Absolute efficiency of a two-stage microchannel plate for electrons in the 30 - 900 eV energy range

TL;DR

This study measures the absolute detection efficiency of a two-stage microchannel plate for electrons between 30 and 900 eV, demonstrating high stability, detailed pulse shape analysis, and event discrimination capabilities.

Contribution

It provides the first precise efficiency measurement of a chevron MCP in the 30-900 eV range and introduces a method to distinguish single- and multi-electron events based on pulse shape analysis.

Findings

Efficiency of (0.489 ± 0.003) with no energy dependence

Pulse shape is quasi-Gaussian with a peak above noise

Method to discriminate electron events within 10 ns

Abstract

We report on an apparatus able to measure the absolute detection efficiency of a detector for electrons in the 30 - 900 eV range. In particular, we discuss the characterisation of a two-stage chevron microchannel plate (MCP). The measurements have been performed in the LASEC laboratory at Roma Tre University, whit a custom-made electron gun. The very good stability of the beam current in the fA range, together with the picoammeter nominal resolution of 0.01 fA, allowed the measurement of the MCP absolute efficiency $\epsilon$. We found an $\epsilon$ = (0.489 $\pm$ 0.003) with no evident energy dependence. We fully characterised the MCP pulse shape distribution, which is quasi-Gaussian with a well visible peak above the noise level. We measured a 68% variation of the average pulse height between 30 and 500 eV. Furthermore, with a deeper analysis of the pulse shape, and in particular of the correlation between pulse height, area and width, we found a method to discriminate single- and multi- electron events occurring within a 10 ns time window.