High power microwave generation at high repetition rates

Generation of microwaves at high power has progressed largely with single shot devices. Yet applications require repetitive operation at substantial repetition rates, implying high average power. This requires operation in a new domain for microwave devices. The technical challenge is to achieve very high electric fields in the source on a repetitive basis. We describe experiments on CLIA, a Compact Linear Induction Accelerator, generating 750 kV, 10 kA using magnetic switching to produce 60 ns pulses. We describe experiments with relativistic magnetrons and klystrons in the 1 GW, 100 Hz domain. As a first application we used CLIA to drive a water-cooled L-band magnetron at repetition rates as high as 250 Hz with no breakdown or pulse shortening. This gave 6.3 kW average power. A short burst at 1 kHz operated at ≈25 kW. In this regime operation is not limited by gas build-up, electrode erosion or microwhisker depletion. We are now operating on CLIA with relativistic klystrons of both the high current and low current varieties. Beams with modulated current powers of ≈ 1 GW have been generated at 200 Hz for bursts as long as 1000 pulses.