Absolute ion detection efficiencies of microchannel plates and funnel microchannel plates for multi-coincidence detection

TL;DR

This paper measures and compares the absolute detection efficiencies of different microchannel plates, including funnel MCPs, demonstrating significant improvements for multi-coincidence detection in molecular fragmentation studies.

Contribution

It provides the first absolute efficiency measurements for funnel MCPs and evaluates their performance in multi-ion coincidence detection.

Findings

Funnel MCPs achieve about 90% efficiency.

Funnel MCPs increase five-fold coincidence detection efficiency by a factor of 24.

Relative efficiencies for multi-fragment detection are characterized.

Abstract

Modern momentum imaging techniques allow for the investigation of complex molecules in the gas phase by detection of several fragment ions in coincidence. For these studies, it is of great importance that the single-particle detection efficiency e is as high as possible, as the overall efficiency scales with e over n, i.e. the power of the number of detected particles. Here we present measured absolute detection efficiencies for protons of several micro-channel plates (MCPs), including efficiency enhanced "funnel MCPs". Furthermore, the relative detection efficiency for two-, three-, four-, and five-body fragmentation of CHBrClF has been examined. The "funnel" MCPs exhibit an efficiency of approx. 90 percent, gaining a factor of 24 (as compared to "normal" MCPs) in case of a five-fold ion coincidence detection.