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

The authors describe measurements, modeling, and mitigation experiments on the effects of anode and cathode plasmas in applied-B ion diodes. They 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. The authors are developing sophisticated spectroscopic diagnostic techniques that allow them to measure the electric and magnetic fields in the A-K gap. They compare these measured fields with those predicted by their 3-D particle-in-cell (PIC) simulations of ion diodes, and measure anode and cathode plasma densities and expansion velocities. The authors 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. Their strategy for improving high power ion diode performance is to employ and expand their capabilities in measuring and modeling A-K gap plasmas and leverage their increased knowledge into an increase in total ion beam brightness to High Yield Facility (HYF) levels