Millimeter-wave radiation generated via plasma three-wave mixing using high-current density counter-streaming electron beams

Abstract

Electron-beam-excited, counterpropagating electron plasma wave (EPWs) interact nonlinearly through the plasma three-wave mixing process to generate electromagnetic radiation at twice the plasma frequency. Radiation saturation is not observed up to beam current densities of 2 A/cm/sup 2/, where the peak power is 8 kW. To investigate the saturation mechanism and maximize the radiation generation efficiency, plasma-cathode electron beams, which can provide up to 20 A/cm/sup 2/ at 30 kV, have been installed. The counterpropagating EPW topology required for three-wave mixing was created using a single high-current-density electron beam by means of a backscattering process. When the background plasma was generated by electron-beam-gas impact ionization, the current density threshold for single-beam radiation emission was about 12 A/cm/sup 2/. Scaling experiments have explored the two-beam and single-beam radiation generation processes.<>