RUI: Searching for WIMP Dark Matter With Superheated Liquids

智力价值：天体物理学中最大的谜团之一是暗物质的性质，目前只能通过它对星系、星系团和宇宙中更大规模结构的影响来间接探测到暗物质。亚原子粒子标准模型的一般扩展预测了弱相互作用大质量粒子(WIMPS)的存在，这是暗物质的极好候选者。预计这些物质很少与普通物质相互作用，因此极难检测到。COUPP和毕加索团队正在开发新的大型暗物质探测器，该探测器源自著名的气泡室技术。带电粒子在气泡室中穿过过热的流体时会产生热量，从而产生小气泡。这些气泡可以在加压前拍摄，揭示这些颗粒的路径。其他非暗物质的触发因素也可能导致沸腾失控。这些限制了经典腔室只能在短时间内保持过热状态。COUPP实验特别关注材料的选择和制造技术，以去除粗糙度和放射性污染，从而使过热状态得以长期存在。毕加索的实验将过热的流体液滴悬浮在凝胶中，凝胶表面如此光滑，以至于液滴可以无限期地保持过热状态。这两个实验都使过热状态存活了足够长的时间来寻找暗物质。这一奖项将允许PI继续他在COUPP和毕加索实验方面的工作。印第安纳大学小组生产的声音传感器已被用于拒绝宇宙射线引发的事件，并区分中等过热流体的放射性信号。这位PI和他的学生已经建造了设备，在现实条件下模拟探测器中的声音传感器进行测试，并测量它们的灵敏度随年龄的变化。该小组还承担了测量流体目标中的污染物的任务，现在准备对流体进行常规分析。广泛的影响：加强本科生的教育是该计划不可或缺的一部分。本科生、高中教师和学生参与了声学换能器的设计、建造和表征、放射性测量和其他项目。此外，PI和他的团队还向其他科学小组提供了声学传感器，以协助其他实验。

Intellectual Merit: One of the great mysteries in astrophysics is the nature of dark matter, which is currently only detected indirectly through its effects on the structuring of galaxies, clusters of galaxies and larger scale structures in the universe. Generic extensions of the standard model of subatomic particles predict the existence of Weakly Interacting Massive Particles (WIMPS), which are excellent candidates for the dark matter. These are expected to interact with ordinary matter rarely and thus be extremely difficult to detect. The COUPP and PICASSO groups are developing new large dark matter detectors derived from the well-known bubble chamber technique. Charged particles traversing the superheated fluid in bubble chambers deposit heat, which creates small bubbles of gas. The bubbles can be photographed before pressurization revealing the paths of these particles. Other non-dark matter triggers can also lead to runaway boiling. These have limited classical chambers to remain in a superheated state for only a short time. The COUPP experiment has paid special attention to material selection and manufacturing techniques to remove roughness and radiocontamination to allow the superheated state to be long lived. The PICASSO experiment suspends superheated fluid droplets in a gel whose surfaces are so smooth that the droplets can stay in a superheated state indefinitely. Both experiments have made the superheated state sufficiently long lived to search for dark matter. This award will allow the PI to continue his work on the COUPP and PICASSO experiments. The sound sensors produced by the Indiana University group have been used for rejecting cosmic ray induced events and distinguishing the radioactive signals for moderately superheated fluids. The PI and his students have built equipment to test the sound sensors under realistic conditions mimicking those in the detectors and to measure changes in their sensitivity as a function of age. The group has also taken on the task of measuring contaminants in the fluid target and is now prepared to routinely assay the fluid.Broader impacts: Enhancing the education of undergraduates is an integral part of this program. Undergraduates, high school teachers and students have participated in design, construction and characterization of acoustic transducers, measurement of radioactivity, and other projects. In addition, the PI and his group has provided acoustic sensors to other scientific groups to assist in other experiments.