8-22 [A0320] Initial stage of underwater wire electrical explosion EFIMOV Sergey, ROSHOSHEK Alexander, TIWORI Somesh W., KRASIK Yakov E. (Physics Department, Technion, Haifa, Israel) Abstract: The results of a recent research of microsecond timescale Page 157

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underwater electrical explosion of single wires made of Cu, Al, Ta, Mo and W will be presented together with parameters of shockwaves generated in water by radial expansion of exploded wires. A pulsed power generator with a discharge current amplitude of ~250 kA and a rise time of ~800 ns was used. To obtain time evolution of the exploded wire and generated shock wave, a shadow streak imaging was applied using SC-10 Optronis streak camera and backlight by 532 nm, 1.5 W CW single mode laser. The obtained shadow images allowed us with nanosecond timescale precision to determine the time of solid-state-liquid-vapor-plasma phase transitions. These data were compared with the results of MHD simulations coupled with EOS of wire materials and water, conductivity models, Ohm law and electrical circuit equation as well as with tabulated values of action intergral. P8-23 [A0624] Numerical simulation of common vacuum diode load of Gamma‐4 facility CHERNYSHEV Eugene, PUCHAGIN Sergey, STRABYKIN Kirill, GORDEEV Vyacheslav, TRUBTSEVA Ruslana (Russian Federal Nuclear Center - All-Russian Research Institute of Experimental Physics, Sarov, Russia) Abstract: Four-module electrophysical facility Gamma-4 aimed at producing bremsstrahlung pulses with duration ~50 ns has been built in RFNC-VNIIEF, Sarov, Russia. The operating mode of the facility in which all its accelerating modules are connected in-parallel to the common vacuum diode is under consideration in the paper. In this mode it is planned to increase the X-ray energy density as compared to the mode in which every module has its own separate vacuum diode load. Numerical optimization of the common vacuum diode design for Gamma-4 facility based on PIC simulations has been performed. The criterion of the optimization process was increasing the efficiency of energy and power transmission from accelerating modules to the load. It is shown that the impedance of the diode can be decreased to required value ~0.7  (matched mode) by changing cathode configuration and adding central anode post. According to the results of simulation it should lead to the rise of the energy and power transmission efficiency by ~30% as compared to the original design of the load. P8-24 [A0802] Predictions of Bremsstrahlung dose output of Gamma‐4 facility TRUNTSEVA Ruslana, PUCHAGIN Sergey, STRABYKIN Kirill, GORDEEV Vyacheslav, CHERNYSHEV Eugene, ZALYALOV Adel (Russian Federal Nuclear Center - All-Russian Research Institute of Experimental Physics, Sarov, Russia) Abstract: Four-module electrophysical facility Gamma-4 aimed at producing bremsstrahlung pulses with duration ~50 ns has been built in RFNC-VNIIEF. The facility is planned to be used in two modes. In the first one the accelerating

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modules are fully electrically independent and each of them ends with separate vacuum diode. In the second one the modules are connected in-parallel to the common diode load to increase the X-ray energy density. The results of calculations of absorbed dose distribution in the near-field are presented for two mentioned operating modes of the facility. The calculations have been made with the aid of S-007 Monte-Carlo code designed in RFNC-VNIIEF. The distributions of absorbed dose in air volume 20x100x100 cm behind the aluminum vacuum barrier have been received.

Poster Session IX- Pulsed Power Applications - Session Chair: SHI Jinshui (BALL ROOM 2#) [13:30-15:00] P9-1 [A0053] Research of electric field characteristics of hard rock in water under high voltage pulse CHEN Wenguang, DENG Xiaoxu, TAN Pingping, JIANG Liming, GUI Chengdong (University of South China) Abstract: Mineral processing has the problems of high energy consumption, low degree of mineral dissociation and low leaching rate. Based on the traditional mineral grinding process and the laboratory data of high voltage pulse discharge in other fields, the high-voltage pulsed discharge to assist in the ore grinding was proposed. The electro-hydraulic effect produced by high-voltage pulses discharge in the water may reduce the mechanical strength of the ore and break the ore. The main research contents and achievements of this thesis are as follows. (1)The equivalent circuit of high voltage pulse discharge system was theoretically analyzed, and the formula of discharge voltage was obtained by the basic theory of high voltage pulse discharge. The high voltage pulse discharge model of a hard uranium rock under water is established in COMSOL Multiphysics using the mechanism of high-pressure pulse under water and the mineral parameters of a uranium deposit. Under the experimental condition of high voltage pulse voltage of 28kV, the electric properties, particle size and location of ore particles under high voltage pulse discharge in a hard rock are numerically simulated. (2)The particle size of ore particles is 12.5mm. the influence of mineral particles with different mineral components on the intensity and the distribution of electric field were discussed. Through the analysis of the experimental data, the following conclusion is drawn: the size and distribution of the electric field intensity depend on the electrical properties of the mineral. In addition, the electric field intensity is focused on the boundary of the mineral, which shows that the electrical crushing is selective rather than accidental. (3) under the experimental conditions of one-component ore samples and the distance between the electrode is equal to the size of the ore, the electric field simulations of different grain sizes were studied. The results show that the size Page 159

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of ore particles also affects the electrical crushing. The maximum intensity decreases almost exponentially with the particle size. (4) The electric field of ores under the same electrode size, composition and the electrode distance was studied. The results show that under other constant conditions, the maximum electric field intensity will decrease with the increase of electrode distance, and the distribution along the uranium ore tends to be uniform. In this paper, the electric field characteristics of high voltage pulsed discharge under the water were studied through numerical simulation experiments. The general rule of high-voltage pulsed electric field under the action of hard rock was got, providing a theoretical guidance and a certain operation method for the application of pulsed discharge in water technology in mineral processing. P9-2 [A0249] High voltage pulse generation system for xenon lamp light sintering CHO Chan-Gi1, SONG Seung-Ho 1, PARK Su-Mi 1, PARK Hyeon-Il 1, JIA Zi-Yi 1, BAE Jung-Soo 2, JANG Sung-Roc 3, RYOO Hong-Je 1 (1. Chung-Ang University, Korea; 2. University of Science and Technology, Korea; 3. Korea Electrotechnology Research Institute, Korea) Abstract: In this paper, we deal with the design and implementation of a 1500 V, 1200 A pulse power supply system for xenon lamp driving in the application field of printed electronics. The high voltage pulse generation power supply for operating the provided xenon lamp is a 1500 V DC power supply using LCC high efficient resonant converter to charge the large capacity capacitor and discharge it to xenon lamp by 1500 V, 1200 A discharge pulse. High voltage pulse discharge is designed with a structure that can set various conditions. The proposed system confirmed its performance through simulation and resistance load experiments, its validity was proved in applicationto an actual xenon lamp system. The system is confirmed stable operation with 185 J/cm2 class xenon lamp for application to printed electronics, and it is expected to be applicable to various printed electronics fields. P9-3 [A0301] Increase of operating temperature of magnetic field sensors based on La–Sr–Mn–O films with Mn excess ZURAUSKIENE Nerija1, Kersulis Skirmantas2, Stankevic Voitech1, Klimantavicius Jonas2, Plausinaitiene Valentina3, Balevicius Saulius1 (1. 1) Center for Physical Sciences and Technology; 2) Vilnius Gediminas Technical University, Vilnius, Lithuania; 2. Center for Physical Sciences and Technology, Vilnius, Lithuania; 3. 1) Center for Physical Sciences and Technology; 2) Vilnius University, Vilnius, Lithuania) Abstract: Recently, it was demonstrated that nanostructured manganite La-Sr-Mn-O films which exhibit the colossal magnetoresistance (CMR) effect can be successfully used for the development of CMR-B-scalar sensors. These sensors allow measurements of absolute magnitude of magnetic flux density during high magnetic field pulses. They were used to measure magnetic field distribution in railguns and non-destructive pulsed-field magnets. It has to be Page 160

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noted that for many industrial applications, such as magnetic welding or forming, sensors operating at higher than room temperature are required. However, the magnetoresistance of manganite films decreases at temperatures higher than ferromagnetic-paramagnetic phase transition temperature. Therefore, it is important to increase operating temperature of CMR-B-scalar sensors, still keeping high sensitivity to magnetic field. In this study, the results of the investigation of magnetoresistance of nanostructured La-Sr-Mn-O films with Mn excess are presented. The films having different Mn excess (5%, 10%, and 15%) were grown using the pulsed-injection metal-organic chemical vapor deposition technique onto a polycrystalline Al2O3 substrate. It was obtained that by increasing Mn excess in the films the phase transition temperature could be increased by 20 degrees. The possibility to apply these films for the development of magnetic field sensors operating up to 60 C is discussed. P9-4 [A0518] Dependence of NOx removal on the operating conditions of nanosecond pulsed discharges LEE Sang Uk, CHUN Kyoung-Jae (Department of Nuclear Engineering, Seoul National University, Seoul, Korea,) Abstract: Nitrogen oxides (NOx) generated by the reaction of nitrogen with oxygen at high temperatures are not only harmful to living organisms but also cause pollution such as photochemical smog and acid rain. For these reasons, regulations on NOx emissions from diesel engines are being tightened. To cope with this, the development of technologies for minimizing NOx emissions is urgent. Among the ways of removing NOx, there is a method using ozone and radicals generated from corona discharges. Especially, using nanosecond pulsed discharges can produce high-energy electrons efficiently, thus removing NOx more effectively. In this study, a diesel vehicle is modified for the installation of a NOx reduction device in the exhaust system. The NOx removal efficiency are investigated by changing the broad range of conditions of a variable high-voltage pulsed power source such as pulse width, operating frequency, and voltage magnitude. From the experimental results, the optimum parameters of the pulsed power source required for the plasma generator are determined. P9-5 [A0614] Improvement of fuel cladding behavior at accidental conditions using pulsed electron beams WEISENBURGER Alfons, AN Wladimir, FETZER Renate, JIANU Adrian, MULLER Georg (Karlsruhe Institute of Technology, Germany) Abstract: Intense pulsed electron beams have been used for surface modification of materials for several years in our laboratory. An improvement of properties like wear, corrosion and oxidation resistance is obtained by the pulsed electron beam treatment of mainly metallic materials. Surface alloying of metal substrates with elements improving oxidation resistance is one of the Page 161

