人类所受到的天然辐射主要来自氡及其子体，氡还是一种重要的示踪核素。中国锦屏地下实验室垂直岩石覆盖达2400米，是世界一流的洁净的低辐射研究平台。目前，静电收集法测氡仪抗干扰性好且能够分辨Rn-222, Rn-220，得到了广泛应用。采用静电收集法测量极低本底氡浓度具有原理上的优势。本项目将建立体积为1000升的静电收集测量腔，解决极低本底氡浓度测量方法学上尚存在的一些关键问题，并进行进一步的理论研究和实验验证。本装置直接测量空气氡浓度的探测下限达到0.1 mBq/m3，超过日本Mitsuda等研制的超高灵敏度测氡仪的探测下限0.3 mBq/m3；利用无镭活性炭纤维对空气中的氡进行富集后，解析后的高浓度氡送入本装置，本装置间接测量空气氡浓度的探测下限达到1 uBq/m3。本项目的研究可以为氡监测和防护提供理论基础和技术手段，为有效评估环境辐射本底对极低本底物理实验的影响提供支撑。

The main natural radiations received by humans are from radon and their daughters. Radon also is an important tracer nuclide. China Jinping underground laboratory vertical rock covering 2,400 meters, it is world-class clean and low-radiation research platform. Now, radon monitors based on electrostatic collection method have been widely applied due to good anti-interference and the ability to distinguish 222Rn, 220Rn. Using the electrostatic collection method to measure very low background radon concentrations has the principle advantage. The project will establish an electrostatic collection measuring chamber witch volume is 1000 liters to solve some still existence key issues on the methodology for measuring very low background radon concentration, and further theoretical research and experimental verification. The detection limit of this device for direct measuring the radon concentration in the air reaches 0.1 mBq /m3, exceeding the detection limit of 0.3 mBq/m3 of ultra-high sensitivity radon detector developed by Mitsuda et al. of Japan. After enriching radon in the air by activated carbon fiber without radium, the desorbed high concentration radon is sent to the device, and the detection limit of this device for indirect measuring the radon concentration in the air reaches 1 uBq /m3. This project will provide a theoretical foundation and technical means for radon monitoring and protection, and support for effectively assessing the background of environmental radiation impacts on the very low background physics experiments.