R&D on the Extension of the MCP-PMT Lifetime

Abstract

A Micro-Channel-Plate PMT (MCP-PMT) has an excellent time resolution, but the disadvantage is a short photocathode lifetime, which means a drop of the quantum efficiency. It is a major issue for application to detectors at high intensity experiments, such as the Belle II experiment. We succeeded in improving the lifetime of the MCP-PMT by suppressing the residual gas and applying atomic layer deposition. To extend the lifetime further, understanding the mechanism of the photocathode deterioration is essential. Therefore we studied correlations of the amount of ions with the lifetime by analyzing the after-pulse. The results indicate that the cause of the photocathode deterioration could be hydrogen ions, heavy ions (mass number larger than 100), or neutral gas.