Low-Temperature Scintillation for Rare-Event Searches

寻找罕见事件，比如可能构成宇宙中大部分物质的暗物质粒子的相互作用，很难在一堆放射性背景中识别出小信号。背景抑制探测器技术的改进推动了这方面的进展。在低温下测量闪烁和声子是一项有前途的技术，适用于许多目标核。为了开发这样的探测器，我们已经建立了一个独特的高效测试平台来测量低至4 K的闪烁。我们将研究纯的和掺杂的NaI，目标是制作抑制背景的闪烁声子探测器。例如，在未来的SNOLAB实验中，它们可以基于仅闪烁设备验证长期存在但有争议的DAMA暗物质主张。我们还将研究其他无机闪烁体，如CsI和ZnWO4，它们可能用于暗物质搜索，如CRESST，以及像ZnMoO4这样的双β衰变感兴趣的材料。此外，我们将探索用于贵重液体探测器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判别来拒绝背景的能力。这将对DEAP等实验感兴趣。我们将研究的另一类材料是液态有机闪烁体，如线性烷基苯，它在室温下是众所周知的，但在低温下还没有研究过。最后，我们将研究作为闪烁体背景的骨折。为此，我们将进行低温实验，测量闪烁体中裂缝发出的光。这些结果可能会对理解最近的CRESST暗物质搜索的有趣结果产生影响。已从法国-加拿大研究基金获得经费，与法国的一个材料小组就这一专题进行交流。总体而言，该项目将培养2名博士后、5名研究生和5名本科生，具备前沿的实验技能和数据分析能力。

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.