The role of anode and cathode plasmas in high power ion diode performance

We describe measurements, modeling, and mitigation experiments on the effects of anode and cathode plasmas in applied-B ion diodes. We have performed experiments with electrode conditioning and cleaning techniques including RF discharges, anode heating, cryogenic cathode cooling and anode surface coatings that have been successful in mitigating some of the effects of electrode contamination on ion diode performance on both the SABRE and PBFA accelerators. We are developing sophisticated spectroscopic diagnostic techniques that allow us to measure the electric and magnetic fields in the A-K gap, we compare these measured fields with those predicted by our 3-D particle-in-cell (PIC) simulations of ion diodes, and we measure anode and cathode plasma densities and expansion velocities. We are continuing to develop E-M simulation codes with fluid-PIC hybrid models for dense plasmas, in order to understand the role of electrode plasmas in ion diode performance. Our strategy for improving high power ion diode performance is to employ and expand our capabilities in measuring and modeling A-K gap plasmas and leverage our increased knowledge into an increase in total ion beam brightness to High Yield Facility (HYF) levels.