Behavior of an arc discharge in a forevacuum plasma source of electrons

The parameters and characteristics of a pulsed arc discharge with a cathode spot used in a forevacuum plasma source of electrons are investigated. It is shown that the accelerating voltage influences arc initiation to a lesser extent compared with an electron source based on a hollow-cathode glow discharge. At forevacuum pressures, two stages of the arc discharge may arise within the current pulse. At the beginning of the pulse (first stage), the arcing voltage is high and the fraction of residual gas ions in the plasma is significant. At the second stage, the arcing voltage drops and ions of the cathode material dominate in the plasma. The duration of the first stage grows with rising gas pressure and decreasing arc current.