Underground Low-Background Nuclear Astrophysics Studies

Caspar(用于执行天体物理研究的紧凑型加速器系统)是美国第一个也是唯一一个深地加速器实验室，也是世界上唯一存在的第二个。它将位于南达科他州铅的桑福德地下研究设施地下近一英里处。核天体物理学将在那里研究，研究的重点将是原始恒星(大爆炸后形成的第一批恒星)轻元素合成的早期阶段。恒星环境中涉及轻元素的核相互作用是宇宙中所有元素产生的基础。这项工作将提供数据来解释天文学家在我们宇宙中最古老的恒星中观察到的元素的丰度；对驱动这些过程的中子来源的调查将提供这些恒星中有助于产生较重元素的核燃烧的更完整的图景。由于大气中宇宙射线相互作用的巨大背景，很难在地球表面附近进行恒星核合成的实验室研究。因此，这项工作将利用位于桑福德地下研究设施(SURF)地下4850英尺处的1兆伏静电加速器来进行利用卡斯帕低宇宙线背景条件的实验。加速和随后用质子和阿尔法离子束轰击一系列感兴趣的元素(例如碳和霓离子)将导致中子和伽马射线的发射，这些中子和伽马射线将用碘化钠(NaI)总和探测器和氚液体闪烁体阵列进行分析。该设施在世界上几乎是独一无二的。它可以与意大利的露娜设施和中国提议的设施相媲美；但两家竞争对手都不会像卡斯帕那样覆盖广泛的能源范围。卡斯帕是圣母大学核天体物理项目的一部分。拟议研究的独特性质将支持对从事核物理工作的研究生的教育和对国家未来核劳动力的培训。Caspar得到了美国国家科学基金会的支持，并与NSF的其他重要倡议，如核天体物理前沿中心(JINA-CEE)和引力波天文台(LIGO)进行了协同。该奖项反映了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。

CASPAR (Compact Accelerator System for Performing Astrophysical Research) is the first and only deep underground accelerator laboratory in the United States and only the second existing in the world. It will be located nearly a mile underground at the Sanford Underground Research Facility in Lead, South Dakota. Nuclear Astrophysics will be studied there and the focus of the studies will be the early stages of light elemental synthesis in primordial stars (the first stars formed after the Big Bang). The nuclear interactions involving light elements in stellar environments are the foundation for the production of all elements in the Universe. This work will provide data to explain the abundance of elements that are observed by astronomers in the oldest stars of our Universe; and an investigation of the source of neutrons that drive these processes will provide a more complete picture of the nuclear burning in these stars that facilitate the production of the heavier elements.Laboratory studies of nucleosynthesis in stars are difficult to perform near the surface of the earth due to an enormous background from cosmic ray interactions in the atmosphere which overwhelm the experiment. Therefore, this work will utilize a 1 Mega Volt electrostatic accelerator located 4850 ft underground at the Sanford Underground Research Facility (SURF) to perform experiments that exploit the low cosmic ray background conditions at CASPAR. The acceleration and subsequent bombardment of a range of elements of interest (for example carbon and neon) with proton and alpha ion beams, will result in the emission of neutrons and gamma rays to be analyzed with Sodium Iodide (NaI) summing detectors and deuterated liquid scintillator arrays. The facility is nearly unique in the world. It is comparable to the LUNA facility in Italy and one proposed in China; but neither competitor will cover as broad an energy range as CASPAR. CASPAR is a part of the nuclear astrophysics program at the University of Notre Dame. The unique nature of the proposed research will support the education of graduate students working in Nuclear Physics and the training of the nation's future nuclear workforce. CASPAR is supported by the National Science Foundation and is synergistic with other important NSF initiatives such as the frontier center for nuclear astrophysics, JINA-CEE and the gravitational-wave observatory, LIGO.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.