EC Systems Status & Prospects

Presented by G.G. Denisov

Institute of Applied Physics, Nizhny Novgorod, 603950, Russia Gycom Ltd, Nizhny Novgorod, 603155 Russia

4th IAEA DEMO Programme Workshop

15–18 November 2016 Karlsruhe, Germany Contributions:

• M.Henderson. ITER IO

• EU team (S. Garavaglia, W. Bin, A. Bruschi, G. Granucci, G.Grossetti, J.Jelonnek, A. Moro N. Rispoli D. Strauss, M.Thumm, Q.M. Tran and T. Franke, …)

• R. Ikeda. QST, Naka, Japan

• T. Kariya. University of Tsukuba, Japan

Russian colleagues from

• Institute of Applied Physics • Gycom Ltd, • Kurchatov Institute • ITER DA • RT Soft

2 OUTLINE

• First steps and main events • List of running and near future EC systems • EC systems: aims and content • ITER EC system • Necessary steps from ITER to DEMO • New developments for future EC systems o Higher gyrotron frequency o Multi-frequency operation o Broad band window o Remote steering launcher Summary

3 • First steps and main events • List of running and near future EC systems • EC systems: aims and content • ITER EC system • Necessary steps from ITER to DEMO • New developments for future EC systems o Higher gyrotron frequency o Multi-frequency operation o Broad band window o Remote steering launcher

4 Some dates from “ancient” history

1964 – first experiments with gyrotrons

70s – 100 GHz/1MW/ 100 mks/ TE22.2 28 GHz/100kW/CW first use to heat plasma at TM-3, TUMAN-2

80s – 100GHz/2.1MW/10mks/coax./ 0.5 MW/sec wide use in plasma experiments

Main Events

1990-2006  First depressed collectors in megawatt gyrotrons  First CVD diamond gyrotron windows  Demonstration of CW operation of MW power gyrotrons  Remote steering antenna concept  MW gyrotron complexes at major fusion installations

Last decade 2007-2016  Great progress in ITER system development • Demonstrated required gyrotron parameters/Reliability tests • Manufacturing began  Results on 1.5-2 MW gyrotron models  Multi-frequency gyrotrons  Higher frequency gyrotrons (first steps)  New ideas

ECW systems (examples)

Running installations with ECW systems:

DIII-D, FTU, TCV, JT-60U, LHD, ASDEX-Upgrade, T-10, W7-AS, … 80-170 GHz/ 2-5 MW/1-10 sec Developments for running machines:

EAST 140 GHz/ 5 MW/ 1000 sec KSTAR 105/140 GHz/ * MW/ 300 sec W7-X 10 1MW/140GHz/ 1800 sec JET just discussions since 2000 Future installations: . ITER 24  1MW/170GHz/3600 sec 2025 . JT-60SA 7  110/138 GHz/100 sec 2019 . DEMO 50 MW/ 230 GHz/ CW

• First steps and main events • List of running and near future EC systems • EC systems: aims and content • ITER EC system • Necessary steps from ITER to DEMO • New developments for future EC systems o Higher gyrotron frequency o Multi-frequency operation o Broad band window o Remote steering launcher

8 How ECH works

mm-wave beams launched from either the upper or equatorial ports

Beam steering from external system (mirrors in upper port) Power absorbed locally, where B satisfies:

Microwaves give energy to electrons when electron cyclotron resonance occurs

9 Heating and Current drive source that is both localized and steerable Barrier(window) is possible

ECH is a surgical tool that can “pen point” a spot in the plasma cross section to heat plasma and/or drive current

Localized: 4cm to 20cm deposition width

Useful for:

Current Profile Tailoring MHD Control deposit ˜0.8MA from center to mid radius deposit ˜0.2MA inside rotating 4cm island

EL

center edge UL

10 EC system includes

Main components

• Gyrotrons (many) • Transmission lines (many) HE11 waveguide or mirrors • Barrier windows (many) Aix components • Launchers (several) • HV and LV power supplies • Control system • Cooling system • Safety EC is used through out the Plasma Discharge

