EXTRACTION OF SUPERTHERMAL ELECTRONS IN A HIGH-CURRENT, LOW-EMITTANCE, STEADY-STATE ELECTRON-GUN WITH A PLASMA CATHODE

Major limitations of plasma cathodes have been overcome in an electron gun based on extraction of superthermal electrons from a discharge ch aracterized by a large component of high energy electrons with a low t hermal spread. A grid is employed to select these electrons for extrac tion while retaining the bulk electrons in the discharge. Steady state extraction of electron beams corresponding to over 60% of the total a re discharge current has been observed. This extracted electron curren t far exceeds the thermal electron flux. A perveance of over 280 micro perv was reached with the extraction of 9 A at 1 keV from a 6 mm apert ure. (C) 1996 American Institute of Physics.