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

Abstract

Energy distributions of electrons in beams from hollow-anode gas discharge electron guns have been determined for electron flight paths of 0.1, 0.3 and 0.6 m. Guns have been operated at potentials between 5 kV and 20 kV in hydrogen, helium, oxygen, air, nitrogen and argon at pressures in tht approximate range 10-100 N m-2. A typical spectrum obtained has a sharp peak at an energy equivalent to that achieved by electrons accelerated to the full cathode potential. A second peak of amplitude 0.05-0.5 times the primary peak amplitude occurs at an energy lower by approximately one ionization potential. This secondary peak is broader, the amplitude falling to approximately zero within an energy range of about 100 eV.

Energy analysis of electron beams from perforated-mesh hollow-cathode gas discharge guns

“…Associated with this lower energy peak is another which is displaced downwards from it by approximately one ionization potential energy. This last feature was also typical of the spectra found from ha guns (Allen and Hale 1970).…”

“…Returning to consideration of the hc gun spectra at higher currents it is apparent that there are similarities between these and those taken with the ha gun (Allen and Hale 1970). The differences are discussed below.…”

“…Experiments were first made to establish which common gas was the most satisfactory for stable gun operation. It was known from previous work (Allen and Hale 1970) that the ha gun performed best in oxygen. However, the inert gases have more commonly been used with the hc gun.…”

“…The gun was mounted in the discharge tank of the energy analyser described elsewhere Hale 1970, Hale andAllen 1971). The analyser was arranged so that the electron current distribution in energy could be determined and in addition the same spectrum could be observed qualitatively on a phosphor screen.…”

“…One possible disadvantage of such beams, particularly if they are magnetically focused to small spots for machining, is the electron energy spread which exists mainly as a result of collisions with gas atoms in the work chamber. Results showing that this is unlikely to be of practical significance in the case of beams from hollowanode guns have already been published (Allen and Hale 1970). However, in the case of the perforated-mesh hollow-cathode gun and developments from it (Boring and Stauffer 1963) the mechanism for the production of the beam is somewhat different and it was thought useful to obtain spectra from such guns.…”