Start-up “Provides “spark” to initiate plasma Plasma Current Ramp-up Good absorption when plasma is not “hot” Helps to build up temperature and current Tailors current profile for stabilising plasma Helps to achieve High confinement mode Burn Startup Ramp Burn Ramp Tailors Current profile up down Controls sawtooth and NTMs maintains “hot” plasma Ramp-down Helps to ramp-down plasma softly Tailors current profile to avoid instabilities EC Power

12 ITER EC Targeted Physics Functions EC “App” Matrix Based on existing practices (AUG, DIII-D, JT-60U, TCV, etc) TID: Targeted and Impacts Design // TND Targeted and Not impacting Design

13 • First steps and main events • EC systems: aims and content • List of running and near future EC systems • ITER EC system • Necessary steps from ITER to DEMO • New developments for future EC systems o Higher gyrotron frequency o Multi-frequency operation o Broad band window o Remote steering launcher

14 ITER Electron Cyclotron System

5 Launchers (20MW) 24 Transmission lines

24 sources (24MW)

Power Supplies (50MW)

Method Advantage Disadvantage Extremely localized heating and current deposition - Indirect heating of ions EC Couples high power Uses external actuators to - Limited long pulse high microwaves to e change deposition location power experience

Effectively 100% coupling 15 NTM control

Upper Launcher is like a ‘predator drone’: it watches plasma from above and hits each island as they rotate in sight

Upper Launcher optics designed for: Deposition 4 to 8cm Power can modulate up to 5kHz 24 beams overlap in plasma (very narrow profiles)

Last mirror steers deposition over 50% of plasma

16 Equatorial Launcher Primary Role

Note that beams now steer in poloidal direction

17 EC Functional Requirements

EC HCD Applications (Baseline and Power Upgrades) First Plasma Operations (inject 6.7MW) Second Plasma Operations (inject 20MW) Upgrade Operations (inject additional ≤20MW) Safety Nuclear Occupational Compliance with Load Specifications Nuclear Vacuum Environmental Seismic Over pressure events Fire Plasma Seismic Combined loads Integration

RAMI (reliability, availability, maintainability, inspectability)

18 DAs have chosen the EC System Procurements Divisions

5 Parties provide in-kind procurement

of the 4 EC subsystems

EU IN JA RF US

PS 8 sets 4 main 8 APS/BPS

RF Source 6MW 2MW 8MW 8MW

TL 24

Launchers 4 (UL) 1 (EL)

19 Plug to Plasma Efficiency Electrical Efficient from Grid to Plasma

Requirement: >39% Achieving: between 39 and 44% (does not include services)

20 Actuators: Launchers Upper launcher 4 ports, 8 entries each Control of MHD activity (NTMs)

20MW

Switch (≤3 sec)

Equatorial launcher: 1 Port, 24 entries Central heating and current drive

21 EC Transmission Line Transmission Line Overview:

Length ˜160m Tokamak Power Handling 1.4MW Pulse length 3’600s (25% duty cycle) Power Transmission Efficiency ≥90% Mode conversion efficiency ≥95% Transmission Line Path

Microwave Sources

22 Actuators: Transmission Line

Universal Polarizer (>99% O or X mode coupling)

Polarization change ≤2 sec

24 switches directing power to either EL or UL 8 switches directing power to UL “upper” or “lower” Steering mirrors

Switching speed ≤3 sec

23 Safety

EC system has to comply with Tritium Confinement

Diamond window All-metal valve Shutter Valve

24 RF Sources (Gyrotrons) 170GHz Gyrotrons are rated for: pulse length of 3’600sec 1MW at window with ≥95% TEM00 mode purity LHe free cryomagnets >50% efficiency (Pout/PCollectorin) (ground) JA RF EU IN Challenges: electron beam Mass production High Reliability Higher Power (≥1.0MW) TBD RF power Long life (≥5 years)(~ 1MW) mode convertorHigh mode purity (≥98%) mm-wavesPartial Power modulation Resonator5kHz SC magnet 0.1mT < |Br| < 0.25mT (or Body (~+30kV)less) 1MW 1MW 0.8MW Cathode (~-60kV) 1000s 1000s 100s @~1’000 C

