Particle Background on the Athena WFI

We are working to understand and mitigate the effect of particle background in future and current space-based X-ray observatories so that we can detect the faintest, most diffuse hot gas in the outskirts of galaxy clusters and intergalactic space.


Particle tracks from 1 million cosmic ray protons

Particle tracks from 1 million cosmic ray protons interacting with the Athena WFI, as simulated by our group using Geant4. This image is just for illustration, as the short individual exposures of the WFI will each contain a handful of such tracks.

The Wide-Field Imager (WFI) due to fly on the ESA-led Athena mission in the 2030s will address astrophysics questions of particular interest to our group, including a planned deep survey to detect groups and clusters of galaxies in the early Universe and to explore the very faint out parts of nearby clusters where they accrete matter from intergalactic space. These challenging observations require a careful removal of the particle-induced background at the expected Athena orbit. Members of our group are working with collaborators in Europe and at several US institutions as part of the Athena WFI Background Working Group to understand the level and variability of this background, largely produced by Galactic cosmic rays whose flux is modulated by Solar activity on a variety of timescales. This work builds on our extensive operational experience with our flight instruments and includes simulating the interaction of  high-energy cosmic-ray protons with the WFI instrument structure. We use the Geant4 tool set, and produce simulated WFI observations that include the background signal generated by these interactions. Our goal is to develop background mitigation strategies to enhance the science return of the WFI deep survey. Further information can be found in the following sources:

Team Members