Non-inductive driven plasma start-up and investigation towards EBWH/CD in QUEST
H. Idei1, H. Zushi1, K. Hanada1, T. Kariya, T. Imai, K. Mishra3, O.Watanabe1, T. Yamaguchi4, A. Ejiri4, Y. Takase4, T. Onchi1, S. Suzukawa3, H. Miura3, K. Nakamura1, M. Hasegawa1, A. Fujisawa1, Y. Nagashima1, N. Yoshida1, H. Watanabe1, K. Tokunaga1, A. Higashijima1, S. Kawasaki1, H. Nakashima1, O. Mitarai5, T. Maekawa6, A. Fukuyama7 and QUEST team1
1Research Institute for Applied Mechanics, Kyushu Univ., Kasuga, 816-8560, Japan 2Plasma Research Center, Tsukuba Univ., Tsukuba, , 305-8577, Japan 3Interdisciplinary Grad. School of Eng. Sci., Kyushu Univ., Kasuga, 816-8580, Japan 4Department of Complexity Sci. and Eng., Univ. of Tokyo, 277-8561, Kashiwa, Japan 5Inst. of Ind. Sci. and Tech. Research, Tokai Univ., Kumamoto, 862-8652, Japan 6Graduate School of Energy Science, Kyoto University, Kyoto 606--8501, Japan 7Department of Nuclear Engineering, Kyoto University, Kyoto 606--8501, Japan
Bi-directional collaboration among National Institute for Fusion Science, Tsukuba Univ. and Kyushu Univ. has been begun since 2011. will be Introduction [ QUEST ] QUEST, Advanced Fusion Research Center QUEST : Q-shu University Experiments with Steady State Spherical Tokamak ) The EBWH and EBWCD are one of attractive candidates of heating and current drive method to sustain the steady-state plasma in the spherical tokamak (ST) .
The establishment of steady-state current drive method is a key issue to study plasma-wall interaction phenomena in the steady-state QUEST plasma.
The 8.2 GHz LHCD system in the previous Major radius : 0.68m TRIAM tokamak has been used to the ECH Plasma minor radius : 0.40m /CD experiments. Magnetic field 0.25T(CW) -max. 0.5T Non-inductive Operation in QUEST
100 kA @1MW
3 8.2GHz Reconstructed flux surfaces Typical time evolutions of HX intensities from forward and backward electrons
3 16x10 FW 12 BW 10 - 20 keV Ip and HX intensity [10-20 keV]
[a.u.] 8 evolution in ramped–up Bz HX 4 -12 8000 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FW 600 30 - 40 keV 3 -10 12x10 BW
[a.u.] 400 Ip -8 I p HX
200 [kA] 8
[a.u.] -6 3000 0.4 0.5 0.6 0.7 0.8 0.9 1.0 HX
50 - 60 keV -4 200 4
[a.u.] -2
HX 100 0 0 0 1.2 1.6 2.0 2.4 0.4 0.6 0.8 1.0 Time [s] B [mT] tangential viewing z The ST plasma with a low aspect ratio of The hard X-ray intensity from current-carrying forward electrons 1.5 was attained in accelerated by the RF injection was increased in the energy range
the 12 kA discharges. of 10~20 keV, following the Ip ramped-up evolution. Current Drive Mechanism QUEST Advanced Fusion Research Center O‐mode cutoff ne Density is lower than the O‐mode cutoff EBWH/CD [ sec ]
10keV Contributions to generate Ip
pitch angle 0.30 -75dgree Co‐ banana 75degree 0.20 moving
vperp/c 0.10 10keV passing passing 0.00 -0.2 0.0 0.2 0.4 0.8 1.2 vpara/c R[m] The anti‐symmetric confinement structure of high energetic electrons on the parallel velocity in a velocity space is one of candidates to explain the generated current. Experimental Scenario QUEST Advanced Fusion Research Center 2nd :28GHz Waveguide
Gyrotron
Anode Power Supply 1st :8.2GHz
EBWH/CD Exp. Scenario： ECH/CD Exp. 1) 1st : 8.2 GHz: production Plasma start‐up and sustainment 2) 2nd : 28 GHz : density ramp‐up with assistance of 8.2 GHz injection 3) 1st : 8.2 GHz : EBWCD Gyrotron Development at Tsukuba University [ 28GHz ] QUEST Advanced Fusion Research Center 28 GHz gyrotron has been developed for Gamma-10/PDX projects at Tsukuba University.
