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arXiv 2104.07987physics.plasm-ph
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用Landau闭合模型研究CFQS等离子体中Alfven本征模的稳定性

Study of the Alfven Eigenmodes stability in CFQS plasma using a Landau closure model

J. Varela, A. Shimizu, D. A. Spong, L. Garcia, Y. Ghai

摘要:

分析了我国第一个准轴对称仿星器(CFQS)中Alfven本征模(AE)的稳定性。AE稳定性的计算使用代码FAR 3d,解决了减少MHD方程描述的线性演化的极向通量和涡度的环向分量在一个完整的3D系统,再加上方程的密度和平行速度矩的高能粒子(EP)物种,包括螺旋耦合和声学模式的影响。通过给定的封闭关系,在模型中加入朗道阻尼和共振失稳效应。模拟结果表明,在慢化过程中,EP对n = 1 ~ 4个AE,特别是n = 1和n = 2个环形AE(TAE),n = 3个椭圆AE(EAE)和n = 4个非圆形AE(NAE)的不稳定性有明显的影响。如果共振是由能量高于17 keV的EP(弱热化EP)引起的,则n = 2个EAE和n = 3个NAE是不稳定的。另一方面,具有低于17 keV的能量的EP(后期热化阶段)导致n = 3和n = 4的TAE的不稳定。离轴NBI注入的模拟表明n = 2至4个AE的进一步不稳定,尽管n = 1个AE的增长率略微降低,因此没有识别出关于NBI沉积区域的明确优化趋势。此外,n = 2,4螺旋AE(HAE)在EP \b{eta}阈值以上不稳定。此外,如果模拟的热\b{eta}增加(更高的热等离子体密度),则等离子体的AE稳定性会提高。包括有限Larmor半径和电子-离子Landau阻尼的影响的模拟表明,稳定的n = 1至4的EAE/NAE以及增长率和频率的n = 1至4的BAE/TAE的下降。

英文摘要:

The aim of this study is to analyze the stability of the Alfven eigenmodes (AE) in the Chinese First Quasi-axisymmetric Stellarator (CFQS). The AE stability is calculated using the code FAR3d that solves the reduced MHD equations to describe the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D system, coupled with equations of density and parallel velocity moment for the energetic particles (EP) species including the effect of the helical couplings and acoustic modes. The Landau damping and resonant destabilization effects are added in the model by a given closure relation. The simulation results indicate the destabilization of n = 1 to 4 AEs by EP during the slowing down process, particularly n = 1 and n = 2 toroidal AEs (TAE), n = 3 elliptical AE (EAE) and n = 4 non circular AE (NAE). If the resonance is caused by EPs with an energy above 17 keV (weakly thermalized EP), n = 2 EAEs and n = 3 NAEs are unstable. On the other hand, EPs with an energy below 17 keV (late thermalization stage) lead to the destabilization of n = 3 and n = 4 TAEs. The simulations for an off-axis NBI injection indicate the further destabilization of n = 2 to 4 AEs although the growth rate of the n = 1 AEs slightly decreases, so no clear optimization trend with respect to the NBI deposition region is identified. In addition, n = 2, 4 helical AE (HAE) are unstable above an EP \b{eta} threshold. Also, if the thermal \b{eta} of the simulation increases (higher thermal plasma density) the AE stability of the plasma improves. The simulations including the effect of the finite Larmor radius and electron-ion Landau damping show the stabilization of the n = 1 to 4 EAE/NAEs as well as a decrease of the growth rate and frequency of the n = 1 to 4 BAE/TAEs.

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