The extraction of ions from a radio-frequency discharge

Abstract

The extraction of ions from the plasma of a gas discharge and their formation into a beam is investigated theoretically. The results are shown to be applicable to a gridded ion gun. The results are also applicable to the design of canal extraction systems, but it is shown that in this case a simpler method exists for obtaining the necessary information. The theory is compared with the results of experiments and some agreement is found for sufficiently high accelerating voltages. The discrepancy is believed to be the result of the partial neutralization of the beam by secondary electrons in the experiments.

The design of canal ion sources, taking account of aperture lens effects

“…Hence using equations ( 4) and ( 5) we may calculate a curve of xl/xz against d/l for optimum performance of the source. This curve is shown in figure 2 together with the curve from figure 9 of the previous paper (Carter and Newton 1969) in which the lens effects were neglected.…”

“…A previous paper by Carter and Newton (1969) discussed, among other topics, the design of the canal ion sources. The theory given of the operation of such a source was not strictly correct in that it took no account of the lens effect of the canal aperture.…”

An experimental study of charge densities and radiofrequency propagation characteristics in an ion-beam/plasma system

“…The principal features of the apparatus are shown in diagrammatic form in figure 1. A full description of the apparatus has been given elsewhere (Carter 1968). The ion beam 7 Now at the Department of Engineering, University of Lancaster.…”

“…The ion beam 7 Now at the Department of Engineering, University of Lancaster. was provided by a radiofrequency argon ion source of the type described by Harrison (1958) and by the present authors (Carter and Newton 1969). The extraction aperture had a diameter of 1.25 cm, and the gun was modified so that the second electrode, a molybdenum grid, could be biased with respect to earth potential and used as an electrontrapping electrode.…”