EXPERIMENTAL INVESTIGATION OF A PLASMA EDGE CATHODE SCHEME FOR PULSED ELECTRON-BEAM EXTRACTION

A scheme with the potential for generation of an electron beam with high brightness and several mu-s pulse duration for microwave generation, electron accelerators, or free electron lasers is investigated experimentally. An electron beam is extracted transversely to the flow of a plasma jet. The transverse boundary of the plasma allows extraction of a space charge limited electron current for 7-mu-s at a current density of 18 A/cm2. At present, a normalized microscopic brightness of 8 x 10(8) A m-2 rad-2 is achieved. Closure of the extraction gap by invasion of plasma has been observed with a typical velocity of 0.1 cm/mu-s. Higher current density and higher brightness are expected for higher plasma densities and larger extraction fields.