Development of coincidence summing and resolution enhancement algorithms for digital gamma ray spectroscopy

Abstract

This paper discusses the correction of some of the main problems of digital gamma ray spectroscopy. These problems are the coincidence summing and energy resolution. The coincidence summing effects are evaluated using analytical techniques. Correction is made at different energies for both ¹³⁷Cs and ⁶⁰Co radioisotopes. A simple relation is derived between the coincidence summing correction factor and the energies under the conditions of the system configuration. This relation is deduced using the least square approximation method. Consequently, correction can be done at different energies of radiation sources under the constraints of the measured conditions. Furthermore, the coincidence summing algorithm is validated through comparison with published experimental results in the literature and good agreement is found. Coincidence summing correction factors are used to correct the values of the Full Energy Peak (FEP) efficiencies. Correction factors were calculated for predominant gamma emissions significantly affected by coincidence summing effects for both ¹³⁷Cs and ⁶⁰Co point sources. Also, a correction algorithm for the resolution–degradation in scintillation (NaI (TI)) gamma ray detectors using derivative methodology is presented. The derivative methodology is implemented by weighted sum of the original signal, the negative of its second derivative and the positive of its fourth derivative. We noticed that using both derivatives in combination improves the energy resolution, which is enhanced by 24.03%. From the obtained results, the FEP efficiency was enhanced by 1.58% due to coincidence summing correction. Consequently, accurate determination for the source activity can be achieved.