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Current Drive Experiments with Oscillating Toroidal Flux in HT-7 Superconducting Tokamak

HT-7. ASIPP. Current Drive Experiments with Oscillating Toroidal Flux in HT-7 Superconducting Tokamak. J.S.Mao, P. Phillips 1 , J.R.Luo, J.Y.Zhao, Q.L.Wu, Z.W.Wu, J.G.Li, and HT-7 team Institute of plasma Physics, Academia Sinica, Hefei, Anhui, 230031, P.R.China

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Current Drive Experiments with Oscillating Toroidal Flux in HT-7 Superconducting Tokamak

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  1. HT-7 ASIPP Current Drive Experiments with Oscillating Toroidal Flux in HT-7 Superconducting Tokamak J.S.Mao, P. Phillips1, J.R.Luo, J.Y.Zhao, Q.L.Wu, Z.W.Wu, J.G.Li, and HT-7 team Institute of plasma Physics, Academia Sinica, Hefei, Anhui, 230031, P.R.China 1. Fusion Research Center, RLM 11-222 UT at Austin. TX 78712 USA * Support by National Natural Science Fund of China

  2. HT-7 ASIPP MOTIVATION  A crucial issue for the extension of advanced tokamak scenarios to long pulse operation is to avoid these MHD instabilities  The control of the low order m / n tearing modes has attracted much research  Various methods proposed to suppress the tearing modes to prevent disruptions  MHD suppression was achieved using resonant magnetic perturbation (RMP) or magnetic feedback  MHD suppressing has been research with new methods  Oscillating plasma current on HT-7 Tokamak  Modulate plasma horizontal position  Modulate LHCD  Modulate IBW

  3. HT-7 ASIPP Experimental Set-up *The feedback control system for the HT-7 tokamak is a multi-variable feedback controller due to the strong coupling between the ohmic heating coil and vertical field coil. Input parameters: plasma current; vertical coil's current; center of the last magnetic surface as measured by the four single flux loops. * The output parameters are the ohmic heating current and the vertical coil's current. Response time of the feedback system is limited by double copper shell to greater than 200ms.

  4. HT-7 ASIPP Experimental Set-up Toroidal flux was modulated by programming the ohmic heating field or by vertical field two types of experiments have been performed Involves modulating plasma current only, while the other experimental parameters are held constant Modulating plasma horizontal position with the plasma current kept constant by a feedback system

  5. HT-7 ASIPP 1 0 3.2 0 1.3 0 1 -1 130 0 (e) (d) (c) (b) (a) Ip Br SX Ne(0) ECE KA a.u. a.u. 1013cm-3 a.u. . 0 100 200 300 400 500 t (ms) Modulating plasma current only, while the other experimental parameters are held constant  Ip=114KA,  dIp/Ip=30%, f=40Hz  Negative Pulses -dIp/dt=5.43MA/s, + dIp/dt =2.4MA/s,  Total radiation (Bol.) modulated and decrease  Te(0) increased  MHD suppressed

  6. HT-7 ASIPP Shot N0. 34448 Shot No. 24230 140 1 0 3.2 0 1.3 0 1 -1 130 0 KA Bol Ne(0) SX(0) Ip a.u. Ip Vl a1 60 3 V 1013cm-3 0 1.0 cm a.u. -1.0 1 I II a.u -1 a.u. 1 a.u -1 KA 200 300 400 500 Time (ms) 363 449 534 620 706 Time (ms) HT-7 Tokamak

  7. HT-7 ASIPP HT-6M Tokamak R=65cm, a=18.7cm, Bt=1.0T , Ip=60kA. Ip=60-70KA, dIp/Ip=14-20%, +dIp/dt=120MA/s, - dIp/dt=5.3MA/s, f<200Hz

  8. HT-7 ASIPP ( II ) (1) Typical Discharge of the HT-7 Tokamak with Modulation Plasma Current

  9. HT-7 ASIPP 120 KA 0 2.7 V 0 2.0 V 0 a.u a.u. 2.0 0 Ip Vp Iv H SX Ne 0 .25 .50 .75 1.0 1.25 time (S) Modulating plasma horizontal position with the plasma current kept constant by feedback

  10. HT-7 ASIPP Plasma Minor Radius Modulated a ~ 3 cm– 5 cm The time and spatial distribution of bolometer signal with the plasma horizontal displacement modulated Raw Data of Soft X-Ray array

  11. HT-7 Shot N0. 34448 140 KA Ip Vl a1 60 3 V 0 1.0 cm -1.0 1 I II a.u -1 1 a.u -1 363 449 534 620 706 Time (ms) ASIPP Ne (r) Te(r) during TFCM

  12. HT-7 ASIPP Shot N0. 34448 2.1 1.8 1.5 1.2 0.9 0.6 140 KA Ip Vl a1 Ne ( 1013cm-3 ) 60 3 V 0 1.0 cm I II -1.0 1 a.u -20 -10 0 10 20 r (cm ) -1 1 a.u -1 363 449 534 620 706 Time (ms) Profile Changes during TFMC

  13. HT-7 ASIPP 2.5 -2.5 4 -4 0 -1 1.57 -1 136 0 V V V V KA LPI HX H Ip 0 420 840 1260 1680 2100 time (ms) Long Pules Discharge without wall condition Suppression of MHD the edge potential fluctuation HX emission

  14. HT-7 ASIPP radiation（10eV-10keV) Modulated IBW heating MHD instability was reduced AC IBW

  15. HT-7 ASIPP LHCD .2 -.2 1.2 -1.2 3 0 120 0 a.u. a.u. V l V I p KA 120 240 360 480 600 Time (ms) MHD modulated with AC curret & AC LHCD AC LHCD

  16. HT-7 ASIPP Conclusion • The plasma equilibrium current modulated by a frequency current has been successful used in suppressing MHD perturbations effectively on the HT-7 superconducting tokamak and HT-6M tokamak • Control of the plasma pressure profile with local modulated IBW heating can be possible to suppression MHD • Modulating and Suppression MHD by modulating LHCD • The resonant magnetic surfaces perturbations with different ways, It is difficult for the instability of the tearing modes to develop in some fixed locations.

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