Calibration of semiconductor detectors in the 200–8500 keV range at VNIIM

Abstract

At the ionising radiation department of the D.I. Mendeleyev Institute for Metrology, a semiconductor detector was calibrated in the energy range 200–8500keV using (n,2γ) and (n,γ) reactions.Separate cylindrical targets (77mm diameter and 10mm height) were made from mercuric sulphate, sodium chloride and metallic titanium. A 252Cf spontaneous fission neutron source, placed in 150mm diameter polyethylene ball, was used to generate thermal neutrons. The optimal target dimensions were determined taking into account the thermal neutron cross-sections and gamma-radiation attenuations in the target materials. The influence of the background radiation induced by neutrons from the walls, floors and ceilings was also taken into account. The shapes of the efficiency curves for point and volume sources in the 200–8500keV range have been investigated. The experimental results are in good agreement with Monte-Carlo calculations.The emission rate of the 6.13MeV photons from a 238Pu–13C source was determined with an expanded uncertainty, Uc, of 10% (k=2).