Electron beam formation in an open discharge

The results of calculations reported for the first time indicate that the electron emission from a cathode, which is necessary to explain the main properties of an open discharge, is stimulated by the cathode bombardment by fast atoms rather than by photons (as was believed for a long time). The calculations are based on the results of measurements of the electric field strength in the discharge region and of the coefficient of electron emission from a cathode bombarded by helium atoms and ions. It is also demonstrated that the efficiency of the gas ionization by fast atom bombardment is significant at a voltage of several keV and becomes comparable with the electron-impact ionization in the anode plasma at a voltage equal to a few tens of keV.