Large-area, triple-layer, microchannel-plate arrays

Abstract

The characteristics of operating an extended-area, triple-layer microchannel-plate assembly are described in detail. The assembly has an anode array to produce 120 channels of information. When run in the pulse-counting mode, gains of up to 5×108 are obtained with very low levels of dark current. A number of special features and problems have been observed during operation. These include unexpectedly high count rates for each channel and severe gain variation along the length of the plate. A model distribution function for a pulse is derived and it is shown that this gain variation is due to space-charge effects that occur in the interstage gaps. This effect, although previously discounted, can consistently explain the data presented here and earlier by other authors. One assembly was rebuilt and now exhibits much greater uniformity in gain. Its pulse-height spectrum also has the unusually small, full-width at half-maximum: gain ratio of typically 50%.