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本文提出了一种适用于航空γ能谱测量的能谱剖面分析方法,该法通常用于高分辨率能谱测量。通过研究能谱剖面中的变化,开发了一种新的算法用于提取全吸收峰,能谱剖面中的数据是用大体积NaI探测器(16L)以短的采样时间(2s)记录的。使用数字滤波并考虑吸收峰的特征,显著减小了计数的起伏,使基于1次和2次微商研究的检测成为可能。吸收峰是通过模拟,然后扣除检测窗中康普顿连续谱而获得的。与传统的剥谱法相比,能谱剖面分析对于天然放射性元素能提供相似的性能。在40K(200Bq·kg-1)、238U(33Bq·kg-1)和232Th(33Bq·kg-1)的天然背景中,137Cs1倍标准偏差的检测限约为1200Bq·m-2。在低能段,很高的连续谱导致本方法的检测限与窗法相近,但是获得的结果更为可靠。然而当存在重叠峰时,要分开这些峰仅用能谱剖面分析是不够的,必须做进一步的处理。环境监测研究机构对能谱剖面分析有很大的兴趣,因为它不需要任何关于核素性质的假设。由于只考虑全吸收的贡献,因此,从获得的结果中计算含量简单而又可靠,从而能够迅速地定量评价放射性异常。
In this paper, an energy spectrum profile analysis method suitable for airborne γ-energy spectrum measurement is proposed, which is usually used for high-resolution energy spectrum measurement. By studying the changes in the spectral profile, a new algorithm was developed for extracting the full absorption peak. The data in the spectral profile was recorded with a large NaI detector (16 L) at a short sampling time (2 s). Using digital filtering and taking into account the characteristics of the absorption peaks, the count fluctuations are significantly reduced, enabling detection based on 1 and 2 derivative studies. The absorption peak is obtained by modeling and then subtracting the Compton continuum in the detection window. Compared with the traditional stripping method, spectrum profiling can provide similar performance for natural radioactive elements. In the natural background of 40K (200Bq · kg-1), 238U (33Bq · kg-1) and 232Th (33Bq · kg-1), the detection limit of 137Cs standard deviation is about 1200Bq · m-2. In the low energy range, the high continuum results in a detection limit similar to the window method, but the results obtained are more reliable. However, when there are overlapping peaks, it is not enough to separate these peaks with only the spectral profile, and further processing is necessary. Environmental monitoring institutes have a great interest in spectral profiling because they do not require any assumptions about the nature of the nuclide. Since only the contribution of total absorption is taken into consideration, the calculation of the content from the obtained results is simple and reliable, and the radioactive abnormality can be rapidly and quantitatively evaluated.