TOTAL SECONDARY IONIZATION COEFFICIENTS AND BREAKDOWN POTENTIALS OF MONATOMIC GASES BETWEEN MILD STEEL COAXIAL CYLINDERS

A study of the breakdown potential at room and elevated temperatures has been made in very pure gas samples of helium, neon, argon, krypton and xenon, using mild steel concentric 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 electrodes from 295-463° K. At constant gas density, and for positive and negative wire (inner electrode), it is shown that the breakdown potential values are independent of gas temperature over the whole pressure and temperature ranges covered. This suggests that heating the electrodes and the gas has a negligible effect on the secondary electron yield in all the rare gases studied. The minimum sparking potential value for the negative wire was found to increase as the ionization potential of the gas decreased, while that of the positive wire was only slightly sensitive to the nature of the gas. It has been found that, when adequate precautions are taken to ensure a high standard of gas and electrode purity, the similarity theorem is obeyed in all the rare gases, for the positive as well as the negative wire breakdown, over a very wide range of gas pressure. The total electron yield due to secondary ionization processes was evaluated for each gas over a wide range of E/p 0. Its value varied over a range of three orders of magnitude, depending on the type of the gas and the value of E/p0.