Control of Reduced Electric Field in the Positive Column of a Pulsed Discharge in Co2

Abstract

The electric field strength in the positive column of dc and bipolar pulsed discharges in carbon dioxide was determined by the method of moving electrodes. It is shown that an increase in the frequency of the pulse voltage leads to the electric field strength increase. The following values of the reduced electric field E/p for a gas pressure of 0.5 Torr were obtained: 22.5 V/(cmTorr) for dc discharge, 30 V/(cmTorr) for pulsed discharge at 20 kHz for lowcurrent mode and 32 V/(cmTorr) for high-current mode, and 36.6 V/(cmTorr) for 75 kHz. We see that in the dc discharge, the reduced electric field is weak, due to which the exchange of vibrational energy between CO2 molecules dominates the conversion process. The increase of the electric field strength in the positive column of a pulsed discharge, especially under conditions of gas heating, allows obtaining E/N > 100 Td when the process of direct dissociation of CO2 molecules by fast electrons makes the main contribution to the conversion process.