Effect of dynamic particle reweighting on plasma swarm parameters in the particle-in-cell code Aleph*

Aleph is a particle-in-cell (PIC) code developed at Sandia National Laboratories for the simulation of a large range of plasma systems. Aleph uses unstructured mesh geometries and contains a rich collection of capabilities for performing electric field solves, plasma chemistry using direct-simulation Monte Carlo (DSMC), plasma-surface interactions, and plasma-photon processes. This large suite of capabilities makes Aleph a robust tool for studying a variety of non-equilibrium plasmas, such as corona discharges, DC glow discharges, vacuum arc breakdown, and dielectric barrier discharges. Beyond these functionalities, Aleph also incorporates a novel dynamic reweighting algorithm capable of modifying computational particle weights on a per-element basis with options that enable the user to optimize performance and accuracy. To ensure that reweighting preserves accurate collisional properties, a set of zero-dimensional simulations were performed to examine a range of swarm parameters for a hydrogen plasma. Aleph simulation results, both with and without electron impact ionization, compare favorably with the two-term Boltzmann solver Bolsig+. Finally, Aleph’s reweighting algorithm is shown to maintain a high degree of accuracy over a large range of particle reweighting strategies.