Parallel Ray Tracing Algorithm for Numerical Analysis of Laser Radiation Absorption in a Plasma

Abstract

An original algorithm was developed for ray tracing across unstructured 3D grid. It is aimed at calculation of a laser energy deposition in plasma. A laser beam is represented as a set of individual rays whose path depends on a plasma density ratio per plasma critical density. A ray may be refracted while going through high density gradient regions. In general case rays approximating a laser beam have to be recalculated at every time step. Therefore calculation of a laser energy absorption in related plasma dynamics simulations require significant computational resources. We present a new ray-tracing algorithm for laser radiation modeling which can be implemented effective via HPC. The set of rays built in a computational domain provides the base for the grid-characteristic computation of radiation transport in the plasma simulations using MPI parallel technique and grid decomposition. The algorithm is implemented as a C++ code and incorporated in 3D magnetohydrodynamic (MHD) Eulerian code [1]. Tracing of different rays within a single MPI-process is carried out in parallel with the use of OpenMP threads. The developed algorithm provides accounting for the anisotropy of the radiation field in complex multiscale 3D MHD simulations.