Impact of increasing plasma-wall gap on plasma response to RMP fields in ITER

IF 2.1 2区 物理与天体物理 Q2 PHYSICS, FLUIDS & PLASMAS
X Bai, A Loarte, Y Q Liu, S D Pinches, F Koechl, L Li, M Dubrov, Y Gribov
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Abstract

The impact of increasing plasma-wall gap on controlling edge-localized modes (ELMs) is numerically evaluated for the ITER 5 MA/2.65 T H-mode scenarios with full tungsten wall, based on the MARS-F computed plasma response to the applied n= 3–5 (n is the toroidal mode number) resonant magnetic perturbation (RMP) fields. Three new scenarios, referred to as standard, clearance and outergap, are considered assuming different plasma-wall gap sizes over a range on which vertically stability can be maintained by in-vessel coils in ITER. The latter are shown to have both direct and indirect effects on the plasma response and hence ELM control in ITER. The indirect and also primary influence occurs via change of the equilibrium edge safety factor q95 , which decreases with increasing the plasma-wall gap (at fixed plasma current and toroidal field), leading to a multi-peaking structure in the plasma response as measured by the plasma displacement near the X-point or the edge-localized resonant radial magnetic field perturbation. The direct, albeit secondary effect, is the reduction of local peak amplitudes with increasing the plasma-wall gap thus weakening the RMP field efficiency for ELM control with a given current in the control coils. A slight reduction of the plasma current, from 5 MA to 4.77, 4.92 and 4.65 MA for the standard, clearance and outergap scenarios, respectively, is found to be sufficient to access the q 95 window for the best ELM control with the n= 3 RMP. The n= 4 coil current configuration with the n= 5 sideband is also found favorable for ELM control in ITER, by producing RMP fields with mixed toroidal spectra compared to n = 3.
增大等离子体壁间隙对等离子体对热核实验堆 RMP 磁场响应的影响
根据 MARS-F 计算的等离子体对应用 n= 3-5(n 为环形模式数)共振磁扰动(RMP)场的响应,对带有全钨壁的热核实验堆 5 MA/2.65 T H 模式情况下,增大等离子体壁间隙对控制边缘定位模式(ELM)的影响进行了数值评估。考虑了三种新情况,即标准、间隙和外隙,假设等离子体壁间隙大小在一定范围内不同,ITER 的舱内线圈可以在此范围内保持垂直稳定性。结果表明,后者对等离子体响应以及热核实验堆中的 ELM 控制有直接和间接影响。间接影响也是主要影响是通过平衡边缘安全系数 q95 的变化产生的,它随着等离子体壁间隙的增大而减小(在固定等离子体电流和环形磁场条件下),从而导致等离子体响应中的多音结构,该结构可通过 X 点附近的等离子体位移或边缘定位共振径向磁场扰动来测量。直接影响(尽管是次要影响)是随着等离子体壁间隙的增大,局部峰值振幅减小,从而削弱了控制线圈中给定电流下 ELM 控制的 RMP 磁场效率。在标准、间隙和外隙方案中,等离子体电流分别从 5 MA 微降至 4.77、4.92 和 4.65 MA,就足以进入 q95 窗口,实现 n= 3 RMP 的最佳 ELM 控制。与 n=3 相比,n=4 线圈电流配置与 n=5 边带通过产生具有混合环形光谱的 RMP 场,也有利于热核实验堆的 ELM 控制。
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来源期刊
Plasma Physics and Controlled Fusion
Plasma Physics and Controlled Fusion 物理-物理:核物理
CiteScore
4.50
自引率
13.60%
发文量
224
审稿时长
4.5 months
期刊介绍: Plasma Physics and Controlled Fusion covers all aspects of the physics of hot, highly ionised plasmas. This includes results of current experimental and theoretical research on all aspects of the physics of high-temperature plasmas and of controlled nuclear fusion, including the basic phenomena in highly-ionised gases in the laboratory, in the ionosphere and in space, in magnetic-confinement and inertial-confinement fusion as well as related diagnostic methods. Papers with a technological emphasis, for example in such topics as plasma control, fusion technology and diagnostics, are welcomed when the plasma physics is an integral part of the paper or when the technology is unique to plasma applications or new to the field of plasma physics. Papers on dusty plasma physics are welcome when there is a clear relevance to fusion.
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