Metal-Dielectric-Washer cathode for long-pulse relativistic magnetron

The UM/L-3 relativistic magnetron operates at -300 kV, 2-5 kA, for durations of 500 ns and is capable of generating microwave pulses of 100´s MW output power at 1 GHz for 100´s ns. Previous research at UM utilized Metal-Oxide- Junction (MOJ) cathodes to exploit triple point field enhancement to stimulate electron emission. These MOJ cathodes generated fast current turn-on, however, the lifetime of the HfO₈ thin film islands were limited in the relativistic magnetron. In order to extend the lifetime, a new Metal- Dielectric-Washer (MDW) cathode has been developed that exhibits high current and expected long lifetime. The MDW cathode consists of alternating washers of OFHC-Cu and BN. Three primary configurations of the MDW cathode are under investigation: 1) Metal washer equal to dielectric washer, 2) Metal washer diameter larger than dielectric washers, 3) Metal washer diameter less than dielectric washers.