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中国物理学会期刊

ITER装置中等离子体旋转和反馈控制对电阻壁模影响的数值研究

CSTR: 32037.14.aps.70.20201391

Numerical study of effect of plasma rotation and feedback control on resistive wall mode in ITER

CSTR: 32037.14.aps.70.20201391
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  • 在托卡马克等离子体中, 电阻壁模是非常重要的磁流体不稳定性, 特征时间在毫秒量级. 对长时间稳态运行下的先进托卡马克, 电阻壁模限制着聚变装置的运行参数空间(放电时间和比压), 影响经济效益, 所以研究电阻壁模稳定性至关重要. 本文使用MARS程序, 针对ITER装置上9 MA先进运行平衡位形, 研究了等离子体旋转和反馈控制对电阻壁模的影响. 结果表明, 在没有反馈控制时, 当比压参数C_\beta 取0.7, 等离子体环向旋转频率达到1.1%的阿尔芬频率时, 可以完全稳定电阻壁模; 在等离子体环向旋转和反馈控制共同作用时, 比压参数C_\beta 取0.7, 反馈增益|G|取0.6时, 稳定电阻壁模所需要的等离子体旋转频率为0.2%的阿尔芬频率. 可见, 单独靠等离子体环向旋转稳定电阻壁模所需的旋转频率较大; 而等离子体环向旋转和反馈控制共同作用可以降低稳定电阻壁模的旋转频率临界值, 符合先进托卡马克的运行. 本文的研究结果对中国聚变工程试验堆CFETR的工程设计和运行具有一定指导意义.

     

    In tokamak plasmas, the resistive wall mode is a very important magnetohydrodynamic instability, and its time scale is on the order of millisecond. For the advanced tokamaks with long-pulse and steady-state operation, the resistive wall mode limits the operating parameter space (the discharge time and the radio of the plasma pressure to the magnetic pressure) of the fusion devices so that it affects the economic benefits. Therefore, it is very important to study the stability of the resistive wall modes in tokamaks. In this work, the influences of the plasma rotations and the feedback controls on the resistive wall modes are studied numerically using MARS code for an ITER 9 MA equilibrium designed for the advanced steady-state scenario. In the equilibrium, the profile of the safety factor has a weak negative magnetic shear in the core region. The safety factor is q_0= 2.44 on the magnetic axis and q_a= 7.13 on the plasma boundary. And, the minimum safety factor q_\min is 1.60. The structure of this kind of weakly negative magnetic shear can generate higher radio of the plasma pressure to the magnetic pressure and it is the important feature of the advanced steady-state scenario. Using MARS code, for two cases: without wall and with ideal wall, the results of growth rates of the external kink modes for different values of \beta _\rm N are obtained. The limit value of \beta _\rm N^\textno-wall is 2.49 for the case without wall, and the limit value of \beta _\rm N^\textideal-wall is 3.48 for the case with ideal wall. Then, a parameter C_\beta = \left( \beta _\rmN - \beta _\rmN^\textno-wall \right)/\left( \beta _\rmN^\textideal-wall - \beta _\rmN^\textno-wall \right) is defined. The research results in this work show that with the plasma pressure scaling factor C_\beta = 0.7 and plasma rotation frequency \Omega _0 = 1.1\% \Omega _A, the resistive wall modes can be completely stabilized without feedback control. And, with the plasma pressure scaling factor C_\beta = 0.7 and the feedback gain \left| G \right| = 0.6, only plasma rotation with the frequency \Omega _0 = 0.2\% \Omega _A can stabilize the resistive wall modes. Therefore, a faster plasma rotation is required to stabilize the resistive wall modes by the plasma flow alone. The synergetic effects of the feedback and the toroidal plasma flow on the stability of the RWM can reduce plasma rotation threshold, which satisfies the requirements for the operation of the advanced tokamaks. The conclusion of this work has a certain reference for the engineering design and the operation of CFETR.

     

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