Experimental study and Monte Carlo simulation using MCC-MT code of a PGNAA HPGe spectrometer with active shielding

This paper presents the experimental study and Monte Carlo simulation of a low-background gamma spectrometer for prompt gamma neutron activation analysis (PGNAA). The gamma spectrometer is based on an HPGe detector with 30 % registration efficiency and an energy resolution of 1.65 keV at 1332 keV. A cylindrical BGO scintillation crystal, 25 mm thick and 100 mm long, was used as an anti-Compton detector. Compton Suppression Factor (CSF) was calculated for the spectra of Cs-137, Co-60 and were 4.3 and 2.4, respectively. Neutron-gamma source based on Cf-252 and Ni-target was used to calibrate and evaluate the performance of PGNAA spectrometer in the range up to 10 MeV. The presented PGNAA-spectrometer was used to test the use of the MCC-MT transport code as a tool for Monte Carlo optimization of similar systems operating on the coincidence/anti-coincidence scheme. For this purpose, a PGNAA spectrometer model was built in MСС-MT and the spectra of Cs-137, Co-60 and Eu-152 were simulated. A comparison of the simulated spectra showed good agreement with the experiment. The calculated CSF values for the simulated spectra of Cs-137 and Co-60 differ from the experimental ones by no more than 20 %. Thus, MCC-MT is an accurate, yet simple and convenient tool for optimizing the design of systems of this type.