Nuclear Science and Techniques

《核技术》(英文版) ISSN 1001-8042 CN 31-1559/TL     2019 Impact factor 1.556

Nuclear Science and Techniques ›› 2016, Vol. 27 ›› Issue (4): 84 doi: 10.1007/s41365-016-0090-x

• NUCLEAR ELECTRONICS AND INSTRUMENTATION • Previous Articles     Next Articles

Extraction of full energy peak of 137Cs from in situ NaI (Tl) gamma-ray spectrum

Le-Le Zhang, Nan-Ping Wang , Bao-Chuan Li   

  1. 1 School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China
  • Contact: Nan-Ping Wang E-mail:npwang@cugb.edu.cn
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (No. 41474107).

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Le-Le Zhang, Nan-Ping Wang, Bao-Chuan Li. Extraction of full energy peak of 137Cs from in situ NaI (Tl) gamma-ray spectrum.Nuclear Science and Techniques, 2016, 27(4): 84     doi: 10.1007/s41365-016-0090-x
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Abstract:

A Levenberg–Marquardt Gaussian fitting algorithm has been used for analyzing the overlap of three peaks (the 583-keV peak of 208Tl, the 609-keV peak of 214Bi, and the 662-keV peak of 137Cs) using an in situ NaI (Tl) scintillation spectrometer. The algorithm, in addition, was compared with a genetic algorithm used for multiple deconvolution. The three fitted peak areas (583, 609, and 662 keV) were calculated from the measured gamma-ray spectra obtained from a simulation experiment in which a 137Cs source was buried at different soil depths (from 18 to 38 cm). The application of the Levenberg–Marquardt algorithm yielded similar results compared to the genetic algorithm. A lack-of-fit test showed that the fitting is good when the instrumental noise levels were estimated from replicated analyses. The relative fitting error of the total net area and the residual standard deviation were within 5 % and 0.04, respectively, and the goodness of the fitting was better than 0.98. While the methods used in this paper give high performance, the results may lead to incorrect estimation when the signal-to-noise ratio is smaller than ?30 dB. This study is useful for the determination of radioactive specific activity of 137Cs by in situ spectrometry.

Key words: NaI (Tl) detector,  Gamma-ray spectrum,  Levenberg–Marquardt algorithm,  Overlapping-peak, decomposition,  Curve fitting