Steepest-descent algorithm for simulating plasma-wave caustics via metaplectic geometrical optics

Donnelly, Sean M.; Lopez, Nicolas A.; Dodin, I. Y.

doi:10.1103/physreve.104.025304

Title: Steepest-descent algorithm for simulating plasma-wave caustics via metaplectic geometrical optics

Journal Article · 12 August 2021 · Physical Review. E

DOI: https://doi.org/10.1103/physreve.104.025304 · OSTI ID:1818945

^[1];

^[2]; Dodin, I. Y. ^[3]

Iowa State Univ., Ames, IA (United States)
Princeton Univ., NJ (United States)
Princeton Univ., NJ (United States); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

The design and optimization of radiofrequency-wave systems for fusion applications is often performed using ray-tracing codes, which rely on the geometrical-optics (GO) approximation. However, GO fails at wave cutoffs and caustics. To accurately model the wave behavior in these regions, more advanced and computationally expensive “full-wave” simulations are typically used, but this is not strictly necessary. A new generalized formulation called metaplectic geometrical optics (MGO) has been proposed that reinstates GO near caustics. The MGO framework yields an integral representation of the wavefield that must be evaluated numerically in general. We present an algorithm for computing these integrals using Gauss-Freud quadrature along the steepest-descent contours. Benchmarking is performed on the standard Airy problem, for which the exact solution is known analytically. Furthermore, the numerical MGO solution provided by the new algorithm agrees remarkably well with the exact solution and significantly improves on previously derived analytical approximations of the MGO integral.

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Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: AC02-09CH11466

OSTI ID:: 1818945

Journal Information:: Physical Review. E, Journal Name: Physical Review. E Journal Issue: 2 Vol. 104; ISSN 2470-0045

Publisher:: American Physical Society (APS)Copyright Statement

Country of Publication:: United States

Language:: English

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70 PLASMA PHYSICS AND FUSION TECHNOLOGY
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