Simulating the secondary electron avalanche of MCP by Geant4

TL;DR

This paper uses Geant4 simulations to analyze how the geometry of curved-channel MCPs affects secondary electron gain, aiming to optimize pore diameter and improve noise performance in high-sensitivity experiments.

Contribution

It introduces a Geant4-based simulation method to study the influence of geometrical parameters on MCP gain and identifies optimal pore diameter for maximum gain.

Findings

Optimal pore diameter for maximum gain identified as 20 um.

Average secondary electron acceleration distance is approximately 20 um.

Curved-channel MCPs significantly reduce ion feedback compared to straight-channel MCPs.

Abstract

Nowadays, Microchannel Plate (MCP), as a kind of electron multipliers based on the secondary electron emission, is widely used in many high-sensitive experiments, such as neutrino detection, which require the noise to be as low as possible, while the conventional straight-channel MCP will inevitably have ion feedback, resulting in the sequential after-pulses being the major source of noise. Normally, the problem can be effectively avoided by coupling two straight-channel MCPs in cascade and combining the channels into a `V` shape known as chevron MCPs, but this method is limited by the manufacturing techniques due to the unavoidable gap between the two pieces that will worsen the resolution and peak-to-valley ratio. However, the ion feedback can be inhibited significantly for MCPs with curved channels. Based on Geant4, we investigate how the geometrical parameters of curved-channel MCP influence the gain and get the optimum pore diameter for an MCP to reach the maximum gain with fixed thickness and applied voltage. Additionally, the track-by-track simulation reveals that the average acceleration distance of a secondary electron inside the curved-channel is approximately 20 um when the applied voltage, length-to-diameter ratio and pore diameter are 950 V, 50:1 and 20 um, respectively.