Oscillation Threshold in the Recirculating Planar Crossed-Field Amplifier

The transition from amplifier to oscillator of the Recirculating Planar Crossed-Field Amplifier (RPCFA) is examined in simulation and experiment. Initially, the RPCFA is zero-drive stable and operates as a high power amplifier with an input signal. By changing the anode-cathode gap, the RPCFA can exhibit oscillations. We explore the cold-tube and beam-loaded device characteristics that cause the transition to oscillation.