Radiative damping of toroidal Alfvén eigenmode in low-shear plasmas

B.N. Breizman , S.E. Sharapov
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Abstract

Instabilities of Alfvén eigenmodes (AEs) are of significant concern because they can enhance the cross-field transport of fusion-born alpha particles beyond the neoclassical level in magnetic fusion plasmas. The threshold value of alpha-particle pressure for exciting AEs depends critically on the damping rate of AEs. The damping mechanisms include kinetic damping due to interactions with thermal particles, continuum damping due to AE frequency crossing Alfvén continuum, and radiative damping due to emitting kinetic Alfvén waves (KAWs). The radiative damping is substantial and can even prevail in high-temperature burning plasmas [1]. We revisit the radiative damping analytic theory for TAE in plasmas with low positive magnetic shear, considering TAE with an eigenfrequency near the bottom of TAE-gap and with poloidal harmonics of the same sign (even TAE). In contrast to earlier papers, we provide the damping calculations in real space rather than Fourier space. This approach is straightforward technically and more enlightening from a physics standpoint for benchmarking numerical calculations of radiative damping. The parametric dependence of the resulting damping rate agrees with that of Refs. [2-5], but it has a smaller numerical factor in front of it.
低剪切等离子体环面alfv本征模的辐射阻尼
在磁融合等离子体中,由于α - δ δ δ的不稳定性可以使聚变产生的α粒子的跨场输运提高到新经典水平,因此引起了人们的广泛关注。激发AEs的α粒子压力阈值主要取决于AEs的阻尼率。阻尼机制包括与热粒子相互作用产生的动能阻尼、声发射频率跨越alfv 连续体产生的连续阻尼和发射动能alfv 波(kaw)产生的辐射阻尼。辐射阻尼是巨大的,甚至可以在高温燃烧等离子体b[1]中普遍存在。我们重新研究了低正磁剪切等离子体中TAE的辐射阻尼分析理论,考虑TAE具有接近TAE间隙底部的特征频率和具有相同符号的极向谐波(甚至TAE)。与以前的论文相比,我们提供了在真实空间而不是傅里叶空间中的阻尼计算。这种方法在技术上是直接的,从物理的角度来看,对辐射阻尼的基准数值计算更具启发性。所得阻尼率的参数依赖性与Refs一致。[2-5],但它前面有一个较小的数值因子。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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