Collector Coils Design Parameters From T. Kariya
Collector Electorn Beam 28GHz 1MW 1s Gyrotorn for PRC(Tsukuba) Frequency 28GHz Out put Window Mirror4 Output Power 1MW Pulse Width 1s RF Beam Mirror3 Output Efficiency 35% (W/O CPD) Mirror2
Mirror1 2413mm Beam Voltage 80kV
Mode Converter Beam Current 40A MIG triode Cavity Cavity Oscillation mode TE8,3 Beam Tunnel Built-in Mode Converter with Output mode Gaussian like Electron Gun Output Window Sapphire Single Disk Aperture diameter 112mm Collector W/O CPD Sweeping coils Gyotron Development at Tsukuba University [ 28GHz ]
QUEST Advanced Fusion Research Center
1MW
[2013] Oscillating Efficiency [%] Oscillating Efficiency Oscillating Efficiency [%] Oscillating Efficiency Oscillating Power ]kW] Oscillating Power Oscillating Power ]kW] Power Oscillating
Beam Current [A] Beam Current [A] 25A @70/75kV ‐‐‐‐ Kyushu University
600 kW power level is available with Kyushu Univ. Power Supply. The oscillating efficiency is improved to attain more than 1MW output. 28GHz-1MW Improvement From T. Kariya
Anode Body
[cm] Electron Cathode Beam 径方向位置
軸方向位置 [cm]
Anode Laminae property Body improvement
Electron Beam Improvement
径方向位置 [cm] Cathode
軸方向位置 [cm] Improvement of laminae property of electron beam in front of Cathode low pitch factor / low spread in high current operations improvement of the efficiency Power Supply System for 28GHz Gyrotron 50kV / 80 mA ・ Commercial HV PWS (50kV/80mA) has been prepared. ・ MOSFET HV switch system was developed for fast HV cut.
Commercial HV PWS HV Probe IA Detection MOSFET Switch
75kV/25A HV PWS The Cathode HV (75kV/25A) was prepared for a previous 170 GHz gyrotron with diode MIG gun in the TRIAM- 1M tokamak experiments. HV(90kV) Isolation TR
・ Fast Anode HV cut within 1s after IA OC detection ・ Fast Cathode HV cut within 5.6s after IA OC detection WG support
Cooling Water Head
Gyrotron Support Tank
Anode Power Supply Cooling Water Pipes Installation of Gyrotron System in QUEST
QUEST Advanced Fusion Research Center
Gyrotron Support SCM
Gyrotron Tank with Heater‐Cathode/Anode/Body electrodes Superposed RF Injection to Ohmic Plasma QUEST Advanced Fusion Research Center RF power is injected into the 30 kA ohmic plasmas controlled by feedback regulation of the center solenoid coil current to maintain the constant plasma current.
w/ and w/o PAA
N// scan Experiments
The densities are clearly increased beyond the cutoff by the RF injection with N//, compared to the perpendicular (without N//) injection, while the changed plasma currents and loop voltages do not depend on the incident N// conditions well. Propagation and Deposition Analysis with TASK/WR + α code QUEST Advanced Fusion Research Center
NO Propagation
Without N//
PAA The minus (‐) sign of N // is changed into positive (+) N//along the propagation after the mode conversion. PAA Any incident (+/‐) N // becomes large positive (+) value in the BernsteinNf wave‐propagation, and are +2 +4 at the Doppler‐ shifted absorption layers, expecting Fish‐Boozer effects so as to increase the plasma current. 0.1 Change of N// sign along propagation QUEST Advanced Fusion Research Center 0 Vertical Group Velocity (Poloidal) -0.1 Ray trajectories N scanning. [m]
Z in poloidal sections
B 0
-0.1 0 0.4 0.8 1.2 R [m] 100 0 >> k B k B
-300 k // k evolutions along In the electrostatic B-wave, N or k contribution 300 k B the propagations is dominant in the N// evolution not near the mid-plane of the torus. Phase Velocity k// 0
k B -200 R [m] 0 0.4 0.8 1.2 28GHz Gyrotron Operation in Kyushu
QUEST Advanced Fusion Research Center
‐‐ Tsukuba test stand ‐‐
2013
270kW ‐‐ QUEST Exp. ‐‐
Gyrotron was operated with the power supply of Kyushu University at the Vk of 70kV.
