Voltage-Bias Effects in 3D Kinetic-Ion Simulations of Simple Magnetic Mirrors

We present 3D kinetic-ion simulations of sheared azimuthal flow induced by voltage bias in simple magnetic mirrors, targeting the Wisconsin High-temperature superconductor Axisymmetric Mirror (WHAM). Laboratory end-wall voltage bias is mimicked in the code Hybrid-VPIC by forcing the azimuthal magnetic field at the mirror's axial ends to drive wall currents and a radial electric potential. In hot (>keV) idealized WHAM-like plasma, a potential well ~1–2x the ion temperature helps stabilize low azimuthal mode number (m ~ 2–4) interchange fluctuations; higher-m drift-cyclotron loss-cone (DCLC) modes are less affected. The same potential well (i) steepens the plasma's radial density profile such that ion ExB and ∇⋅P drifts partly cancel, (ii) induces gyroviscous shear-flow stress that qualitatively agrees with Braginskii. We also discuss varying bias radial profile, bias amplitude, plasma composition, and limitations and next steps towards more faithful numerical schemes.