50-55% 53% 25 HVPS: Main and Body for EU and RF gyrotrons

Main High Voltage Power Supply Body Power Supply (PSM based) (PSM based)

Parameter Value Parameter Value Voltage ∼55kV Voltage ∼35kV Current ∼110A Current <100mA Pulse Length 3’600 sec Pulse Length 3’600 sec Duty cycle 25% Duty cycle 25%

Current increased for 1.2 to 1.4 MW Gyrotrons

EU contract signed with Ampegon

26 Schedule: Objective at System Level

General ITER EC Planning

2025: first plasma (1 UL, 8MW EC for plasma initiation and maybe EL) 2028: second plasma and full 24MW EC system <2035: D-T phase

EC manufacturing, assembly and Operation Schedule

2018: Access to RF Building 2018-9: Start installation of PS, Gyrotrons, TL 2023-24: 1 UL plug and 8MW ready for operation 2024: All ex-vessel installed, ≥1 year commissioning for First Plasma 2027: All launchers installed 2028: Full system operating 2031: (Full NB and IC operating)

27 Current activities. Russian team. IAP/GYCOM

Gyrotrons/TL components for plasma fusion (2015-2016)

• ITER activity • EAST (first ECW experiment) +1 • KSTAR (first delivery in 2015, acceptance test completed) +1 • Asdex Upgrade • TCV • EU DA…. • New developments

28 ITER RF Source prototype

False floor removed

Gun Coil Power Supply Collector DC coil Power Supply Temperature Monitor X and Y Correction coils Power Supplies Super Conductive Magnet Power CathodeSupply Filament Power Supply Collector Sweep coil Power Supply

Ion Pump Power Supply PROTOTYPE OF RF-DA RF POWER SOURCE, TEST REPORT May 11 – 15, 2015, Nizhny Novgorod, Russia

Gyrotron together with SCM, MOU and relief load in the support structure left picture

Waveguide with terminal load and cooling manifolds top right

Operator console with control &protection cubicles bottom right Russian ITER RF Source pre-prototype

Gyrotron run test (2014) at 1MW output power with pulse duration 500s and 1000s

1100 regular cut-off internal arc 1000

900 Reliability > 95%

800 New tube conditioning 700

600 500s – 160 pulses

500

pulse duration, s duration, pulse 1000s – 55 pulses 400

300

200

100

0 1 51 101 151 201 251 pulse sequencial number PROTOTYPE OF RF-DA RF POWER SOURCE TEST REPORT (Section 5) May 11 – 15, 2015, Nizhny Novgorod, Russia

PRFS testing was carried out on Factory site following RF source prototype FAT Program IDM_NCNC85 v.1.0 in presence of ITER organization (IO) representatives: C. Darbos, F. Gandini and P. Vertongen.

5. PRFS main output parameters Required Measured measurement and verification for compliance for specified ones:

- operation frequency, 170±0.25 GHz 170.07 GHz - power at the MOU output, ≥0.96 MW 0.96 MW (±5%) - generation efficiency ≥50% 58%

- НЕ11 mode content at MOU output ≥95% 97±1%

- pulse length ≥1000s 1000s - duty factor ≤1/4 1/4

FDR, October 2015; Manufacturing began in 2016 Other gyrotrons for fusion installations (2/6)

Two-frequency 140 / 105 GHz gyrotron with 1 MW output power and maximum pulse duration 300 s. The parameters were successfully demonstrated at the customer site – NFRI / Korea. At present time gyrotron operates at plasma machine KSTAR. Second two-frequency gyrotron is planned for delivery to NFRI at the end of 2017.

