Method of making the cathode of a diode image intensifier tube

Abstract

A method of making the cathode of a diode image intensifier tube by evaporating some alkali metals and antimony on to the inner surface of a cathode window which by means of a layer of frit is joined to a metallic cathode flange, and in which there is provided between the cathode and the cathode flange, or, as the case may be, the cathode housing, an electrical resistance of a pre-determined value such that at light levels at which there is a danger of the anode being burnt, the diode image intensifier tube is defocussed or cut off, and wherein prior to the evaporation of the metals an alkali-resistant and insulating layer is applied to the frit layer, and that the evaporation of the antimony is carried out so that there is formed between the cathode and the cathode flange an area extending around the cathode and where no antimony is present, and that at least one galvanic connection is passed vacuum-tight outside the diode image intensifier tube, and one end of said connection is arranged at the place of the cathode to be formed for supplying voltages of a pre-determined magnitude to the cathode during its manufacture and later during operation of the tube.