HALO - High Voltage System

SNOLAB的HALO探测器被设计成一个长寿命，低维护的专用超新星中微子探测器。从某种意义上说，它也是一个机会探测器，它主要是由以前的实验提供给HALO合作的回收材料建造的。特别是从一个废弃的宇宙射线站获得79吨铅块；世界上放射性最低的氦-3中子探测器阵列，最初是为SNO实验建造的；以及来自SNO实验的读出电子设备，使得HALO的建设只需要非常适度的公共投资。超新星是大质量恒星生命周期结束时发生的灾难性事件。核心坍缩超新星的特点是瞬间发射天文数字的中微子。就像我们用中微子观察太阳的核心，并证实它是由核聚变提供能量一样，我们可以通过探测超新星爆炸产生的高能中微子，观察我们银河系内任何地方的一颗爆炸的恒星。详细了解控制超新星发生过程的所有物理定律是当前计算物理学的重大挑战之一。从本质上讲，超新星具有根本的重要性和兴趣，因为它们是重元素产生的场所，并且它们负责这些元素在星系内的分散。超新星中微子的探测提供了一种可能性，通过提供数据来测试计算模型，从而提高我们的知识。通过这样的比较，有很大的潜力可以了解超新星的过程，以及中微子的性质和相互作用。HALO利用铅作为目标来探测超新星中微子。高能中微子从铅核中喷射出中子，然后被HALO的氦-3中子探测器捕获。2012年5月8日，HALO探测器首次全面运行。从那时起，它通过调试阶段一直处于近乎连续的运行状态。我们期待在不久的将来加入世界范围的超新星早期预警系统（SNEWS），由于中微子在爆炸本身到达恒星表面之前就会逃逸，因此中微子探测器可以在超新星出现前10小时通知天文学家。与其他超新星探测技术（如水切伦科夫和液体闪烁体探测器）相比，HALO主要对电子中微子敏感，而不是电子反中微子，这使得HALO具有独特的潜力，可以为下一个银河系超新星的物理结果做出贡献。由于星系核心坍缩超新星是罕见的事件，每世纪只发生几次，而且它们也是中微子发射持续时间不到一分钟的短暂事件，因此HALO必须争取非常长的生存时间，以确保其科学影响。HALO的初始电子设备和数据采集配置，虽然可以运行并且对我们银河系中的超新星完全敏感，但它是由现有的SNO电子设备创建的，其中一些已经有20年的历史了。它没有必要的冗余和可靠性，以保证HALO在探测器的长期预期寿命内保持运行。在更新电子设备的关键部件、建立冗余和消除单点故障方面，已经取得了很大进展。在这一点上，唯一剩下的需要更新的检测器元件是高压系统。这项拨款申请的目标是缩小这一差距，并完成HALO的电子升级。

The HALO detector at SNOLAB has been designed to be a long-lifetime, low-maintenance dedicated supernova neutrino detector. It is also a detector of opportunity in the sense that it has been constructed largely from recycled materials made available to the HALO collaboration by previous experiments. In particular, the availability of 79 tonnes of lead blocks from a decommissioned cosmic ray station; an array of the world's lowest-radioactivity Helium-3 neutron detectors, originally built for the SNO experiment; and readout electronics also from the SNO experiment, has permitted the construction of HALO for a very modest public investment. Supernovae are cataclysmic events that occur at the end of the life cycle of a massive star. Core-collapse supernovae are characterized by the fleeting emission of astronomical numbers of neutrinos. Just as we have used neutrinos to look into the core of the sun, and to confirm that it is powered by nuclear fusion, we can, by detecting the energetic neutrinos from a supernova explosion, look into an exploding star anywhere within our galaxy. The detailed understanding of all the physical laws that govern what happens during a supernova is currently one of the grand challenges of computational physics. Intrinsically, supernovae are of fundamental importance and interest due to the fact that they are the site for the creation of the heavy elements, and that they are responsible for the dispersion of these elements within the galaxy. The detection of supernova neutrinos offers the possibility of advancing our knowledge by providing data against which computational models can be tested. There is a great potential to learn things both about the supernova process as well about the nature and interactions of neutrinos by making such a comparison. HALO detects supernova neutrinos by using lead as a target. Energetic neutrinos eject neutrons from the lead nuclei which are then captured by HALO's Helium-3 neutron detectors. On May 8th 2012 the HALO detector was fully operated for the first time. Since then it has been in near-continuous operation through a commissioning phase. We look forward in the very near future to joining the world-wide Supernova Early Warning System (SNEWS) which, since neutrinos escape an exploding star before the explosion itself actually reaches the surface of the star, permits neutrino detectors to inform astronomers of an impending supernova up to 10 hours before it is visible. HALO, in contrast to other supernova detector technologies, such as water Cherenkov and liquid scintillator detectors, is primarily sensitive to electron neutrinos, rather than electron anti-neutrinos, giving HALO a unique potential to contribute to the physics that will result from the next galactic supernova. Since galactic core-collapse supernovae are rare events occurring only a few times per century, and since they are also brief events with neutrino emission lasting less than a minute, HALO must strive for very high livetime to ensure its scientific impact. The initial electronics and data acquisition configuration of HALO, although operational and fully sensitive to a supernova in our galaxy, was created from the available SNO electronics, some of which was 20 years old. It did not have the redundancy and reliability needed to guarantee that HALO will remain live over the long anticipated life of the detector. Much progress has been made in working towards renewing critical components of the electronics, building in redundancy, and eliminating single points of failure. The only remaining detector element in need of renewal at this point is the High Voltage System. The objective of this grant application is close this gap and complete the electronics upgrade of HALO.