140 GHz / 1 MW / 1000 s gyrotron operates at EAST machine / ASIPP / China since mid of 2015 year. Second tube passed factory tests at July, 2016 and delivered to China.

The deliveries besides the gyrotrons include other components: cryomagnets (JASTEC, Japan), matching optic units, elements of evacuated transmission lines and full power evacuated dummy load.

Gyrotrons at factory and customer sites • First steps and main events • EC systems: aims and content • List of running and near future EC systems • ITER EC system • Necessary steps from ITER to DEMO • New developments for future EC systems o Higher gyrotron frequency o Multi-frequency operation o Broad band window o Remote steering launcher

34 Necessary steps from ITER to DEMO

• Frequency increase 170 −−−> 230 GHz • Module power increase 1.0 −−−> 1.5 MW • Eff./reliability enhancement 50 −−−> 60 % / 95 --> 98%

• Multi-frequency operation avoid wide angle scanning • Remote steering remove mirrors from magnetic field and plasma

Mutual contradictions in goals

e.g. - Higher frequency and higher power require bigger gyrotron cavity, higher operating mode (affect gyrotron efficiency) - More critical transmission line alignment (for higher f and P)

35 • First steps and main events • List of running and near future EC systems • EC systems: aims and content • ITER EC system • Necessary steps from ITER to DEMO • New developments for future EC systems o Higher gyrotron frequency o Multi-frequency operation o Broad band window o Remote steering launcher

36 New developments, Russian team

• higher power and higher frequency gyrotrons • phase locking of gyro-oscillator by external signal

Aim: • Provide single mode gyrotron operation at very high-order modes • Stabilize frequency while e-beam parameters are not stable • Enhance efficiency • Lock frequency and phase / Make several gyrotrons coherent

37 38 39 40 41 42 Development of Over MW Gyrotrons for Fusion at Frequencies from 14 GHz to Sub-terahertz FIP1-6Rcz Presented by T. Kariya (Univ. Tsukuba) T. Kariya, T. Imai, R. Minami, T. Numakura, K. Tsumura, Y. Ebashi, Y. Endo, R. Ikezoe, Y. Nakashima : Plasma Research Center (PRC), University of Tsukuba

K. Sakamoto, Y. Oda, R. Ikeda, K. Takahashi, T. Kobayashi, S. Moriyama : National Institutes for Quantum and Radiological Science and Technology (QST)

T. Shimozuma, S. Kubo, Y. Yoshimura, H. Takahashi, H. Igami, S. Ito, K. Okada, S. Kobayashi, T. Mutoh : National Institute for Fusion Science (NIFS)

H. Idei, K. Hanada : Research Institute for Applied Mechanics, Kyushu University

K. Nagasaki : Institute of Advanced Energy, Kyoto University

M. Ono : Princeton University Plasma Physics Laboratory (PPPL)

T. Eguchi, Y. Mitunaka : Toshiba Electron Tubes and Devices Co., Ltd (TETD)

Univ. of Tsukuba is developing over 1 MW gyrotrons of 14GHz to sub-THz for Fusion Devices and for Demo-Reactor in collaboration with QST, NIFS, Kyushu Univ., Kyoto Univ., PPPL and TETD, based on 2 MW level result on the LHD 77 GHz gyrotron tube Develop. of Sub-Terahertz (300 GHz) Gyrotron For ECH and ECCD at the DEMO reactor (Collabo. with QST) Achieved 299.8 GHz, 522 kW, 2 ms with TE32,18 single-mode

Mode maps (cavity vs. gun coil current) 295.65 GHz, 542 kW (TE31,18) Output Window Reflectance : With SiO2 disk 301.8 GHz, 528 kW 0% for TE , 23% for TE 20% for TE ,2% for TE

32,18 30,19 32,18 30,19 (TE30,19)

Gun Coil Current [A] Gun Coil Current [A] Window reflection affects

[A] [A]

the oscillation mode

characteristics, which can

Current Current

be removed by installing a Coil

Coil built-in mode converter.

