An experimental X-ray image intensifier incorporating a channel electron multiplier plate

A channel electron multiplier plate has been used in an X-ray image intensifier to produce a full size distortion-free viewing system with sufficient image brightness to obviate the need for dark adaption. The useful diameter of the tube is 120 mm and the thickness is only a few centimeters. The characteristics of a channel plate are discussed and related to the requirements of an X-ray intensifier. Practical considerations such as field emission and gas desorption, which affect the design and performance of the tube, are also considered. The resolution capability is comparable with other X-ray image converters as it is primarily determined by the X-ray detecting layer. It is shown that the efficiency of this layer also determines the signal-to-noise ratio of the output picture and an expression is derived to show that a photocathode of only moderate sensitivity is adequate to reduce the effect of the exponential pulse height distribution of the channel plate output to negligible proportions. In addition to quantitative details of the tube performance a subjective assessment has been made relating the minimum visually perceptible detail with contrast for various X-ray dose rates.