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processes being developed using the GESA (Gepulste Elektronen Strahl Anlage) facilities with the following parameters: accelerating voltage 80–150kV; power-density up to 2 MW/cm2; beam-diameter 4–10cm; pulse-duration 4– 450µs. Such pulses applied on material surfaces previously coated with specific elements lead to a change in microstructure and in chemical composition resulting in surface graded materials. Surface alloying of Al into steels increase their oxidation resistance in liquid lead alloys by the selective formation of alumina scales. Such scales prevent the degradation of mechanical properties in Pb alloys and are an effective barrier against liquid metal attack. The surface modification with pre-alloyed thicker coatings is at time considered as one of the advanced surface mitigation strategies in Pb alloy cooled nuclear systems. At present zirconium-based alloys are used as fuel cladding material for water cooled nuclear reactors. In the Fukushima Daiichi accident, the Zr-cladding overheated and acted as a catalyst for water splitting, and hydrogen production followed by the subsequent hydrogen explosion. To prevent such scenario accident tolerant fuel claddings are under development in several international projects. Two options consider the use of pulsed electron beams (GESA); one focus on heat impact for the final synthesis of MAX-phase coatings, the other rely on surface alloying of Alumina and Chromia formers into the Zr-cladding material. The latter should allow the formation of Cr-rich oxide scales at nominal operating conditions (330°C 150 bar) and the formation of Alumina at accidental conditions. The parameters for the MAX-PHASE processing using the GESA facility were determined simulating the GESA pulse and the heat transport in the respective material architecture. The presentation will give an overview on the pulsed electron beam treatment, the respective simulations and will present the actual status of the heat treatment and the surface alloying of alumina- and chromia-formers into the Zr-cladding. P9-6 [A0702] Study of the thermodynamic and hydrostatic effects on the electrical breakdown in IMBERT Tony1, REESS Thierry2, DE FERRON Antoine2, PECASTAING Laurent2, DEMOL Gauthier1, GUEGAN Baptiste1 (1. ITHPP, Thégra, France; 2. UNIV PAU & PAYS ADOUR/E2S UPPA, LABORATOIRE DES SCIENCES DE L'INGÉNIEUR APPLIQUÉES À LA MÉCANIQUE ET AU GÉNIE ELECTRIQUE – IPRA, EA4581, 64000, PAU, France) Abstract: Geo-energy has recently seen the emergence of a new method of drilling using electric impulses in extreme thermodynamic and hydrostatic conditions. This new method has huge potential for improving drilling productivity. It is essential to ensure that the initiation of the electrical breakdown happens independently of the fluid conditions. For arc initiation, the conductivity of the drilling fluid plays an important role. Indeed, the temperature and the static pressure of the drilling fluids evolve gradually according to the depth of the well. The depth conditions of well were experimentally simulated in a pressurised and temperature controlled chamber. This paper presents experimental findings following the study of the voltage breakdown of a liquid Page 162

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gap as a function of its conductivity, with applied static pressures and temperatures. It exposes the required energy consumption to initiate the breakdown. A comparison of results obtained for two different fluids (drilling mud and salt water) with the same conductivity also be presented.. P9-7 [A0868] A new type of seismic source for seismic exploration FU Rongyao, SUN Yaohong, XU Xuzhe, YAN Ping (Institute of Electrical Engineering, Chinese Academy of Sciences, China) Abstract: There is a corresponding requirement for the frequency and amplitude of the shock wave in the seismic exploration. The main frequency and magnitude of the shock wave directly determine the propagation distance and the exploration resolution. In this paper, a new type of seismic source was developed and a regulation technology of trigger discharge in time series was proposed. The rising time, amplitude and pulse width of discharge current can be adjusted in a certain range through the technology, and different kinds of shock waves can be got. Based on the mathematical relations of discharge current and shock wave in the past references, the circuit simulation of sixteen discharge systems is carried out. Each discharge source is 2 kJ, and the maximum discharge current is 10 kA. The simulation result shows the feasibility of the shock wave control technology. P9-8 [A0981] Integrated high voltage trigger and simmer power supply for the xenon lamp sintering CHO Chan-Gi, SONG Seung-Ho, PARK Su-Mi, PARK Hyeon-Il, JIA Zi-Yi, RYOO Hong-Je (Chung-Ang University, Korea) Abstract: In this paper, we will deal with the development of a xenon lamp driving trigger and a simmer power supply for application to electronic printing. The proposed 15 kV DC trigger and the 1 kV simmer power supply are new structures sharing the primary side. It has the feature of using one full bridge inverter and two transformers to reduce the number of elements and the volume of the system. A 15 kV DC Trigger circuit for ionization of xenon molecules is composed of a voltage multiplier circuit and utilizing the characteristics charged by a current source makes it possible to charge a higher voltage than the number of multiplier circuits. In addition, the simmer power supply shows the ability to drive with a wide switching frequency up to 700 kHz at 135 kHz to directly react changes in lamp impedance. The proposed auxiliary power supply system is expected to be able to effectively use it as a xenon lamp driving power source in the field of printed electronics by confirming stable operating performance through simulation, lamp lighting and continuous operation experiments.

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EAPPC & BEAMS 2018 / Programme Wednesday 19 September 2018 P9-9 [A1562] Study of exhaust air treatment from a ship building factory painting facility using pulse plasma technology with adsorption solution. JIN Hee-sung, SONG Seung-Ho, RYOO Hong-Je (Chung-Ang University, Korea) Abstract: With increasingly strict regulations from the year 2018 to 2022, on exhaust air from large sized painting facilities, in order to treat Total Hydro Carbon (THC) gases from large sized Block painting facility like ship building factory, the air treatment system is constructed and tested using pulse power supply plasma and adsorption solution at exhaust air side from the painting facility of a ship building factory. It was constructed with pre-treatment, adsorption + plasma system, post-treatment as one system and our system met the regulation on the exhaust air, which was tested and approved by an official test lab. And it showed the advantage in operation cost, which is much lower than other solutions. P9-10 [A1780] Inactivation of a gram positive coccus cell model using ceramic coated electrodes under pulsed electric field treatment RAMASWAMY Ramya1, GOWRISREE V2, RAMACHANDRAN Raja Prabu1 (1. B.S. Abdur Rahman Crescent Institute of Science and Technology, India ; 2. College of Engineering, Anna University, India) Abstract: Using three dimensional electromagnetic simulation, a coccus cell model in suspension medium was placed in the inactivation area under pulsed electric field treatment. A high permittivity ceramic was adhered with electrodes, which avoided direct contact of electrodes with liquid food paving way for successful noninvasive PEF method, which overcomes the drawback of electrolysis. Electric field analysis was performed using these electrodes and the transmembrane potential was measured across the cell membrane. The electrodes were made of stainless steel which is the state of art material used in most PEF applications. Different liquid food was used as suspension medium and the effect of conductivity change on critical electric field was observed. The ceramic coated electrodes satisfied electroporation phenomenon which paves a way to improve PEF processing. P9-11 [A3225] Magneto‐forming research at Loughborough University ALOTAIBI T., NOVAC B. M., SENIOR P., NEKOUIE V., ROY A., SILBERSCHMIDT V. (Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, U.K.) Abstract: The paper describes various experimental studies of magneto-forming technology, undertaken at Loughborough University and using the existing 2 MA/100 kJ Quattro capacitor bank as power supply. Many Page 164

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practical arrangements were used, but the results presented focus only on: Cold welding aluminium cylinders with galvanized steel cylinders in theta-pinch geometry cold welding stainless steel cylinders with stainless steel cylinders in theta-pinch geometry- forming magnesium plates in flat plane geometry For cold welding results, the joining quality obtained with magneto-forming was analyzed at the interface as well in the adjoined materials in comparison with their pre-manufacture (as delivered) state. The used characterisation techniques included micro- and nano-indentation as well as X-ray diffraction, optical microscopy and scanning electron microscopy. P9-12 [A0162] Transient thermal effects and rail damage in electromagnetic launching DONG Zonghao (Computer Control Engineering of Hebei Province, Yanshan University, Qinhuangdao, China) Abstract: When solid armature moves along rail at high speed, the thermal effect will destroy good contact between armature and rail in the process of electromagnetic rail propulsion. In this paper, the simulation, measurement and characteristic analysis of the contact surface temperature are carried out for the high speed sliding electrical contact between armature and rail. Based on the theory of electrical contact, it has analyzed the temperature source of the armature and rail contact surface, established the temperature model, and studied the different effects of different contact temperature on the armature and rail. Based on infrared radiation thermometry, measurement system measured contact temperature between rail and armature in the device. The correctness of the simulation was verified by the data comparison of experiment and simulation. The analyzing experimental result has been obtained the influence of different parameters on the temperature characteristics of armature and rail’s contact surface. Comparison of the rail’s damage under the different conditions, further analysis combined the temperature effect with the damage result. The simulation result shows that the temperature model could obtain macroscopic characteristics, such as temperature, displacement, velocity, etc. The experimental results also reflect the rail’s damage with the temperature change of contact temperature between rail and armature in the electromagnetic rail propulsion. It provides an effective basis for the contact analysis of armature and rail. P9-13 [A0731] Options for an electric launcher system HUNDERTMARK Stephan, SCHNEIDER Markus, LIEBFRIED Oliver (ISL, Saint Louis, France) Abstract: Railguns are current driven guns that allow large muzzle velocities and energies. In the military context, the long range artillery scenario makes use of these two capabilities to enable the launch of hypervelocity projectiles to target distances above 100 km. As of today, the most advanced railgun project is conducted by the Office of Naval Research (ONR) and features railguns with Page 165

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a muzzle energy of 32 MJ. Such large artillery railgun systems, with efficiencies above 30 % are feed by a pulsed power system (PSU) with a nominal energy content of about 100 MJ. In contrast to this, experiments with ISLs most powerful railgun, PEGASUS, has reached muzzle energies of 2 MJ, only. In the near future the railgun group at ISL has to answer two questions: - Is the railgun technology adequate for the long range artillery scenario ? - Can the railgun launch the hypervelocity projectile which is being developed by other groups in ISL ? To do so and to support the development of the hypervelocity projectile a larger railgun installation with a significant increase of the energy and free flight capability is proposed. For this a new railgun including the PSU has to be developed. In this study, three different railgun systems were investigated using an electric circuit simulation code. The systems are referred to by the energy being stored in the capacitors as 25 MJ, 50 MJ and 100 MJ. The aim of this study is to investigate what masses can be accelerated to the relevant velocity range for the long range artillery scenario by these different primary energies. P9-14 [A1392] Research on the release time of the additional discharge modules in the electromagnetic launch system WANG Zhenchun, BAO Zhiyong, LIU Fucai, ZHAN Zaiji (Yanshan University, China) Abstract: When the design of the railgun system is completed, especially when the pulse power module is filled with the specified voltage, the only parameter that can be adjusted in the armature motion process is the discharge time. The state of the load at the moment has a great relationship with the change of the muzzle velocity by the discharge module. In this paper, firstly, the model of electromagnetic launch system is described by nonlinear differential equations, which combines the model of discharge circuit with the dynamic model of the armature. Secondly, the relationship between the release time and the muzzle velocity is obtained by the model of electromagnetic launch system which takes into account the different release time of the additional discharge modules. In the end, considering the contact state between the armature and rail presents the solid-liquid state at a high velocity, the feedback algorithm can be used to determine the time of the additional discharge modules to improve the accuracy of muzzle velocity. In conclusion, the relationship between the release time of the additional discharge modules and the muzzle velocity is established. Meanwhile，the accuracy of muzzle velocity can be guaranteed by the control algorithm under the high velocity of the armature in simulation. P9-15 [A0506] Theoretical and numerical research of magnetically driven one‐sided flyer plate experiment KAN Mingxian, XIAO Bo, WANG Ganghua, DUAN Shuchao, ZHANG Zhaohui, WANG Guilin, GU Zhuowei (Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, 621999,China)

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Abstract: The one-sided calculation model and the two-sided calculation model are used to simulate the magnetically driven one-sided flyer plate experiment. Numerical simulations show that the MHD code can correctly simulate the free surface velocity of flyer plate for both one-sided and two-sided calculation models. Only that the effective coefficients of current adopted in the two calculation models are slightly different, for the coefficient in the one-sided calculation model being slightly smaller than that in the two-sided calculation model. Numerical simulations also show that the reason the magnetically driven one-sided flyer plate experiment can be correctly calculated by the one-sided calculation model is not that the cathode face keeps still, but that the depth of the melted region on the cathode face is small and remains nearly unchanged in the middle to later stage of the experiment. P9-16 [A1180] Characteristics of nanosecond‐pulse surface flashover under different electrical fields SUN Chuyu, ZHANG Guowei, WANG Haiyang, XIE Linshen (Northwest Institute of Nuclear Technology, Xi'an, China) Abstract: The weakness of surface insulating in SF6 gas is one of the predominant factors to restrict the development of gas insulating pulse power devices. In order to explore the characteristics of surface flashover in different electric fields, experiments under positive and negative pulses whose rise time were about 32 ns were conducted in 0.4 MPa SF6 gas. And polymethyl methacrylate (PMMA) and polyimide (PI) samples were tested. Two types of figure electrodes were employed with or without ground plate – a stainless plate which located just below the sample and whose potential was bound to zero. The results show that the polarity effect appears in both electrodes types, the negative flashover voltage was higher than the positive one, especially under the electrodes with ground plate. The introduction of ground plate would increase the electric field nonuniformity and enhance the vertical components of electric field vector, and consequently, influence the distribution of space charge. The spectral analysis shows that the surface of PI sample has been damaged during nanosecond pulses, since the CFn peaks have been identified. The subsequent test of SEM and EDS also suggests that in flashover zone of PI sample, the roughness increased and element F has been discovered.