The aimed design single Main Main mode would be realized. Develop. of Sub-Terahertz (300 GHz) Gyrotron For ECH and ECCD at the DEMO reactor (Collabo. with QST) Stable single mode oscillation at each tuned freq. in 225–254 GHz band

220 - 240 GHz Oscillation by 300 GHz Gyrotron Magnetic Field Beam Radius Estimated Estimated at Cavity [T] [mm] Oscillation Mode Frequency [GHz] (-) 10.11 5.57 TE28,15 253.99 (-) 9.80 5.58 TE27,15 250.04 (-) 9.60 5.59 TE28,14 243.9 (+) 9.54 5.59 TE25,15 242.1 9.43 5.6 ? ? (+) 9.07 5.61 TE24,14 228.13 (-) 8.90 5.62 TE26,13 225.96 300kW short pulse, efficiency It was found that designed ultra-high volume mode of sub-THz would be stably obtained with conventional cylindrical cavity. Step tunable single mode oscillations were also confirmed. These result contributes greatly to the step frequency tunable gyrotron in the sub-THz region for the DEMO-Reactor. Design study of 154/116 GHz Dual-frequency gyrotron ----- For ECH and EBW heating at LHD (Collab. With NIFS) Three 77 GHz and two 154 GHz gyrotrons have contributed greatly to extending the LHD plasma performance with their total plasma injection power of 5.4 MW.

• High Te plasma : Te = 20 keV 19 -3 • Steady-state plasma : line averaged ne = 1.1× 10 m Te = 2.5 keV was sustained for 2351 s. Based on the above and the 2 MW level 77 GHz gyrotron development results, a new 154/116 GHz dual-frequency gyrotron is desired for expanding the LHD plasma parameters. Best matching of cavity, Mode convertor and window was obtained with combination of Cavity oscillation modes TE28,9 at 154 GHz and TE21,7 at 116 GHz. The simulation of the MIG indicates the operation at α = 1–1.2 with Δα/α < 5 %, implying high efficient oscillations in the cavity. 1.5MW 1.5MW Oscillations with the power exceeding 1.5 MW are expected at 154 and 116 GHz. DEMO EC System Conceptual Design by EUROfusion The Conceptual Design of the EC System bases on: Physical requirements EC Task Power (MW) Localization (ρ) Mode Assisted Break-down 6-10 < 0.3 Heating Ramp up and L-H transition 50 < 0.3 Heating/CD Main Heating 50 < 0.3 Heating/CD Sawtooth Control 2 0.3 CD NTM control (2,1) and (3,2) 10-15 0.85; 0.75 CD Ramp down 40 0.3 - 0.5 Heating Main DEMO EC tasks with corresponding power required and deposition location, assuming the design value of 50 MW. For all these functions, a 100 % reliability is expected. Main Heating/CD if requested 50 Considerations for RAMI Ramp-up & 40 L-H I EC transition Flat top 100 % reliability p [MW]* Ramp-down 10 maximum availability + NTM stabilization BKD ~200- ~2h ~200-300s ~10s 300s G. Granucci et al., “Conceptual Design of the DEMO EC-System: Sketch of DEMO1 Pulse Main Developments and R&D Achievements”, 26th IAEA FEC, Kyoto, 2016 * EC power required - w/o NBI, IC EC System Architecture and Concept Studies

The EC DEMO system architecture is organized in identical CLUSTERs (6), allowing modularity, reducing requirement for special components. In each CLUSTER there is one gyrotron in stand-by to enter in case of fault.

