Cathode development for the hard-tube MILO

Summary form only given, as follows. The hard-tube MILO (magnetically insulated transmission line oscillator) is a multigigawatt cross-field microwave tube powered by a 500-kV, 60-kA electron beam. During the initial experiments with a 300-ns beam pulse, a simple velvet cathode configuration was used. However, after extending the beam pulse to 600 ns, problems mainly involving cathode flares compelled cathode design changes to be made. We report on modifications made to the velvet cathode as well as on recent results using a CsI-coated, graphite-fiber cathode. The performance characteristics and relative merits of each cathode are presented.