CAGE：用于HPGe表征的内部源扫描低温真空装置
CAGE: An Internal Source Scanning Cryostat for HPGe Characterization
AI总结：
CAGE系统通过高精度扫描HPGe探测器表面，用于研究和减少无中微子双β衰变实验中的表面背景。
摘要：
当前及未来一代无中微子双β衰变实验的成功依赖于消除或减少杂背景的能力。除了使用放射纯材料构建实验并在地下实验室中操作外，还需要在数据分析中理解和减少已知的背景。大型富锗实验（LEGEND）通过使用富76Ge的高纯度锗探测器浸入活性液氩 veto 中来寻找这种衰变。LEGEND 中的一个显著背景是来自探测器表面浅层撞击辐射的表面事件。在本文中，我们介绍了Collimated Alphas, Gammas, and Electrons（CAGE）扫描系统，一种内部源扫描真空低温装置，用于在表面实验室中对HPGe敏感表面的表面事件进行研究。CAGE具有一个被移动的红外屏蔽保护的放射性核素源，能够利用三个独立的电机阶段对探测器表面进行高精度扫描。这使得能够详细研究脉冲形状作为源位置和入射角函数的变化，其中可以提取和利用特征以在LEGEND的数据分析中去除表面背景。在本文中，我们描述了CAGE并用241Am进行验证运行。验证运行在源正入射时完成，我们估计束斑精度为3.1毫米，包括定位不确定性和束斑大小。使用241Am的59.5 keV伽马能级，我们展示了接近保护表面的低能光子事件的上升时间随着从探测器中心的径向距离增加而增加。我们建议一个特定的度量标准，可用于区分具有类似特征的低能伽马背景。
英文摘要：
The success of current and future-generation neutrinoless double beta decay experiments relies on the ability to eliminate or reduce extraneous backgrounds. In addition to constructing experiments using radiopure materials and handling in underground laboratories, it is necessary to understand and reduce known backgrounds in data analysis. The Large Enriched Germanium Experiment for Neutrinoless double beta Decay is searching for this decay using 76Ge-enriched high-purity germanium detectors submerged in an active liquid argon veto. A significant background in LEGEND is surface events from shallowly-impinging radiation on detector surfaces. In this paper we introduce the Collimated Alphas, Gammas, and Electrons (CAGE) scanning system, an internal-source scanning vacuum cryostat, designed to perform studies of surface events on sensitive surfaces of HPGe in a surface-lab. CAGE features a collimated radionuclide source inside a movable infrared shield that is able to perform precision scans of detector surfaces by utilizing three independent motor stages for source positioning. This allows detailed studies of pulse shapes as a function of source position and incident angle, where defining features can be extracted and exploited for removing surface backgrounds in data analysis in LEGEND. In this paper, we describe CAGE and demonstrate its performance with a commissioning run with 241Am. The commissioning run was completed with the source at normal incidence, and we estimate a beam spot precision of 3.1 mm, which includes positioning uncertainties and the beam-spot size. Using the 59.5 keV gamma population from 241Am, we show that low-energy photon events near the passivated surface feature risetimes that increase with radial distance from the detector center. We suggest a specific metric that can be used to discriminate low-energy gamma backgrounds in LEGEND with similar characteristics.
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