Review of the particle background of the Athena X-IFU instrument
  X-ray observations are limited by the background, due to intrinsic faintness
or diffuse nature of the sources. The future Athena X-ray observatory has among
its goals the characterization of these sources. We aim at characterizing the
particle-induced background of the Athena microcalorimeter, in both its low
(Soft Protons) and high (GCR) energy induced components, to assess the
instrument capability to characterize background dominated sources such as the
outskirts of clusters of galaxies. We compare two radiation environments,
namely the L1 and L2 Lagrangian points, and derive indications against the
latter. We estimate the particle-induced background level on the X-IFU
microcalorimeter with Monte Carlo simulations, before and after all the
solutions adopted to reduce its level. Concerning the GCR induced component the
background level is compliant with the mission requirement. Regarding the Soft
Protons component, the analysis does not predict dramatically different
backgrounds in the L1 and L2 orbits. However, the lack of data concerning the
L2 environment labels it as very weakly characterizable, and thus we advise
against its choice as orbit for X-ray missions. We then use these background
levels to simulate the observation of a typical galaxy cluster from its center
out to 1.2 R200 to probe the characterization capabilities of the instrument
out to the outskirts. We find that without any background reduction it is not
possible to characterize the properties of the cluster in the outer regions. We
also find no improvement of the observations when carried out during the solar
maximum with respect to the solar minimum conditions.
