A Study on Efficiency Error in Distance Inverse Square Law using Cylinder NaI(Tl) Scintillation Detector

Abstract

Generally, it's known fact that intensity of radioactivity satisfies inverse-square law. However, the law was dissatisfied with practical experiment because of limited shape of scintillation detector. Especially, in the case of near distance between the surface of detector and the radioactive source, the difference grows larger. In the present study, reason of this difference was confirmed by experiment with 2˝×2˝ø NaI(Tl) scintillation detector and 60 Co(1.174 MeV, 1.333 MeV)and 137 Cs(0.662 MeV) gamma ray sources. From the experiment, the correction coefficient was obtained with gamma ray detection efficiency and geometrical volume. In the result of the present study, the efficiency difference of the detector was corrected with the coefficient. In the present result, we obtained that the inverse-square law experiment have to consider the efficiency and geometrical value of the detector.