Current pulses in SF6glow discharges

Sharp current pulses, with amplitudes of the order of hundreds of mA and frequencies of the order of 100 kHz, occur in SF 6 glow discharges in the pressure range 1 to 10 Torr for average discharge currents up to 20 mA. The pulses are shown to be a phenomenon associated with a constricted positive column and a negative voltage-current discharge characteristic. A series of experiments is reported in which the amplitudes and frequencies of the current pulses are measured as functions of average discharge current, SF 6 pressure, electrode separation, tube diameter and interelectrode capacitance. The results are described in terms of the charge stored on the interelectrode capacitance, and the dependence of the discharge processes of ionisation and attachment on E/N (axial electric field/neutral density) in the positive column. Further support for this description is provided by an examination of current pulses in high-pressure glow discharges through argon and neon. In these discharges electron-ion recombination plays a similar role to that of attachment in SF 6 discharges.