Development of a semi-empirical method to determine the efficiency of a gamma radiation detector

Abstract

In the present work we present the development of a new method to calibrate the Full energy peak (FEP) efficiency of a gamma radiation detector. The method consists of the experimentally determination of the detector efficiency for an energy using a monoenergetic gamma source and from this value to extrapolate constructing the complete detector efficiency curve using the physics of first principles of gamma detection theory. For this reason the proposal method corresponds to a semi-empirical method.In this first work we show the application and the study for the validation of the method by means of simulations based on the Monte Carlo method using FLUKA code. The energies considered in the simulations correspond to those emitted by the radioisotopes 137Cs, for the determination of the efficiency for one energy we will call reference efficiency, and 152Eu, to perform the extrapolation of the intrinsic efficiency from the reference efficiency.So far, we have calibrated the total instrinsic efficiency of a bare cylindrical detector by applying the proposed method. A systematic difference between the expected values of the intrinsic efficiency obtained by statistical count for the 152Eu gamma energies, and those determined by the proposed method is observed. Despite this, the results show a good agreement with relative biases less than 5% in most cases.One of the principal advantages of this method is that it let us obtain a calibration curve with all phenomenology involved in the detection, such as the resonance peaks.