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Oral Session 16 - Compact and Repetitive Pulsed Power Systems - Session Chair : RYOO Hongje (BALL ROOM 1#)[15:00-17:30] 15:00 O16-1(Invited) [A1230] Research progress on high power repetition frequency long pulse power source SONG Falun, LI Fei, JIN Xiao (Science and Technology on High Power Microwave Laboratory, Institute of Applied Electronics, CAEP, China) Abstract: With the development of pulsed power technology, the pulsed power sources with high peak power cannot meet the demand of diverse applications, and the compact repetition frequency pulsed power source is more and more concerned by researchers. In recent years, based on the requirement of increasing energy utilization efficiency and the demand of high power microwave, compact repetition long pulse power source has become one of the focuses of researchers. It is one of the main directions for the development of the future pulse power technology to develop the repetition frequency pulsed power source of miniaturization, light quantization and high pulse energy. This paper mainly introduces the research progress and the breakthrough achievements of the key technologies on repetition frequency long pulse power sources in the Institute of Applied Electronics, CAEP. It mainly includes the energy storage and pulse forming integration technology, the low jitter and repetition frequency gas switch technology, the low jitter high energy trigger technology, the compact Marx generator technology and so on. At the same time, several typical high power repetition frequency pulsed power devices developed by the Institute of Applied Electronics are introduced: repetition frequency long pulse power source based on Linear Transformer Driver, compact pulsed power source based on kapton-film dielectric line, the modular low impedance compact Marx generator, compact high energy repetition frequency pulsed power source. The research of key technology and its development status are discussed, which can provide reference for the future development and application direction of the miniaturization of pulsed power sources. 15:25 O16-2 [A1638] All‐solid‐state bipolar high voltage nanosecond pulse adder with output parameters adjustable WANG Yonggang, HUANG Yifan, GAO Ming, JIANG Ming (Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China) Abstract: Nanosecond high voltage pulse generators are widely used

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in dielectric barrier discharges, plasma jets, corona discharges in water, etc. In this paper, a novel bipolar pulse adder with output parameters adjustable is proposed. Several full bridge MOSFET units are connected in series. And the storage capacitors in each unit is charged isolated by a high-frequency resonant power supply. In order to solve voltage unbalance between storage capacitors, a third winding is added to each magnetic core transformer. The mechanism of eliminating voltage difference by third windings is analyzed in theory, and validated by simulation and experiments. Optic fibers, together with gate drivers, are used to drive MOSFETs. Thus, each switch can be turned on or off independently and the rising/falling time of each pulse is adjustable. A 6-stage prototype is implemented in laboratory. The pulse adder can generate 5 kV bipolar pulses with voltage polarity, amplitude, repetition rate, pulse width, and rising/falling time adjustable independently. The experimental results are shown in this paper and discussed at last. 15:40 O16-3 [A1668] Amplification of nano‐second pulsed power by synchronization of double inductive energy storage circuits SUGAI Taichi1, YAWATA Kosuke1, TOKUCHI Akira2, JIANG Weihua1 (1. Nagaoka University of Technology, Japan; 2. Pulsed Power Japan Laboratory Ltd., Nagaoka University of Technology, Japan) Abstract: For environmental application using pulsed corona discharge, scale-up of reactor and nano-second pulsed power generator will be required at step of actual use. To amplify the pulsed power, we connected two same inductive energy storage (IES) circuits in series or in parallel and attempted to synchronize them. The IES circuit consists of the primary and secondary circuits via the pulse transformer. The secondary circuit consists of a capacitor, a coil, and the semiconductor opening switch (SOS). When the IES circuits are connected in series, double inductive voltage is obtained at a load. In case of parallel connection, current through a load is double. In this presentation, the detail of the circuit and the effect of the synchronization will be described. 15:55 O16-4 [A1880] A compact, high‐repetition frequency, all solid‐state pulsed power source LI Hongtao, LUAN Chongbiao, XIAO Jinshui, MA Xun, HUANG Chuanwei, HUANG Yupeng (Key Laboratory of Pulsed Power, Institute of Fluid Physics, CAEP, China) Abstract: A novel Si photoconductive semiconductor switch (PCSS) with reflected cavity was studied and the measured lifetime of prepared Si PCSS working at 13kV/1.1kA/73ns/1kHz is longer than 1.2×106 shots. And a PFL with curve electrode structure was Page 169

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designed and the measured longevity of prepared PFL working at 21.6kV/4.4kA/1kHz is longer than 1.1×106 shots. Then, a compact, high repetition frequency, all solid state pulsed power source with 20 stages Marx generator structure was studied. When it works with charging system, control system, circulatory cooling system and laser triggering system at one time, the durative time for the prepared pulsed power generator, which works with output voltage 113kV, output current 1.1kA, pulse width 50.8ns, rise time 14.5ns, and repetition frequency 1kHz, is longer than 6min. 16:10 O16-5 [A2112] Design of a compact high power repetitive Marx generator HAO Shirong, DAI Wenfeng, CAO Longbo, FENG Chuanjun, WANG Minhua, WU Wei, HAN Wenhui (Key Laboratory of Pulsed Power, Institute of Fluid Physics, CAEP) Abstract: A experimental device of a compact high power repetitive Marx generator has been designed which consists of 15-stage energy storage units made up of capacitors, convergence transmission lines, two-stage trigger switches, self-breaking spark-gap switches and isolation inductors. By adopting three capacitors in parallel as each stage energy storage unit and combined with Integration and low inductance structure and layout design of energy-storage unit, convergence transmission line and switch, the inductance of the Marx generator can be reduced, and consequently the resistance can be reduced to about 12Ω. The simulation results show that an output power of 30GW can be obtained on a 10Ω～15Ω load. According to the designed volume of the Marx generator，we can figure out the power density at 150MW/L. The Marx generator can operate at repetitive frequency of 40Hz. 16:25 O16-6 [A2516] A compact underwater pulsed current source with remote controlling function ZHOU Haibin, FAN Jiangwei, XU Haisheng, JU Yang, YU Jingfeng (Systems Engineering Research Institute, China) Abstract: A typical application of pulsed power technology is underwater pulsed discharge, which will generate shock waves (SWs). Underwater plasma acoustic source and anti-frogmen devices are typical practical equipment. Underwater discharge will generate plasma and wide-band sound waves. In which, the high frequency waves will help to improve the imaging resolution, and the low frequency waves have better penetrability and can detect further. Besides, this kind of acoustic source has the advantages of controllable repetition frequency and low cost. Underwater acoustic waves have effective damage to frogmen, and these acoustic waves Page 170

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are not easily defended also because of the wide-band characteristics. However, these devices are usually used in the field, so their power supply and controlling are not easy. In this paper, an underwater pulsed current generator was built, which is a multi-functional current source. If the discharge load is water gap (two electrodes at a certain distance immersed in water) or thin metal wires, acoustic waves will be produced, and if the discharge is some kind of antennas, the electromagnetic waves will be produced. The pulsed current source is composed of a charging subsystem, a discharge device, a trigger subsystem, and a synchronous control subsystem. The charging subsystem contains several 48V storage batteries and a high voltage direct current source with the voltage of 50kV maximum. The discharge device uses coaxial structure. The energy is stored in several pulsed capacitors arranged in a metal tank filled with oil and packaged with insulation materials. Pulsed current will be generated when the coaxial field distortion switch is triggered. The discharge device has a general interface to connect different type of discharge loads. The trigger subsystem also has an independent power supply, and will export a 500ns/30kV voltage pulse through a high voltage coaxial cable. The trigger can by controlled by the synchronous control subsystem with an optical fiber. The synchronous control subsystem is based on the GPS, and has atomic clocks, which will guarantee the same time base between the discharge device and the detecting devices or other receivers. Furthermore, the discharge device can be controlled remotely by the synchronous control subsystem, which is very convenient in outdoor applications. 16:40 O16-7 [A2678] Investigation on quasi‐square pulses generation with a two‐node PFN‐Marx generator LI Zhiqiang, ZHANG Haoran, SHU Ting (College of Advanced Interdisciplinary Studies, National University of Defense Technology, China) Abstract: A three-stage two-node PFN-Marx generator, which can produce quasi-square pulses, is presented in this paper. At present, the two-node PFN-Marx is difficult to obtain quasi-square pulses. To address this problem, a specific topology circuit is introduced in this paper. The circuit bases on the identical inductors and capacitors network and the capacitance in one stage is changed (with others keep unchanged) to realize the modulation of the output waveform. The simulation results show that several two-node PFN-Marx circuits, which have three-stage, five-stage and ten-stage, can produce quasi-square pulses. A three-stage two-node PFN-Marx is established to verify the feasibility of this method. The experimental results show that the three-stage two-node PFN-Marx can generate a quasi-square pulse with the amplitude of 4 kV, the rise-time of about Page 171

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33ns and the flat-top of about 107 ns with ±3% voltage variation.

Oral Session 17 - HPEM Effects; Theory and Simulation - Session Chair: HE Juntao

(INTERNATIONAL HALL）)[15:00-17:30] 15:00 O17-1 [A0363] Self‐channeling of an ultra‐high power sub‐ns microwave beam in plasma CAO Yang, LEOPOLD John G., BLIOKH Yuri P., SHAFIR Guy, KRASIK Yakov (Physics Department, Technion-Israel Institute of Technology Haifa, Israel) Abstract: When a high-power, sub-ns microwave beam interacts with gas ionization-induced self-channeling of the beam occurs. Our experiments demonstrated for the first time that the plasma, generated by impact ionization of the gas, has a radial density distribution with minimum density close to the beam axis, where the microwave field is the highest, thus forming a channel for microwave beam propagation. We present new experimental results showing self-channeling of a ≤500 MW, 9.6 GHz, <1 ns microwave beam injected into a preliminarily formed plasma of ~3×1011 cm-3 density generated by an inductively coupled rf discharge in He gas at ~13 Pa. The experimental data obtained using microwave diagnostics and optical visible spectroscopy are in good agreement with the results of the numerical modeling carried out by the Lsp (Large scale plasma) code. 15:15 O17-2 [A0533] Analysis of the damage mechanism and pulse width effect of EMP in IC ZHANG Yonghua, HUANG Wenhua, LI Ping, YANG zhi qiang, REN Weitao, ZHU Zhanping (Science of Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: For several kinds of commonly used digital integrated circuits (ICs) and analog ICs, the electromagnetic pulse (EMP) injection experiment is carried out, the damage threshold is obtained, and the variation of damage threshold with the EMP width is analyzed. According to the failure analysis, it is found that transient strong electromagnetic field is formed by EMP in micrometer metal gap of IC, and breakdown along the surface of a metal gap is caused. Then a self-holding discharge electric field is formed and a plasma zone is produced, which causes short circuiting and large current between adjacent metal strips. At last, large area of IC is over current burnout and the IC function is disabled. Combining the Page 172

