High-Voltage Glow Discharges inD2Gas. I. Diagnostic Measurements

Pulsed glow discharges in ${\mathrm{D}}_2$ gas at currents of the order of 1 amp and voltages in the range 40-80 kv are experimentally examined to determine the mass and energy distribution of ions incident on the cathode, the secondary electron emission due to various particles incident on the cathode, the energy spectrum of the electrons incident on the anode, the potential distribution along the glass walls, and the temperature and density of the electrons in the plasma which develops in the anode end of the discharge. The experimental results are discussed together with available cross-section data from the literature to establish the relative importance of the various collision processes which contribute to the sustainment of the discharge. Several processes peculiar to the extremely high operating potential (not of particular importance in ordinary glow discharges) are shown to assume dominant roles. These include electron backscattering from the anode, ionization of the gas by fast ions and fast neutral atoms, and ionization in the plasma region due to the secondary electrons released from the glass walls. The necessity of a complete revision of the usual theoretical point of view regarding electron ionization in the cathode region of the discharge and in the anode (plasma) region is indicated.