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arXiv 2108.07077physics.plasm-ph
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混合全波马尔可夫链方法计算刮除层灯丝的射频波散射

A hybrid full-wave Markov chain approach to calculating radio-frequency wave scattering from Scrape-off Layer filaments

Bodhi Biswas, Syunichi Shiraiwa, Seung-Gyou Baek, Paul Bonoli, Abhay Ram, Anne White

摘要:

射频(RF)波与边缘湍流的相互作用改变了入射波谱,对托卡马克中的RF加热和电流驱动产生重要影响。以前的LH散射模型要么使用弱湍流近似,或处理更现实的,在光线跟踪限制的附加湍流。在这项工作中,引入了一个新的模型,保留了全波效应的射频散射在湍流。首先,米氏散射技术模拟入射波与单个高斯灯丝的相互作用。接下来,一个有效的微分散射宽度推导出的统计合奏的细丝。最后,马尔可夫链求解板几何中的透射波谱。该模型适用于电流驱动的左发动。由此产生的波谱在波数角空间中不对称加宽。在以前的LH散射模型中没有考虑这种不对称性。修改后的波谱耦合到射线追踪/福克-普朗克求解器(GENRAY/CQL 3D),以研究其对电流驱动的影响。所得的电流分布被极大地改变,并且轴上电流显著增加,离轴峰值减小。这归因于修改后的波谱的一部分,其在第一次通过期间强烈地在轴上阻尼。

英文摘要:

The interaction of radio-frequency (RF) waves with edge turbulence modifies the incident wave-spectrum, and can significantly affect RF heating and current drive in tokamaks. Previous LH scattering models have either used the weak-turbulence approximation, or treated more realistic, filamentary turbulence in the ray-tracing limit. In this work, a new model is introduced which retains full-wave effects of RF scattering in filamentary turbulence. First, a Mie-scattering technique models the interaction of an incident wave with a single Gaussian filament. Next, an effective differential scattering-width is derived for a statistical ensemble of filaments. Lastly, a Markov chain solves for the transmitted wave-spectrum in slab geometry. This model is applied to LH launch for current drive. The resulting wave-spectrum is asymmetrically broadened in wave-number angle-space. This asymmetry is not accounted for in previous LH scattering models. The modified wave-spectrum is coupled to a ray-tracing/Fokker-Planck solver (GENRAY/CQL3D) to study its impact on current drive. The resulting current profile is greatly altered, and there is significant increase in on-axis current and decrease in off-axis peaks. This is attributed to a portion of the modified wave-spectrum that strongly damps on-axis during first-pass.

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