Using SRG/eROSITA to predict soft proton induced ATHENA backgrounds

Soft protons populating the space environment have affected the performance of the X-ray detectors on board Chandra and XMM-Newton, and they pose a threat for future high energy astrophysics missions with larger aperture, such as ATHENA. In this paper, we aim to predict the soft proton induced ATHENA backgrounds from the modelling of the orbital flux obtained using eROSITA on board SRG. To this end, we analysed the background measured by eROSITA and with the help of simulations we defined a range of values for the potential count-rate of quiet-time soft protons focused through the mirror shells. We used it to derive an estimate of the orbital soft proton flux, from which the induced background for the WFI and X-IFU detectors can be predicted, assuming ATHENA in the same L2-orbit as SRG. The scaling, based on the computed proton transmission yields of the optics and optical/thermal filters, indicates that the soft proton induced WFI and X-IFU backgrounds could be expected within the requirement. Regardless of where ATHENA will be placed (L1 or L2), our analysis also suggests that increasing somewhat the thickness of the WFI optical blocking filter, e.g. by ∼30%, would help to further reduce the soft proton flux onto the detector, which might be worth in case the planned magnetic diverters perform worse than expected due to soft proton neutralisation at the mirror level.