标题： DAMIC实验中高电阻率硅电荷耦合器件的放射性污染测量 显示英文标题

标题： Measurement of radioactive contamination in the high-resistivity silicon CCDs of the DAMIC experiment

摘要： 我们介绍了在DAMIC实验中用于搜索暗物质粒子的高电阻率硅电荷耦合器件（CCDs）中的放射性污染测量结果。 开发了新颖的分析方法，利用CCDs独特的空间分辨率来识别$\alpha$和$\beta$粒子。 通过$\alpha$光谱测量了CCD主体中的铀和钍污染，在95%置信度下，$^{238}$U ($^{232}$Th) 的衰变率上限为5（15）kg$^{-1}$d$^{-1}$。 我们还搜索了时间上分离最多达几十天的空间相关电子轨迹对，这符合$^{32}$Si-$^{32}$P 或$^{210}$Pb-$^{210}$Bi 序列的$\beta$衰变预期。 $^{32}$硅的衰减率被发现为$80^{+110}_{-65}$千克$^{-1}$天$^{-1}$（95% 置信区间）。 一个关于$\sim$35 kg$^{-1}$ d$^{-1}$的$^{210}$铅衰变率的上限为 95% 置信度，该结果通过$\alpha$光谱学和$\beta$衰变序列搜索独立获得。 这些放射性污染水平足够低，足以使即将推出的 100 g DAMIC 探测器中的电荷耦合器件成功运行。 显示英文摘要

摘要： We present measurements of radioactive contamination in the high-resistivity silicon charge-coupled devices (CCDs) used by the DAMIC experiment to search for dark matter particles. Novel analysis methods, which exploit the unique spatial resolution of CCDs, were developed to identify $\alpha$ and $\beta$ particles. Uranium and thorium contamination in the CCD bulk was measured through $\alpha$ spectroscopy, with an upper limit on the $^{238}$U ($^{232}$Th) decay rate of 5 (15) kg$^{-1}$ d$^{-1}$ at 95% CL. We also searched for pairs of spatially correlated electron tracks separated in time by up to tens of days, as expected from $^{32}$Si-$^{32}$P or $^{210}$Pb-$^{210}$Bi sequences of $\beta$ decays. The decay rate of $^{32}$Si was found to be $80^{+110}_{-65}$ kg$^{-1}$ d$^{-1}$ (95% CI). An upper limit of $\sim$35 kg$^{-1}$ d$^{-1}$ (95% CL) on the $^{210}$Pb decay rate was obtained independently by $\alpha$ spectroscopy and the $\beta$ decay sequence search. These levels of radioactive contamination are sufficiently low for the successful operation of CCDs in the forthcoming 100 g DAMIC detector.