Cathode improvements for a magnetically insulated transmission line oscillator (MILO)

Summary form only given. Recent experimental and computer simulation results on MILO have indicated that the large beam current density emitted from each end of the cathode leads to anode plasma formation via stimulated desorption. The presence of bipolar space-charge flow in the anode-cathode (A-K) gap causes significant microwave power reduction and RF pulse-shortening on a 600-ns time scale. We report on implementation of the miniature Pierce focusing electrode concept of Umstattd et al. (2000) on MILO as a way to minimize the beam current density at both ends of the cathode. MAGIC2D simulations for two focusing electrode configurations are presented. Also, preliminary experimental results using the same focusing electrodes in a smooth-bore anode configuration (no RF) are shown.