Characterisation of the LAPPD, a large area microchannel-plate PMT

TL;DR

This paper thoroughly characterizes the LAPPD Gen-II MCP-PMT, analyzing its timing and charge distribution, developing models to predict performance, and providing insights for optimizing detectors in physics and medical imaging.

Contribution

It introduces a comprehensive analytical model for the LAPPD Gen-II MCP-PMT, linking device geometry and materials to performance metrics.

Findings

Timing resolution of approximately 30 ps achieved

Model accurately reproduces measured properties

Framework enables performance optimization for various applications

Abstract

We present a comprehensive characterization of the LAPPD Gen-II, a large-area microchannel-plate photomultiplier tube (MCP-PMT) equipped with a capacitively coupled sensing (readout) electrode. Two detector variants with different geometries and materials were investigated using a picosecond pulsed laser system. We measured the single-photon timing response and spatial charge distribution on segmented readout electrodes. The prompt timing peak exhibits a resolution of approximately 30 ps, with the overall timing structure explained by photoelectron propagation and back-scattering effects from the MCP input surface. We developed analytical models that describe the propagation of photoelectrons and the induced charge spread on the sensing electrodes, including secondary electron backscattering from the resistive anode. The model accurately reproduces the measured device properties and enables performance extrapolations for various detector geometries and dielectric properties. These results provide a predictive framework for optimizing MCP-PMTs for timing- and imaging-critical applications such as RICH detectors in high-energy physics and TOF-PET systems for medical imaging.