基于Boosted-Gold算法的γ能谱反演分析

Analysis of the unfolded γ energy spectrum based on Boosted-Gold algorithm

为了利用低能量分辨率探测器γ能谱分析获取未知放射性核素的特征信息,提高γ能谱中重峰及弱峰分析的准确性和有效性,本文开展了基于Boosted-Gold算法的Na I(Tl)探测器γ能谱分析研究.采用MCNPX建立Na I(Tl)探测器模拟模型,获得了维度201×200的探测器响应矩阵.基于Boosted-Gold算法开发了γ能谱反演程序.实验测量了γ源22Na,133Ba和152Eu的探测器响应能谱,并以不同γ射线能量、不同能差(△E)、不同相对强度为条件构建了3组低分辨率模拟γ能谱,结合响应矩阵及反演程序对实测γ能谱和模拟γ能谱进行反演.以IAEA数据库核素标准特征信息对反演结果进行分析.结果表明:Boosted-Gold算法对实测γ能谱特征能量反演误差最大为2.17%(;Ba源0.276Me V),反演强度与标准强度最大差为0.197(;Eu源1.408Me V).对模拟γ能谱核素特征能量均可准确分析,反演强度与标准强度差值保持在0.01以内;当增强系数p≤14时,Boosted-Gold算法有利于γ放射性核素的定量分析,对于相对强度大于10%的γ射线,该算法具有更好的分析准确性.

To obtain the characteristic information of unknown radionuclides by analyzing the γ-energy spectrum of a low-resolution detector, and to improve the accuracy and validity of the analysis of overlapping and weak peaks in the γ-energy spectrum, in this paper we analyze the γ-energy spectrum of NaI(Tl) detectors based on the Boosted-Gold algorithm. A simulation model of NaI(TI) detector is established by using MCNPX, and a detector response matrix with dimension 201 × 200 is obtained. The γ-energy spectrum unfolding program is developed based on the Boosted-Gold algorithm. The detector response spectra of the γ radioactive sources ^(22) Na, ^(133)Ba, and ^(152)Eu are measured. Three groups of low-resolution γ spectra are constructed with different g-ray energy, different energy differences (△) and different relative intensities by simulation. Combining the response matrix and the unfolding procedures, the measured and simulated γ energy spectra are unfolded. The unfolding results are analyzed with the nuclide standard characteristics information from the IAEA database. The results show that the maximum unfolding error of the characteristic energy of the measured γ-energy spectrum is 2.17% (0.276 MeV for ^(133)Ba source) by the Boosted-Gold algorithm, and the maximum deviation between the unfolded intensity and the standard intensity is 0.197 (1.408 MeV for ^(152)Eu source). For the simulated γ energy spectrum, the characteristic energy of nuclide can be accurately analyzed, and the deviation between unfolded intensity and standard intensity maintains 0.01. When the enhancement factor p ≤ 14, the Boosted-Gold algorithm is beneficial to the quantitative analysis of γ-radionuclides. For the relative intensity of γ-rays greater than 10%, this algorithm has better analysis accuracy.