Extraction of superthermal electrons in a high current, low emittance, steady state electron gun with a plasma cathode

Abstract

Major limitations of plasma cathodes have been overcome in an electron gun based on extraction of superthermal electrons from a discharge characterized by a large component of high energy electrons with a low thermal spread. A grid is employed to select these electrons for extraction while retaining the bulk electrons in the discharge. Steady state extraction of electron beams corresponding to over 60% of the total arc discharge current has been observed. This extracted electron current far exceeds the thermal electron flux. A perveance of over 280 microperv was reached with the extraction of 9 A at 1 keV from a 6 mm aperture.