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arXiv · 1712.03751

Microwave beam broadening due to turbulent plasma density fluctuations within the limit of the Born approximation and beyond

Alf Köhn·Lorenzo Guidi·Eberhard Holzhauer·Omar Maj·Emanuele Poli·Antti Snicker·Hannes Weber
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Abstract

Plasma turbulence, and edge density fluctuations in particular, can under certain conditions broaden the cross-section of injected microwave beams significantly. This can be a severe problem for applications relying on well-localized deposition of the microwave power, like the control of MHD instabilities. Here we investigate this broadening mechanism as a function of fluctuation level, background density and propagation length in a fusion-relevant scenario using two numerical codes, the full-wave code IPF-FDMC and the novel wave kinetic equation solver WKBeam. The latter treats the effects of fluctuations using a statistical approach, based on an iterative solution of the scattering problem (Born approximation). The full-wave simulations are used to benchmark this approach. The Born approximation is shown to be valid over a large parameter range, including ITER-relevant scenarios.

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Alf Köhn, Lorenzo Guidi, Eberhard Holzhauer, Omar Maj, Emanuele Poli, Antti Snicker, Hannes Weber. 2017-12-11. Microwave beam broadening due to turbulent plasma density fluctuations within the limit of the Born approximation and beyond. https://doi.org/10.1088/1361-6587/aac000

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