PROTON-INDUCED BACKGROUND IN LEGRI

The Low Energy Gamma Ray Imager (LEGRI) on board the Spanish MINISAT-0 1 mission is a position-sensitive gamma-ray instrument with a 10x10 Hg I2 elements array on the detector plane. This telescope is dedicated t o imaging of astrophysical sources in the 20-200 keV spectral range. I n the framework of LEGRI sensitivity evaluations, one of the focal poi nts is the determination of the background noise induced by the cosmic and trapped proton flux. To achieve an accurate estimation of this ba ckground noise component, small HgI2 crystals were irradiated with hig h energy protons at SATURNE (Saclay, France). After the identification of the unstable isotopes generated by the proton flux, their producti on rates were calculated. The experimental data were compared with the results obtained by a Monte Carlo simulation code. Since a good agree ment between both experimental and simulation results was observed, th ese last ones have been used to perform full calculations of the proto n-induced background in LEGRI. The information provided by these calcu lations has been used to estimate an upper limit of LEGRI sensitivity.