On the Hollow Cathode Effect Mechanism

Abstract

On basis of new results concerning the dependence of the discharge current on the intercathode spacing and the cathode fall potential, the main characteristics of the hollow cathode effect (H.C.E) in a plane-parallel geometry are defined.In order to explain the particularities of the H.C.E., a mechanism is p r o p e d that regards the discharge current amplifications and the enhancement of the negative glow plasma as a consequence of the plasma beam instabilities.

Beam-plasma interactions in a hollow cathode

“…In this section we show that the repeated bursts of electrical noise from our discharge tube are consistent with an interaction of secondary electrons and a decaying plasma in a similar way to that suggested by Popovici et al (1967) for self-sustaining hollow-cathode discharges. In our case successive bursts appear to correspond to resonances of progressively lower mode number, terminated either when all the plasma is swept from the hollow-cathode or when the fundamental frequency is reached.…”

“…Young (1968) detected bursts of microwave emission at the onset of these discharges. From this and other evidence he concluded that the beam plasma interaction proposed by Popovici et al (1967) was probably responsible for the ionization. The present work does not fully support this conclusion ; it is concerned with a form of beam-plasma interaction which does not appear to contribute significantly to the ionization, but is undoubtedly a hollow-cathode 1292 0.…”

“…In this geometry, no self-sustained discharge was observed but the deionization current to the double cathode showed repeatable and regular disturbances ; an example of these is shown in figure 2(a). We suspected that the disturbances might be connected with the beam-plasma interactions of Popovici et al (1967) and Young (1968). With this in mind a crude microwave detector was set up which consisted of a diode directly coupled to a 50 mm dipole (chosen to match approximately the expected plasma frequency).…”

“…Since 191 6, many workers, including Giintherschulze and Penning, have studied this effect at pressures from 0.1 mTorr to 10 Torr. Little and von Engel (1954) and Popovici et al (1967) give fairly full bibliographies of the earlier work.…”

“…This led Giintherschulze (1923) to suggest that an increased electron path length due to trapping might explain the enhanced ionization. More recently, Popovici et al (1967) have proposed that beam-plasma interactions share the energy of fast secondary electrons among the plasma electrons and thus increase their ionizing efficiency. The enhanced electron emission from the hollow cathode has been accounted for by several processes.…”