Development of Low Background Sodium Iodide Scintillation Detectors for Dark Matter Research

暗物质的起源是我们这个时代的主要科学问题之一。意大利格兰萨索地下实验室（LNGS）的DAMA/LIBRA实验报告了一个信号，据称该信号是暗物质以弱相互作用大质量粒子（wimp）的基本粒子形式存在的证据。然而，他们的结果似乎与其他寻找暗物质却没有结果的实验相冲突。在较低背景下用碘化钠（NaI）探测器进行独立实验之前，情况尚不清楚。该奖项将为开发用于灵敏暗物质搜索的低本底碘化钠闪烁晶体提供资金。先前的研究是由NSF EAGER资助的，重点是用于生产NaI粉末的前体材料的纯化。该奖项计划的活动将包括：a)解决与用高纯度NaI粉末生长的高纯度低本底NaI闪烁晶体的发展有关的问题；b)开发一种灵敏的方法来测量晶体中的钾放射性，以验证暗物质研究所需的极低水平。可能的第二阶段研究将是在低背景环境中部署一系列这样的探测器，这将允许以比DAMA/LIBRA实验更低的背景和更高的灵敏度搜索WIMP暗物质。更广泛的影响：了解暗物质的本质将影响许多科学领域，从最大规模的天文学到最小规模的基本粒子物理学。它是一种神秘的物质形式，一旦被理解，它将连接到所有领域。此外，这里开发的技术，对超纯材料的需求，将有利于其他依赖这些材料的领域，如半导体和纳米技术设备。

The origin of dark matter is one of the major scientific questions of our time. The DAMA/LIBRA experiment at the Underground Laboratory at Gran Sasso, Italy (LNGS) has reported a signal that is claimed to be evidence for dark matter in the form of elementary particles called Weakly Interacting Massive Particles (WIMPs). However, their results seem to be in conflict with other experiments that have searched for dark matter with null results. The situation will be unclear until an independent experiment with Sodium Iodide (NaI) detectors is done with lower background.This award will provide funds to develop low-background sodium iodide scintillation crystals for a sensitive dark matter search. Prior research, which was supported by an NSF EAGER grant, focused on the purification of precursor materials that are used for producing NaI powder. The activities planned with this award will be to a) address issues concerning the development of high purity low background NaI scintillation crystals grown with the high purity NaI powder and b) develop a sensitive method to measure the potassium radioactivity in the crystals to verify the very low levels needed for dark matter research. A possible second phase of research will be to deploy an array of such detectors in a low background environment that will allow a search for WIMP dark matter with lower background and higher sensitivity than achieved in the DAMA/LIBRA experiment.Broader impacts: Understanding the nature of dark matter would impact many fields of science from the largest scale of astronomy to the smallest scale of elementary particle physics. It is a mysterious form of matter that will connect to all fields once it is understood. In addition, the technology developed here, with demands on ultrapure materials, will benefit other fields that rely on such materials, such as semiconductors and nanotechnology devices.