Speaker
Description
Authors: M.-C. Lépy 1, C. Thiam 1, M. Anagnostakis 2, C. Cosar 3, A. De Blas del Oyo 4, H. Dikmen 5, M.A. Duch 4, R. Galea 6, M.L. Ganea 3, M. Hult 7, S. Hurtado 8, K. Karfopoulos 9, A. Luca 3, G. Lutter 7, I. Mitsios 2, H. Persson 9, C. Potiriadis 10, S. Röttger 11, N. Salpadimos 10 M.I. Savva 12, O. Sima 3,13, T.T. Thanh 14, R. Townson 6, A. Vargas 4, T. Vasilopoulou 12, L. Verheyen 15, T. Vidmar 15
Affiliations: 1 LNHB, France, 2 NTUA, Greece, 3 IFIN-HH, Romania, 4 UPC, Spain, 5 TENMAK, Turkey, 6 NRC, Canada, 7 JRC-Geel, Belgium, 8 U-Sevilla, Spain, 9 Mirion Technologies, Inc, USA, 10 EEEA, Greece, 11 PTB, Germany, 12 NCSR “Demokritos”, Greece, 13 U. Bucharest, Romania, 14 VNUHCM, Vietnam, 15 SCK-CEN, Belgium.
Monte Carlo simulations are now widely used in gamma-ray spectrometry to calculate either the detection efficiency or the true coincidence summing correction factors. However, running the calculations is not always easy for new users, and errors in defining the geometry files for the Monte Carlo computer codes, as well as misinterpretations of their outputs, often lead to incorrect results. Within the ICRM Gamma-ray Spectrometry Working Group (GSWG), an action had been initiated to prepare sample geometry files for the commonly used Monte Carlo software for selected calculation cases in order to provide a benchmark for new users. The first part of this action was devoted to the calculation of detection efficiencies [1]. A further step focuses on coincidence summing corrections. In this second part, the same simulated measurement setups were considered as for the calculation of efficiencies and the relatedgeometry description files for the different Monte Carlo codes had already been made available on the ICRM GSWG webpage [2]. The resulting coincidence summing correction factors for the eight simulated setups concerned radionuclides with characteristic decay schemes: 60Co and 134Cs are beta minus emitters, 133Ba decays by electron capture accompanied by intense X-ray emission, while 22Na decays by both electron capture and beta plus emission, the latter leading to the emission of annihilation photons.Seven different computer codes (EFFTRAN, EGSnrc, EGS4, GEANT, GESPECOR, MCNP and PENELOPE) were considered in this exercise and 20 series of results were collected from the participants and analysed.Initially discrepancies were observedbetween the results of different users of the same code, especially for 133Ba and the N-type detector model, which emphasized the important role of proper treatment of X-rays in the calculations. A comparative analysis of the decay data tables used by the different codes showed that they are not a major source of deviations between the results. The importance of the peak area determination procedures(subtraction of the background) was highlighted. Further calculations with harmonized simulation conditions were conducted to reach better agreement between the participants. The results of this collaborative work make possible a derivation of practical recommendations for the training of new users, in order to avoid typical simulation errors. The benchmark results (correction factors) will be made available and discussed on the ICRM GSWG webpage, along with practical recommendation for their use.
[1] Applied Radiation and Isotopes, Volume 154, December 2019, 108850
[2] http://www.lnhb.fr/icrm_gs_wg/icrm_gs_wg_benchmarks/
