共振磁扰动控制托卡马克等离子体芯部杂质浓度的研究

Impurity transport is very important for improving the confinement of fusion plasma and reducing radiation loss. Impurity ions accumulate in the plasma core will dilute the concentration of main plasma ions, resulting in plasma radiation loss and even plasma disruption, especially for medium and high Z impurity ions. Therefore, it is urgent to develop effective impurity control methods to reduce the impurity concentration in the core and improve the confinement performance of the plasma. At present, significant progress has been made in the research on the impurity transport in the core, but the existing theories cannot well explain the experimental results, and the transport of light impurities and heavy impurities in the core is quite different, so it is necessary to explore the transport mechanism of heavy impurities in the core. As a method to control the edge localized modes on ITER, resonant magnetic perturbations (RMP) can also be applied to the study of impurity transport. By changing the magnetic topological structure of the plasma, RMP can control the edge impurities entering the core of the plasma and change the confinement time between the impurity ions and the main ions, so as to effectively control the concentration of impurities in the core. This project intends to carry out experimental study on the influence mechanism of RMP on the impurity transport in the core of plasma on J-TEXT, and study the process and mechanism of RMP affecting the impurity transport in the core by combining experimental and numerical simulation methods, so as to provide necessary reference for the high confinement and steady operation of ITER.

杂质输运研究对于提高聚变等离子体约束，降低辐射损失极其重要。杂质离子，尤其是中高Z杂质离子在等离子体芯部聚集会稀释等离子体主离子浓度，造成等离子体辐射损失，甚至引发等离子体破裂。因此急需发展有效的杂质控制手段来降低芯部杂质含量并提高等离子体约束。目前芯部杂质输运研究已经取得了很大的进展，但是现有理论还无法很好地解释实验现象，且轻杂质与重杂质在芯部的输运相差较大，需要探索芯部重杂质的输运机制。共振磁扰动（RMP）作为ITER上控制边界局域模的方法，同样可以应用到杂质输运的研究中。RMP通过改变等离子体磁拓扑结构来控制边界杂质进入等离子体芯部，并可以改变杂质离子与主离子的约束时间，从而实现芯部杂质含量的有效控制。本项目拟在J-TEXT上开展RMP对等离子体芯部杂质输运影响机制的实验研究，并结合实验和数值模拟两种方法研究RMP影响芯部杂质输运的过程与机理，为ITER的高约束稳定运行提供必要参考。

杂质输运及其约束是聚变等离子体研究中的重要问题。磁约束聚变等离子体中杂质的含量过高会对等离子体的约束造成不好的影响，其中高电离态的杂质聚芯更是会造成芯部冷却和稀释主等离子体浓度，因此芯部杂质研究对于磁约束聚变等离子体是不可忽视的。我们的研究内容围绕托卡马克等离子体芯部杂质控制展开，取得的主要进展有：（1）在J-TEXT上首次验证了弯晶谱仪用于研究芯部杂质输运的可行性，并获得了不同等离子体电流和电子密度下的氩杂质输运行为；（2）外加共振磁扰动会加强等离子体芯部的类氦氩离子朝着等离子体中心输运，同时促进类氦氩离子朝着等离子体的边界区域扩散；（3）开展了电子回旋共振加热对芯部杂质输运的研究，证实了电子回旋共振加热可以通过调制锯齿上的前兆振荡来影响芯部氩离子朝着边界输运，当电子回旋共振加热功率沉积在锯齿反转面以内时的杂质输运更为明显；（4）通过一维杂质输运代码STRAHL获得了J-TEXT上芯部氩杂质的输运系数演化，为上述实验结果提供了解释。这些工作为托卡马克等离子体芯部杂质控制提供了有效的解释，为将来例如ITER装置高参数、高约束运行提供了参考依据。