arXiv 1201.00722012-01astro-ph.IM

South Pole冰中天体物理中微子的声学探测

Acoustic detection of astrophysical neutrinos in South Pole ice

Justin Vandenbroucke

备注：: PhD thesis, UC Berkeley, 2009, posting for archival purposes

摘要：

当高能粒子在稠密介质中相互作用产生粒子簇射时，大部分簇射能量作为热量沉积在介质中。这导致介质局部膨胀并发射具有10 kHz量级的介质相关峰值频率的冲击波。特别是在南极冰中，介质的弹性特性已经被理论化，以提供粒子能量与声能的良好耦合。理论上，声衰减长度为几公里，这可以使一个稀疏的仪器大体积探测器搜索来自高能天体物理中微子的罕见信号。我们模拟了IceCube阵列的混合光学/无线电/声学扩展，专门用于同时用多种方法检测宇宙成因（GZK）中微子，以实现对所发现信号的高置信度，并测量GZK中微子的角度，时间和光谱分布。这项工作推动了南极声学测试装置（SPATS）的设计、部署和运行。SPATS的主要目的是测量南极的声衰减长度、声速剖面、本底噪声和瞬态噪声源\emph{in situ}。我们描述了SPATS的设计，性能和结果。我们测量了200米和500米深度之间的完全致密的冰的声速为3878 $\pm$ 12米/秒的压力波和1975.8 $\pm$ 8.0米/秒的剪切波。我们测量的声振幅衰减长度为316 $\pm$ 105 m。我们测量的背景噪声是高斯的，并且在从一秒到两年的所有时间尺度上都非常稳定。最后，我们在一年多的高质量瞬态数据采集中发现了一组有趣的重建良好的瞬态事件。最后，我们讨论了SPATS的下一步是什么和声学中微子探测冰的前景。

英文摘要：

When high-energy particles interact in dense media to produce a particle shower, most of the shower energy is deposited in the medium as heat. This causes the medium to expand locally and emit a shock wave with a medium-dependent peak frequency on the order of 10 kHz. In South Pole ice in particular, the elastic properties of the medium have been theorized to provide good coupling of particle energy to acoustic energy. The acoustic attenuation length has been theorized to be several km, which could enable a sparsely instrumented large-volume detector to search for rare signals from high-energy astrophysical neutrinos. We simulated a hybrid optical/radio/acoustic extension to the IceCube array, specifically intended to detect cosmogenic (GZK) neutrinos with multiple methods simultaneously in order to achieve high confidence in a discovered signal and to measure angular, temporal, and spectral distributions of GZK neutrinos. This work motivated the design, deployment, and operation of the South Pole Acoustic Test Setup (SPATS). The main purpose of SPATS is to measure the acoustic attenuation length, sound speed profile, noise floor, and transient noise sources \emph{in situ} at the South Pole. We describe the design, performance, and results from SPATS. We measured the sound speed in the fully dense ice between 200 m and 500 m depth to be 3878 $\pm$ 12 m/s for pressure waves and 1975.8 $\pm$ 8.0 m/s for shear waves. We measured the acoustic amplitude attenuation length to be 316 $\pm$ 105 m. We measured the background noise floor to be Gaussian and very stable on all time scales from one second to two years. Finally, we have detected an interesting set of well-reconstructed transient events in over one year of high quality transient data acquisition. We conclude with a discussion of what is next for SPATS and of the prospects for acoustic neutrino detection in ice.

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英文摘要：

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