The Formation and Maintenance of Electron and Ion Beams

Abstract

The radial potential distribution in an ionic beam of circular cross section is calculated and the maximum beam current which can be obtained in a beam of given radius and boundary conditions is computed. In the case of ions the maximum beam currents may be quite small. The ions in such beams have a considerable velocity distribution which in turn leads to a greater beam divergence than former calculations indicate. In Section 3 a method is worked out for holding the beam together during the initial accelerations. A disadvantage of cylindrical lenses is pointed out in this connection. The use of electrostatic lenses for holding together a beam composed of high energy particles is discussed in some detail. Calculations show the special arrangements of the lenses necessary for producing convergence of the beam. A few other arrangements to prevent divergence which were tried experimentally are described.

Maximum intensity, transmission limited cold electron beams from GaAs photocathode in the eV and sub-eV kinetic energy range

“…(3). The Poisson equation for this case can be solved numerically, or by power-series expansion as considered by Smith and Hartman [18]. This yields a relation between the total current and the relative space-charge potential x defined by a function fðxÞ such that…”

“…where the second expression includes the perveancerelated parameter s 2 ρ resulting from the solution of the space-charge Poisson equation as discussed in [18] …”

“…4(b). Values of fðxÞ and ϕðrÞ in the present work were found applying series expansion Smith and Hartman [18] until sixth order members using TSR geometry with the drift tube to beam radii ratio of R=ρ ¼ 7.46. The series expansion was then compared to numerically solved nonlinear Poisson equation and within the parameters range of interest (0 < x < 0.41) the agreement of numeric solution with sixth order expansion is better than 1% while for the second order expansion it yields better than 5% discrepancy through the entire range.…”

Sur la neutralisation de la charge d'espace des faisceaux d'ions positifs par accumulation d'électrons; étude du temps de neutralisation

“…Divergence due à la charge d'espace. -De nombreux auteurs ont calculé la divergence de faisceaux d'ions sous l'action de la charge d'espace [4]. Ils donnent [5], dans le cas d'un faisceau à symétrie plane, d'ions de masse atomique A, d'intensité I(A/cm) et accélérés sous une différence de potentiel V (Vp our un faisceau initialement parallèle, Zo étant l'épaisseur initiale du faisceau et Z celle qu'il prend à la distance d (cm).…”

Sputtering and Secondary Electron Emission of Metals Bombarded by Argon Ions

“…One would, however, encounter difficulties in attempting accurate measurements under the conditions of low sputtering rates. 22,23 It should be mentioned that the conditions of sputtering in the glow discharge may be quite different, and in that case aggregates of atoms rather than single atoms may sometimes leave the bombarded cathode. A target to be sputtered is first deposited by evaporation within a high vacuum, and thus its density is easily determinable.…”