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high power microwave (HPM) breakdown mechanism and the pulse width effect on the coaxial cable and connector, it is concluded that the air breakdown along the surface of the media is one of the important damage mechanisms of the electronic systems. 15:30 O17-3 [A0903] Theoretical modeling of thermal breakdown in semiconductor devices affected by pulse repetition frequency ZHANG Cunbo, YAN Tao, REN Weitao,ZHU Zhanping (Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: Thermal breakdown has been identified as one of the principal failure mechanisms in semiconductor devices. The pre-existing theoretical modeling of thermal breakdown in semiconductor devices is summarized, through which the influence of pulse width and frequency on thermal breakdown is analyzed. On this basis the theoretical modeling of thermal breakdown in semiconductor devices affected by pulse repetition frequency is established in this paper. The influence of pulse repetition frequency and duty cycle on heat generation and heat conduction in the hot zone is introduced into the theoretical modeling. The heat transfer equation is solved by Green’s function method and the error function is approximated. Then, the expressions of temperature in the hot zone and failure power including pulse repetition frequency and duty cycle are derived. The change rules of temperature and failure power versus pulse repetition frequency are obtained. Meanwhile, the physical interpretation of the influence on failure power affected by pulse repetition frequency is given. 15:45 O17-4 [A0390] Cavity design tool for a CARM oscillator DI PALMA Emanuele, DATTOLI Giuseppe, CECCUZZI Silvio, SABIA Elio, RAVERA GianLuca, SPASSOVSKY Ivan, DORIA Andrea, TUCCILLO Angelo, GALLERANO GianPiero, MIRIZZI Francesco (ENEA Fusion Department, C.R. Frascati, Via E. Fermi 45, 00044 Frascati, Roma, Italy) Abstract: The interest in developing controlled fusion reactors as alternative sources of clean energy is growing worldwide in the course of, at least, the last 50 years. One of the most important components required for successful performance of these reactors is the source of the millimeter-wave power required for electron cyclotron resonance plasma heating (ECRH) and current drive (ECCD). The required frequency and power involved for a future large-scale fusion reactor, like DEMO, affects the microwave tube efficiency. At present, this millimeter-wave power is produced by Page 173

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gyrotrons capable of generating MW-level continuous power at frequencies above 200 GHz with the efficiency in the range of 30% - 50%. A different device based on cyclotron auto-resonance maser (CARM) oscillator mechanism operating in the frequency range around 250GHz will be revisited. The design for a CARM cavity oscillator, composed by a short smooth cylindrical waveguide section delimited by two Bragg reflectors, is a challenging task, aimed at realizing the conditions to select the right operational mode and to limit the growth of the competing modes. The most urging problem when dealing with the chosen cavity configurations is the competition between the selected operating mode and the neighboring parasitic (spurious) modes. Therefore, the radio frequency circuit design must be supported by a numerical model allowing to accurately simulate the intra-cavity beam wave interaction. The large length of the full resonator (80 cm) compared to the wavelength under investigation impairs the effectiveness of a classical PIC code, based on the discretization of the Maxwell equations, due to the huge amount of computer memory and CPU time required by the resulting mesh sizes. The main idea to solve the problem is based on the derivation of the semi-analytical formula and scaling law, that allow to optimize the cavity design with a manageable tools before to run the full 3D simulation. These formulae derived from the free electron laser oscillator theory give a computer-aided design (CAD) tool for the optimization of the electrodynamics system. The benchmarking with a commercial PIC code (CST Microwave Studio) simulation, the homemade 1D code (GRAAL) and literature results will be presented. 16:00 O17-5 [A0665] A first principle approach to calculate electron inelastic scattering cross section HU Jing, CAO Meng, LI Yongdong (Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Department of Electronic Science and Technology, School of Electronic and Information Engineering, Xi'an Jiaotong University, China) Abstract: Secondary electron emission is a major cause of degradation of performance for some instruments such as the multipactor effect in high power microwave components. Inelastic scattering is the key process in secondary electron emission. Calculation of inelastic scattering cross section is helpful to examine the microcosmic mechanism of secondary electron emission and further to find the method to suppress secondary electron emission and increase the multipactor threshold. In this work, we present a first principle approach to calculate the electron inelastic scattering cross section in metal with the following steps: 1. For a stable crystal model of atom arrangement with lowest system energy, the wave function and eigenvalues of ground state electron are obtained by Page 174

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solving the corresponding Schrödinger equation. The density functional theory is used to solve the time-independent Schrödinger equation and to determine the wave function and the energy of the quantum many-body system in a stationary state. Quantum Espresso, the integrated suite of open-source computer codes based on density-functional theory, plane waves, and pseudopotentials is used. 2. Based on the obtained electron wave functions and density functions, the excited state properties are further calculated. Here we use the Yambo code which relies on many-body perturbation theory and time-dependent density functional theory. The quasiparticle energies are calculated within the GW approximation for the self energy. The optical properties are then calculated by using the adiabatic local approximation with time-dependent density function theory. 3. The optical dielectric function is then used to describe electron energy loss and the associated secondary electron excitation according to the Penn’s dielectric theory. The electron energy loss function is derived from optical dielectric constants. This algorithm is used to calculate electron inelastic scattering cross section including energy loss cross and scattering angular distribution required for a Monte Carlo simulation. To verify the feasibility of our first principle approach, the secondary electron emission of Cu is simulated by using a Monte-Carlo method in which the calculated inelastic scattering cross section were used. The simulation results are in agreement with the experimental data. 16:15 O17-6 [A2067] A nonlinear theory of the intermediate cavity excitation by modulated electron beam in relativistic klystron amplifier HE Hu (China Academy of Engineering Physics, Mianyang, China) Abstract: According to Maxwell equations and Lorenz force equation, the self-consistent equations of the intermediate cavity excitation by modulated electron beam in relativistic klystron amplifier are developed. Properties of the intermediate cavity excitation by the beam are described in terms of the phase shift Φ and amplitude Aof RF axial electric field. When the gap length is 1.7cm, the gap voltage calculated from self-consistent equations are consistent with the results of PIC simulation and the equivalent circuit model, and the phase shift between ac current at the entrance of the gap (model B) and the gap voltage (model A) agrees well with the results of the self-consistent equations. The temporal curves of gap voltage and phase calculated from self-consistent equations are similar to the results of PIC simulation. When the gap length approaches 0, the phase shift ∆ ( the equivalent circuit model) is the limit of the phase

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shift Φ. 16:30 O17-7 [A2214] Multi‐physical simulation of aircraft anti‐/de‐icing with perfect metamaterial absorber under microwave heating ZHANG Zehai1, YUAN Yuzhang1, LIU Xiyue2 (1. College of Advanced Interdisciplinary Studies, National University of Defense Technology (NUDT), Changsha, China ; 2. College of Basic Education, National University of Defense Technology(NUDT),Changsha, China) Abstract: A possible in-flight anti-/de-icing method under microwave heating for aircraft with Perfect metamaterial absorber (PMA) as the thermal source is proposed in this paper. The PMA is thin planar composite and can totally absorb incident microwave at single frequency and then transform the absorbed electromagnetic (EM) energy into thermal energy due to heating effect of microwave. The electromagnetic property of a hollow square ring PMA is investigated with commercial high frequency software and a set of parameters corresponding to reflectivity of -19.6dB at 2.45GHz is achieved. Kept parameters unchanged, an EM and thermal co-simulation is carried out with multi-physical software COMSOL. The co-simulation shows that the maximal temperature rise within PMA reaches 18℃ after 300s planar microwave radiating with its power density of 200W/m2. While volumetric weighted mean temperature rise of the entire PMA due to energy deposited within it is 4℃ in this situation. This primary study reveals that the PMA has the property to transfer EM energy into thermal energy, and indicating the PMA a possible material for anti-/de-icing in aircraft. Further study is going to be carried out to find the EM thermal energy conversion efficiency of the PMA and related experiments is expected to be arranged. 16:45 O17-8 [A2904] Preliminary design of a TM31 mode extended interaction oscillator at Ka‐band BI Liangjie, YIN Yong, WANG Bin, LI Hailong, ZHANG Ping, MENG Lin (Vacuum Electronic National Laboratory, China) Abstract: The application of a high order mode in a ladder RF circuit (ladder cavity) permits a significant increase in the output power for millimeter wave extended interaction oscillators (EIOs). The analysis of the mode shows the TM31 mode can overcome the transverse dimension limits of the ladder cavity operated in the fundamental mode for a given frequency. A TM31 mode Ka-band EIO is proposed. The circuit design exploits the advantages of large power capacity with the TM31 mode in the large cavity, to achieve high power. To demonstrate its feasibility, an electron beam with 50 kV and 3 A was Page 176

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used to drive the EIO. Through 3-D PIC simulation technology in CST, an output power over 8.4 kW is obtained with the frequency of 34.71 GHz. The corresponding field distribution shows the EIO actually operates at the TM31 mode. The high order mode operation provides an effective way in the high power EIOs and extended interaction klystrons (EIKs) at millimeter wavelength. 17:00 O17-9 [A1007] Relativistic S‐band magnetron studies SAYAPIN Arkadi, KRASIK Yakov (Physics Department, Technion, Israel) Abstract: We present main results of experimental studies of relativistic S-band 6-cavity magnetron powered by a Linear Induction Accelerator (350 kV, 2.5 kA, 150 ns). A proper frequency stabilization of the microwaves (250 MW, ~100 ns) generated by the magnetron, allows us to efficiently pump a travelling wave resonator and to obtain at its output microwave pulses with a power of 1.15±0.05 GW and duration of 12±2 ns. We will report also about the distribution of field intensity in the magnetron cavities showing electric field gradually increase along the series of cavities indicating on magnetron operation with an open series of five coupled resonators. Using these data, the microwaves, extracted from three cavities and radiated in free space by horn antennas, were coherently added to each other resulting the power flux density at desired location, which would require a source radiating in free space through one antenna ∼1.7GW. Finally, we will report about recent results of magnetron operation with internal permanent magnets which allows one to design a compact high-power microwave source.

Oral Session 18 -Industrial and Commercial Applications - Session Chair : JIN Yunsik (BALL ROOM 3#)[15:00-17:30] 15:00 O18-1 [A2523] Empirical formulas of underwater Cu‐wire electrical explosion generated shock waves ZHOU Haibin1, ZHANG Huan 1, ZHANG Yongmin 2 (1. Systems Engineering Research Institute, China ; 2. School of Electrical Engineering, Xi’an Jiaotong University, China) Abstract: With different kinds of discharge loads, pulsed power technology will produce acoustic, optical, mechanical, electromagnetic, thermal effects, and so on. When the load is a thin metal wire immersed in water, shock waves (SWs) can be generated because of the fast and dramatic volume expansion of water pushed by electrical explosion plasma and hot metallic vapor. The SW

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technology has been well applied in mineral prospecting, SW reservoir stimulation, electrohydraulic forming, extracorporeal shock wave lithotripsy, food non-thermal processing, and many other fields. The process and physical mechanism of underwater electrical wire explosion (UEWE) has been carefully studied for several tens of years. Magneto hydrodynamics (MHD) models have been developed to describe discharge and SW generation process. With this method, the peak pressure of SWs can be roughly obtained. However, the MHD methods heavily rely on the precision of material parameters and the experimental data. This method is not suitable for practical applications also because of the algorithmic complexity. Tucker model is usually used to predict the discharge waveform of electrical wire explosion in air, and it will not be available if the discharge medium is far denser than air. In this paper, an empirical model was proposed to build the relationship between discharge parameters and SW parameters. With the help of this model, the SW strength and energy can be estimated under certain discharge parameters. This model can help to guide the design of pulsed power devices and the selection of the matched electrical wires. It has very large theoretical and practical significance. As the discharge parameter changes, discharge process have three types. The SW generation process of UEWE contains two stages. Stage 1 is the hot metallic vapor expansion process, and stage 2 is the metallic plasma expansion process. SWs can be generated in both of the two stages. If the two SWs merge, a much stronger SW can be obtained, and we name this discharge “type A”. We studied the SWs and discharge characteristics of this discharge type. Cu-wires with different length and diameters were applied on a certain pulsed current source to generate SWs. Both the discharge waveforms and the SW waveforms were measured. The discharge process were divided into several phases, and deposited electrical energy, power, and consumed time was calculated. The SW peak pressure and total mechanical energy were also calculated. Then, through the multi-parameter fitting method, the empirical formula of peak pressure and shockwave energy was deduced, which is the exponential function of the above electrical parameters. Results show that the relative mean deviation between the fitting result of the shockwave energy and the measured data is 12.2%, and the relative average deviation of the peak pressure is 8.45%. The given empirical formulas can give a satisfying estimation of shock waves under a certain discharge circuit.

