Enabling Multiscale Particle-in-Cell simulations using PUMI Multi-Block Boundary Layer Meshes in hPIC2

In order to simulate large plasma domains including boundary regions of high-field-gradient, such as plasma sheaths formed in front of material surfaces, we have incorporated a Multi-Block Boundary Layer (MBBL) mesh in the hPIC2 Particle-in-Cell code. MBBL mesh is part of the PUMI mesh infrastructure developed at RPI. MBBL mesh allows to merge together multiple blocks with either uniform cell spacing, or geometrically graded boundary layer type spacing, thus enabling large freedom of sampling. We tested the MBBL mesh capability on a rectified Scrape-Off Layer (SOL) problem, and performed a number of semi-analytical verification of the PIC results against a fluid solution. Simulations were performed for a range of domain sizes ranging from 100 Debye lengths to 1 million Debye lengths (~33 m) with both uniform and block-structured MBBL meshes. We show that for MBBL meshes, the code allows the solution of even larger plasma domains, spanning over a full connection length (~100 m). When hPIC2 is run with dynamic coupling to the RustBCA sputtering code, it facilitates the investigation of impurity production at the divertor plates under simplified (rectified) SOL conditions.