Photoelectron backscattering in the microchannel plate photomultiplier tube

Highlights: • The physical processes leading to an output pulse of the MCP-PMT are analyzed. • The effects of the secondary emission yield (SEY) property of the MCP input facet and the electric field on the photoelectron backscattering are investigated. • Both the timing and the collection efficiency of the later pulses are studied. • Solutions to improve the collection efficiency and the timing performance of the MCP-PMT are discussed. The late pulse occurring in photomultiplier tubes (PMTs) is attributed to photoelectron backscattering. The small effective open area of microchannel plates (MCPs) increases the probability of photoelectrons bouncing on the front surface of MCPs and aggravates late pulses. In this work, a three-dimensional MCP-PMT model is developed in CST particle studio, a powerful electromagnetic field simulation program, to evaluate the effects of secondary emission yield (SEY) property of the MCP input facet and electric field on the photoelectron backscattering. Timing properties and the number of collected electrons are extracted without smearing due to electronic noise and finite pulse width. Results predict that the collection efficiency (CE) and the time performance can be improved by coating the MCP Nickel–Chromium input electrode with a high SEY material and operating in a proper photocathode-MCP bias voltage.