The Development of Spark Discharges in Hydrogen

Abstract

SummaryStreak photography has been used to supplement the earlier shutter photo. graphic investigation of Doran and Meyer (1967) using the same coaxial cable discharge circuit. Additional information has also been obtained from measurement of the potential distribution between the electrodes at two stages in the spark development. Redistribution of space charge is shown to give rise firstly to a transient diffuse glow discharge that has a close similarity with a normal d.c. glow discharge. It has also been shown that, even while the diffuse glow discharge expands, a partial constriction occurs in which most of the current flows along a narrow axial column. The resulting maximum in electron density eventually causes a rapid increase in dissociation of molecular hydrogen on the axis of the discharge brought about by a rise in the gas temperature. Owing to its greater electrical conductivity this axial column soon carries the entire current and the discharge becomes filamentary though still being maintained by a high cathode fall field, which exists until a sudden change in the cathode mechanism gives rise to the low voltage arc channel. Both the filamentary glow and arc columns are observed to expand according to an r cc ti law.

Possible Hall Effect Due to Semimetallic Cathodes in Short-Duration Arcs

“…1 " 3 The short-duration arc, when formed, seems to be like its longer counterpart in that it appears to stretch from the anode to the cathode without exhibiting any dark spaces as in the glow discharge, and has approximately the same diameter throughout its length. 1 The present note reports observation of an odd visible form of discharge which occurred between both bismuth and antimony electrodes.…”

Generation of a planar direct-current glow discharge in atmospheric pressure air using rod array electrode

“…This estimation method is only valid for homogeneous plasmas, whose cross-section is relatively regular to reduce the measurement error 32 . By an extrapolation method 35 , voltage fall of the positive column is obtained to calculate E p . Through this method, n e can be estimated, as shown in Fig.…”

Analysis of the radiation characteristics of large-aperture exciplex laser systems utilizing a three-dimensional transfer equation

“…Recently Meyer and Lee (1971) have shown that the glow characteristics are independent of the source impedance. Cavenor (1970) has confirmed the existence of the glow phase at overvoltages up to 100% and a pressure of 500 Torr, and Cavenor and Meyer (1969) also showed that this diffuse glow subsequently constricts to a filamentary discharge which still shows a cathode dark space at the cathode and which causes a further drop in the gap voltage. There is a progressive increase in the current through the filament until, finally, a discontinuity at the cathode accompanied by the disappearance of the dark space leads to a sudden increase in luminosity and electrical conductivity and the gap voltage collapses to very low values.…”

“…His model is based on a constriction process due to changes in gas density and therefore electrical conductivity resulting from expansion of the heated discharge region with a consequent progressive localization of the discharge current. He used the experimental data of Cavenor and Meyer (1969) taken at 500 Torr to calculate the temporal variation of the diameter of the diffuse glow which lasted, in this case, about 60 ns. Rogoff suggests that the sudden final constriction to the spark channel phase is connected with the onset of appreciable dissociation and consequently an increased ionization rate, as pointed out earlier by Cavenor and Meyer and others, and confirmed later by Kekez et a1 (1970).…”

“…It is now known that when the initial electrons are provided over the whole of the discharge gap, as in the present work, the first luminous event to be observed is a diffuse glow. The glow has a structure similar to a high-pressure DC glow discharge and its appearance accompanies the first noticeable drop in the gap voltage (Cavenor and Meyer 1969). Recently Meyer and Lee (1971) have shown that the glow characteristics are independent of the source impedance.…”