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EAPPC & BEAMS 2018 / Programme Wednesday 19 September 2018 15:15 O18-2 [A0695] Electrical discharges in water: experimental determination of discharge regimes as a function of the fluid conductivity IMBERT Tony1, REESS Thierry2, DE FERRON Antoine2, PECASTAING Laurent2, DEMOL Gauthier1, GUEGAN Baptiste1 (1. ITHPP, Thégra, France; 2. UNIV PAU & PAYS ADOUR/E2S UPPA, LABORATOIRE DES SCIENCES DE L'INGÉNIEUR APPLIQUÉES À LA MÉCANIQUE ET AU GÉNIE ELECTRIQUE – IPRA, EA4581, 64000, PAU, France) Abstract: It is widely accepted that the breakdown field in tap water is affected by the duration of the applied voltage. For pulses shorter than a microsecond in duration, breakdown fields can increase up to a few MV/cm. The reverse is also true, Voltage impulses longer than a microsecond lead to a decrease in the values of the breakdown fields (from 100kV/cm to a few tens of kV/cm as the duration increases). This phenomena is explained by the physical processes associated with the two different discharge regimes that occur during the arc development in water: the supersonic mode and subsonic one. Depending on the potential practical applications (generating shock waves, electrical rock drilling or medical applications), the controlling of the electrical discharge regimes is key. In particular, it is important to understand whether the temporal limits that define the two discharge regimes are modified by changes in fluid properties. This paper presents an experimental study of a water gap voltage breakdown as a function of water conductivity. It exposes the required Energy consumption to initiate the breakdown. A comparison of results obtained for two different fluids (drilling mud and salt water) with the same conductivity also be presented. It conclude by establishing the general influence of fluid conductivity on the breakdown thresholds. 15:30 O18-3 [A1269] Preliminary experimental study of pulse discharge in water TONG Deen, ZOU Xiaobing, ZHU Xinlei, WANG Xinxin (Department of Electrical Engineering, Tsinghua University, Beijing 100084, China) Abstract: To study the development of pulse discharge in water and the physical fields’ distribution such as electromagnetic field, temperature in water, and systematically analyze the influencing factors of underwater pulse voltage discharge, an underwater pulse discharge system was designed and built. The system is mainly composed of a capacitor bank, a gas filled switch and a water gap, with maximum charging voltage of 10 kV and maximum storage capacity of 15kJ. The contrast experiments were conducted under Page 179

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pulse voltage with the amplitude of several kilovolt by changing the distance between electrodes in the water and the conductivity of the water. Numerical simulation and experimental results show that increasing the electrical conductivity of water increases the energy loss in the water before the breakdown of the water gap. Under a certain voltage waveform, the energy consumption in the water first decreases then increases with the increase of the water conductivity, which suggests that under a certain electrodes distance, the utilization of electricity energy for water gap breakdown can achieve its maximum value. With the experiments of pulse discharge in water, the curves of breakdown voltage in water under different water gap distances and water conductivities were measured, which can provide a beneficial help for the engineering application of the underwater discharge. 15:45 O18-4 [A1762] Inactivation of coccus cell model using metal coated parallel plate electrodes under pulsed electric field treatment RAMASWAMY Ramya1, GOWRISREE V 2, RAMACHANDRAN Raja Prabu 1 (1. B.S. Abdur Rahman Crescent Institute of Science and Technology ; 2. College of Engineering, Anna University, India) Abstract: Pulsed Electric Field (PEF) treatment has been successful in inactivating various food borne pathogens in liquid food for the past two decades. Here, the electrodes and subsequent electric field distribution play a major role in inactivating various kinds of microorganisms through application of ultrashort high voltage pulses. While several previous studies in PEF treatment involved direct contact of electrodes with liquid food, recent research focuses on using coated electrodes to improve overall PEF processing and requires more research. These electrodes are believed to provide significant reduction of metallic ion release thereby improving the quality of PEF treated product. In this simulation work, the inactivation efficiency was observed by placing a gram positive coccus cell model in suspension medium, in the treatment area between high voltage and ground electrode. The electrodes are made up of titanium. The microbial cell model in the suspension medium was tested for its inactivation through satisfying electroporation phenomenon. Based on results, these coated electrodes satisfied electroporation and opens a further pathway to improve PEF processing.

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EAPPC & BEAMS 2018 / Programme Wednesday 19 September 2018 16:00 O18-5 [A2342] Pulsed electric field equipment for the food industry REDONDO Luis1, PEREIRA Marcos 2 (1. Lisbon Engineer Superior Institute, GIAAPP/ISEL, Portugal; 2. EnergyPulse Systems, Lisbon, Portugal) Abstract: The applications of pulsed electric fields, PEF, for enhancing the mass transfer of valuable inner cellular contents and for inactivation of microorganisms is a scientific demonstrated technique for the food industry, based on the electroporation phenomenon. However the use of this method in the industry has encountered several difficulties due to the industrial requirements and the lack of equipment with the cost, efficiency, flexibility and reliability to meet the desirable performance. A new set of monopolar/bipolar semiconductor based modulators up to 25 kV, 500 A and 10.5 kW designed for the food industry, with flow rates up to dozens of T/h, and applications in the mass transfer and inactivation processes will be described, as well as the associated treatment chambers. Examples of the equipment’s operations in several applications, such as in the apple juice, wine, and olive oil industries, as well as, the microalgae cultures, show that the application of PEF to the industry is valuable. The difficulties encountered at the industrial level and the solutions to circumvent these will be described. In addition, the requirements put by these loads to the PEF systems will be evaluated and solutions encounter shall be discussed in order to achieve the best performance. 16:15 O18-6 [A2500] Study on the assisted extraction of Proantho Cyanidins by high‐voltage pulse discharge LIU Yang, LIU Yi, LIN Fuchang (State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science & Technology, Wuhan, Hubei Province, China) Abstract: Grape seed extract is a type of polyphenols, the main ingredient of it is Proantho Cyanidins, which is one of the most efficient antioxidants of plant origin found so far. The extraction rate of natural products depends to a large extent on the degree of ragmentation of cells. The method of breaking cell wall is divided into physical and chemical. As a purely physical method widely used in rock breaking and underwater discharging, the high-voltage pulsed technique can effectively break down the biological cell wall and cell membrane, and maintain the activity of natural products well. The effect of high-voltage discharge on grape extracts is mechanical, electric and chemical. The high-voltage pulse causes a liquid breakdown between the electrodes, which may generate a shockwave. The shockwave propagates to the wall of reaction vessel

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to form a secondary reflection wave, which produces mechanical disruption to plant cells. Therefore the permeability of the cell has been changed. In addition to the direct measurement of the content of procyanidins, the degree of fragmentation of the cell can be indirectly measured by the change of the solution conductivity. In order to evaluate the influence of electrical parameters of high-voltage pulse discharge on the extraction rate of procyanidins, a test platform for discharge of high-current liquid electric pulse and related optical and presure measurement systems were constructed in the paper. The feasibility of extracting Proantho Cyanidins by high-voltage pulse discharge was analyzed, and the influence of electric field intensity, injection energy, and shockwave size on the extraction rate of Proantho Cyanidins was quantitatively evaluated. An electrical parameter with fruitful effect was available for industrial production as a reference. 16:30 O18-7 [A0103] A review on the recent results on production of low‐energy, high‐current electron beams OZUR Grigory, KIZIRIDI Pavel (Institute of High Current Electronics, Siberian Branch of Russian Academy of Sciences, Russia) Abstract: Low-energy (up to 35 keV), high-current (up to 25 kA) electron beams (LHEBs) formed in the guns with plasma anode and explosive-emission cathode are widely used for the surface treatment of metallic materials. High energy density (up to 15 J/cm2) and short pulse duration (1−5 μs) allow one to release the beam energy in a thin (0.5−5 μm) surface layer providing its melting and even partial evaporation. High speeds of heating (up to 1010 K/s) and cooling (up to 109 K/s) of the surface layer provide the formation of such structure-phase states which could not arise under steady-state conditions. Besides, pulsed melting cleans the surface layers and smoothes the microrelief. Pulsed melting of film–substrate systems makes it possible to produce nonequilibrium surface alloys, including amorphous ones. Taken together, these capabilities of LHEB treatment technology allow one to solve a variety of problems in modifying the surface layers of materials and products: to improve their corrosion resistance, biocompatibility, wear resistance, electric strength of vacuum insulation, etc. In the report, the method for improvement of stability of explosive-emission cathode operation based on resistive decoupling of emitters as well as the method providing the treatment of massive metal workpieces based on the use of additional permanent magnet, which corrects the guide magnetic field in the workpiece, are presented.

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EAPPC & BEAMS 2018 / Programme Wednesday 19 September 2018 16:45 O18-8 [A2568] Influence of plasma channel impedance model on electrohydraulic shockwave simulation LIU Yi1, LIN Fuchang1, ZHANG Qin1, Ren Yijia2, LIU Siwei2 (1. State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, China; 2. School of Electrical and Electronic Engineering Huazhong University of Science and Technology, Wuhan, China) Abstract: The simulation of electrohydraulic shockwaves is the key technology for its application and device design. The analytical approach of underwater pulsed current discharge is described using the dimensionless analysis method, which combines energy based hydrodynamic equations and electrical differential equation describing the discharge characteristics of the circuit. A constant plasma channel impedance model based on experimental results and an improved time-varying plasma channel impedance model based on Braginskii equation are proposed and presented. The plasma channel impedance has a great influence on the deposited energy into the plasma channel, then affects the calculation and analysis of the shockwave propagation. The electrical characteristics and fluid physical properties are taken into consideration, and the results are compared. The application range of different impedance models is summarized, and the time-varying impedance model can provide a more accurate result in the simulation of shockwave propagation. The dimensionless analysis method, together with time-varying impedance model, could be a useful tool for evaluation of the electrohydraulic shockwave in practical applications and applied physics research of underwater spark discharge.

