DarkSide

天文观测提供了强有力的证据，证明已知的物质只占宇宙观测到的总质量-能量的一小部分。一个主要的暗物质候选者是所谓的弱相互作用大质量粒子，或WIMP，一种预测的大爆炸遗留粒子。对暗物质的直接（非引力）探测将是一个对科学具有根本重要性的变革性发现，开启了对暗宇宙的新研究。这样的暗物质的第一次测量可能是通过WIMP核碰撞检测在低背景，低能量阈值探测器能够区分少量的核反冲从WIMP碰撞在一个长的曝光时间。 液态氩已被确定为具有独特的光发射特性，其为这种WIMP碰撞提供优异的灵敏度，同时提供强的背景抑制。 该奖项为下一代WIMP暗物质实验DarkSide-20 k的制造提供支持。DarkSide国际合作率先使用高放射性纯度的液态氩来寻找罕见的WIMP相互作用。 DarkSide-20 k探测器的设计基准曝光量约为20 kT的低背景液态氩，将在INFN Nazionali del Gran Sasso地下实验室运行。 美国NSF DarkSide团队通过该奖项获得支持，以建造中央暗物质探测器液氩时间投影室，包括相关的高压输送，低温，纯化和校准系统。获得资助的活动涉及可转让的技术，包括：生产低放射性地下氩用于实验以及核禁试核查和放射性测年;地下气体源研究;开发低本底、大面积、单光子低温硅光电倍增管光电传感器;用于增强癌症筛查的液态氩飞行时间正电子发射断层扫描系统;世界上最高的低温蒸馏塔，以提高医疗和能源应用中稳定稀有同位素的可用性。 还包括培训和教育机会，包括在科尔特斯-杜兰戈地区的暑期学校体验，这将为STEM中代表性不足的群体提供更多的机会。美国DarkSide计划领导了DarkSide-50实验计划，该计划证明了液氩中无背景搜索的可行性。DarkSide-20 k实验将在横截面与质量范围内将WIMP暗物质搜索的灵敏度扩展到4.6e-48 cm-2（90%置信限排除），并在500 t-yr曝光后将1 TeV/c-2 WIMP质量的5 sigma发现显著性扩展到1.5e-47 cm-2。 美国在稀有液体探测器制造方面的独特专业知识被用来确保下一代探测器的成功。该项目的规模和由此产生的灵敏度超过了目前运行的探测器，导致发现，确认或排除WIMP暗物质假设的水平，从大气中微子的相干散射成为一个不可还原的背景。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Astronomical observations have provided strong evidence that the known matter accounts for only a small fraction of the observed total mass-energy of the Universe. A leading dark matter candidate is the so-called weakly interacting massive particle, or WIMP, a predicted relic particle of the Big Bang. Direct (non-gravitational) detection of dark matter would be a transformational discovery of fundamental importance broadly to the sciences, opening new investigations of the dark universe. Such first measurements of dark matter may be possible via WIMP-nucleus collisions detectable at low-background, low-energy threshold detectors capable of distinguishing a small number of nuclear recoils from WIMP collisions over a long exposure period. Liquid argon has been identified to have unique light emission properties that provide excellent sensitivity for such WIMP collisions while providing strong background suppression. This award provides support for the fabrication of a next-generation WIMP dark matter experiment, DarkSide-20k. The DarkSide international collaboration has pioneered the use of liquid argon with high radiopurity to search for rare WIMP interactions. The DarkSide-20k detector, with a designed fiducial exposure volume of approximately 20kT of low-background liquid argon, will operate in the INFN Laboratori Nazionali del Gran Sasso deep underground lab. The US NSF DarkSide team is supported via this award to build the central dark matter detector liquid argon time-projection chamber, including the associated high-voltage delivery, cryogenic, purification and calibration systems. The awarded activities involve transferable technologies that include: the production of low-radioactivity underground argon for the experiment as well as for nuclear test ban verification and radiometric dating; studies of underground gas sources; development of low-background, large-area, single-photon cryogenic silicon photomultiplier photosensors; liquid argon-based time-of-flight positron emission tomography system for enhanced cancer screening, and; the world’s tallest cryogenic distillation tower to improve availability of stable rare isotopes for medical and energy applications. Also included are training and education opportunities, including a summer school experience in the Cortez-Durango region that will offer increased access to underrepresented groups in STEM.The US DarkSide program led the DarkSide-50 experimental program that demonstrated the viability of background-free searches in liquid argon. The DarkSide-20k experiment will extend the sensitivity of WIMP dark matter searches in the cross-section vs. mass range to 4.6e-48 cm-squared for the 90% confidence limit exclusion, and to 1.5e-47 cm-squared 5 sigma discovery significance for a 1 TeV/c-squared WIMP mass after a 500t-yr exposure. Unique US expertise in the construction of noble liquid detectors is leveraged to ensure the success of this next generation detector. The scale of project, and its resultant sensitivity, exceeds that of detectors currently operating, leading to discovery, confirmation, or exclusion of the WIMP dark matter hypothesis to the level where coherent scatters from atmospheric neutrinos become an irreducible background.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.