Lifetime of MCP–PMT

To examine the lifetime of a micro-channel plate photo-multiplier tube, we measured its basic performance, gain, quantum efficiency (QE), transit time spread and dark counts as a function of the integrated amount of irradiated photons up to 2.8×1014photons/cm2, corresponding to a 14-year time duration under supposed super-KEKB experimental conditions. The effect of the ion-feedback protection layer was clearly detected and the deterioration of the photo-cathode functioning was examined in terms of the QE spectrum on the light wavelength.