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EAPPC & BEAMS 2018 / Programme Thursday 20 September 2018

Thursday, 20 September 2018

Oral Session 19 - Generators and Networks - Session Chair: ZURAUSKIENE Nerija (BALL ROOM 1#)[08:30-10:30] 08:30 O19-1( Invited) [A2316] Current progress on the development of semiconductor based pulse generators at KIT SACK Martin, HOCHBERG Martin, HERZORG Dennis, FLEIG Johannes, MUELLER Georg (Karlsruhe Institute of Technology, Germany) Abstract: At Karlsruhe Institute of Technology/Institute for Pulsed Power and Microwave Technology semiconductor based pulse generators for pulsed electric field processing of biological material and driving a pulsed electron beam device are currently under development. Thereby, each design is tailored to the specific needs of the application. Processing of biological material comprises batch processing of small amounts of material for lab-scale experiments towards the efficient preparation of food. To comply with the requirement for a simple design, a Marx circuit employing charging coils and IGBTs as pulse switches has been developed. The generator has been designed for a total charging voltage of 30 kV and a pulse current of 500 A. It is part of an RLC pulse circuit enabling an operation of the IGBTs under soft-switching conditions and, hence, delivers unipolar pulses. For generating consecutive bipolar rectangular pulses, a pulse generator for continuous operation based on a stacked H-bridge design has been designed. One bridge is designed for a DC bus voltage of 1 kV and a pulse current of 600 A. For lab-scale experiments an 8-stage generator has been set up. The stages are controlled via fiber-optic links for synchronized switching. A rise time of less than 150 ns has been achieved for voltage and current at an electrolytic load. For experiments on growth stimulation of algae a Blumlein generator with a stacked MOSFET switch has been developped. The switch has been designed as closing switch for a voltage of up to 10 kV and a current of up to 200 A at a pulse repetition rate of up to 100 kHz. A rise time of approximately 8 ns has been achieved for both voltage and current at the switch. A two-switch design of the Blumlein generator allows for an adjustment of pulse polarity and pulse length. Driving the pulsed electron beam device is a single pulse application. The triode design of the device requires a rectangular pulse voltage

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in the range of 90 kV  120 kV with a rise-time of less than 100 ns and a precise flat-top with a ripple factor of less than 0.5 % at a current of up to 600 A at its cathode and additionally a fine tunable grid control voltage. The design consists of 150 stages, each designed for a stage voltage of 1 kV and equipped with a microcontroller enabling individual switching of each stage according to a pre-programmed pattern. The contribution presents an overview of the generator designs and highlights selected design aspects. 08:55 O19-2 [A1734] A Marx and modular multilevel cell‐based pulse generator with adjustable rising time WAN Hui, MI Yan, BIAN Changhao, LI Pan, LIU Quan (Chongqing University, China) Abstract: In this paper, a new type of rising time-adjustable high voltage nanosecend pulse generator based on Marx generator and half-bridge modular multilevel cell (MMC) is proposed. The concept of this generator is charging the capacitors in parallel, and then connecting the capacitors in series through a given sequence to generate a multilevel pulse. When the duration times of the levels (except the last level) are set to a tiny range, all levels except the last can be regarded as the rising time of the pulse. By changing the control signals of the fast solid-state switches, the number of levels as well as the duration time of each level can be controlled. Thus, the rising time of pulse can be adjusted. The simulated models of this generator have been investigated in a PSPICE platform, and a laboratory prototype has been implemented in laboratory. The simulation and test results verify the feasibility of the proposed topology. 09:10 O19-3 [A1740] A bipolar pulse generator based on Marx and pulse transformer GUI Lu, MI Yan, DENG Shengchu, DONG Shoulong (Chongqing University, China) Abstract: In order to develop a modular bipolar pulse voltage source to simulate the insulation electrical stress of saturable reactor, based on saturable reactor of 1100kV HVDC converter valve, a new circuit topology that combines the topology structure of Marx generator and pulse transformer is proposed. Based on the required waveform parameters and theoretical design, the proposed circuit is simulated by using PSPICE software. The simulation results are consistent with the required waveform parameters, and the feasibility of the designed circuit proves to be correct. Finally, the generator can produce positive pulses with amplitude of 0-11kV, pulse width of 12s, rise time of 1.1s and repetition rate 50Hz and negative pulses with amplitude of 0-2.24kV, pulse width of 68s and rise time of 21.38s. Page 185

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Modular design and compact design are used in the generator. The bipolar pulse voltage source can provide a hardware platform for further study of partial discharge mechanism and aging failure mechanism of reactor epoxy resin under power frequency pulse voltage. 09:25 O19-4 [A2423] Development of a GW‐level solid‐state long pulse generator GAO Jingming, YANG Hanwu, LI Song, QIAN Baoliang, ZHANG Jun (National University of Defense Technology, China) Abstract: Solid-state pulsed power systems are characterized by high repeatability, high reliability, long lifetime, free maintenance and easy usage. Such systems with moderate peak power (100 MW level) are widely applied in high average power region; however, many issues are still to be researched to obtain GW-level peak power. In this paper, a high power solid-state pulse generator delivering GW-level quasi-rectangle pulse is developed to investigate electrical characteristics of the generator. (1) System design is accomplished considering features of series connected thyristor switches and magnetic switches, which is verified via circuit simulation. (2) Key technologies such as series connected thyristor switches, magnetic compressor, Blumlein type low impedance Pulse Forming Network (PFN) and Induction Voltage Adder (IVA) are investigated for sub-systems construction. (3) At present, the experimental results achieved on a dummy load are peak pulsed power of 5.2 GW, pulse width of 170 ns, repetitive rate of 20 Hz, and operation time of 5 s with good waveform repeatability. The generator could be potentially applied for High Power Microwave (HPM) generation, X-ray sources and industrial applications such as material surface treatment and Pulse Electric Field (PEF) sterilization.

Oral Session 20 - High Energy Density Physics; Theory and Simulation - Session Chair: CONG Peitian

(INTERNATIONAL HALL）[08:30-10:30] 08:30 O20-1 [A1804] Development for the compact X‐ray system of high energy and focal spot ZOU Jian, ZENG Naigong, WANG Chuan, ZHANG Tianjue, JIANG Xingdong (China Institute of Atomic Energy, China) Abstract: A mini-Marx generator with fast rise time and low inductance is introduced as the trigger power. The design energy Page 186

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storage of the pulse X source power supply is 35J. Under the condition of charging 22.5kV, the load 52Ω can obtain the front 20ns, pulse 100ns, and amplitude 180kV pulse wave. Then the driving pulse X-ray tube produces X rays. Finally, the size of the pulse X-ray point source is compressed by the X-ray capillary optics to obtain the microfocal spot with a certain photon energy, which is used to study the phase-contrast imaging of the biological samples. 08:45 O20-2 [A0970] Electrical explosion of wires arrays in water and glycerol KRASIK Yakov, ROSOSHEK Alexander, NITISHINSKI Mikhail, EFIMOV Sergrey, YANUKA David, TEWARI Somech (Physics Department, Technion, Israel) Abstract: The results of experimental research and HD simulations of shockwave (SW) generated by underwater cylindrical wire arrays exploded on ns- and μs-timescales, showed that even in the case of initial azimuthal non-symmetry, the SW self-repairs in the final stages of its convergence, lead to a uniform implosion down to the r=30μm. To increase liquid compression, electrical explosions of spherical wire arrays in water and glycerol were carried out showing significantly faster SW convergence in glycerol than in water. It was shown that increasing the initially stored energy (for identical array diameters) or decreasing the sphere diameter (for identical stored energy) leads to an increase in parameters of compressed liquid in the vicinity of the implosion. Also, it was shown that convergence of the SW becomes self-similar beginning about identical radii for different timescales of explosion of array with the same deposited energy. Finally, we will report results of underwater electrical explosion of single wire array made of Al, Cu, W, Ta and Mo. 09:00 O20-3 [A1645] The application of fiber ytterbium laser for yttria and alumina nanopowders production KRUTIKOVA Irina, IVANOV Maxim (Institute of Electrophysics UB RAS, Yekaterinburg, Russia) Abstract: Yttria and alumina nanopowders are important materials for high-density ceramics production, which have high light transmittance in the visible and infrared spectral range, high thermal and chemical resistance, and are a promising material for solid-state lasers, phosphors and scintillators. The use of nanoscale particles can lower the sintering temperature, and reduce optical losses in ceramics as well. An increase in scintillation efficiency can also be organized by reducing non-radiative relaxation as long as the method of nanoparticle synthesis ensures the formation of a defect-free nanoparticle structure. Optimization of methods for obtaining and Page 187

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compacting nanoparticles in order to reduce the amount of defects in the obtained particles are urgent problems, the solution of which is necessary for the creation of new generation scintillators. Among the number of preparation methods, laser supported material, evaporation and subsequent vapor condensation is particularly promising, since it yields perfect, highly pure, weakly agglomerated, spherical nanoparticles with a narrow size distribution, while ensuring high productivity and low specific energy consumption. In the present work, yttria and alumina nanopowders were synthesized by material evaporation with an ytterbium fiber laser YLR-1000 (IPG Photonics, Russia) with the wavelength of 1.07 µm. Nanopowder mixtures were compacted to a pellet and then evaporated by laser radiation in an evaporation chamber with air atmosphere. The ytterbium fiber laser was operated with a modulation frequency of 5 kHz at laser pulse duration of 100 µs and average laser power of 500W. The intensity of the laser radiation in the focal spot was about 106 W/cm2 with close-to-Gaussian profile. The nanoparticles were produced when the evaporated material was mixed with air in the gas phase, at the same time as the cooling and condensation occurred. The nanoparticles were collected in an electrostatic filter. The average output rate of europium doped yttria nanopowder production was about 25 g/h, for alumina – 8 g/h, for neodymium doped yttria – 24 g/h. The paper will discuss the influence of laser radiation regimes on the properties of nanopowders obtained.The reported study was funded by RFBR according to the research project № 18-32-00531/18-52-53039-ГФЕН_а. 09:15 O20-4 [A1860] Design of dynamic materials properties experiments for PTS ZHANG Zhaohui, WANG Guilin (Key Laboratory of Pulsed Power, Institute of Fluid Physics, CAEP,, China) Abstract: The Primary Test Stand (PTS), located in Institute of Fluid Physics, Mianyang, China, has been developed to an important platform for high pressure physics and dynamic materials properties, with the capability of attaining the quasi-isentropic compression wave in different materials. The facility is a multi-terawatt pulsed power facility, consisting of 24 modules connected in parallel. When the PTS is fired, a pulse of electrical current, typical 4-8 MA in magnitude and having 230-750 ns risetime, is delivered to the central target. To date, we have developed and improved a series of design methods for different purpose, such as measuring the EOS data, monitoring the phase transition, obtaining the strength properties. In the present study, results of isentropic experiments to exceeding 200 GPa, strength measurement of metal, are reported. Lagrangian analysis techniques were utilized to analyze the loading and unloading process. Page 188

EAPPC & BEAMS 2018 / Programme Thursday 20 September 2018 09:30 O20-5 [A2242] Thermal conductivity measurement for warm dense matter using laser induced fluorescence and isochoric pulsed‐power discharge SASAKI Toru, KUSANO Shingo, TAKAHASHI Kazumasa, KIKUCHI Takashi (Nagaoka University of Technology, Nagaoka, Japan) Abstract: To observe the transport properties of warm dense matter, we used laser-induced fluorescence to measure its thermal conductivity confined within a rigid, ruby capillary tube. We determined the density and temperature of the plasma generated by an isochoric heating device using a pulsed-power discharge. We found the thermal conductivity to be approximately 30 W/K m, thus demonstrating that the thermal conductivity of warm dense matter states can be directly evaluated using the proposed method.

