Short High-Current Electron Beams and High-Powermicrowave Pulses in the Forevacuum Pressure Range

We study the formation of a high-current electron beam with a duration of 1 ns in a magnetically insulated coaxial diode with a cold cathode under varying residual gas pressure. It is demonstrated that before the transition from explosive electron emission in vacuum to the electron runaway regime in a gas, an increase in the beam current with increasing pressure in the diode is observed, and for this pressure range the transformation of accelerating pulse at the cathode is determined by dynamic reflectometry. The effect of the residual gas plasma on the formation of microwave superradiance pulses in the Ka-band relativistic backward-wave oscillator, where an increase and then a decrease in the generation power take place in a narrow pressure range, is analyzed. It is shown that ionization effects in the gas lead to a loss of microwave oscillation at a lower pressure compared to the condition of the oscillator electrodynamic structure breakdown by a test microwave pulse with a power of 300 MW.