CALIBRATION OF DETECTORS FOR SOFT GAMMA-RAY ASTRONOMY - THE MONTE-CARLO APPROACH APPLIED TO THE SIGMA-TELESCOPE

The general problem of calibrating soft gamma-ray (100 keV-1 MeV) detectors is illustrated in the case of the SIGMA experiment. Particularly, the advantage of coded mask experiments for spectroscopy and the related specific calibration difficulties are considered. It is shown that a Monte Carlo simulation can separate in the spectrum the components due to the experiment itself and those due to the scattering in the environment and permits to take into account experimental configuration modifications after the calibrations. A very detailed geometrical description of the SIGMA telescope is proposed and its in-flight energy response is estimated from Monte Carlo simulations.