Detection method for U and Th isotopes at ppt order with ultra low-background nuclear β-γ spectroscopy

提出了一种高灵敏度检测U链和Th链放射性同位素的新方法。它基于超低背景β -伽马光谱学，探测器由堆叠的无机闪烁体板组成，面积达180mm×180mm。在Oto地下实验室进行了长时间的运行，对U和Th污染物的灵敏度分别达到0.8ppt和2.2ppt。

A new method for high-sensitivity detection of radioisotopes in U and Th chains was developed. It is based on an ultra low-background beta-gamma spectroscopy, and the detector is made of stacked inorganic scintillator plates with areas as wide as 180mm×180mm. A long-time run was performed in the Oto underground laboratory to investigate the performances of the detector, and the sensitivities of 0.8ppt and 2.2ppt were achieved for the contaminations of U and Th, respectively.