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

Abstract

In the present work, we introduce the theoretical development and a new approach to validate a novel method to calibrate the efficiency of a gamma radiation detector for point sources, which we have named the “Efficiency Extrapolation Method”.

The method consists in the determination of the detector efficiency using a set of monoenergetic gamma sources, which we will refer to as reference efficiencies. From these values, we will extrapolate the detector efficiency to the complete energy range using the first principle physics of gamma radiation detection theory. Therefore the proposed method corresponds to a semi-empirical one.

The determination of reference efficiencies must be done experimentally, but in this work, simulations were performed using FLUKA code. The reference energies will be: 59,54 keV, 661,66 keV and 1 274,54 keV associated to the isotopes ²⁴¹Am, ¹³⁷Cs and ²²Na respectively. The second part of the method, the extrapolation from the reference energies to the gamma range, will be done over the energies emitted by ¹⁵²Eu and ¹³³Ba.

In general, the results are very good. While the obtained results for energies 53,16 keV and greater than 344,3 keV show an excellent agreement, the results obtained for energies in the middle range are only good.