Calibration of a low-level anti-Compton underground gamma-spectrometer by experiment and Monte Carlo

•A Compton-suppressed spectrometer using a big n-type HPGe detector was calibrated.•Coincidence effects on peak efficiency (suppressed and direct modes) were evaluated.•GESPECOR code was extended for simulation of the Compton-suppressed spectrometer.•Monte Carlo results are in good accordance with experimental values.•The code is useful for spectrometer calibration as well as geometrical optimization.

In this work we present the experimental and Monte Carlo calibration of the Compton-suppressed spectrometer of the IAEA's Environment Laboratories, Monaco. For this purpose the GESPECOR code was extended to include the specific geometry and to implement the veto logic, integrated with the coincidence summing module of the code. The simulation results are in good accordance with experimental calibrations. The code is fast and user-friendly, able to evaluate the efficiency and the correction factors for nuclides with arbitrary complex decay schemes.