Abstract
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.
Highlights
As one of the most promising sources of power,1–6 the outputs of relativistic backward oscillators (RBWOs) at GW power levels are severely limited by pulse shortening due to unexpected plasma, especially for operations with a long period of life and a high repetitive rate
The simulation model of the RBWO working in the TM01 mode is shown in Fig. 1(a), which principally includes the annular cathode, the resonant reflector, the corrugated SWS, and the extracting cavity
The effects of plasma emitted from the surfaces of a resonant reflector and an extracting cavity of an X-band RBWO were investigated
Summary
As one of the most promising sources of power, the outputs of relativistic backward oscillators (RBWOs) at GW power levels are severely limited by pulse shortening due to unexpected plasma, especially for operations with a long period of life and a high repetitive rate. The effects of plasma emitted from the surfaces of the resonant reflector and the extracting cavity of an X-band RBWO are investigated using the particle-in-cell (PIC) method. The dominant rule of the microwave emission termination or RF pulse shortening of the RBWO for the reflector case is the disturbance of the phase relationship between the modulating field and the synchronous harmonic field. This increases the device output frequency, decreases the modulation depth of the beam current, excites the mode competition, and leads to the termination of the fundamental microwave radiation.
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