Collaborative Research: MRI-R2 Instrument Development of the Askaryan Radio Array, A Large-scale Radio Cherenkov Neutrino Detector at the South Pole

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。天文学和天体物理学中最突出的问题之一是产生最高能量（UHE）宇宙射线的宇宙加速器的起源和演化。这个问题可能最好通过观察UHE宇宙中微子来解决，这些中微子从它们的源头出发，不受银河系和星际磁场的偏转，也不受宇宙微波背景辐射（CMB）相互作用的阻碍。然而，宇宙中微子通量预测的不确定性使得设计具有足够灵敏度的阵列来收集具有统计意义的事件样本变得困难。在非常高的能量（高于10^15 eV）下，中微子可以通过阿斯卡扬效应在密集的射频（RF）透明介质中最有效地检测到。覆盖南极的丰富的冷冰，其特殊的射频清晰度，已经主持了几个开创性的努力，以开发这种射频方法。根据在这些实验中获得的专业知识，并利用美国南极计划开发的基础设施，建议开发可以构成阿斯卡里安无线电阵列（ARA）的无线电监听设备，并将其安装在地理南极附近的冰上。ARA阵列的主要目标将是通过适度数量的事件建立绝对的宇宙中微子通量。由于所提议的无线电天线部署在冰洞中，冰洞延伸至冰层以下200米深，因此它们将有能力区分地表噪声和源自冰盖深处的噪声源（否则在气球载实验中是不可能的）。ARA将有足够的灵敏度来确定宇宙射线与CMB相互作用产生的次级UHE中微子的存在与否。这样一个天文台还将提供一个独特的探测器，探测任何人造中微子束都无法实现的长基线高能中微子相互作用。采用阵列的集群几何（其中单个局部集群可以充当独立阵列）将允许以精确的角度分辨率换取增加的事件率。在操作数量有限的观测站时所获得的通量测量和经验，将构成未来扩展阵列所需的性能要求，以便以更高的角度精度测量更多数量的中微子，以研究它们的光谱和起源。该项目将通过将研究生和本科教育与技术和仪器开发相结合，继续为培养下一代科学家做出重大贡献。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). One of the most outstanding questions in astronomy and astrophysics addresses the origin and evolution of the cosmic accelerators that produce the highest energy (UHE) cosmic rays. This question may be best addressed through the observation of UHE cosmogenic neutrinos that travel from their source undeflected by galactic and interstellar magnetic fields and unimpeded by interactions with the cosmic microwave background (CMB) radiation. However, uncertainties in the predicted cosmogenic neutrino fluxes make it difficult to design an array with sufficient sensitivity to collect a statistically meaningful sample of events. At very high energies (above 10^15 eV), neutrinos could be most efficiently detected in dense, radio frequency (RF) transparent media via the Askaryan effect. The abundant cold ice covering the Antarctic, with its exceptional RF clarity, has been hosting several pioneering efforts to develop this RF approach. From the expertise gained in these experiments and utilizing the infrastructure developed by the U.S. Antarctic Program, it is proposed to develop radio-listening equipment that can constitute the Askaryan Radio Array (ARA) and install it in the ice near the geographical South Pole. The primary goal of the ARA array will be establishing the absolute cosmogenic neutrino flux through the modest number of events. As the proposed radio antennae are deployed in ice holes extending below the firn layer to 200-m depth, they will have the ability to distinguish surface noise from sources originating deep in the ice cap (otherwise not possible in balloon-borne experiments). The ARA will have sufficient sensitivity to establish the presence or absence of the secondary UHE neutrinos produced by the interaction of cosmic rays with CMB. Such an observatory would also provide a unique probe of long-baseline high-energy neutrino interactions unattainable with any manmade neutrino beam. The adopted clustered geometry of the array (in which a single localized cluster may act as a standalone array) would allow trading the precise angular resolution for the increased event rates. The flux measurement and experience gained in operating the limited number of stations would frame the performance requirements needed to expand the array in the future to measure a larger number of neutrinos with greater angular precision in order to study their spectrum and origins. The project will continue contributing significantly to the training of the next generation of scientists by integrating graduate and undergraduate education with the technology and instrumentation development.