EXO: Technical Design for a Tonne-Scale Enriched Xenon DoubleBeta Decay Experiment

EXO：吨级富集氙双贝塔衰变实验的技术设计

• 批准号: 0918469
• 负责人: Giorgio Gratta
• 金额: $ 170万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Cooperative Agreement
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0918469&HistoricalAwards=false
• 关键词: EXO; Technical; Design; Tonne; Scale

This proposal will fund the search for neutrino-less double beta decay process in Xenon-136. The discovery of neutrino oscillations can be regarded as the first window provided by experiments on physics beyond the standard model. The search for neutrino less double beta decay represents the next step in this exciting field of physics and provides an opportunity to perform transformational science addressing universal topics such as the origin of mass, the role of Dirac?s equation in describing spin half fermions and connections between particle physics and cosmology. Many experiments tackled the double beta decay over the last thirty years, setting half-life limits for this mode of the order of 10**25 years, corresponding to a Majorana neutrino mass just below 1 eV. A new generation of much larger experiments will push this sensitivity to 10**28 years or Majorana masses below 10 meV, exploring much of the parameter space compatible with the oscillation results. Those searches require tones of specific isotopes that, in order to result in viable measurements, must be produced by isotopic enrichment. They also require unprecedented reductions of radioactive backgrounds and substantial attenuation of the cosmic ray flux, making their location deep underground imperative. This proposal plans to establish the engineering and project management infrastructure to design a full scale double beta decay experiment, the ?Enriched Xenon Observatory? (EXO), using a few tons of the isotope Xenon 136. The isotope choice capitalizes on the relative simplicity of xenon enrichment and purification and on its versatility as a detection medium in a liquid or gas phase Time Projection Chamber. The substantial investment in isotopic enrichment can, in this way, result in more than one detector, making it possible to cross check results and upgrade detectors as new technologies become available. In addition a scheme being developed by the EXO collaboration to tag the atomic final state of the decay has the promise of drastically reducing radioactivity backgrounds. Data soon to be collected with EXO-200 will provide very important input for the design work on a multi-ton detector for DUSEL. The broader impact plan of the EXO collaboration is to develop a cross-disciplinary program involving the techniques ranging from nuclear/particle detector physics to AMO and surface science. Therefore many intermediate results may have spin-offs in a broad range of fields. EXO R&D has trained students in a variety of disciplines and a vibrant outreach program at several EXO institutions brings the excitement of science to grade school students and to high school teachers who spend their summer in some of our labs. As part of this proposal we plan to enhance this last component, by connecting it with the DUSEL outreach program.

这项提议将为氙-136中的无中微子双β衰变过程的研究提供资金。中微子振荡的发现可以被看作是标准模型之外的物理实验提供的第一个窗口。寻找中微子较少的双β衰变代表了物理学这一令人兴奋的领域的下一步，并提供了一个机会，以执行转换科学解决普遍的主题，如质量的起源，狄拉克的作用？的方程描述自旋半费米子和粒子物理学和宇宙学之间的联系。许多实验都是为了解决双贝塔问题 衰变在过去的三十年，设置半衰期极限为10**25年的顺序，对应的马约拉纳中微子质量略低于1 eV的这种模式。新一代更大的实验将把这种灵敏度推到10**28年或马约拉纳质量低于10 meV，探索大部分与振荡结果兼容的参数空间。这些研究需要特定同位素的色调，为了进行可行的测量，必须通过同位素浓缩产生。它们还需要前所未有地减少放射性背景和大幅度衰减宇宙射线通量，使其位于地下深处势在必行。该提案计划建立工程和项目管理基础设施，以设计一个全面的双β衰变实验，该？浓缩氙天文台？(EXO)使用几吨同位素氙136。同位素的选择利用了氙富集和纯化的相对简单性以及其作为液相或气相时间投影室中的检测介质的多功能性。在同位素浓缩方面的大量投资可以通过这种方式产生一个以上的探测器，从而有可能随着新技术的出现而交叉核对结果和升级探测器。此外，EXO合作组织正在制定一项计划，以标记衰变的原子最终状态，有望大幅减少放射性背景。不久将用EXO-200收集的数据将为DUSEL的多吨探测器的设计工作提供非常重要的投入。EXO合作的更广泛的影响计划是开发一个跨学科计划，涉及从核/粒子探测器物理到AMO和表面科学的技术。因此，许多中间成果可能在广泛的领域产生副产品。EXO R D已经培训了各种学科的学生，并且在几个EXO机构开展了一个充满活力的推广计划，为在我们的一些实验室度过暑假的小学生和高中教师带来了科学的兴奋。作为该提案的一部分，我们计划通过将其与DUSEL外展计划联系起来来加强最后一个组成部分。