TOTAL SECONDARY IONIZATION COEFFICIENTS AND BREAKDOWN POTENTIALS OF HYDROGEN METHANE ETHYLENE CARBON MONOXIDE NITROGEN OXYGEN CARBON DIOXIDE BETWEEN MILD STEEL COAXIAL CYLINDERS

Breakdown potentials of hydrogen, methane, ethylene, carbon monoxide, nitrogen and carbon dioxide were measured at room and at elevated temperatures, and oxygen at 296° K, using mild steel cylindrical electrodes. The gas pressure was varied over a range of almost four orders of magnitude, and the temperature of both the gas and the metal electrodes from 294-468° K. Two discharge tubes, having different electrode diameters but the same material composition, were employed. The breakdown potential values at constant gas density, and for positive and negative wire (inner electrode), were found to be independent of gas temperature over the whole of the pressure and temperature ranges covered. It has been found that, with the exception of nitrogen, the similarity theorem is obeyed in the gases studied. This theorem was found to hold for positive as well as negative wire breakdown over a very wide range of gas pressure. The total electron yield due to secondary ionization processes was evaluated over a wide range of E/po values. The value of the total secondary ionization coefficient varied over a range of seven orders of magnitude, depending on the nature of the gas and the ion energy. The total secondary ionization coefficient was found to be independent of target and gas temperature in the gases studied, over the range 294-468° K.