Coincidence Techniques in Gamma-ray Spectroscopy

Abstract

Abstract In many different gamma-ray detection systems, the events are registered in coincidence, i.e. within short time interval, by two or more detectors. Depending on purpose of an experiment, these events can be rejected (anticoincidence counting) or acquired (coincidence counting). The construction, setup and application of several coincidence systems in Laboratory for nuclear physics of Department of Physics in Novi sad are presented. The anti-Compton shield for HPGe detector based on big annular NaI(Tl) detector and corresponding measurement which proved existing of 283 keV level in Ba-137 populating by beta decay of Cs-137, is described. The application of this system (in addition with NaI(Tl) plug detector) where HPGe detector is actively shielded by NaI(Tl) detector for investigation of double beta decay of positron emitters (Cr-50, Zn-64,) is also shown. The improving of detection limit of HPGe detector by the active shield consisting of five plastic scintillation detectors is presented, as well as the measurements of cross sections for X-ray production, induced by interaction of cosmic-ray muons with massive lead shield. We found that the prompt and delayed coincidence events between plastic veto detector and Ge detector can be sharply divided in two groups. Also, the bremsstrahlung and annihilation events can be time resolved from (n,n’) events, although all these events belong to the group of delayed events.