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EAST 等离子体启动

EAST 等离子体启动. 肖炳甲 2009/02/23. Plasma Startup: 击穿和建立、电流上升、成形. 物理问题. 低环电压 breakdown 降低磁体端电压、减小磁通消耗和降低逃逸 上升段电流、位置、位形的控制 磁场、平衡重建 , 导体间的耦合，等离子体模型，真空室的三维结构的影响 … 电流上升与不稳定性的关系， Profile 控制 , operation limits. 击穿与初始上升实现. PF/PS 系统 ＝ 》 合适的欧姆场和垂直场 充气 ＝ 》 在合适的时间内合适的气体压力

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EAST 等离子体启动

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  1. EAST等离子体启动 肖炳甲 2009/02/23

  2. Plasma Startup: 击穿和建立、电流上升、成形

  3. 物理问题 • 低环电压breakdown • 降低磁体端电压、减小磁通消耗和降低逃逸 • 上升段电流、位置、位形的控制 • 磁场、平衡重建, 导体间的耦合，等离子体模型，真空室的三维结构的影响… • 电流上升与不稳定性的关系，Profile控制, operation limits

  4. 击穿与初始上升实现 • PF/PS系统 ＝》合适的欧姆场和垂直场 • 充气 ＝》在合适的时间内合适的气体压力 • Wall conditioning => Low impurities • Pre-ionization aided by ICRF or LHW • Enough seed electrons in longer duration to meet the Townsend Avalanche in a not well-controlled stray field and Loop Voltage. • RF heating aiding to overcome radiation barrier • IP**2*R + Paux > Etransport + Eradiation

  5. 基本模型 • 系统构成： • PF线圈 • PF电源及电阻 • 真空室及被动结构 • 击穿后，等离子体 • 模型方程

  6. 线圈系统

  7. 线圈系统： • PF互感 快控： 被动结构

  8. Coil No. Rated current (kA) Max. voltage (kV) load steady voltage (V) R1 (R2) (mΩ) PS1 1 -14.5~ 14.5 1.2 280 150 PS2 2 -14.5~ 14.5 1.2 280 150 PS3 3 -14.5~ 14.5 1.2 280 150 PS4 4 -14.5~ 14.5 1.2 280 150 PS5 5 -14.5~ 14.5 1.2 280 150 PS6 6 -14.5~ 14.5 1.2 280 150 PS7 7 ,9 -14.5~ 14.5 2.4 560 150 PS8 8,10 -14.5~ 14.5 2.4 560 150 PS9 11 -14.5~ 14.5 0.6 280 150 PS10 12 -14.5~ 14.5 0.6 280 150 PS11 13 -14.5~ 14.5 0.26 160 1500 PS12 14 -14.5~ 14.5 0.26 160 1500 ASIPP Parameters of PF Power Supply • Note: • (1) Coil 7 and Coil 9 is in series, they share one power supply, same as Coil 8 and Coil 10. • (2)Max. Voltage is only used as plasma initiation and fast rising. • R1 =R2, it is designed according to the plasma scenario some years ago. They (PS1—PS10) can be respectively changed from zero to above value in step 7.5mΩ, Other (PS11—PS12 ) is in step 50mΩ .

  9. EAST 等离子体控制中的电磁测量 极向场线圈电流(Rowgowski)：12 等离子体电流(Rogowski, in-/ex-vessel) ：2 磁通环：37 磁探针：38 内部线圈电流：1 控制目标： R ~ 1.8, a~0.4 Ip ~ 0.5 MA (1 MA, 1.5MA) delta 0.3-0.6 k ~ 1.5 – 2.0 DN/SN

  10. 击穿条件 1. 足够长的连接长度和环电压 Or Emin = 950p/ ln(3.88pL) For EAST: MPF-IP~3Vs/8kA, dI/dtmax=20 kA/s so Vmax=MdI/dtmax~ 7.5 V E~6 V/2PiR~0.5 V/m (0.7 for JET， 0.3 for ITER) Bp<10 Gauss @Bt=2 T Bp<1 Gauss @Bt=0.2 T (Itf~1kA) 2. 合适的气体压力 1. Tanga et al., in Tokamak Startup 2. Lloyd B et al., Nucl Fusion 31

  11. 击穿优化方法 • 初始零场 • CS尽可能达到最大 • 选取预期初始等离子体圆周上数点，调节线圈电流，用最小二乘得到IM state • 击穿电压及零场 • Idot总数：4 • CS以相同的下降率 • 上下对称 • 预期击穿时间及环电压（或电场） • 基于给定PF电压，得到Idot求解回路方程,得到Ivv，从而计算磁场和环电压，与目标值作最小二乘优化得到Idot和VS • Ip＝0，RPF＝0,

  12. Optimization target: • Initial Flux • Null region • Emax~ 0.5 V/m • Initial ramp-up rate and Bz • Field Curvature • Limitation: • Imax, Idotmax Courtesy to J. Leuer,

  13. 初始上升 • Bz＝m0Ip/R0[ln(8R0/a)+li/2+b-1.5] • LPdIP/dt＝V0-Vres • Assume: Vres/V0=0.5 • dIP/dt~ 0.5-1 MA/s • Spitzer Resistivity： • (ne=1e19,Te=100eV=>Rp~20mW） • Lp~4.8mH

  14. 击穿电阻及PCS waveform • RPF＝mean(Vtraj/Itraj) • 再次求解（1），得到新的V和I • Itraj: Feedback Current Control • Vtraj: Feedforward • Note：根据实际的电阻可调整最近的RPF，重新计算（1）

  15. 优化1：R0＝1.7，a=0.35， psi＝3 Vs

  16. 磁通（角向分布）

  17. 优化2：R0＝1.7，a=0.35不考虑初始上升

  18. 优化3：R0＝1.8，a=0.4不考虑初始上升

  19. PF current /PS Voltage Trajectory @ Plasma Current Ramp-up: #8815

  20. 等离子体电流上升（环电压＝1V only） 对极向场电压的要求

  21. Proposal: Startup optimization • Objectives: • Robust startup • Low loop voltage initiation • Flux consumption reduction • Shaping while ramping, position control at earlier time, impurity reduction • MHD avoidance while ramping up, ramping-up margin & operation limits, preliminary profile control • Methods • Null field adjustment, various IM states and BD resistor tuning • Gas filling scan • Ramp-up rate adjustment in accordance with Bv variation • Assistance of ICRF(100 kW?) pre-ionization • LHW (200 kW?) in the startup, time: just after plasma initiation is possible? • Bt scan • Diagnostics • Magnetics, CCD, density, Te, P(RF), magnetics at the PS end, Bolometry, Impurity • Modeling: • Reconstruction, breakdown, TSC, DIII-D analysis tools • Machine times: > 2 effective days

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