Spectral analysis of current-driven instabilities relevant to anomalous transport in hollow cathode plumes

Large-scale current-driven instabilities in plasma plumes can generate energetic ions responsible for sputtering and subsequent degradation of hollow cathodes. While fluid and hybrid plasma simulations have been used to model these plasmas with the aid of model coefficients for anomalous transport, thorough investigation of high-energy ion formation requires a fully kinetic solver. A 2D2V grid-based Vlasov-Poisson (direct kinetic) solver is used to study the transient characteristics and nonlinear saturation of these instabilities over a range of initial electron Mach numbers. The degree to which recently developed nonuniform grid capabilities can reduce computational cost while preserving accuracy in quantities of interest is explored. Physical aspects and spectral characteristics of the growth process are analyzed for a variety of initial perturbations to determine the sensitivity of turbulence generation and energetic ion formation to initial conditions. This multidimensional study sheds light on the effects of a transverse density gradient on longitudinal plasma instabilities.