Oral Session 21 - Transmission Lines and Transformers - Session Chair: JAMES Dickens (BALL ROOM 3#)[08:30-10:30] 08:30 O21-1 [A0117] A repetitive e‐beam accelerator for HPM studies YANG Hanwu, ZHANG Zicheng, GAO Jingming, XUN Tao, LI Song (National University of Defense Technology, China) Abstract: Studies of a multi-gigawatt high power microwave (HPM) tube require an e-beam accelerator in the tens gigawatt GW level. Such a repetitive accelerator is built and it has a Tesla transformer (TT) and a helical liquid insulated forming line (PFL). The primary capacitor of the transformer is charged by a constant-current high voltage power supply of 120 kJ/s and the capacitor is discharged via a pseudo-spark switch. The TT is an open-core autotransformer, with coupling above 0.9 and output up to 1.2 MV. The co-axial forming line is insulated with water-ethanol mixture, to achieve an optimum dielectric constant and line impedance. A transmission line is installed before outputting to the HPM load, to further increase the load voltage. A ceramic interface is used for improving vacuum level. The accelerator operates well with 5 Hz repetition, 80 ns FWHM and ~30 GW peak power. 08:45 O21-2 [A0469] Design of a 4‐way ultra‐wideband coaxial‐waveguide power divider SHI Yiping, FAN Yajun, YI Chaolong, ZHANG Xingjia (Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: A 4-way and a 16-way coaxial waveguide UWB power

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divider are proposed in this paper. The 4-way power divider, with 140mm input diameter, is constructed by a 1-4 ports X-shaped power divider (which owns a normal outer and a smoothly tapered inner) and four 90 degrees coaxial turns. Simulations show that from DC to 1GHz, the return loss is greater than 18dB, the insertion loss is less than 0.2dB. And the measurements agree well with the simulations. The 16-way power divider is constructed by four 5-times-smaller 4-way power divider in series. The simulations show that from DC to 6.3GHz, the return loss is greater than 14dB. 09:00 O21-3 [A1329] A coaxial‐output cable‐loaded annular pulse forming line QIU Xudong, SU Jiancang, LI Rui, CHENG Jie, YU Binxiong, ZHANG Yu, XU Xiudong, ZHAO Liang, ZENG Bo (Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: A coaxial-output cable-loaded annular pulse forming line is developed to make the pulse forming line (PFL) smaller and lighter, reduce the fluctuation of the top of the output pulse and improve the quality of the output waveform produced by a Tesla-PFN type pulse generator. First, a high voltage coaxial cable with the insulating layer made of multilayer polypropylene films is developed. It can withstand the pulse voltage of 100kV, with a cross section diameter of 7.5mm, an impedance of 17.6 Ω and an electrical length of 26ns. Then an annular PFN module is designed, which is composed of three high voltage coaxial cables. The annular PFN module can run more than one million times under the pulse voltage of 75kV, with an impedance of 2.93Ω and an electrical length of 13ns . Six cable terminals of the annular PFN module discharge in parallel, which is much closer to the coaxial output than the former design. The connection inductance of the inter-stage is significantly reduced when the multi-stage annular pulse forming lines are connected in series. Finally, a multi-stage annular PFL consists of 15 series annular PFL modules is designed, with a characteristic impedance of 44 Ω, an electrical length of 13ns, and a sustaining voltage of 1 MV. The simulation result show that the PFL can output the electrical pulses with the fluctuation of the top of the output pulse less than 3.5% 09:15 O21-4 [A1342] Two methods on pulse shaping for a series coaxial multi‐layered film‐winded pulse‐forming line ZHAO Liang, SU Jiancang, LI Rui, CHENG Jie, YU Binxiong, QIU Xudong (Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: A coaxial multi-layered film-winded pulse forming line (shortened as winded PFL) is a novel compact device to produce pulses with amplitude up to 100 kV and width about several tens of Page 190

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nanoseconds, which was put forward by Su, et al. [A coaxial multi-layered film-winded pulse forming line, Rev. Sci. Instrum., 88, 150-155(2017).] . A pulse with amplitude larger than 1 MV can be formed by this series winded PFL unit when several stages of winded PFLs are connected in series and put in a tapered outer conductor. The output pulse of this series PFL unit is not ‘flat’, with a ‘recess’ about 10% of the main pulse, which is due to the discontinuity of the structure and the electromagnetics coupling of the different stages of the winded PFLs. By analyzing the wave-transmission process, it is found that this ‘recess’ is resulted from an increased equivalent impedance. Two methods are put forward to shape the output pulse of the series winded PFL unit in order to decrease the equivalent impedance. One is to fill a polymer insulator in a proper position between the tapered outer conductor and the series winded PFLs, the other is to re-design the configuration of the outer conductor. Via transient wave-process simulation, it is found that the first method can reduce the recess to 5.5% and the second can reduce the recess to 2.5%. In the end, the feasibility of the first method is verified by experiments. 09:30 O21-5 [A1975] The development of pulse forming lines (PFLs) with liquid of high energy density in our laboratory YANG Jianhua, CHENG Xinbing, YANG Xiao, QIU Yongfeng, CHEN Rong, GENG Jiuyuan (National University of Defense Technology, Changsha, China) Abstract: Liquid of high energy density still have a broad application prospect with the application of maintenance-free liquid. With the application of spiral line technology, the adjustment between the length and radial dimension can be made, the length can be reduced through properly increasing the radial dimension, the range of impedance of PFL is broadened, the generator based on the PFL with high dielectric constant liquid can drive HPM device with a high impedance such as BWO. The storage energy density of liquid in PFL is connected with the structural styles of PFL and the polarity characteristics of breakdown strength field of liquid. It is found that for a strong polarity liquid, such as de-ionized water, the average energy density of single line is more than two times larger than that of a coaxial double line. It is also found that for a non-polarity liquid, such as glycerin, the average storage energy density of a coaxial double line is larger than that of a single line. The problem of a coaxial double line is to resolve the quality of pulse forming when the spiral line is introduced in a coaxial double line. There are three stages of development history of PFL in our laboratory: a coaxial double line filled with de-ionized water is replaced by a single spiral line with de-ionized water; a novel double line composed of two separated single lines with de-ionized water and its mixture is invented for a Page 191

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long time repetition running and driving HPM devices with a high impedance; a coaxial double line with two spiral lines filled with glycerin is developed, which is very compact and maintenance-free. 09:45 O21-6 [A1997] Influence of microbubbles on the withstand voltage in repetitive pulsed glycerin pulse forming line YANG Xiao, YANG Jianhua, CHENG Xinbing, GENG Jiuyuan, QIAN Baoliang (National University of Defense Technology, Changsha, China) Abstract: The experimental research is carried out to solve the decline of the withstand voltage in repetitive pulsed glycerin pulse forming line (PFL). The study shows that under the effect of multiple pulses the withstand voltage of glycerin medium associated with the size and number of the microbubbles which depend on a series of processing methods on the glycerin. The experiment result shows that removing air bubbles can make the capability of glycerin withstanding more repetitive pulses increase greatly. By high-speed camera technology the behavior of microbubbles in the process of withstanding repetitive pulses is studied. The bubbles exist discharge phenomenon, and their volume changes with the pulse, but the glycerin will not lead to a breakdown. However the discharge process in bubbles will repeat and the change of bubbles’ volume will accumulate, eventually make glycerin breakdown. Minimizing bubbles would prolong the process, and then the glycerin will withstand more pulses.

Oral Session 22 -High Voltage Power Supplies - Session Chair: YAKOV Krasik (BALL ROOM 1#)[10:30-12:00] 10:30 O22-1 [A1582] Heat dissipation analysis of transient burst mode high frequency pulse power supply HAN Jing, GAO Yinghui, LIU Kun, SUN Yaohong, YAN Ping (Institute of Electrical Engineering, Chinese Academy of Sciences, China) Abstract: High energy and high power of the charging pulse power supply are the important technical indexes in the field of electromagnetic launch technology, which needs to output very high energy in a short time. This causes the heat flux in the power supply to increase rapidly, thus increasing the design difficulty of the heat dissipation system. Based on an 40KW/7KV charging power supply, the heat dissipation in the transient high frequency condition is analyzed and studied in this paper. The main heating devices in the charging pulse power supply are analyzed, including the switch devices and the high frequency transformer, and their power loss are Page 192

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calculated specifically. Then the thermal design is carried out based on transient thermal impedance．Meanwhile, the thermal resistance model of heating devices is established by the ICEPK thermal simulation software, which can simulate transient conditions. The temperature rise curve of the heating devices are obtained, and the temperature rise law is summed up, which verifies the analysis above. The research of this paper provides a strong basis for the problem of heat dissipation in the miniaturization and high power density of the charging power source of the electromagnetic emission technology. 10:45 O22-2 [A1699] A novel paralleled topology of all solid‐state Marx generator for high current WANG Yifan, LIU Kefu, QIU Jian (Institute of Electrical Light Source, Fudan University, China) Abstract: Marx generator using solid-state devices has been studied for many years. Higher parameters are always the demand for new applications. Traditional Marx generator can output high voltage due to its series structure, but the current is always limited by the switch. In this paper, we proposed a paralleled topology of Marx generator for high current. Compared to linear transformer driver (LTD), they both can output controllable pulsewidth, high voltage and high current, but LTD has low efficiency, mostly less than 60%, due to leakage current around the magnetic cores. Also, LTD has to consider magnetic flux restoration which makes the system more complex. On the contrary, Marx generator has high efficiency over 90% without the magnetic cores, and this new paralleled topology breaks the bottleneck (current limited by switch) for Marx generator. The circuit of paralleled topology has been analyzed, the lack of synchronization of the driven signals and switch fault which may cause unbalance of current and overcurrent problems are studied in this paper, and some methods have been carried for current balancing and overcurrent protection in this new topology. A self-protection circuit used for overcurrent protection and abnormal occurrence detecting has been developed and a current self-balancing structure has been designed. For experimental demonstration, we constructed a twenty-stage Marx modulator with eight metal-oxide-semiconductor-field-effect transistors (MOSFETs) paralleled in one stage, using 600V MOSFETs to operate at 500V DC input voltage. The output pulses have max voltage of ~10kV, max current of ~1.2kA (depending on the load), rise time of ~30ns, fall time of ~50ns, controlled pulsewidth from 100ns to 1000ns.

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EAPPC & BEAMS 2018 / Programme Thursday 20 September 2018 11:00 O22-3 [A2046] Research of a high‐voltage silicon stack‐isolating‐type Marx generator CHEN Rong, YANG Jianhua, CHENG Xinbing, QIAN Baoliang (National University of Defense Technology, Changsha, China) Abstract: Marx generator is a kind of voltage boosting device in pulsed power system, where the Marx capacitors are charged in parallel and discharge in series. In this paper, isolated inductances in typical Marx generator have been substituted by high-voltage silicon stacks. Experiments about the inductance-isolating-type and high-voltage silicon stack-isolating-type Marx generator were both carried out, indicating that the high-voltage silicon stack-isolating-type Marx generator can not only eliminate the pre-pulse existed on the load when using the isolated inductance in traditional Marx generator, but also help to improve the energy efficiency of the Marx generator. Experimental results show that the high-voltage silicon stack-isolating-type Marx generator can increase the voltage step-up ratio to 3.39, up from 3.17 of the inductance-isolating-type Marx generator. This kind of high-voltage silicon stack-isolating-type Marx generator is able to upgrade the voltage capacity and energy efficiency of the pulsed power system. 11:15 O22-4 [A3012] Parameterized bipolar high voltage square pulse generator without H bridge based on Marx generator LIU Ying, FAN Rui, LI Xiaohuan, ZHANG Jun, TU Zhentao, ZHANG Xiaoming (1. Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, China; 2. School of Electronic and Information Engineering, Xi'an Jiaotong University, China) Abstract: A parameterized bipolar high voltage pulse generator without H bridge is developed, in which the positive and negative pulse circuits are directly connected and conventional H bridge is canceled because of special circuit topology and control timing. The bootstrap and isolated drive method to MOSFETs used in the proposed circuit topology is adopted. The results of simulation and experiment shows that the parameters of positive and negative pulses such as rising and falling time, amplitude, repetitive frequency, pulse width, the time interval between positive and negative pulses, even the pulse polarity can all be set or programed according to the requirement. The ability of generating bipolar pulses is with 0 to ±15 kV, 0 to 1 ms width (top flat), 50 to 500 ns or more rising/falling time, below 5% overshoot, and a maximum 5 kHz repetitive frequency at ±15 kV on a matched 0-100 pf capacitance load. The peak power of each pulse is more than 1.5 MW. All of the parameters of the Page 194

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generating bipolar pulses can be programmed and combined freely. The developed bipolar pulses generator can be used in DBD, plasma jets, plasma ignition, needle-plate discharge, and so on.

