Using PCMS to Accelerate Coupling of Gyrokinetic Microturbulence with Neutral Particle Transport

Atomic and molecular (neutral) reactions represent key sources and sinks in the in the gyrokinetic Boltzmann equation that need to be carefully characterized to understand radiation diagnostics, divertor detachment, and refueling. The most prominent neutral transport codes, DEGAS2 and EIRENE, use a Monte Carlo method to evolve the neutral distribution functions. The evaluation of the neutral sources and sinks during the plasma solution requires tight coupling. One challenge with this coupling is that there is a mismatch in the needs for discretization for the plasma and neutral solvers. In this talk, we describe a new scheme to tightly couple DEGAS2 with the XGC gyrokinetic PIC code through the Parallel Coupler for Multimodel Simulation (PCMS). In this new scheme, the discretization for DEGAS2 is decoupled from that of XGC. This new coupling scheme will be demonstrated and evaluated on the LTX reactor geometry.