An updated approach to the study of proton propagation in the eROSITA mirror system

The German telescope eROSITA will be the first X-ray instrument orbiting around the L-2 lagrangian point. Therefore, modelling the radiation environment in that region of space and its interaction with the instrument is particularly important, as no measured data of other X-ray detectors can be used as a reference to predict how the space conditions will impact the instrumental capabilities. The orbit around L-2 extends well beyond the Earth's magnetosphere, where the flux of galactic cosmic particles is cut by the geomagnetic field, and fluxes of energetic particles one order of magnitude higher than in low Earth orbits are expected. Furthermore, as experienced by Chandra and XMM-Newton, softer protons may be scattered through the mirror shells and funneled to the focal plane, representing a potential additional source of background. To investigate and assess this component we are developing a ray tracing simulator for protons, that follows the track of each proton from the entrance pupil down to the focal plane. In this paper we report on an updated version of the code that allows to propagate protons in both the polar and azimuthal directions in elastic regime.