COUPP-500 kg: Design of a large-Mass Bubble Chamber for Dark Matter Detection

该提案将通过芝加哥大学资助COUPP（芝加哥地下粒子物理天文台）合作项目。该提议是采用室温气泡室形式的适度过热液体来寻找暗物质候选粒子。一个包含2kg CF3I的小型工程原型已经成功部署并在浅深度下运行，从而提高了自旋依赖的wimp -核耦合的限制。在过去的一年里，合作采取了防止氡渗透到活动体积中的措施，加上更长的暴露时间，使该技术的估计范围提高了大约两个数量级。WIMP搜索相对于其他探测技术的优势在于它对自旋依赖耦合的敏感性。在进行这些研究的同时，合作已经完成了两个更大的实验室，一个包含15公斤的目标质量，另一个包含60公斤的目标质量。在FNAL的NUMI画廊进行了短暂的调试后，第二个腔室将于2009年在SNOlab的6000米等效水深部署。由该提案资助的下一步是合作启动500公斤模块的概念设计。该设计是基于一个适度的外推系统已经开发和测试在60公斤的腔。最终目标质量仅受大型合成二氧化硅容器的商业可用性的限制。这并不被认为是一个障碍，因为出于方便、安全和成本等其他原因，在DUSEL进行多吨试验的可能扩展可以很好地形成这种模块的小型阵列。最初的500公斤模块由一个中等厚度的垂直水箱屏蔽，作为初始DUSEL实验的一部分将是完全足够的。这种检测暗物质的方法成本相对较低，这使得更大质量的选择成为现实的可能性。这项提案的影响将包括本科生参与研究的新机会，以及研究生和博士后教育。在技术方面，将COUPP技术应用于货物裂变材料筛选可产生重大影响。整个暗物质搜索领域本身，一个真正的低背景探测器技术的广泛影响将是非常大的。

This proposal will fund the COUPP (The Chicago-land Observatory for Underground Particle Physics) collaboration through the University of Chicago. The proposal is to employs moderately superheated liquids in the form of room-temperature bubble chambers, to search for dark matter particle candidates. A small engineering prototype containing 2 Kg of CF3I, has been successfully deployed and operated at a shallow depth resulting in an improved limits on spin-dependent WIMP-nucleus couplings. The collaboration has over the past year, introduced measures against radon percolation into the active volume, this together with longer exposures have improved the estimated reach of the technique by approximately two orders of magnitude. COUP WIMP search advantage over other detection technique is its sensitivity to spin dependence couplings. In parallel to these studies the collaboration has completed two larger chambers, one containing 15 kg of target mass, and the second 60 kg. After a short commissioning period in the NUMI gallery at FNAL the second chamber will be deployed during 2009 at the 6000 meter water equivalent depth at SNOlab. The next step funded by this proposal is for the collaboration to initiate a conceptual design of a 500 kg module. The design is to be based on a modest extrapolation of the system already developed and tested in the 60 kg chamber. The ultimate target mass is only limited by the commercial availability of large synthetic silica vessels. This is not considered to be an impediment, since for other reasons of convenience, safety and cost, a possible extension into the multi-ton experiment at DUSEL can very well take form as a small array of such modules. An initial 500-kg module shielded by a modest thickness vertical water tank would be a perfectly adequate as part of the initial set of DUSEL experiments. The relatively low cost of this approach to dark matter detection leaves an option of larger masses as a realistic possibility. The boarder impact of this proposal will include new opportunities for undergraduate participation in research in addition to graduate student and postdoc education. On the technical front, the application of the COUPP technique to cargo screening for fissile materials could have an significant impact. The whole field of dark matter search itself, the broad impact of a truly low-background detector technique would be very large.