A 3D unstructured mesh based particle tracking code for impurity transport simulation in fusion tokamaks 

A fully 3D unstructured mesh based global impurity transport code, GITRm is presented in this paper. It is a high-performance Monte Carlo particle (neutral atom and ion) tracking code, based on the trace approximation, to simulate the erosion, ionization, migration, and redistribution of material from plasma -facing components in magnetically confined fusion devices. It is designed to target complex geometries including non-axisymmetric local features such as bumpers, probes, tile gaps etc., and uses strongly graded and anisotropic elements to accurately represent the plasma fields. GITRm is built on the PUMIPic infrastructure [1], executes using distributed meshes and is performant on GPU accelerated computer systems. Three example cases, including a weak scaling study with about 1.5 billion particles on up to 144 GPUs, are used to demonstrate the utility of GITRm.& COPY; 2023 Elsevier B.V. All rights reserved.