Pulse shortening phenomena in relativistic backward wave oscillator

In this paper, the pulse shortening phenomena in relativistic backward wave oscillator(RBWO) are studied by means of the particle-in-cell method under two conditions of filling He gas or remaining background gas in the tube. The calculation results predict that the background gas in the tube is one but not the most important factor resulting in pulse shortening, and in order to broaden the pulse width of the gas-filled RBWO, the pressure of the filled gas must be controlled in a proper value. The intense electric field RF breakdown inside the tube and gas molecule explosive emission on inner surface of the slow wave system may be more important factors resulting in the pulse shortening phenomena in the high power microwave tube．