Monte Carlo simulations and experimental study of a symmetric AGATA prototype detector

This work presents a Monte Carlo (MC) and experimental study of a segmented AGATA prototype germanium (Ge) detector called S003 which has been delivered by Canberra France. The study aims to compare the simulated and measured absolute efficiencies for the whole detector and the individual segment´s photo-peak efficiencies. The absolute efficiency of the detector and the intensity profiles of each segment of the detector are measured with the IPN CSNSM Orsay scanning system. The same quantities are estimated by detailed MC simulations with the PENELOPE v. 2008 code. Qualitatively, both methods agree on the expected features of a segmented detector - the efficiency is higher near the centre of the segments and decreases near the segment boundary. However, the experimental decrease of the efficiency near the segment edges is steeper than the simulated one. There are also differences between the MC efficiency profiles and experimental data. According to the MC simulations the highest efficiency of the detector should be obtained near the edges of the fourth ring, which is not observed in the experimental data. Another disagreement is observed between the efficiency profiles of the first and second rings. According to the MC simulations the segments on the second ring should have considerably higher efficiency compared to the segments on ring one. According to the experimental data, the segments on ring one have higher efficiencies than those on ring 2. The MC estimated efficiencies of the detector for a ¹⁵²Eu source at 25 cm are systematically higher than the measured efficiencies, reported in Ref. [1]. Work is in progress to identify the origin of these discrepancies.