Simulation Design of a New MCP-PMT With Large Photocathode Area and High Time Resolution

Large area photomultiplier tube (PMT) based on microchannel plate (MCP-PMT) is newly developed and applied in Jiangmen Underground Neutrino Observatory (JUNO). Large photocathode diameter is designed to improve the photocathode coverage rate of the main detector in JUNO, which certainly induces poor time resolution. In this article, a new MCP-PMT with large photocathode and high time resolution is proposed. A novel conical focusing system with three separated electrodes is designed to generate the accelerating and focusing electric field. Three-dimensional models are developed in CST to validate its feasibility. The effects of the size and bias voltage of the focusing system and MCP are studied in detail using the finite integral technique and Monte Carlo method. Based on the simulation results, a set of geometry and operating parameters are chosen to obtain short transit time spread (TTS) and high collection efficiency (CE). Results show that the CE of the new MCP-PMT is expected to be 94.0%. The mean TTS of photoelectrons from the whole photocathode achieves 1.68 ns.