Summing coincidence in rare event gamma-ray measurements under an ultra-low background environment

Full-energy peak (FEP) efficiencies of a HPGe detector equipped with an ultra-low background shield system are calibrated with the Monte Carlo method and further examined using summing peaks in a numerical way. Radionuclides $^{241}$Am, $^{137}$Cs, $^{60}$Co, $^{133}$Ba and $^{152}$Eu are used to construct the simulation model with the toolkit GEANT4. True summing \mbox{coincidence} factors (TSCFs) of $^{60}$Co, $^{133}$Ba and $^{152}$Eu are calculated and result in an improvement up to about 20\% in the FEP efficiency curve. Counts of summing coincidence $\gamma$ peaks in the spectra of $^{60}$Co and $^{152}$Eu can be well reproduced using the corrected efficiency curve within an accuracy of 3\%.

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Affiliations: 1Tsinghua University, china, 2Tsinghua University, china, 3Chinese Academy of Sciences, China, 4Chinese Academy of Sciences, China, 5Tsinghua University, china, 6Tsinghua University, china, 7Chinese Academy of Sciences, China, 8Tsinghua University, china, 9Chinese Academy of Sciences, China, 10Tsinghua University, china, 11Tsinghua University, china, 12Tsinghua University, china, 13Tsinghua University, china, 14Chinese Academy of Sciences, China, 15Chinese Academy of Sciences, China, 16Tsinghua University, china, 17Chinese Academy of Sciences, China, 18Chinese Academy of Sciences, China, 19Chinese Academy of Sciences, China, 20Chinese Academy of Sciences, China, 21Tsinghua University, china

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