Undoped NaI/CsI Directly Coupled to PMTs at 77 K for Rare-Event Searches

未掺杂的 NaI/CsI 在 77 K 下直接耦合到 PMT，用于稀有事件搜索

• 批准号: 1506036
• 负责人: Jing Liu
• 金额: $ 33.05万
• 依托单位: University of South Dakota Main Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506036&HistoricalAwards=false
• 关键词: Undoped; NaI; CsI; Directly; Coupled

Dark matter and neutrino properties are among the most compelling problems to be studied in modern physics. Dark matter particles may be detected through the observation of nuclear recoils produced when they scatter with nuclei in a target. Nuclear recoils can also be created when neutrinos coherently scatter with nuclei. This process, if ever observed, would help in probing non-standard neutrino interactions, searching for sterile neutrinos, and understanding the explosion mechanism of core-collapse supernovae. Both scattering rates increase dramatically as the energies of nuclear recoils go down. The lower the energy threshold of a detector, the more events can be detected. Recent activity in the SURF underground laboratory stimulated support from the South Dakota state to the expansion of PhD programs at state universities. The activity planned with this award provides an opportunity for a PhD student to take part in research related to underground science. The activity may also pave the way for practical applications of undoped NaI/CsI at 77 K in civil uses. For example, un-doped NaI at 77 K has a much faster scintillation signal than NaI/CsI(Tl) at room temperature. It can be used to improve the time and position resolution of PET, resulting in more precise imaging of the concerned tissue of a patient.A straight forward way to lower the energy threshold of a scintillation detector is to increase its light yield. This award is focused on optimizing the light readout from un-doped NaI/CsI at 77 K. Both sodium iodide and cesium iodide doped with thallium, NaI/CsI(Tl), are excellent scintillators at room temperature. The PI plans to couple un-doped NaI/CsI directly to the photomultiplier tubes (PMTs), cool them down to 77 K to maximize the light readout. Low temperature properties of the PMTs will be compared; dimensions and various surface treatments of un-doped NaI/CsI crystals will be examined to optimize the light collection efficiency. The goal is to verify whether it is possible to lower the energy threshold by a factor of two by increasing the light yield by a factor of two, compared to existing experiments utilizing NaI/CsI(Tl) at room temperature. The decay times of scintillation light from un-doped NaI/CsI at 77 K are quite different from those of NaI/CsI(Tl) at room temperature. Their effect on signal and background discrimination will also be examined.

暗物质和中微子特性是现代物理学中最引人注目的问题之一。通过观察核后坐力在目标中散射出核后坐力时，可以检测到暗物质颗粒。当中微子与核一致散射时，还可以产生核后坐力。如果曾经观察到这个过程，将有助于探测非标准的中微子相互作用，寻找无菌中微子以及了解核心偏离超新星的爆炸机制。随着核后坐力的能量下降，这两种散射率都大大增加。检测器的能量阈值越低，可以检测到更多的事件。冲浪地下实验室的最新活动刺激了南达科他州的支持，以扩大州立大学的博士学位计划。该奖项计划的活动为博士生提供了与地下科学有关的研究的机会。这项活动还可以为在民用用途中以77 K处的NAI/CSI的实际应用铺平道路。例如，在77 K处的未掺杂NAI的闪烁信号比室温下的NAI/CSI（TL）快得多。它可用于改善PET的时间和位置分辨率，从而更精确地对患者的组织组织进行更精确的成像。直接降低闪烁探测器能量阈值的直接方法是增加其光线的产量。该奖项的重点是优化77 K处的未掺杂NAI/CSI的轻读数。碘化钠和碘化钠均以thallium，nai/csi（TL）掺杂的碘化钠，在室温下都是出色的闪光灯。 PI计划将未掺杂的NAI/CSI直接搭配到Photolultiplier管（PMTS），将其冷却至77 K，以最大程度地提高光线读数。将比较PMT的低温特性；将检查尺寸和未掺杂NAI/CSI晶体的各种表面处理，以优化光收集效率。目的是与在室温下使用NAI/CSI（TL）的现有实验相比，通过将光的产量提高两倍，验证是否有可能将光阈值提高两个倍。在77 K处，未掺杂的NAI/CSI的闪烁光的衰减时间与室温下NAI/CSI（TL）的衰减时间完全不同。还将检查它们对信号和背景歧视的影响。