The Electrostatic Focusing of High Speed Ion and Electron Beams

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Abstract
The paper gives a description of some tests carried out in preparation for the construction and development of an apparatus for artificial atomic disintegrations. The problems involved are (i) the focusing of a beam of 10–30 kv hydrogen ions from a canal-ray ion source (glow discharge type) and (ii) the behavior of a cascade acceleration tube of the Coolidge type. In particular it was necessary to know the efficiency of the latter, i.e., the ratio of output to input currents. The general properties of electrostatic focusing systems are first treated briefly, and adequate references are given to enable those interested in the problem to pursue the matter further. It is pointed out that in view of the aberrations present, the constants of our lenses cannot be accurately calculated and we have therefore concentrated our attention on presenting the results in a concise form. Several lens systems were used to focus the canal-ray beams and details are given in tables. It was found possible to focus at least 50 percent of the ion beam emerging from the canal into an area 1–2 cm in diameter at distances of 20–50 cm. Point foci could be obtained but the focused currents were low, i.e., spherical aberration was large. Similar performances could be obtained with a 6′ acceleration tube.

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