High-Power Amplification Experiments on a Recirculating Planar Crossed-Field Amplifier

The recirculating planar crossed-field amplifier (RPCFA) was designed, constructed, and tested at the University of Michigan. The RPCFA was driven by a number of RF sources ranging in frequency from 2.40 to 3.05 GHz and powers of 1 to 800 kW. Pulsed voltage was delivered to the cathode by the Michigan electron long beam accelerator with ceramic insulator (MELBA-C) which was configured to supply pulses of −300 kV, 1-10 kA, with 0.3-1.0- \mu \text{s} pulse lengths. The RPCFA demonstrated zero-drive stability and a bandwidth of 15%. Amplification of microwave signals, at the design frequency of 3 GHz, below 150 kW, was observed with a mean gain of 7.87 dB and high variability, \sigma = 2.74 dB. Filtering this data set to only include shots with identical voltage and current profiles yielded a gain of 6.6 ± 1.6 dB. The mean gain increased to 8.71 dB and the variability decreased to \sigma =0.63 dB when the injected microwave power increased beyond 150 kW. Peak output powers of nearly 6 MW were achieved with RF breakdown limiting the maximum output power of the device.