Measured and simulated spectra for a 22Na source in a well counter

• Published in: Radiation measurements Vol. 121; pp. 77 - 85
• Main Authors: de Meijer, Robert J., Lindsay, Robbie, Tijs, Marco, van der Veeke, Steven, Limburg, Han
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2019
• Subjects: 22Na decay; Gamma-rays; Monte Carlo simulations; NaI well-counter; True and accidental coincident summing; Monte Carlo simulations; 22Na decay; True and accidental coincident summing; Gamma-rays; NaI well-counter
• ISSN: 1350-4487; 1879-0925
• DOI: 10.1016/j.radmeas.2018.11.009

This paper presents a test of a methodology to describe the shape of true and accidental coincidence gamma-ray spectra. The effect of the coincidence summing was enhanced by using a 50 kBq 22Na source in a NaI well counter. The spectra were described by convoluting Monte Carlo simulated spectra in a spreadsheet for true, as well accidental coincidence summing. In this paper we show that applying convolution techniques to the MCNP simulated probability spectra, not only allows a reconstruction of the shape of the true coincidence spectrum, but the simulations also prove to be an invaluable tool to understand the continuum in the spectra made up of double and even triple random coincidences. Each of these summing processes was used to generate so-called standard spectra that may be used in a full-spectrum analysis of the measured spectra to quantitatively derive the contributions of each of the summing processes. For the case presented it is shown that the accidental coincidences can be accounted for to a 0.1% level, a considerable improvement to the precision in previous papers. •A methodology is tested to describe true and accidental coincidence γ-ray spectra by convoluting MC spectra in a spreadsheet.•The simulations prove to be invaluable to understand the continuum in the spectra by 2nd and triple random coincidences.•Accidental coincidences can be accounted for to a 0.1% level, a considerable improvement in precision.