Proton-induced background in LEGRI

The Low Energy Gamma Ray Imager (LEGRI) on board the Spanish MINISAT-01 mission is a position-sensitive γ-ray instrument with a 10 × 10 HgI2 elements array on the detector plane. This telescope is dedicated to imaging of astrophysical sources in the 20–200 keV spectral range. In the framework of LEGRI sensitivity evaluations, one of the focal points is the determination of the background noise induced by the cosmic and trapped proton flux. To achieve an accurate estimation of this background noise component, small HgI2 crystals were irradiated with high energy protons at SATURNE (Saclay, France). After the identification of the unstable isotopes generated by the proton flux, their production rates were calculated. The experimental data were compared with the results obtained by a Monte Carlo simulation code. Since a good agreement between both experimental and simulation results was observed, these last ones have been used to perform full calculations of the proton-induced background in LEGRI. The information provided by these calculations has been used to estimate an upper limit of LEGRI sensitivity.