Effect of distribution of electric field on low-pressure gas breakdown

Abstract

A low-pressure gas breakdown in a gap of the non-uniform electric field between two plane-parallel electrodes was studied. The experiments were specially designed to neatly separate the effect of a centered dielectric tube in between the electrodes on the breakdown from the effect of the electric field distribution determined by the electrode geometry on the breakdown. For a given electrode radius and an interelectrode distance, when the diameter of the centered dielectric tube in between the electrodes is smaller, the breakdown voltage is lower, which is most possibly as a result of the flashover more easily happening along the surface of the smaller tube on which the more charged particles are accumulated. When the dielectric tube in between the electrodes is removed, the breakdown voltage depends not only on the product of gas pressure and gap length but also on the aspect ratio of the gas gap, i.e., Ub = f(pd, d/r). Furthermore, Ub = f(pd, d/r) was proved to automatically fulfill two necessary conditions for the similar discharges in the non-uniform electric field, which implies that Ub = f(pd, d/r) is an expression of the similarity theorem in the breakdown of a gap between two plane-parallel electrodes and confirms Townsend's prediction that the general similarity theorem can be applied equally to the breakdowns in non-uniform fields.