The X-IFU instrument background
ATHENA (Advanced Telescope for High Energy Astrophysics) is the second large mission in ESA Cosmic Vision 2015-2025, with a launch foreseen in 2028 towards the L2 orbit. The mission addresses the science theme “The Hot and Energetic Universe”, by coupling a high-performance X-ray Telescope with two complementary focal-plane instruments. One of these, the X-ray Integral Field Unit (X-IFU) is a TES (Transition Edge Sensor) based kilo-pixel array, providing spatially resolved high-resolution spectroscopy (2.5 eV at 6 keV) over a 5 arcmin FoV.
Given the lack of data on the background of X-ray detectors in L2, the only viable solution to predict the background level is with the use of Geant4 simulations. The particles-induced background for this kind of detectors accounts for two components, namely the low energy particles (< ~100 keV) concentrated by the mirrors and reaching the detector from inside the field of view, and the high energy particles (> ~100 MeV) crossing the spacecraft and reaching the focal plane from every direction. In particular, these high energy particles lose energy in the materials they cross, creating secondaries along their path that can induce an additional background component. We present here the latest results obtained by the X-IFU team in the estimate and reduction of these two background components thanks to Monte Carlo simulations.