Low-Temperature Scintillation for Rare-Event Searches

寻找罕见的事件，比如暗物质粒子的相互作用，可能构成宇宙中的大部分物质，很难在堆积如山的放射性背景中识别出微小的信号。背景抑制探测器技术的进步推动了这一进展。一种适用于许多靶核的有前途的技术是在低温下测量闪烁和声子。为了开发这样的探测器，我们建立了一个唯一有效的测试台来测量低至4K的闪烁。我们将研究纯NaI和掺杂NaI，目标是制作出背景抑制闪烁声子探测器的原型。例如，在SNOLAB未来的一次实验中部署，它们可以验证长期存在但有争议的DAMA基于纯闪烁设备的暗物质主张。我们还将研究在暗物质研究中可能有用的其他无机闪烁体，如CSI和ZnWO4，以及对双β衰变感兴趣的材料，如ZnMoO4。此外，我们还将探索贵重液体探测器中使用的各种材料的闪烁特性，这些特性可能会影响它们使用脉冲形状辨别来抑制本底的能力。这将对像DEAP这样的实验感兴趣。我们将研究的另一类材料是液体有机闪烁体，如直链烷基苯，在室温下是众所周知的，但在低温下没有研究。最后，我们将以闪烁体中的骨折为背景进行研究。为此，我们将在低温下进行一项实验，以测量闪烁体中的裂缝发出的光。这一结果可能会对理解CRESST暗物质搜索最近有趣的结果产生影响。与法国的一个材料小组就这一主题进行交流的资金已从法国-加拿大研究基金获得。总体而言，该项目将培训2名博士后、5名研究生和5名本科生，掌握前沿实验技能和数据分析。

Searches for rare-events, like interactions of the dark matter particles that may make up the bulk of the matter in the Universe, struggle to identify small signals in a haystack of radioactive background. Progress has been driven by improvements in background-rejecting detector technology. One promising technology applicable to many target nuclei is the measurement of scintillation and phonons at cryogenic temperatures. To develop such detectors, we have set up a uniquely efficient test bed to measure scintillation down to 4 K. We will study pure and doped NaI, with the goal of prototyping background-rejecting scintillation-phonon detectors. Deployed in a future experiment at SNOLAB for instance, they could verify the longstanding but controversial DAMA dark matter claim based on scintillation-only devices. We will also investigate other inorganic scintillators like CsI and ZnWO4 that may be of use in dark matter searches such as CRESST, as well as materials like ZnMoO4 of interest for double beta decay. In addition, we will explore the scintillation properties of various materials used in noble liquid detectors that could affect their ability to reject background using pulse-shape discrimination. This will be of interest to experiments like DEAP. A different class of materials we will investigate are liquid organic scintillators like linear-alkyl-benzene, well-known at room temperature, but not studied at low temperatures. Lastly, we will examine fractures as a background in scintillators. For this, we will pursue to low temperatures an experiment to measure the light emitted by fractures in scintillators. The results could have implications for understanding the recent intriguing results of the CRESST dark matter search. Funding for exchanges with a materials group in France on this topic has been obtained from the France-Canada Research Fund. Overall, this program will train 2 postdocs, 5 graduate students, and 5 undergraduates in leading-edge experimental skills and data analysis.