Influences of plasma on a relativistic backward wave oscillator with a resonant reflector and an extracting cavity

Using the particle-in-cell method, the influences of the plasma produced in the resonant reflector and extracting cavity of an X-band relativistic backward oscillator are investigated. For the reflector case, the dominant rule of the microwave emission termination of the TM01 mode is the disturbance of the initial phase relationship between the RF fields of the modulated electron and the synchronous harmonic, which increases the generation frequency, excites a high-order mode competition, and then leads to microwave pulse shortening. For the extracting cavity case, the influence of plasma on the beam–wave interaction process is relatively negligible. A notable reduction in the output power is principally caused by the absorption of plasma electrons, which has been preliminarily validated in experiments.