Study of the homogeneity of a NaI(Tl) detector

Resumo

The NaI(Tl) detector is one of the most used in gamma ray spectrometry because it presents high counting efficiency for gamma rays in a wide range of energy. The crystal can have a lower efficiency that can be indicated by the effects of its aging by several factors such as: the reaction of sodium iodide with magnesium oxide, absorption of water vapor by crystal, and problems related to photomultiplier. Through the spectrum of a measurement, it is possible to know the counting area of the photopeak. In an experiment, several measures can be take and when a doubt exists between one of the measured values it is possible to use a statistical test. Grubbs test is designed to verify the presence of extreme values in sample observations. This work presents a methodology that has the objective of evaluating the homogeneity of a NaI(Tl) scintillation detector using the Grubbs test to validated the crystal homogeneity. For this, it was necessary to calculate the means and the standard deviation for the determined points in the detector. The value found for such measures was 17384 and 157.367, for points P1, P2, P3 and P4 and 20706.67 and 146.4423 for point Center, respectively. Was used a standard source of 137Cs.