Comparative Lifetesting Results for Microchannel Plates in Windowless EUV Photon Detectors

Microchannel plates (MCP´s) from seven manufacturers were subjected to a series of tests to determine their suitability for the Extreme Ultraviolet Explorer satellite. Comparative data are presented for sixteen MCP tandem pairs with channel length to diameter ratios (I/d´s) ranging from 40:1 to 60:1 and for two saturable (curved channel) MCP´s with I/d´s of 80:1. Results for MCP´s with funnelled channel throats are also discussed. Properties of the MCP´s which were monitored include: background count rate, output charge pulse height distribution (PHD), modal gain, PHD full width half maximum (FWHM), and extreme ultraviolet (EUV) photon quantum efficiency. Five detectors were chosen for further lifetime testing consisting of a mild bake to 100°C, and charge extraction to 10-2 coulombs, repeated high voltage cycling and reexposure to one atmosphere conditions. The results of these tests and their implications for the flight detectors are discussed. Erratic events in the detector background were recorded, probably due to field emission from high voltage surfaces or the absorption of water vapor into the electrode following exposure to air. The steps taken to control the detector background are discussed.