DETERMINATION OF THE COINCIDENCE SUMMING CORRECTION FACTOR IN THE MEASUREMENT OF THE EXPERIMENTAL EFFICIENCY OF SEMICONDUCTOR DETECTOR

Tóm tắt

The detection efficiency of the semiconductor detector is an important factor, which directly impacts the experimental results of the instrumental neutron activation analysis. The efficiency curve was determined by the measurements of some standard sources including 137Cs, 109Cd, 133Ba, 60Co, 152Eu, 57Co. However, for the multi-energy radioisotopes emitting more than two gammas, the coincidence summing effect appears when both gammas originating from a disintegration of an excited nucleus are detected within the resolving time of the detector. The coincidence effect is more significant at near source-detector distances and the measured efficiency is thus significantly different from the true value. In this paper, the coincidence effect has been determined at four positions and evaluated at two positions from the detector window as well. The activities of 133Ba and 60Co sources were determined at the positions H3 and H1 by using the corrected efficiency with the bias deviations were -3.9% and -4.2% for 133Ba. Besides, the bias deviations obtained -3.4% and -0.3% for 60Co source. This result was significantly better than the result which was determined by the experimental efficiency with the bias deviations of 5.7%and 12% for 133Ba and -0.9%and 4.1% for 60Co.