Optimization of the performance of a tandem microchannel plate detector as a function of interplate spacing and voltage

Abstract

The effect of varying the size of the gap and the voltage between two microchannel plates (MCP’s) in a tandem configuration has been investigated. It was found that increasing the voltage in the gap increased the gain of the pair and also produced a narrower Gaussian pulse-height distribution. Beyond a critical voltage the gain of the channel plate pair was found to plateau. These observations can be explained in terms of a model involving both the nonlinear gain behavior of individual microchannels and the behavior of the electron cloud emitted from the first MCP as it spreads out between the two MCP’s and hits the surface of the second. From this model the plateau voltage is calculated as a function of the gap size, the gain of each MCP, and the diameter of the channels, and is found to match the observed results. It is concluded that interplate gaps of up to several millimeters can be accommodated without a significant degradation in pulse-height distribution.