Generation of focused high-current electron beam with millisecond pulse duration by a forevacuum plasma-cathode electron source based on cathodic arc

Abstract

We describe our work on the generation of low-energy (up to 10 keV) pulsed high-current electron beams with pulse duration up to 7 ms, compressed (focused) by a magnetic field in the forevacuum pressure range (3–30 Pa). We show that the focusing system, consisting of two coaxially arranged coils, provides effective compression of the beam. In the forevacuum pressure range, the gas pressure and type of gas affect the focusing of the beam at fixed emission current, accelerating voltage and magnetic field. Increased pressure leads first to increased beam current density, but beyond a certain optimal value further pressure increase leads to a decrease in the current density of the electron beam. The use of gas with greater ionization cross-section results in stronger compression of the beam at lower gas pressure, but also leads to decreased maximal operating gas pressure of the plasma-cathode electron beam source. Variation of magnetic fields provides control of the beam current density and the position of the beam crossover (focus). A low-energy electron beam with current density up to 15 A·cm−2 and pulse duration up to 7 ms is obtained in the forevacuum pressure range. The use of the focused beam for evaporation of high-temperature ceramics is demonstrated.