Oral Session 23 - High Power Microwave Devices - Session Chair: ZHANG Jun

(INTERNATIONAL HALL）[10:30-12:00] 10:30 O23-1( Invited) [A0291] Recent advances on a relativistic magnetron with diffraction output and no physical cathode SCHAMILOGLU Edl, FUKS Mikhail, LIU Meiqin, ANDREEV Dmitrii, KUSKOV Artem (University of New Mexico, US) Abstract: The University of New Mexico has been studying relativistic magnetrons for over 15 years. Our initial contribution was the invention of the “transparent cathode” (TC) that increased magnetron beam-to-microwave conversion efficiency and decreased the time-for-start of oscillations. Next, we showed that a TC in a magnetron with diffraction output (MDO) can achieve 70% beam-to-microwave efficiency, provided that axial loss current can be suppressed. We demonstrated how the use of endcaps on a TC can greatly diminish axial loss current. We then proposed a permanent magnet solution to a compact MDO where, for the price of decreased efficiency, a very compact HPM source without the bulky extraction section can be realized. We next proposed a relativistic MDO without a physical cathode where a virtual cathode forms in the interaction region to power the MDO with efficiency comparable to that of an MDO with a TC. Most recently we proposed a magnetic mirror field for an MDO that can completely eliminate axial loss current. This half-cusp magnetic field configuration replaces the downstream virtual cathode that was described in our earlier work. This presentation describes these advances in detail and gives an overview of an experimental campaign to validate the simulations. 10:55 O23-2 [A0088] Phase control and power summation of two X‐band klystron‐like relativistic backward wave oscillators XIAO Renzhen, DENG Yuqun, CHEN Changhua, SHI Yanchao, SUN Jun (Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: We demonstrate both theoretically and experimentally the possibility of phase control and channel power summation of two X-band klystron-like relativistic backward wave oscillators (RBWOs). A modulated electron beam induced by an external signal can lead the microwave field with an arbitrary initial phase to a same Page 195

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equilibrium phase, which is determined by the initial phase of the external signal. A high-current dual-beam accelerator was built to drive the two RBWOs. An external signal was divided into two channels with an adjusted relative phase and injected into the two RBWOs through two TE10-TEM mode converters. The generated microwaves were combined with a power combiner consisting of two TM01-TE11 serpentine mode converters with a common output. In the experiments, as the input power for each channel was 150 kW, the two RBWOs output 3.1 GW and 3.7 GW, respectively, the jitter of relative phase of two output microwaves was about 20°, and the summation power from the power combiner is 6.2 GW, corresponding to a combination efficiency of 91%. 11:10 O23-3 [A0306] Simulation of a Ku‐band oversized coaxial relativistic Cerenkov generator with low guiding magnetic field WU Xiaoling1, CHEN Changhua2, XIAO Renzhen2, TENG Yan2, WU Ping2, SHI Yanchao2, CAO Yibing2 (1. Department of Engineering Physics, Tsinghua University, Beijing, China; 2.Northwest Institute of Nuclear Technology, Xi’an, China) Abstract: Coaxial relativistic Cerenkov generator(CRCG) is a promising high power microwave device to operate with high frequency under low guiding magnetic field, due to that the average radius of its inner and outer slow wave structure ripples can be enlarged proportionally to mitigate the space charge effect while the operation frequency maintains unchanged. Therefore, the oversized CRCG has paid much attention in recent years in the attempt to realize high microwave conversion efficiency under low magnetic field. In this paper, A Ku-band oversized coaxial Cerenkov generator is proposed and designed. A large diameter anode is adopted to reduce radial electric field in the diode region, and a focusing cathode with solid structure，producing an annular beam，is explored，both in order to restrict the radial spread of the relativistic electron beam and thus further lower the guiding magnetic field. After numerical optimization, under the diode voltage and current of 540 kV and 4.45kA, microwave generation with the power of 720 MW and the conversion efficiency of 30% are obtained at the frequency of 15.6GHz. 11:25 O23-4 [A0517] A compact relativistic travelling wave tube operating at low guiding magnetic field SHI Yanchao, DENG Yuqun, XIAO Renzhen, WANG Dongyang, Li Shuang, CHEN Changhua, SUN Jun (Northwest Institute of Nuclear Technology, Xi’an, China)

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Abstract: A compact X-band relativistic travelling wave tube (RTWT) operating at low guiding magnetic field is studied. The electron beam interacts with the forward fundamental wave in the 4-periods SWS, the microwave frequency is adjusted so that the electric field distribution is benefit for interaction with the electron beam at low magnetic field. A dual-cavity reflector and a middle cavity constitute the electron beam modulation structure. A dual-extraction cavity is utilized to provide a moderate amount of end reflection and to increase the efficiency. Compared with the normal RBWO, the length of the device reduced remarkably, and PIC simulation indicates that with electron beam voltage 530kV and current 6.4kA, microwave pulses at 9.3GHz with power 1.35GW and conversion efficiency about 40% are achieved, and the magnetic field is 0.5T. 11:40 O23-5 [A0726] Relativistic oversized Ka‐band surface‐wave oscillator based on 2D periodical slow wave structure MALKIN Andrey, GINZBURG Naum, ILYAKOV Evgeny, KULAGIN Igor, PESKOV Nikolay, SERGEEV Alexander, ZASLAVSKY Vladislav (Institute of Applied Physics RAS, Russia) Abstract: We report the first successful experiments on the cylindrical oversized Cherenkov surface-wave oscillators (SWO) with two-dimensional distributed feedback (2D DFB) operating in Ka band undertaken at the IAP RAS (Nizhny Novgorod, Russia). For spatially extended electron beams, use of two-dimensional distributed feedback is beneficial for providing spatial coherence of radiation and can be exploited in order to increase total radiation power in microwave generators. Such feedback is realized in planar and coaxial 2D Bragg resonators having double-periodic corrugation. Experimental studies of FEMs based on the novel feedback mechanism were performed in Ka-band at the University of Strathclyde and in W-band at the Budker Institute. Ka-band Cherenkov SWO was realized based on SATURN accelerator equipped with thermionic emission cathode forming electron beams with a current of 100 A and particles' energy of about 300 keV. Hollow electron beam with a diameter of 4.2 cm is focused by magnetic field of 0.7 T inside 2D slow-wave structure with a diameter of 4.6 cm. Experimental investigation of the SWO with 2D DFB demonstrated the stable narrow-band generation at 32.5 GHz. Calorimetric measurements indicate the power level of 1.5 - 2 MW in up to 200 ns-long radiation pulses, which corresponds to the electron efficiency of ~ 5%.

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Oral Session 24 - Free Electron Lasers; Theory and Simulation - Session Chair: YANG Hanwu (BALL ROOM 3#)[10:30-12:00] 10:30 O24-1( Invited) [A1179] The influence of multipactor discharge on dynamic field‐buildup in accelerator RF cavity DONG Ye1, LIU Qingxiang2, PANG Jian3, ZHOU Haijing4, DONG Zhiwei4 (1. School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, China; Institute of Applied Physics and Computational Mathematics, Beijing, China; 2. School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, China; 3. Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, China; 4. Institute of Applied Physics and Computational Mathematics, Beijing, China) Abstract: The hybrid model is established based on the equivalent circuit for describing dynamic RF field buildup and PIC (Particle-In-Cell) method for describing two-sided multipactor discharge in accelerator cavity. By using the 1D3V-PIC code for multipactor discharge and fully equivalent circuit code for RF field buildup programmed by authors, the fully physical process of multipactor discharge influence on dynamic RF field buildup of accelerator is numerically investigated. The numerical results could be concluded as follows. In the condition of no multipactor discharge in dynamic process of RF field buildup, the higher Q-value, the long buildup-time. The input energy is equal to the sum of stored and consumed energy in cavity, the speed of energy storing is higher than the speed of energy consuming at the beginning stage of RF field buildup and then the speed of energy storing becomes lower than the speed of energy consuming. When the process of RF field buildup is finished, the average power of input is equal to the average consumed power in cavity. In the condition of multipactor discharge loading in dynamic process of RF field buildup, the higher Q-value, the later start-time and long interaction time-interval of multipactor discharge. The bigger area of secondary electron emission, the higher peak-value of secondary electron current. The failure of RF field-buildup is caused by continuous loading of multipactor discharge. The higher Q-value or bigger area of secondary electron emission, the lower probability of RF field buildup success.

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EAPPC & BEAMS 2018 / Programme Thursday 20 September 2018 10:55 O24-2 [A0576] Design and optimization of CARM oscillators DATTOLI Giuseppe, Di PALMA Emanuele (ENEA, Frascati (Rome) , Italy) Abstract: We develop a description of CARM theory using the formalism already exploited to treat Free Electron Laser devices. We establish the common features between these two generators of coherent radiation and provide a set of correspondences allowing the translation of the equations ruling the CARM dynamics into those already exploited to study the FEL behavior under a variety of conditions. Albeit apparently academic, such an effort allows the possibility of adapting the wealth of scaling formulae, currently exploited for the design and the optimization of FEL devices, to the case of CARM. We compare the results obtained on the basis of such a procedure with those deriving from an "ab initio" numerical treatment and find a fairly good agreement. We discuss the relevant use to study CARM operation in either amplifier and oscillator regimes and discuss the limits of applicability of the method. We finally present the use of the procedure for the design and optimization of the ENEA CARM project. 11:10 O24-3 [A0488] Dynamic study on the effect of secondary electron on ion beam quality DONG Zhiwei2, MENG Xiaohui1 (1. China Academy of Engineering Physics, Graduate school, Beijing, China; 2. Institute of Applied Physics and Computational Mathematics, Beijing, China) Abstract: This paper uses the technique of Particle-In-Cell and builds an external circuit self-consistently to simulate the electron effect of deuterium ion beam bombarding the target surface and analyze the influence of secondary electrons on acceleration voltage, quality of deuterium ion beam and energy beam bombarding the target dynamically. The result indicates that the acceleration voltage will decrease 45% when there is 0.06A electron current, which then lead to the deterioration of deuterium ion beam’s quality and the decrease of energy beam bombarding the target. 11:25 O24-4 [A2357] Flash X‐ray source for diffraction application DENG Minghai, DENG Jianjun, MA Xun, MA Chenggang, WU Hongguang, FENG Yuanwei, LI Hongtao (Key Laboratory of Pulsed Power, Institute of Fluid Physics, CAEP, Mianyang, China) Abstract: A flash X-ray source has been developed to provide powerful tool for inspect on crystal material resulting from shock wave. The diagnostic is based on measurements of the diffraction angles changing before and after shock wave using X-ray. The Page 199

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source, which consists of a 25-stage Marx bank high voltage pulse generator, couples to an electron beam diode produce bremsstranhlung and characteristic X-ray with pulse width of ~50ns. The details of the source, including theoretical analysis, certain electrical parameters, and diffraction performance have been shown. Through this study, we intend to find some patterns to help obtain high intensity characteristic X-ray. The capability of our source is exhibited by registering single-shot diffraction signals of single crystals, LiF and Cu. Improvements for the ability to make quantitative measurement for shock wave are briefly discussed.

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