GITR: An accelerated global scale particle tracking code for wall material erosion and redistribution in fusion relevant plasma-material interactions

The global impurity transport code (GITR - pronounced “guitar”) has been developed as a high-performance Monte Carlo particle (neutral atom and ion) tracking code to simulate the erosion, ionization, migration, and redistribution of plasma-facing components in magnetically confined fusion devices. The trace impurity assumption allows for a highly parallel computational model that enables increased scaling in the number of particles simulated as well as the domain size and geometric fidelity. Novel custom algorithms that query the 3D surface geometry has alleviated the need for traditional meshing needs. Presented here is the physics model, numerical schemes, algorithmic implementation, and example simulations.