Comparison of Conventional PIC and δf using GEM-X

GEM-X is a fast time to solution gyrokinetic particle-in-cell (PIC) simulation that models turbulent transport in the edge region, including the scrape-off layer (SOL) and X-point geometry. By using a very high-resolution structured grid in (R,Z), the PIC gather/scatter operations are extremely efficient. GEM-X uses the PETSc library to solve the gyrokinetic quasi-neutrality condition within a specified mask to account for the plasma boundary. GEM-X supports both δf and full-f PIC schemes. Benchmarking between GEM-X with GEM (which is thoroughly benchmarked with continuum codes) is presented along with comparisons between δf and conventional PIC. GEM-X is studying the wide-pedestal quiescent H-mode (WPQH), a reactor relevant scenario aimed at avoiding edge-localized mode (ELM) behavior.

Work funded by DOE Frontiers in Leadership Gyrokinetic Simulation SciDAC and Advanced Profile Prediction for Fusion Pilot Plant Design FIRE Collaborative.