Experimental investigation of plasma-neutralized operation of a gyrotron

Summary Form only given, as follows. An experiment to investigate the effects of a neutralizing background plasma on the operation of a gyrotron oscillator is underway. Previous experiments operating without a neutralizing background plasma achieved output powers P=100-250 MW at a frequency f=35 GHz, with beam voltages in the range V=0.60-1.35 MV and beam currents I=1.3 kA. A completely ionized plasma is injected into a gyrotron interaction region from an upstream array of plasma guns. The peak plasma density available from the plasma guns exceeds 10/sup 13/ cm/sup -3/. A high-current electron beam from a field-emission electron gun enters the plasma-filled gyrotron cavity from the upstream side. The density of the neutralizing plasma is varied by changing the delay between the firing of the plasma guns and the VEBA accelerator. Measurements of the transmitted electron beam current as a function of the neutralizing plasma density, the accelerating voltage, the pitch ratio, and the electron beam radius have been carried out. Gyrotron oscillators that utilize the enhanced capabilities have been designed.<>