Evaluation of long life (L/sup 2/) microchannel plates for X-ray photon counting

An evaluation is presented for Galileo long-life (L/sup 2/) microchannel plates (MCPs) operated in pulse counting mode. Modal gain, pulse height FWHM, gain uniformity, and high-count-rate performance data are compared with measurements made with MCPs of conventional glass composition. Despite the absence of potassium (and hence, of the beta -emitter /sup 40/ K) from the L/sup 2/ glass, dark count rates for the L/sup 2/ MCPs are about five-times higher than those of standard MCPs, due to the presence in the glass of the radioisotope /sup 87/Rb. The measurements indicate that Galileo L/sup 2/ MCPs, even those with short channel lengths, have several desirable characteristics for photon-counting applications. They also confirm that changing the radioisotope composition of channel plate glass influences the dark noise count rate, further supporting an internal radioactivity noise model developed by the authors.<>