Neutron Detector R&D for HALO-1kT TDR

氦铅天文台（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。使用铅作为靶材料使HALO对电子中微子具有独特的灵敏度，与世界各地的其他探测器相辅相成。HALO是超新星预警系统的成员。请求为哈洛系统的持续运行和维护提供支助。II型超新星是由大质量星星核心的引力坍缩提供动力的。炽热的原中子星星主要通过在几十秒内发射各种各样的中微子来冷却。大约99%的引力势能以~ 10 MeV的中微子形式释放出来。从概念上讲，HALO是80吨装有He-3中子探测器的铅。来自超新星的中微子通过带电电流（CC）和中性电流弱相互作用激发铅核，使其处于一个或两个中子被射出的状态。在HALO的He-3探测器中探测到这些中子是银河系超新星的信号。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。铅的中子过剩提供了对νe通量的CC相互作用的主导灵敏度。结合观测数据的超新星模型，提供了提取基本中微子性质的可能性，以及推进我们对超新星机制的理解。SNOLAB的HALO大小适中，受到统计数据的限制，超新星越远，中微子能量越低。意大利LNGS的OPERA探测器退役后，有1.3千吨的铅可用于建造新的探测器HALO-1千吨，其灵敏度比HALO高30倍。此外，美国能源部新提供的He-3为建造更多的He-3中子计数器开辟了道路。 要求为编写技术设计报告所需的研究提供原理测量证明支持。**我们还希望加入COHERENT合作组织，在超新星相关能量下首次测量中微子-铅截面。 位于橡树岭国家实验室的中微子源（SNS）从静止的π介子和μ介子衰变中产生强烈的中微子脉冲。现有的HALO发展数据采集系统，加上备用的He-3中子探测器，将使我们能够很容易地测量中微子-铅截面。需要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-1千吨的能力。现有的和计划中的中微子探测器只对我们银河系内发生的超新星敏感。预计每世纪只有2-3个，因此用许多不同特性和灵敏度的探测器观察下一个是很重要的。从SN 1987 A的20个事件中可以学到很多东西。下一颗银河系超新星应该有更多的可能性。

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.**