THE REGISTRATION OF Cs-134 BY GAMMA DETECTOR PAIRS AT AN ANGLE OF 90°

Three NaI(Tl) detectors and two pairs of NaI(Tl) detectors at an angle of 90 -from the six-crystal spectrometer PRIPJAT-2M (Faculty of Natural Sciences and Mathematics, University of Montenegro, Podgorica), were used to determine registration efficiencies for the most intense gamma rays in de-excitation of 134 Ba, following beta minus decay of 134 Cs.The 134 Cs liquid calibration standard was used for acquiring spectra over 18 000 s real time in the energy range (200-3000) keV -in the integral, non-coincident and mode of double gamma-gamma coincidences.All the spectra from individual detectors and detector pairs in all the counting modes clearly showed peaks at the 605 and 796 keV.The experimental registration efficiency of the 605 keV gamma ray by individual detectors in different modes of counting was found to be with an average of 0.055 (integral), 0.032 (non-coincident) and 0.021 (double coincidences), whilst in the case of two detector pairs -0.112 (integral), 0.065 (non-coincident) and 0.042 (double coincidences).In regards to the 796 keV, average detection efficiencies were 0.04 (integral), 0.026 (non-coincident) and 0.013 (double coincidences) -in the case of individual detectors, and 0.076 (integral), 0.048 (non-coincident) and 0.026 (double coincidences) -for the detector pairs.Obtained results are baselines for the future development of the coincidence method for 134 Cs measurement -using multidetector systems with measuring geometry close to 4π, with the 796 keV photopeak in a coincidence mode as appropriate for 134 Cs detection in a sample containing 137 Cs and decay products of 226 Ra and 232 Th.