Absolute full-energy peak efficiency calibration of a Clover–BGO detector system

An absolute full-energy peak efficiency calibration of a Clover-type composite germanium gamma-ray detector system is presented. The efficiency curve was measured in the energy range of 120 keV–12.2 MeV for the first time, using the combination of proton-capture nuclear reactions and radioactive sources, such as 56Co, 60Co, 66Ga and 152Eu. At high energies gamma-ray pairs from proton resonance capture on 27Al, 23Na, 39K and 11B were employed using evaporated Al, Na2WO4, K2SO4 and LiBO2 targets, respectively. The experimental data were fitted with a single polynomial function on log–log scale using a recently developed method. The add-back factor is found to increase quadratically with the energy, in contrast to the previously suggested linear relationship. The efficiency gain with respect to a single detector is about one order of magnitude at 10 MeV energy.