Reducing the Athena WFI charged particle background: Results from Geant4 simulations

TL;DR

This paper presents Geant4 simulation results to understand and reduce charged particle background in the Athena WFI, aiming to improve detection of faint cosmic X-ray sources.

Contribution

It introduces a novel analysis of cosmic ray interactions with Athena's WFI using Geant4 simulations to identify background reduction strategies.

Findings

Identification of correlations between cosmic ray tracks and false X-ray events.

Potential methods for flagging or rejecting background events in ground processing.

Insights applicable to other silicon-based space X-ray detectors.

Abstract

One of the science goals of the Wide Field Imager (WFI) on ESA's Athena X-ray observatory is to map hot gas structures in the universe, such as clusters and groups of galaxies and the intergalactic medium. These deep observations of faint diffuse sources require low background and the best possible knowledge of that background. The WFI Background Working Group is approaching this problem from a variety of directions. Here we present analysis of Geant4 simulations of cosmic ray particles interacting with the structures aboard Athena, producing signal in the WFI. We search for phenomenological correlations between these particle tracks and detected events that would otherwise be categorized as X-rays, and explore ways to exploit these correlations to flag or reject such events in ground processing. In addition to reducing the Athena WFI instrumental background, these results are applicable to understanding the particle component in any silicon-based X-ray detector in space.