Formation of Pulsed Low-Energy Electron Beam by a Plasma-Cathode Electron Source Based on Cathodic Arc in the Forevacuum Pressure Range

Abstract

The research of formation of pulsed large-radius low-energy (up to 10 keV) electron beam by a plasma-cathode electron source based on the cathodic arc in the forevacuum pressure range is presented. A hollow anode and a redistributing electrode have been used to generate broad, uniform emission plasma. Increase of the diameter of hollow anode and increase of diameter of emission aperture (window in the plane part of the anode covered by metal mesh) up to inner diameter of hollow anode has provided, as expected, an increase in efficiency of electron extraction from the arc plasma. However, increase of emission aperture has led to decrease maximal operating gas pressure due to intensification of the influence of back-streaming ion flow on the emission (arc) plasma. The use of two emission meshes with different cell sizes has provided generation electron beam with current of up to tens of amperes and pulse duration up to 5 ms at gas pressure of up to 15 Pa (N2). The maximal operating pressure and optimal efficiency of electron extraction from arc plasma (at low pressure) are provided in case of the first mesh with large cell sizes is mounted inside the hollow anode, and second fine mesh covers the emission window on side, facing the extractor (optimal distance between meshes is about 2 mm). The use of the redistributing electrode and two emission meshes provided an increase in the uniformity of the current density distribution across the electron beam.