Metaplectic geometrical optics for ray-based modeling of caustics: Theory and algorithms

The optimization of radio frequency-wave (RF) systems for fusion experiments is often performed using ray-tracing codes, which rely on the geometrical-optics (GO) approximation. However, GO fails at caustics such as cutoffs and focal points, erroneously predicting wave intensity to be infinite. This a critical shortcoming GO, since caustic quantity interest, e.g., RF heating. Full-wave modeling can used instead, but computational cost limits speed optimizations performed. We have developed less expensive alternative called metaplectic geometrical optics (MGO). Instead evolving waves in usual [Formula: see text] (coordinate) or (spectral) representation, MGO uses mixed representation. By continuously adjusting matrix coefficients along rays, one ensure that remains valid coordinates without singularities. caustic-free result then mapped back onto original space transforms. Here, we overview theory review algorithms will aid development an MGO-based code. show how orthosymplectic transformations leads considerable simplifications compared previously published formulas. also prove explicitly exactly reproduces standard when evaluated far from (an important property until now has only been inferred numerical simulations), relate other semiclassical caustic-removal schemes literature. discussion augmented by explicit comparison computed spectrum bounded between two cutoffs.