Shortening of the radiation pulse from a plasma relativistic microwave generator in numerical calculations with plasma simulation by the particle-in-cell method

Spontaneous shortening of radiation pulses of Cherenkov microwave generators based on the interaction of a high-current relativistic electron beam with preliminarily generated plasma was studied in a numerical model. Microwave pulse shortening is caused by the appearance of a gradually expanding region near the collector, from which plasma is expelled by an electrostatic field of relativistic electrons. The absence of plasma results in a severalfold decrease in the plasma wave reflectance from the collector and violation of generator self-excitation conditions. The microwave emission duration increases with the plasma ion mass.