Abstract
Effect factors of the absorption of the source, air, entrance window, and dead layer of a detector must be considered in the measurement of monoenergetic alpha particles, along with statistical noise and other factors that collectively cause the alpha spectrum to exhibit a well-known low-energy tail. Therefore, the establishment of an alpha spectrum detector response function from the perspective of a signaling system must consider the various factors mentioned above. The detector response function is the convolution of an alpha-particle pulse function, two exponential functions, and a Gaussian function, followed by calculation of the parameters of the detector response function using the weighted least-squares fitting method as proposed in this paper. In our experiment, 239Pu alpha spectra were measured by a high-resolution, passivated implanted planar silicon (PIPS) detector at 10 levels of vacuum and 10 source-detector distances. The spectrum-fitting results were excellent as evaluated by reduced Chi-square (χ 2) and correlation coefficients. Finally, the variation of parameters with vacuum level and source-detector distance was studied. Results demonstrate that σ, τ1, and τ2 exhibit no obvious trend of variation with vacuum in the range 2000–20,000 mTorr, and at a confidence level of 95%, the values of τ1 and τ2 decline in a similar fashion with source-detector distance by the power exponential function, while the value of σ declines linearly.
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This work was supported by the National Natural Science Foundation of China (Nos. 41374130 and 41604154), Opening Foundation of Sichuan Provincial Key Lab of Applied Nuclear Techniques in Geosciences (No. gnzds2014003), and the Open Fund of Robot Technology Used for Special Environment Key Laboratory of Sichuan Province (13zxtk04).
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Shi, R., Tuo, XG., Li, HL. et al. 239Pu alpha spectrum analysis based on PIPS detector response function and variations with vacuum and distance. NUCL SCI TECH 28, 4 (2017). https://doi.org/10.1007/s41365-016-0163-x
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DOI: https://doi.org/10.1007/s41365-016-0163-x