Secondary Processes under the Influence of Bombardment by Inert-Gas Ions

Abstract

Electron emission under the influence of gas ions (under gas-discharge conditions) was first studied by Penning [50] in 1928. Penning found that in the case of bombarding a copper target with positive Ne⁺ ions at E₀ ~100 eV the value of γ = I^-/I⁺ equalled ~3%. However, the inadequate precision of experiments on ion—electron emission in a gas discharge (inhomogeneity of the ion composition and the large energy spread, complex conditions on the cathode surface, back diffusion of secondary electrons into the target) impeded any explanation of the results obtained. For this reason all subsequent investigations were carried out with independent ion sources by vacuum-separating the source and target spaces with special diaphragms, using differential pumping [257].