利用光谱数据的动态量子聚类在搜索应用中检测核源
Detection of Nuclear Sources in Search Applications using Dynamic Quantum Clustering of Spectral Data
摘要：
在搜索场景中，使用移动探测器-光谱仪在短采集间隔内连续测量核背景光谱。由于光谱的低信噪比（S/N）、天然存在的放射性物质（NORM）导致的大且高度变化的背景以及核探测器有限的光谱分辨率导致的谱线展宽，从测量数据检测源是困难的。我们已经发明了一种使用光谱数据的聚类来检测源的方法。我们的方法利用了这样一个物理事实，即源不仅在其光谱发射区域产生计数，而且通过康普顿连续谱对整个探测器光谱产生影响。这允许使用多个数据特征来表征低S/N光谱，而没有明显的同位素线。我们已经表明，噪声光谱与低S/N可以分组的整体光谱形状相似性使用的数据聚类技术称为动态量子聚类（DQC）。然后可以对同一簇中的光谱进行平均以增强同位素谱线的S/N。这将提高同位素鉴定的准确性，降低误报率。我们的方法在原理验证研究中使用碘化钠检测器以一秒间隔测量的光谱数据集进行了验证。该数据集包括在城市背景测量中获得的7000多个光谱，以及大约70个Cs-137和Co-60源的测量结果。利用DQC分析，我们已经观察到，所有的光谱含有Cs-137和Co-60的信号集群远离背景。
英文摘要：
In a search scenario, nuclear background spectra are continuously measured in short acquisition intervals with a mobile detector-spectrometer. Detecting sources from measured data is difficult because of low signal to noise ratio (S/N) of spectra, large and highly varying background due to naturally occurring radioactive material (NORM), and line broadening due to limited spectral resolution of nuclear detector. We have invented a method for detection of sources using clustering of spectral data. Our method takes advantage of the physical fact that a source not only produces counts in the region of its spectral emission, but also has the effect on the entire detector spectrum via Compton continuum. This allows characterizing the low S/N spectrum without distinct isotopic lines using multiple data features. We have shown that noisy spectra with low S/N can be grouped by overall spectral shape similarity using a data clustering technique called Dynamic Quantum Clustering (DQC). The spectra in the same cluster can then be averaged to enhance S/N of the isotopic spectral line. This would allow for increased accuracy of isotopic identification and lower false alarm rate. Our method was validated in a proof-of principle study using a data set of spectra measured in one-second intervals with Sodium Iodide detector. The data set consisted of over 7000 spectra obtained in urban background measurements, and approximately 70 measurements of Cs-137 and Co-60 sources. Using DQC analysis, we have observed that all spectra containing Cs-137 and Co-60 signal cluster away from the background.
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