Effects of energetic particle phase space modifications by instabilities on integrated modeling
Effects of energetic particle phase space modifications by instabilities on integrated modeling
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DOI：
10.1088/0029-5515/56/11/112005
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发表时间：
2016-11-01
期刊：
影响因子：
3.3
通讯作者：
White, R. B.
中科院分区：
文献类型：
--
作者：
Podesta, M.;Gorelenkova, M.;White, R. B.
托卡马克等离子体可以通过中性束注入或聚变反应产生大量高能粒子（EP）。反过来，高能粒子可以驱动不稳定性，从而影响驱动 EP 群体，导致原始 EP 分布函数和依赖于它的数量的扭曲。后者包括例如中性束 (NB) 电流驱动和通过 EP 热化的等离子体加热。必须考虑到这些影响，才能对现有设备的放电进行可靠且定量的模拟，并预测未来燃烧的等离子体。 EP 输运简化模型正在成为托卡马克等离子体长时间尺度集成模拟的有效工具，可能包括不稳定性对 EP 动力学的影响。可用模型的不同之处在于不稳定性如何修改 EP 分布属性，例如就实数空间或相空间中的梯度而言。因此，评估输运模型中的不同假设在多大程度上影响预测量（例如 EP 分布、能量分布、NB 驱动电流以及向热群体的能量/动量转移）至关重要。这项工作使用了新开发的冲击模型来研究这些问题，其中包括通过真实空间和速度空间中的不稳定性对 EP 分布进行修改。与 TRANSP 仿真相结合，冲击模型用于分析具有不稳定阿尔芬本征模 (AE) 的 NB 加热 NSTX 和 DIII-D 放电。结果表明，不稳定性会强烈影响 EP 分布函数，并且修改会传播到宏观量，例如 NB 驱动的电流分布和转移到热等离子体物质的 NB 功率。这些重要方面只能通过仅基于高能离子径向扩散的更简单的快速离子传输模型来定性捕获。
Tokamak plasmas can feature a large population of energetic particles (EP) from neutral beam injection or fusion reactions. In turn, energetic particles can drive instabilities, which affect the driving EP population leading to a distortion of the original EP distribution function and of quantities that depend on it. The latter include, for example, neutral beam (NB) current drive and plasma heating through EP thermalization. Those effects must be taken into account to enable reliable and quantitative simulations of discharges for present devices as well as predictions for future burning plasmas. Reduced models for EP transport are emerging as an effective tool for long time-scale integrated simulations of tokamak plasmas, possibly including the effects of instabilities on EP dynamics. Available models differ in how EP distribution properties are modified by instabilities, e.g. in terms of gradients in real or phase space. It is therefore crucial to assess to what extent different assumptions in the transport models affect predicted quantities such as EP profile, energy distribution, NB driven current and energy/momentum transfer to the thermal populations. A newly developed kick model, which includes modifications of the EP distribution by instabilities in both real and velocity space, is used in this work to investigate these issues. Coupled to TRANSP simulations, the kick model is used to analyze NB-heated NSTX and DIII-D discharges featuring unstable Alfven eigenmodes (AEs). Results show that instabilities can strongly affect the EP distribution function, and modifications propagate to macroscopic quantities such as NB-driven current profile and NB power transferred to the thermal plasma species. Those important aspects are only qualitatively captured by simpler fast ion transport models that are based on radial diffusion of energetic ions only.