Microchannel plate operation at high count rates: New results

We describe an experimental study of two distinct microchannel plate (MCP) detector configurations with extended dynamic range. First, we report on measurements made with single MCPs of very low resistance (less than or equal to 500 k Omega) bonded to a Peltier cooler. Stable, reproducible operation for a rear-cooled MCP with 10 mu m diameter channels of length-to-diameter ratio 60:1 was achieved for biases up to 1320 V. At this point, the MCP strip current was 5.1 mA and the rate of internal heat generation, 0.78 Wcm(-2) A maximum count rate of 10(8) cm(-2)s(-1), limited by the available intensity of UV illumination, was observed, coupled to a dark noise count rate of less than 1 cm(-2)s(-1). Second, we describe a substantial (up to 20-fold) improvement in count rate capability for two-stage MCP multipliers incorporating plates with gold, rather than nichrome, electrodes. We also present, in support of the experimental study, a thermal model of bonded, conductively-cooled MCPs which we use to determine critical parameters for stable detector operation.