Operation Features of a Planar Magnetron Discharge Forming Emission Plasma in a Pulsed Forevacuum Plasma-Cathode Electron-Beam Source

We have used a planar magnetron discharge to form emission plasma in a forevacuum plasma electron source (FPES) generating pulsed low-energy (up to 10 keV) electron beam at gas pressure of 4–16 Pa (Ar, N2). The operation features of the magnetron discharge and emission properties of its plasma in the FPES have been investigated. Initiation voltage and delay time of initiation of the magnetron discharge decrease with increasing accelerating voltage, gas pressure, and acceleration gap length, as well as when Ar is used instead of N2. The observed decrease in the initiation voltage and delay time is due to influence of a “parasitic” high-voltage glow discharge appearing in an accelerating gap, when high voltage is applied. An increase in pressure leads to higher emission current (beam current), that is typical for FPESs based on other discharge types. This increase in emission current is caused by a “back-streaming” ion flow from beam-produced plasma. Operating voltage of the planar magnetron discharge is lower during electron beam generation at gas pressure more than 4 Pa, which is also due the influence of the “back-streaming” ion flow penetrating into discharge system of the planar magnetron. The use of the planar magnetron discharge in the FPES provides generation of the wide-aperture (with radius of up to about 40 mm) low-energy electron beam with rather high homogeneity, pulse duration up to 10 ms and current up to 15 A.