Breakthrough in the lifetime of microchannel plate photomultipliers

Abstract Cherenkov detectors using the DIRC (Detection of Internally Reflected Cherenkov Light) principle are foreseen for particle identification in the P ¯ ANDA experiment at FAIR. Promising sensors for the detection of the Cherenkov light are the so-called micro-channel plate (MCP) photomultipliers (PMT). They have an excellent time resolution, can be operated at high gain for single photon detection and have a high resistivity against magnetic fields. The disadvantage of these devices was their limited lifetime, due to damage by feedback ions on the photocathode. The lifetime of various types of MCP-PMTs from different manufactures has been tested under conditions similar to that in the P ¯ ANDA experiment. The sensors are assembled in one setup, to ensure the same illumination conditions. The measurement procedure requires permanent monitoring of the illumination and interruptions after about 2–3 weeks to measure dark count rate, gain and spectral quantum efficiency of all sensors. Furthermore surface scans of the whole photocathode are done every 2–4 months to determine faster aging areas. The latest results show very good lifetime performance for MCP-PMTs, where the MCPs have been treated with the atomic layer deposition (ALD) technique.