Each CLUSTER is composed by: 8 gyrotrons /2 MW  total power 16 MW  14 MW injected HVPS Gy1 1 multi-beam EQO TL 1 HVPS with 8 outputs + 8 anode PSs +8 series switches Gy2 1 plug-in launcher with 8 launching points

Gy3

RSA upper Gy4 row

RSA lower Gy5 row

Gy6 Number of clusters: Gy7 4 + 1 for Equatorial Port + 1 for Upper Port To guaranty 100 % of reliability for 50 MW Gy8 at any time of DEMO pulse

G. Granucci et al., “Conceptual Design of the DEMO EC-System: Main Developments and R&D Achievements”, 26th IAEA FEC, Kyoto, 2016 Conceptual Studies on Transmission Line + Antenna

Main requirements for transmission lines: Proposal of Evacuated Quasi-Optical Multiple beam TL - Efficiency target: 90 % .Multi-Beam QO TL enclosed in a vacuum vessel - Power handling capability: 2MW cw .Reference design: mirror confocal layout - Multi-frequency (or broadband) .Vacuum duct: straight tubes with constant diameter - Tritium compatibility .Mirrors (1 curved + 1 Plane) forming doglegs for TL bend .Pumping system at each unit length .L=distance between 2 focusing mirrors

Main requirements for antennas: • Different tasks to be addressed (Heating, Off-axis CD…) • No movable parts in the proximity of plasma • Several Identical plug-in launchers

RSA feasibility study aims for: • Wide steering for deposition control • Optimal range for CD efficiency maximization • Multi-frequency operation G. Granucci et al., “Conceptual Design of the DEMO EC-System: Main Developments and R&D Achievements”, 26th IAEA FEC, Kyoto, 2016 Targets for EC Gyrotron R&D

• Operate at heating and at optimum current drive frequency  Frequency for current drive: >200 GHz (up to 240 GHz)

• Keep the number of gyrotrons as low as possible  Output power: >1 MW (target: 2 MW @ >200 GHz)

• Keep a high energy gain for the power plant  Total efficiency for a gyrotron >60 %

• Allow multi-purpose operation at optimum heating and current drive frequencies (including a possible compatibility to ITER frequency)  Multi-purpose at n·l/2 of window resonances Leaps of about ~34 GHz (e. g. at 136/170/204/238 GHz)

• Allow fast frequency step-tunability (2-3 GHz, ±10 GHz total bandwidth)  Broadband window technologies

Gyrotron Concepts under Consideration to Achieve the Target of 2 MW Output Power at >200 GHz

TE43,15-mode TE49,29-mode Conventional hollow-cavity design Coaxial-cavity design

+ simpler construction + Less dense spectrum of competing modes - more dense mode spectrum  operation at very high-order mode  lower possible operating mode  higher output power  less output power + Reduced voltage depression

- Risk of misalignment and too high thermal loading of inner conductor Towards >60 % Efficiency: Fundamental Studies on Possible Multi-Stage Collector Concepts

Example for a collector using advanced ExB drift concept: A gyrotron interaction efficiency of 35 % requires a concept for a depressed collector which consists of minimum 2-stages (휂푐표푙 > 74 %).

Two concepts under consideration:

Non-adiabatic concept E- and B-field profiles using axial symmetric E- and B-field components ExB drift concept  using non-axial symmetric field components as proposed by I. Pagonakis, 2008 Electron trajectories Towards CVD-Diamond Disc Brewster Angle Windows for Frequency Step-Tunable Gyrotrons Targets: - Fast frequency step-tunability (2-3 GHz, ±10 GHz total bandwidth) - Waveguide diameter >50 mm (min. 63.5 mm)

 Innovative production technologies for large-size (>140 mm) CVD diamond discs  Advanced cooling technologies  New joining technologies

Summary • DEMO requirements much more stronger than ITER • But great progress in gyrotrons in last 20 years 1 MJ (0.5MW/1 sec)  1 GJ (1MW/1000 sec), eff. 30  55% this brings some optimism

• Lack of long pulse operation experience with TL and launchers the experience will come soon

• Aims of the new developments are: • Reliability of the system operation • Higher power and higher frequency • Multi-frequency operation • Remote steering antenna Thank you!

54