ThunderBoltz: An Open-Source DSMC-based Boltzmann Solver for Plasma Transport, Chemical Kinetics, and 0D Plasma Modeling

Plasma-neutral interactions, including reactive kinetics, are often either studied in 0D using ODE based descriptions, or in multi-dimensional fluid or particle based plasma codes. The latter case involves a complex assembly of procedures that are not always necessary to test effects of underlying physical models and mechanisms for particle-based descriptions. Here we present ThunderBoltz, a lightweight, publicly available 0D Direct Simulation Monte Carlo (DSMC) code designed to accommodate a generalized combination of species and arbitrary cross sections without the overhead of expensive field solves. It can efficiently produce high-quality electron, ion, and neutral velocity distributions in applied AC/DC $E$-field and static $B$-field scenarios. The code is built in the C++ standard library and includes a convenient Python interface that allows for input file generation (including compatibility with cross section data from the LXCat database), electron transport and reaction rate constant post-processing, input parameter constraint satisfaction, calculation scheduling, and diagnostic plotting. In this work we compare ThunderBoltz transport calculations against Bolsig+ calculations, benchmark test problems, and swarm experiment data, finding good agreement with all three in the appropriate field regimes. In addition to this, we present example use cases where the electron, ion, and background neutral particle species are self consistently evolved providing an ability to model the background kinetics, a feature that is absent in fixed background Monte Carlo and n-term Boltzmann solvers. The latter functionality allows for the possibility of particle-based chemical kinetics simulations of the plasma and neutral species and is a new alternative to ODE based approaches.