Developing chemistry, visualization, and RF sheath modeling tools for fusion and low-temperature plasma simulations

Summary form only given. We present an overview of ongoing enhancements to VSim, a plasma modeling code capable of both PIC/MCC and fluid FDTD representations. A new sub-grid kinetic sheath boundary condition¹ enables the physical effects of DC and RF sheath physics to be included in macroscopic-scale plasma simulations that need not explicitly resolve sheath scale lengths. We demonstrate that evolution of sheath potentials, together with the ensuing particle fluxes and sputtering effects, can thus be simulated on complex plasma-facing components such as the ICRF antenna in the Alcator C-Mod fusion device. Generalizations of the sheath boundary condition to include multiple ion species and other relevant physical effects (e.g. secondary electron emission) will also be presented.Complex chemistry scenarios arising in low-temperature plasmas can be modeled in VSim via an interface with MUNCHKIN, a standalone python/C++/SQL code that identifies reaction paths for a given set of input species, solves 1D rate equations to analyze the time-dependent chemical evolution of the system, and generates corresponding VSim input blocks with appropriate cross-sections or reaction rates. These features, together with others such as calculation of reaction rates from user-specified distribution functions, principal path analysis (for reducing the number of simulated chemical reactions while retaining accuracy), and parallelization for high-performance analysis, will also be discussed. In addition, we will demonstrate the reconstruction of time-varying species energy and angular distribution functions from PIC data, enabling key physics processes in existing experimental and industrially relevant plasmas to be explored. A variety of techniques, including singular-value decomposition and binning, can be used for this reconstruction, and a comparison of techniques will be shown. We will also discuss how the VisIt² visualization software can be used to generate co- plex physics animations from VSim data.