Voltage-current characteristics of a high current diffuse discharge

High-current-density diffuse discharges in high-pressure, electronegative gas mixtures have been studied in an impedance-matched (50 Omega ) transmission line system. A traveling voltage waveform with an amplitude up to 40 kV, a risetime of 2 ns, and a total pulse width of 100 ns was used. Gas mixtures of C/sub 3/F/sub 8/ and He in the pressure range between 100 and 600 torr were investigated in a uniform field formed by plane parallel electrodes. The low-current-density diffuse discharge operates at a constant voltage. At a current density of about 100 A/cm/sub 2/ and higher additional ionization processes related to power loading cause the operating voltage to drop. A further increase in current density would, however, enhance the recombination rate, causing the operating voltage to rise. The objective of this work was to identify the minimum operating voltage and corresponding current density. A decrease in the operating (E/N)s of a diffuse discharge in a 50:50 mixture of C/sub 3/F/sub 8/:He is shown as a function of reduced current density. Additional decreases of (E/N)/sub s/ observed during the discharge are indicated. Both results are a consequence of power loading.<>