Effect of Ion and Electron Impact Secondary Electron Emission on Sheath Formation in the Presence of Biased Potential Walls

As shear flow stabilized Z-pinch thermonuclear fusion reactor experiments scale to higher energies, the effects of ion impact electron emission on the sheath formation near the electrodes become more important. It is hypothesized that ion impact electron emission at the cathode can increase the saturation current in a plasma bounded by two walls with an electric potential difference between them. A semi-empirical ion impact electron emission boundary condition is implemented for the Vlasov equation that considers the energy spectra of the impacting ions and emitted electrons. A proton-electron plasma is simulated using the Vlasov-Poisson system in the code Gkeyll in pulsed-power fusion relevant regimes, such as FuZE (Fusion Z-pinch Experiment). The wall material choices are copper for the anode and graphite for the electrode. A parametric scan of bias electric potentials ranging from 0 to 10 kV is performed to understand how the inclusion of ion impact electron emission affects the particle and heat fluxes at the electrodes along with the general sheath structure. In addition, we examine how the saturation current is affected by the secondary electron emission.