Simulation study of energetic-particle driven off-axis fishbone instabilities in tokamak plasmas
Simulation study of energetic-particle driven off-axis fishbone instabilities in tokamak plasmas
复制标题
托卡马克等离子体中高能粒子驱动离轴鱼骨不稳定性的模拟研究
DOI：
10.1088/1741-4326/ac3e85
复制
发表时间：
2021
期刊：
影响因子：
3.3
通讯作者：
Jialei Wang
中科院分区：
文献类型：
--
作者：
Hanzheng Li;Y. Todo;Hao Wang;M. Idouakass;Jialei Wang
采用动力学-磁流体动力学混合方法研究了托卡马克等离子体中被囚禁的高能离子扰动的离轴鱼骨模（OFM）的线性增长和非线性演化。在q = 2磁通面内，OFM的空间分布主要由m/n = 2/1模组成，而在q = 2磁通面外，OFM的空间分布主要由m/n = 3/1模组成，其中m和n分别为极向模和环向模数，q为安全系数。在极向平面上，OFM的空间分布是一个强烈的剪切形状，表明与高能离子相互作用的非微扰效应。在线性生长阶段，OFM的频率与囚禁高能离子的进动漂移频率一致，而在非线性生长阶段，频率啁啾下降。发现了囚禁离子与OFM之间的两种共振条件，第一种共振条件是进动漂移频率与OFM频率相匹配，第二种共振条件是进动漂移频率与反弹频率之和与OFM频率相匹配.第一类共振是OFM失稳的主要共振。分析了基于每个谐振粒子的非线性轨道的进动漂移频率和反弹频率定义的谐振频率，以理解频率啁啾。将能量传递到OFM的粒子的共振频率啁啾下降，这可能导致OFM频率的啁啾下降。对相空间中高能离子分布函数的详细分析表明，分布函数沿E′ =常数线的梯度沿着驱动或稳定不稳定性，其中E′是能量和环正则动量的组合，在波粒相互作用过程中是守恒的.在非线性阶段，分布函数沿E′ =常数线沿着变平，导致不稳定性饱和。
Kinetic-magnetohydrodynamic hybrid simulations were performed to investigate the linear growth and the nonlinear evolution of off-axis fishbone mode (OFM) destabilized by trapped energetic ions in tokamak plasmas. The spatial profile of OFM is mainly composed of m/n = 2/1 mode inside the q = 2 magnetic flux surface while the m/n = 3/1 mode is predominant outside the q = 2 surface, where m and n are the poloidal and toroidal mode numbers, respectively, and q is the safety factor. The spatial profile of the OFM is a strongly shearing shape on the poloidal plane, suggesting the nonperturbative effect of the interaction with energetic ions. The frequency of the OFM in the linear growth phase is in good agreement with the precession drift frequency of trapped energetic ions, and the frequency chirps down in the nonlinear phase. Two types of resonance conditions between trapped energetic ions and OFM are found. For the first type of resonance, the precession drift frequency matches the OFM frequency, while for the second type, the sum of the precession drift frequency and the bounce frequency matches the OFM frequency. The first type of resonance is the primary resonance for the destabilization of OFM. The resonance frequency which is defined based on precession drift frequency and bounce frequency of the nonlinear orbit for each resonant particle is analyzed to understand the frequency chirping. The resonance frequency of the particles that transfer energy to the OFM chirps down, which may result in the chirping down of the OFM frequency. A detailed analysis of the energetic ion distribution function in phase space shows that the gradient of the distribution function along the E′ = const. line drives or stabilizes the instability, where E′ is a combination of energy and toroidal canonical momentum and conserved during the wave–particle interaction. The distribution function is flattened along the E′ = const. line in the nonlinear phase leading to the saturation of the instability.