MRI Instrument Development for Liquid Xenon Dark Matter Searches: An Atom Trap Trace Analysis System to Measure Ultra-Low Krypton Contamination in Xenon

关于暗物质本质的主要假设是，它由大爆炸后瞬间产生的新基本粒子组成，通常被称为弱相互作用大质量粒子。在地球实验中探测它们的一种方法是测量它们在与正常物质的罕见相互作用中产生的低能核反冲。一个关键的要求是控制和减少背景到超低水平。惰性液体靶中痕量的放射性同位素提供了内在背景。对于氙靶，关注的同位素是氪-85。尽管与正常氪相比，这种同位素的丰度非常小，但氪污染必须降低到万亿分之一（ppt）的水平，以便在氙等实验中可以忽略氪-85的背景。原子陷阱痕量分析（ATTA）方法有可能完成这项任务。该合同旨在开发一种基于激光冷却、捕获和计数单原子的ATTA系统，其具体目的是确定氙样品中放射性氪原子的数量，从而验证氪/氙污染减少到ppt水平。这个为期三年的仪器开发项目是氙暗物质小组和原子、分子和光学（AMO）小组之间的合作努力。该计划将对暗物质搜索和其他基于贵重液体的低背景物理实验产生广泛的科学影响。该项目将单原子的激光冷却和俘获与当今物理学中最基本的问题——暗物质的本质——联系起来。拟议的研究可以在许多方面影响社会：冷原子技术广泛应用于量子信息领域，超灵敏的氪分析用于地质考古年代测定和研究大气、海洋和地下水的运输过程。

The leading hypothesis for the nature of dark matter is that it consists of new elementary particles produced moments after the Big Bang, generally referred to as Weakly Interacting Massive Particles. One way to detect them in an Earth-bound experiment is to measure the low energy nuclear recoils they produce in rare interactions with normal matter. A key requirement is control and reduction of background to an ultra-low level. Traces of radioactive isotopes in noble liquid targets contribute an intrinsic background. For Xenon targets, the isotope of concern is Krypton-85. Even though the abundance of this isotope compared to normal Krypton is extremely small, the Krypton contamination must be reduced to the part per trillion (ppt) level in order for the Krypton-85 background to be negligible in an experiment like XENON. The Atom Trap Trace Analysis (ATTA) method has the potential to accomplish this task.This award is to develop an ATTA system based on laser cooling, trapping, and counting single atoms, with the specific purpose of determining the number of radioactive Krypton atoms in Xenon samples and hence verifying the reduction of the Krypton/Xenon contamination to the ppt level. This three-year instrumentation development project is a collaborative effort between the XENON Dark Matter group and the atomic, molecular, and optical (AMO) group. The program will have a broad scientific impact on dark matter searches and other low background physics experiments based on noble liquids. The project connects laser cooling and trapping of single atoms with the most fundamental question in physics today, the nature of dark matter. The proposed research can impact society in many ways: cold atom techniques are used widely in the field of quantum information and ultra-sensitive Krypton analysis is used in geology for archaeological dating and studies of transport processes in the atmosphere, oceans and groundwater.