托卡马克理想导体壁与磁流体不稳定性  

Ideal conductive wall and magnetohydrodynamic instability in Tokamak

作　　者：沈勇[1] 董家齐[1,2] 何宏达[1] 潘卫[1] 郝广周 Shen Yong;Dong Jia-Qi;He Hong-Da;Pan Wei;Hao Guang-Zhou(Southwestern Institute of Physics,Chengdu 610041,China;Institute for Fusion Theory and Simulation,Zhejiang University,Hangzhou 310027,China)

机构地区：[1]核工业西南物理研究院,成都610041 [2]浙江大学聚变理论与模拟中心,杭州310027

出　　处：《物理学报》2023年第3期175-185,共11页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:12075077);国家重点研发计划(批准号:2017YFE0301200,2019YFE03050003)资助的课题。

摘　　要：为了探索等离子体磁流体力学(MHD)不稳定性的导体壁效应以及壁设计思想,研究了基于HL-2A托卡马克偏滤器位形的、自由边界和多种形式的理想导体壁条件下的等离子体MHD不稳定性与装置MHD运行β极限.在稳定性计算中,考虑的是n=1扭曲模,该模对托卡马克等离子体MHD不稳定性有决定性的影响.研究着眼于验证多种形状导体壁抑制内、外扭曲模的有效性,观察运行β极限的变化,并讨论分析相关物理.研究发现在离等离子体适当距离处放置一个理想导体壁,可有效抑制外扭曲模.在壁与等离子体表面的平均距离相同、且足够小的条件下,圆截面壁并不一定是最佳选择,设置一个经过优化的多边形导体壁能更有效地抑制MHD不稳定性,它使本装置的理想MHD运行β极限β_(N)提高到2.73,比自由边界条件下(即假设壁设置在无穷远处的)装置的运行β极限值(~2.56)提高了约6.5%.这暗示需要根据有拉长、有变形的等离子体的极向截面形状,优化制作一个离等离子体表面平均距离尽可能近的多边形导体壁,才能取得抑制外扭曲模、提高β极限的最佳效果.In order to explore the conductive wall effect of plasma magnetohydrodynamic(MHD)instability and the wall designing idea,the various forms of ideal conductive walls based on divertor equilibrium configurations in the HL-2A Tokamak and their role in suppressing kink modes are studied.The MHD instabilities and the ideal MHD operationalβlimits under free boundary or ideal wall conditions are compared.In the stability calculation,n=1 kink mode is considered,which has a decisive influence on the MHD instability of Tokamak plasma.The research focuses on verifying the effectiveness of various shapes of conductive walls in suppressing internal and external kink modes,and observing the operationalβlimit changes,and discussing and analyzing related physics.It is found that an ideal conducting wall placed at a suitable distance from the plasma can effectively suppress the external kink modes.Under the condition that the average distance between the wall and the plasma surface is the same and small enough,the circular cross-section wall is not necessarily the best option.Setting an optimized polygonal conductive wall can more effectively suppress the MHD instability.It makes the ideal MHD operationalβlimit of the device,β_(N),increase to 2.73,which is about 6.5%higher than that for the device with a wall assumed to be set at infinity(~2.56).This implies that it is necessary to optimize and make a polygonal conductive wall as close as possible to the average distance from the plasma surface according to the poloidal-section shape of the elongated and shaped plasma,so as to achieve the suppression of external kink mode and increase the operationalβlimits.The physical mechanism of the stabilizing effect of the ideal wall on external kink modes is analyzed.With the development of the kink mode,when the plasma column is twisted closely to the wall,the plasma column will squeeze the magnetic field in the vacuum area,making the magnetic field line compressed and bent.At this time,the magnetic pressure and the component force o

关 键 词：托卡马克 理想导体壁 磁流体不稳定性 扭曲模 运行β极限 

分 类 号：TL631.24[核科学技术—核技术及应用]