标题： JUNO场地空气中的定量铀/钍沉积和清洁度控制策略 显示英文标题

标题： Quantitative U/Th deposition and cleanliness control strategies in the JUNO site air

摘要： 江门地下中微子观测站（JUNO）由一个20千吨液体闪烁体（LS）探测器组成，位于地下700米深处。 为了满足所有物理要求，LS中的$^{238}$U/$^{232}$Th含量需要达到10$^{-17}$ g/g的水平。 然而，空气中灰尘的放射性大约高出12个数量级，因此对现场安装环境的清洁度有极高的要求。 在本研究中，在JUNO地下实验主大厅的120,000 m$^3$空间内实施了洁净室管理方式，以将环境清洁度控制在相当于10,000-100,000级洁净室的水平。 此外，我们设计了一种直接测量$^{238}$U/$^{232}$Th在探测器表面沉积率的方法。 基于ICP-MS检测，对$^{238}$U/$^{232}$Th浓度的灵敏度可达到皮克（pg）级别。 这有助于实施清洁度控制策略，并评估探测器建造过程中外部污染的水平。 显示英文摘要

摘要： The Jiangmen underground neutrino observatory (JUNO) is made of a 20 kt liquid scintillator (LS) detector at a depth of 700 m underground. In order to meet all physics requirements, the $^{238}$U/$^{232}$Th content in the LS is required to reach a level of 10$^{-17}$ g/g. However, the radioactivity of dust in the air is about 12 orders of magnitude higher than that, so there is an extremely high requirement for the cleanliness of the installation environment on site. In this study, a clean room management mode was implemented in the 120,000 m$^3$ space of the JUNO underground experimental main hall, to control the environmental cleanliness at a level equivalent to a class 10,000-100,000 clean room. Additionally, we designed a method to directly measure the deposition rate of $^{238}$U/$^{232}$Th on the surface of the detector. Based on ICP-MS detection, the sensitivity to $^{238}$U/$^{232}$Th concentrations can reach the level of picograms (pg). This helps to implement the cleanliness control strategies and to assess the level of external contamination during the construction of the detector.