The abnormal glow discharge in mercury vapour and xenon

Abstract

Measurements have been made of the current-voltage characteristics of abnormal glow discharges in mercury vapour and xenon, both with a mercury cathode, over a pressure range from 0·5 to 15 mm Hg. Measurements have also been made of the cathode fall distance as a function of the voltage, but at low voltages only.A theoretical description is presented and is in good agreement with experiment. The main features of the theory are: at high current densities, the gas density increases towards the cathode as a result of momentum-exchanging collisions between the positive ions and the gas molecules; the dominant secondary emission process is photoelectric emission by photons from the negative glow, except near the glow-arc transition where emission by excited atom bombardment makes a small but significant contribution; and only a small fraction of the photons produced in the negative glow reach the cathode, because of frequent reabsorption and subsequent ionization.

Energy dissipation in the cathode of a vacuum arc

“…A better agreement may be expected if the movement of the spot is taken into account. This view was put forward by Holmes (1974), who calculated a power loss per unit area Ucon Ja=pCpT V/3. Here p is the specific mass, Cp the specific heat and V the spot velocity (see also von Engel and Robson 1957).…”

Hydrogen desorption from sand-blasted and acid-etched titanium surfaces after glow-discharge treatment

“…Taking into account the different treatment duration times, treatment doses differing by at least one order of magnitude were used. [23][24][25] …”

A simplified analytical model for an anchored cathode root in a DC mercury vapour arc

“…On the other hand, few theoretical investigations have been reported. One theory was proposed by Holmes (1974). His theoretical model for the arc cathode spot permitted a quantitative description of the parameters of the arc spot, and showed that values of the spot parameters calculated for mercury and copper cathode arcs agreed in part with experimental measurements.…”

“…Although these values are larger than our theoretical values, both values agree within an order of magnitude. Holmes (1974) proposed that the maximum radius of an arc root for which there is a solution to the equations derived theoretically by him was 9.1 X cm. His value was calculated assuming a constant current density ( J = 1.5 X lo6 A cm-2) and constant cathode-fall voltage (Vc = 7.7 V) over the whole arc current range.…”

“…Figures which indicate the relationships between I, and a , between I, and T , and between I, and have been drawn with parameter V,, which has been measured in the range 7-20V (Kesaev 1964, Holmes 1974.…”