Zl. Petrovic et Av. Phelps, TEMPORAL AND CONSTRICTION BEHAVIOR OF LOW-PRESSURE, CATHODE-DOMINATEDARGON DISCHARGES, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 56(5), 1997, pp. 5920-5931
Measurements of quasi-steady-state voltage-current characteristics, lo
w-current voltage and current oscillations, and constriction formation
are reported for cathode-dominated discharges in low-pressure Ar. Pul
sed a discharges (similar to 5 ms long at 1-3 Hz) reduce heating and i
mprove the accuracy of differential voltage measurements. Values of pr
essure p times the separation d of the parallel-plane electrodes are 0
.12 to 2 Torr cm corresponding to discharge breakdown voltages of 2 kV
to 230 V. Discharge currents range from 2 mu A to 40 mA. The quasi-st
eady-state discharge voltages decrease from their breakdown values in
direct proportion to the current, i.e., the negative-differential-volt
age-to-current ratio is constant. At currents below the onset of self-
sustained sustained oscillations and at the higher pressures, the freq
uency and damping of transient oscillations are in agreement with a pe
rturbation model based on changes in ion-induced electron emission at
the cathode caused by space-charge electric fields. At the higher curr
ents and low pressures transient voltage and current waveforms show th
e growth of low-frequency oscillations accompanying the onset of const
rictions. Rotation of the constricted discharge is observed at these p
ressures. At the higher pressures the constrictions are stable during
the pulse and emission scans parallel to the electrodes provide quanti
tative data on constricted discharge areas and emissivity per unit cur
rent as the discharge increases in size with increasing current. Compa
risons are made of these experiments with recent models where possible
.