外加扰动场对托卡马克等离子体撕裂模影响的实验研究

Externally applied resonant magnetic perturbations (RMPs) are usually used to correct intrinsic error field, control edge localized modes (ELMs) and suppress the tearing modes. However, the RMPs, when exceed a critical amplitude, can penetrate into plasma inducing locked mode and degrade plasma confinement. Up to now the experimental and theoretic researches on mode suppression and field penetration are under development. A set of SFX coils has been installed outside the vacuum vessel of J-TEXT tokamak and mode suppression and penetration have been observed. In order to generate more abundant perturbation field mode, another set of RMP coils are designed. In this proposal we plan to scan the amplitude and phase of RMPs under a certain discharge condition to estimate the intrinsic error field of J-TEXT and correct it. Then, the responses of tearing modes to RMPs are investigated by adjusting plasma parameters (such as electron density, plasma current and toroidal field, et al.). To compare with experimental results, nonlinear numerical modeling based on reduced MHD equations has been carried out. With experimental parameters as input, both the mode suppression and penetration by RMPs will be investigated from numerical modeling.Based on both experimental results and numerical calculations, an effective analytic model can be established to enhance comprehension of interaction between RMPs and tearing mode.

外加扰动场通常用来矫正误差场或控制边界局域模，也可以用来抑制撕裂模不稳定性，同时也可能导致扰动场在等离子体中穿透（penetration）产生非转动的撕裂模（locked mode）等不良的效果。目前外加扰动场对撕裂模抑制或穿透两种对立作用的实验研究和理论解析仍不完善，需要进一步研究。J-TEXT托卡马克真空室外部现已具备一套扰动场线圈，在实验中已经观察到扰动场抑制撕裂模和磁场穿透等现象，为了丰富外加扰动场的模式和波形，另外一套安装在真空室内部的扰动场线圈也将投入实验。本研究拟通过在固定等离子体参数下对扰动场幅值和空间相位进行调制，评估装置固有误差场并进行修正；通过调节等离子体参数（电子密度，等离子体电流，纵场等），在实验上探索在不同的等离子体参数下外加共振磁扰动对撕裂模产生和发展的影响；并结合磁流体数值模拟代码开展理论分析，加深对共振磁扰动与等离子体撕裂模作用机理的理解。

在托卡马克等离子体放电过程中，撕裂模会显著降低等离子体粒子和能量约束性能，甚至引发等离子体大破裂损害装置，是未来实现磁约束核聚变能商用化必须解决的问题之一。本课题对外加扰动场（RMP）作用在撕裂模上的影响进行了实验与理论研究。用锁模阈值、穿透阈值以及撕裂模转动的对称性三种方法对J-TEXT上误差场的强度以及相位进行了测量，成功利用J-TEXT上的静态扰动场系统（SRMP）实现了误差场补偿。利用RMP在实验上实现了撕裂模抑制，发现了扰动磁场对撕裂模的作用效果与撕裂模初始转动频率的相关性：撕裂模频率较高时，RMP会完全抑制撕裂模，反之会使得撕裂模锁模；并且就该方面内容进行了数值模拟，获得了RMP对撕裂模的作用区间。本课题还对扰动场在等离子体中的穿透现象从实验和数值模拟两方面进行了研究，实验上获得了RMP穿透阈值与电子密度的定标关系，模拟结果与实验结果符合度很高。这对将来利用外加扰动场控制撕裂模提供很好的参照依据与科研基础。