Neutron Detector R&D for HALO-1kT TDR

氦和铅天文台（HALO）是一个低成本、高寿命、低维护的超新星探测器，自2012年5月以来一直在SNOLAB运行。使用铅作为目标材料使HALO对电子中微子具有独特的灵敏度，与世界上其他探测器互补。HALO是超新星预警系统的成员之一。要求对HALO的持续操作和维护提供支助。****** II型超新星是由大质量恒星核心的引力坍缩提供能量的。热的原中子星主要是通过发射各种形式的中微子在几十秒内冷却下来的。释放的重力势能中约99%以~10MeV的中微子形式出现。从概念上讲，HALO是80吨的铅，配有氦-3中子探测器。来自超新星的中微子通过带电电流（CC）和中性电流的弱相互作用激发铅核，从而产生一个或两个中子。在HALO的He-3探测器中探测到这些中子是一颗星系超新星的信号。光度、味道和平均中微子能量的时间演化为超新星动力学提供了一个直接的窗口。铅的中子过剩对ν通量的CC相互作用具有主要的敏感性。超新星模型与观测数据相结合，提供了提取中微子基本性质的可能性，并推进了我们对超新星机制的理解。SNOLAB的HALO规模不大，受统计数据的限制，超新星越远，或者中微子能量越低，就越受限制。意大利液化天然气公司OPERA探测器的退役使1.3 kT的铅可用于建造一个新的探测器，HALO- 1kt，灵敏度比HALO高30倍。此外，来自美国能源部的氦-3的新可用性为建造更多的氦-3中子计数器开辟了道路。为编写技术设计报告所需的研究，要求支持原理测量的证明。******我们还希望加入相干协作，在超新星相关能量下首次测量中微子-铅的横截面。橡树岭国家实验室的散裂中子源（SNS）从静止的介子和介子衰变中产生强烈的中微子脉冲。现有的HALO开发数据采集系统，加上备用的He-3中子探测器，将使我们能够轻松地测量中微子-铅的截面。要求支持将此硬件传输到SNS和从SNS传输。这一测量将完成HALO的校准，并有助于确定HALO- 1kt的能力。******现有的和计划中的中微子探测器只对银河系内发生的超新星敏感。每个世纪预计只有2-3个，所以用许多不同特征和灵敏度的探测器观察下一个是很重要的。从SN 1987A的20个事件中学到了很多东西。下一颗银河系超新星应该会带来更多的可能

The Helium and Lead Observatory (HALO) is a low cost, high livetime, low maintenance supernova detector running at SNOLAB since May 2012. The use of lead as the target material gives HALO unique sensitivity to electron neutrinos, complementary to other detectors worldwide. HALO is a member of the SuperNova Early Warning System. Support is requested for the ongoing operation and maintenance of HALO.******A type II supernova is powered by the gravitational collapse of the core of a massive star. The hot proto-neutron star cools primarily by the emission of neutrinos, of all flavours, in some tens of seconds. About 99% of the gravitational potential energy liberated emerges as ~10MeV neutrinos. Conceptually, HALO is 80 tonnes of lead instrumented with He-3 neutron detectors. Neutrinos from the supernova excite lead nuclei via both charged current (CC) and neutral current weak interactions to states from which one or two neutrons are ejected. The detection of these neutrons in HALO's He-3 detectors signals a galactic supernova. The time evolution of the luminosity, flavours and average neutrino energy give a direct window into supernova dynamics. The neutron excess of lead provides for a dominant sensitivity to CC interactions of the νe flux. Modeling of supernovae combined with observational data, offers the possibility of extracting fundamental neutrino properties as well as advancing our understanding of the supernova mechanism. HALO at SNOLAB is modest in size and limited by statistics, more so the further the supernova, or the lower the neutrino energy. The decommissioning of the OPERA detector at LNGS in Italy makes 1.3 kT of lead available for the construction of a new detector, HALO-1kT, up to 30 times more sensitive than HALO. Also the new availability of He-3 from the US DOE opens a path to build more He-3 neutron counters. Support is requested for proof of principle measurements for the studies necessary to write a Technical Design Report.******We also wish to join the COHERENT Collaboration to make the first measurement of neutrino-lead cross sections at supernova-relevant energies. The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory produces intense pulses of neutrinos from pion and muon decay at rest. The existing HALO development data acquisition system, together with spare He-3 neutron detectors would enable us to easily measure the neutrino-lead cross section. Support is requested to transport this hardware to and from the SNS. This measurement would complete the calibration of HALO as well as help define the capabilities of HALO-1kT.******Existing and planned neutrino detectors are only sensitive to supernovae occurring within our Galaxy. Only 2-3 are expected per century, so it is important to observe the next one with many detectors of diverse characteristics and sensitivities. Much was learnt from the 20 events from SN 1987A. Much more should be possible from the next galactic supernova.**