MRI Consortium: Development of Instrumentation for the PICO-500 Bubble Chamber

多个天文观测已经确定，宇宙中大约85%的物质不是由已知粒子组成的。破译这种所谓的暗物质的性质对宇宙学、天体物理学和高能粒子物理学具有根本的重要性。一个主要的假设是，它是由弱相互作用大质量粒子（WIMP）组成的，这些粒子是在大爆炸后产生的。如果WIMP是暗物质，那么它们在我们星系中的存在可能是通过位于地下深处的探测器中的原子核散射来检测的，以帮助排除宇宙射线造成的背景。皮科是PICASSO和COUPP合作的合并，采用室温过热液体来寻找暗物质粒子候选者。皮科之前在SNOLAB的努力已经导致了世界领先的自旋相关WIMP-质子耦合灵敏度。最近在声学识别α粒子和粒子诱导背景方面的进展将使下一代皮科气泡室也能够在低于10 GeV/c^2的WIMP质量范围内对自旋无关耦合产生灵敏度。该小组通过制造专门设计的传感器来帮助更广泛的科学界。一些天体物理学实验现在正在使用声学粒子识别。该小组还一直在与一个制琴师合作，开发技术，以衡量木材性能和设计爵士乐拱形顶部吉他与可预测的声音。一个液体氙气泡室实验配备了低温安全的传感器相关的闪烁光与气泡图像。PSU集团开发了新型的放射纯压电陶瓷，其性能比目前最好的PZT配方灵敏度高出10倍。该奖项提供资金，使印第安纳州大学南本德（IUSB），东北伊利诺伊大学（NEIU），和宾夕法尼亚州立大学集团开发吨级皮科的硬件和软件组件，500个气泡室，这将是对各种各样的暗物质粒子候选者最敏感的探测器，并将为世界各地的20多个研究小组服务。皮科使用过热的液体来寻找由于与暗物质碰撞而反冲的原子核留下的微小能量沉积。这些沉积物导致液体爆炸性地转化为气体。IUSB小组已经为以前的探测器设计和制造了所有的声换能器。2008年，该小组发现，可以将核反冲产生的气泡声音与α衰变（主要背景）产生的气泡声音区分开来。NEIU团队一直致力于改进操作探测器所需的控制和显示软件。PSU团队一直负责用放射性纯氧化物制造压电陶瓷。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Multiple astronomical observations have established that about 85% of the matter in the universe is not made of known particles. Deciphering the nature of this so-called Dark Matter is of fundamental importance to cosmology, astrophysics, and high-energy particle physics. A leading hypothesis is that it is comprised of Weakly Interacting Massive Particles, or WIMPs, that were produced moments after the Big Bang. If WIMPs are the dark matter, then their presence in our galaxy may be detectable via scattering from atomic nuclei in detectors located deep underground to help reject backgrounds due to cosmic rays. PICO, a merger of the PICASSO and COUPP collaborations, employs room-temperature super-heated liquids to search for dark matter particle candidates. Previous efforts by PICO at SNOLAB have resulted in a world-leading sensitivity to spin-dependent WIMP-proton couplings. Recent progress in acoustic discrimination against alpha particles and particulate-induced backgrounds will enable the next-generation of PICO bubble chambers to also lead in sensitivity to spin-independent couplings in the WIMP mass range below 10 GeV/c^2. The group has aided the broader scientific community by fabricating specially designed transducers. Several astrophysics experiments are now using acoustic particle identification. The group has also been working with a luthier to develop techniques to measure wood properties and design jazz arch top guitars with predictable sound. A liquid xenon bubble chamber experiment was outfitted with cryogenic-safe transducers to correlate scintillation light with bubble images. The PSU group has developed novel radiopure piezoceramics with properties suggesting ten times greater sensitivity than the best current PZT formulations.This award provides funds to enable the Indiana University South Bend (IUSB), North Eastern Illinois University (NEIU), and Penn State groups to develop hardware and software components of the ton-scale PICO-500 bubble chamber which will be the most sensitive detector for a wide variety of dark matter particle candidates and will serve over 20 research groups around the world. PICO uses superheated liquids to search for the tiny energy depositions left by nuclei recoiling due to collisions with dark matter. These depositions cause the liquid to explosively transform into gas. The IUSB group has designed and fabricated all of the acoustic transducers for the previous detectors. In 2008 the group discovered that it is possible to differentiate the sounds of bubbles created by nuclear recoils from those initiated by alpha decay (the main background). The NEIU team has worked on improving the control and display software necessary for operating the detector. The PSU team has been responsible for fabricating piezoelectric ceramics from radiopure oxides.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.