Analyzing Thomson-Scattered Spectra from non-Maxwellian Velocity Distribution Functions in Multi-Species Plasmas*

Electron and ion velocity distribution functions (VDFs) are important for understanding the dynamics occurring within nonlinear plasmas such as those of magnetized collisionless shocks. These VDFs can be measured with Thomson scattering diagnostics, but due to their non-Maxwellian nature, can be difficult to interpret with existing analysis tools. We present an open-source software that can be used to analyze the Thomson-scattered spectra of plasmas with non-Maxwellian VDFs. Using numerical methods, we forward-modeled arbitrary VDFs of multi-species plasmas to their corresponding Thomson-scattered spectra, using existing PlasmaPy code that handles strictly Maxwellian VDFs as a benchmark. This was then used as a foundation for studying an inversion algorithm to extract plasma parameters from spectra Thomson-scattered from arbitrary VDFs. The inversion algorithm was tested on PSC particle-in-cell (PIC) simulations of nonlinear multi-species plasmas with known VDFs and successfully reproduced the observed plasma parameters.