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

多项天文观测证实，宇宙中约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本质对宇宙学、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，它是由相互作用很弱的大质量粒子组成的，这些粒子是在大爆炸后不久产生的。如果WIMP是暗物质，那么它们在我们银河系中的存在可能是通过位于地下深处的探测器中原子核的散射来检测到的，以帮助排除宇宙射线的背景。Pico是毕加索和COUPP合作的合并，它使用室温过热液体来搜索候选暗物质粒子。PICO在SNOLAB之前的努力已经导致了对自旋相关的WIMP-质子耦合的世界领先的灵敏度。在对阿尔法粒子和粒子诱导背景的声学识别方面的最新进展，将使下一代皮科气泡室能够提高对WIMP质量范围低于10GeV/c^2的自旋无关耦合的灵敏度。该小组通过制造专门设计的换能器，帮助了更广泛的科学界。几个天体物理实验现在正在使用声学粒子识别。该组织还一直在与一家乐器制造商合作，开发测量木材特性的技术，并设计具有可预测声音的爵士拱顶吉他。液体氙气泡室实验配备了低温安全的传感器，以将闪烁光与气泡图像相关联。PSU小组开发了新型放射性纯压电陶瓷，其性能表明其灵敏度是目前最好的PZT配方的十倍。该奖项提供资金，使印第安纳大学南本德(IUSB)、东北伊利诺伊大学(NEIU)和宾夕法尼亚州立大学小组能够开发吨级Pico-500气泡室的硬件和软件组件，该气泡室将是对各种暗物质候选粒子最灵敏的探测器，将为世界各地的20多个研究小组提供服务。Pico使用过热的液体来寻找由于与暗物质碰撞而导致的原子核反冲留下的微小能量沉积。这些沉积会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学换能器。2008年，该研究小组发现，有可能将核反冲产生的气泡声音与阿尔法衰变(主要背景)引发的气泡声音区分开来。NEIU团队致力于改进操作探测器所需的控制和显示软件。PSU团队一直负责利用放射性纯氧化物制造压电陶瓷。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.