HALO at SNOLAB

氦和铅天文台（HALO）是一个超新星中微子探测器，目前正在SNOLAB建造。HALO是一种长期、低成本、高寿命、低维护的专用超新星探测器。核心坍缩的超新星是由大质量星星核心引力坍缩释放的能量提供动力的。核心转变为一颗炽热的原中子星星，并通过各种中微子的释放而迅速冷却。事实上，大约99%的总能量是以~ 10 MeV中微子的形式在几十秒内释放的。直接测量的时间演化的光度，味分区，平均中微子能量是我们最好的实验窗口到具有挑战性的领域的超新星动力学，预计将导致一个更好的理解超新星和中微子的基本属性。铅作为超新星探测的介质特别令人感兴趣，因为它的成本低，中微子截面高，中子吸收截面低。铅中的中微子相互作用将中子从铅核中排出，使探测到的中子爆发成为超新星探测的标志。从概念上讲，HALO是一个装有中子探测器的铅体，并通过水与环境中子屏蔽。虽然其他超新星探测器主要对电子反中微子敏感，但铅的核物理学使得HALO通过带电电流相互作用对电子中微子和通过中性电流相互作用对所有中微子都敏感。这些互补的敏感性确保了来自HALO的超新星数据对于解开超新星中微子信号和从下一个银河系超新星中提取物理学至关重要。建造HALO所需的公共投资保持在适度水平，因为可以从退役的深河宇宙射线站获得79吨铅，并从SNO实验的最后阶段获得600多米长的He-3中子探测器。这些资产价值约700万美元，已用于在SNOLAB建造HALO。

The Helium and Lead Observatory (HALO) is a supernova neutrino detector currently under construction at SNOLAB. HALO is a long term, low cost, high livetime, and low maintenance, dedicated supernova detector. A core-collapse supernova is powered by the energy liberated in the gravitational collapse of the core of a massive star. The core is transformed to a hot proto-neutron star that rapidly cools by the emission of neutrinos of all flavours. In fact, about 99% of the total energy is released in the form of ~ 10 MeV neutrinos, in some tens of seconds. The direct measurement of the time evolution of the luminosity, flavour partition, and average neutrino energies are our best experimental window into the challenging field of supernova dynamics which is expected to lead to an improved understanding of supernovae and of fundamental neutrino properties. Lead is particularly interesting, as a medium for supernova detection, due to its low cost, high neutrino cross-section and low neutron absorption cross-section. Neutrino interactions in lead expel neutrons from the lead nuclei making a burst of detected neutrons the signature for the detection of a supernova. Conceptually HALO is a volume of lead instrumented with neutron detectors and shielded from environmental neutrons by water. While other supernova detectors are primarily sensitive to electron antineutrinos the nuclear physics of lead makes HALO dominantly sensitive to electron neutrinos through the charged current interaction and to all flavours of neutrinos through the neutral current interaction. These complementary sensitivities ensure that supernova data from HALO will be vital to unravelling the supernova neutrino signal and extracting physics from the next galactic supernova. The public investment required for the construction of HALO was kept modest by having access to 79 tonnes of lead, from the decommissioned Deep River Cosmic Ray Station, and more than 600 meters of He-3 neutron detectors from the final phase of the SNO experiment. These assets, valued at approximately seven million dollars, have been employed in the construction of HALO in SNOLAB.