Glow discharge beam techniques

Cathode contamination effects in a high-voltage glow discharge

“…The present observations support our previous findings and indicate that heating of glow-discharge cathodes removes the volatile contaminants responsible for glow-to-arc transitions Dugdale 1966, Dugdale et al 1968). The results and interpretation are also consistent with the findings of workers concerned with vacuum emission microscopes (Grivet 1965).…”

“…Commercially available cylinder gases were employed without purification. If required, fine control of the current can be achieved by means of the auxiliary electrode, positioned inside the anode, by varying its voltage with respect to the anode in the range 0 to k 100 v (see Dugdale et al 1968).…”

“…In previous work (Maskrey and Dugdale 1966) superficial volatile contamination was found to play a vital role in arc initiation on cathode surfaces in a low-pressure gas discharge. It was also discovered that glow-to-arc transitions do not readily occur in the high-voltage low-pressure glow discharge if the cathode temperature is maintained above about 200"c (Dugdale 1967; see also Dugdale et al 1968). The very marked effect of heating the cathode was attributed to the removal or decomposition of the volatile contaminants, such as water or organic substances, which were thought to increase the gas density locally during a transition to the arc.…”

Energy distribution of fast electrons present in beams from hollow-anode gas discharge electron guns

“…Electron guns which produce well-collimated electron beams from glow discharges have received considerable attention since about 1960 (van Paassen et al 1962, Boring andStauffer 1963). Beams from such guns have already been developed for material processing purposes (Dugdale 1966, Dugdale et al 1969.…”

“…The production of electron beams is somewhat different in the two cases. In the hollow-anode gun, which has been found to be particularly suitable for micromachining work (Dugdale et al 1969), gas ions from the discharge are focused on the centre of the cathode by the action of the electric fields in the vicinity of the cathode. Secondary electrons produced at this 'point', a circle about 0.2 mm diameter, emerge as a parallel or slightly diverging beam through the hollow anode.…”