500kW ( with 10% MOU loss) 450kW ( with 10% MOU loss) ‐‐‐ Dummy load ‐‐‐ DC break
QUEST vacuum window (Sapphire Single Disk)
QUEST 63.5 mm Corrugated Waveguides 28 GHz Gyrotron
8.56 GHz CPI Klystron 28GHz Incident Condition
1.2m Propagation
WG Launcher was installed at R ~ 1.5m. The beam is launched with rather Cold Resonance of 28 GHz large N// > 0.5, even for perpendicular is located at R ~ 0.32m. RN=const. injection. 28GHz Coupling Condition
Resonance layer is R<=0.32 m
Resonant P|| range depends on Local N||(r) & f/fec(r) Non-inductive Start-up and Sustainment [28GHz] High Density Operation QUEST Advanced Fusion Research Center
8.2GHz Cutoff Thomson Scattering Density
28GHz 220kW 1s
Including Bremss 4 gas puffing Ztop
Zbottom
Rout Non-inductive Start-up and Sustainment [28GHz] Low Density / High Temperature Operation QUEST Advanced Fusion Research Center
The plasma current of 25 kA was sustained in low density plasma.
28GHz 2２0kW 1s Shot # 22445
0.5
0.4
0.3
0.2
0.1
0 Z [m]
The density was as low as -0.1
a half of 8.2 GHz cutoff -0.2
density with no gas puffing. -0.3
-0.4
-0.5
0.2 0.4 0.6 0.8 1 1.2 R [m] Non-inductive Start-up and Ramp-up [28 GHz] QUEST Advanced Fusion Research Center
28GHz 270kW 1s Non-inductive Start-up and Sustainment [28 GHz] QUEST Advanced Fusion Research Center ]
28GHz 270kW 1.7s -2 m 18 Line-integrated density [10 Line-integrated density Inductive Start-up and Non-inductive Sustainment [28GHz] High Current Operation QUEST Advanced Fusion Research Center
Inductive 28GHz
28GHz 350kW 1s Trial to control density profile from inboard to outboard gas puffing QUEST Advanced Fusion Research Center
Trial to control density profile from inboard to outboard gas puffing
2 x 1018m‐3： high degnsity Good symmetry on up and down 28 GHz 2nd Resonance 8.2 GHz 1st Steep density gradient at the edge? Resonance Heating effect at 1st resonance for 8.2 GHz
Inboard gas puffing outboard gas
outboard gas 28GHz(270kW)+8.2GHz@35kW (constant small Bz case)
28GHz
8.2GHz
When 8.2 GHz (25 kW)is injected, Natural 27 Separatrix is formed. 28GHz(270kW)+8.2GHz@35kW Ip could be sustained at higher Bz
2nd @28GHz
Outer region
1st @8.2GHz
28 By rising Bz SBD increases and stray power does not increase Summary QUEST Advanced Fusion Research Center
Bi-directional collaboration among National Institute for Fusion Science, Tsukuba Univ. and Kyushu Univ. has been begun since 2011. 2011-2012: Preparation of Anode Power Supply System and Gyrotron Tank 2012-2013: Installation of Gyrotron System and Transmission Line 2013- QUEST Experiments
450 / 500 kW (with MOU loss) for 0.2 s in Dummy load Operation 250 / 300 kW (with MOU loss) for 1.7 s in QUEST Operation
The plasma current of 25 kA was non-inductively started up and sustained as high-density plasmas ( > 1 x 1018 m-3). The high plasma current ( > 50kA) was non-inductively sustained for 1 sec.
No clear dependence of Ip on incident N// with the 8.2 GHz injection for the 28GHz plasma
Future Plans 600 kW 2 sec Oscillation QO Steering Mirror System for Oblique Injection