First ray-tracing simulations of mode conversion using metaplectic geometrical optics
Abstract
Advanced scenarios of radiofrequency power deposition into magnetically confined fusion plasmas, particularly those using electron Bernstein waves, involve linear mode conversion (energy transfer between separate dispersion branches) in regions where the waves experience reflection. Full-wave simulations of this conversion are time-consuming, and geometrical-optics (GO) modeling is problematic because it is typically restricted to single waves and leads to spurious singularities at cutoffs. Here, we report the first reduced simulations that overcome these limitations without resorting to approximate analytical formulas for the conversion efficiency. The algorithm is based on the recently developed metaplectic geometrical optics (MGO), which eliminates GO's spurious singularities by metaplectic transformations, provided that the symplectic curvature of the rays R−1 is small. To prove the concept, we simulate one-dimensional O--X mode conversion caused by the plasma-density gradient near the critical density, a problem for which an approximate analytical solution is available and can be compared with. Numerical MGO demonstrates good agreement with said theory. This opens a way for fast and accurate ray-tracing modeling of any linear mode conversion at R−1 ≪ 1.
Related
- DeboRheo v2.0: Improved Robustness for Geometrical VOF Simulations of Viscoelastic Two-Phase Flows
- Integrated robust universal linear optics based on white-boxed multi-plane light conversion
- The Free Particle--Oscillator--Inverted Oscillator Triangle: Conformal Bridges, Metaplectic Rotations and osp(1|2) Structure
- A Cartan-geometrical perspective on torsion and non-metricity
- Boundary-induced geometrical frustration in a square Rydberg-atom lattice
BibTeX
@misc{lee2026first,
title = {{First ray-tracing simulations of mode conversion using metaplectic geometrical optics}},
author = {Rui Kai Lee and Valerian H. Hall-Chen and I. Y. Dodin},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.06114},
eprint = {2611.06114},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.06114},
}
RIS
TY - UNPB
TI - First ray-tracing simulations of mode conversion using metaplectic geometrical optics
AU - Rui Kai Lee
AU - Valerian H. Hall-Chen
AU - I. Y. Dodin
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2611.06114
UR - https://arxiv.org/abs/2611.06114
AB - Advanced scenarios of radiofrequency power deposition into magnetically confined fusion plasmas, particularly those using electron Bernstein waves, involve linear mode conversion (energy transfer between separate dispersion branches) in regions where the waves experience reflection. Full-wave simulations of this conversion are time-consuming, and geometrical-optics (GO) modeling is problematic because it is typically restricted to single waves and leads to spurious singularities at cutoffs. Here, we report the first reduced simulations that overcome these limitations without resorting to approximate analytical formulas for the conversion efficiency. The algorithm is based on the recently developed metaplectic geometrical optics (MGO), which eliminates GO's spurious singularities by metaplectic transformations, provided that the symplectic curvature of the rays R^−1 is small. To prove the concept, we simulate one-dimensional O--X mode conversion caused by the plasma-density gradient near the critical density, a problem for which an approximate analytical solution is available and can be compared with. Numerical MGO demonstrates good agreement with said theory. This opens a way for fast and accurate ray-tracing modeling of any linear mode conversion at R^−1 ≪ 1.
ER -