Liu Chang, Lvovskiy Andrey, Paz-Soldan Carlos, Jardin Stephen C, Bhattacharjee Amitava
Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA.
General Atomics, San Diego, California 92121, USA.
Phys Rev Lett. 2023 Aug 25;131(8):085102. doi: 10.1103/PhysRevLett.131.085102.
Alfvénic modes in the current quench (CQ) stage of the tokamak disruption have been observed in experiments. In DIII-D the excitation of these modes is associated with the presence of high-energy runaway electrons (REs), and a strong mode excitation is often associated with the failure of RE plateau formation. In this work we present results of self-consistent kinetic-MHD simulations of RE-driven compressional Alfvén eigenmodes (CAEs) in DIII-D disruption scenarios, providing an explanation of the CQ modes. Simulation results reveal that high energy trapped REs can have resonance with the Alfvén mode through their toroidal precession motion, and the resonance frequency is proportional to the energy of REs. The mode frequencies and their relationship with the RE energy are consistent with experimental observations. The perturbed magnetic fields from the modes can lead to spatial diffusion of REs including the nonresonant passing ones, thus providing the theoretical basis for a potential approach for RE mitigation.
在托卡马克破裂的电流猝灭（CQ）阶段，阿尔文波模已在实验中被观测到。在DIII-D装置中，这些波模的激发与高能逃逸电子（REs）的存在有关，并且强烈的波模激发通常与RE平台形成的失败有关。在这项工作中，我们展示了在DIII-D破裂场景下由RE驱动的压缩阿尔文本征模（CAEs）的自洽动力学磁流体动力学模拟结果，为CQ波模提供了解释。模拟结果表明，高能捕获REs可以通过其环向进动运动与阿尔文波模发生共振，并且共振频率与REs的能量成正比。波模频率及其与RE能量的关系与实验观测结果一致。来自这些波模的扰动磁场可导致REs的空间扩散，包括非共振通过的REs，从而为一种潜在的RE缓解方法提供了理论基础。
