Water Cherenov detector is a vital part in most of neutrino or cosmic ray research. As detectors grow in size, the water attenuation length (WAL) becomes increasingly essential for detector performance. It is essential to measure or monitor the WAL. While many experiments have measured WAL in the lab or detector, only the Super-Kamiokande experiment has achieved values exceeding 50 meters in the detector with a moving light source. However, it is impractical for many experiments to place a moving light source inside the detector, necessitating an alternative method for investigating long WAL. A novel system has been proposed to address the challenge of investigating long WAL. This system focuses on ample water Cherenkov detectors and features a fixed light source and photomultiplier tubes (PMTs) at varying distances, eliminating the need for moving parts. The static setup demands high precision for accurate measurement of long WAL. Each component, including LED, diffuse ball, PMTs, and fibers, is introduced to explain uncertainty control. Based on lab tests, the system's uncertainty has been controlled within 5\%. Additionally, camera technology is also used during the evaluation of the system uncertainty, which has the potential to replace PMTs in the future for this measurement. Monte Carlo simulations have shown that the system can achieve a 5\% measurement uncertainty at WAL of 80 meters and 8\% at WAL of 100 meters. This system can be used in experiments with large Cherenkov detectors such as JUNO water veto and Hyper-K.
STRAW (STRings for Absorption length in Water): pathfinder for a neutrino telescope in the deep Pacific Ocean
本文报道了一个可能的大尺度中微子望远镜“水中吸收长度弦”（STRings for Absorption Length in Water，简称STRIN）的设计和初步性能。2018年6月，该系统被部署在加拿大海洋网络运营的卡斯卡迪亚盆地，并从那时起一直在收集数据。在大约2600米的深度，两个120米高的系泊缆由三个“精密光学校准模块”（POCAM）和五个数字光学传感器（sDOM）组成。我们描述了仪器部署和第一光在太平洋。
Measurement of Muon-induced High-energy Neutrons from Rock in an Underground Gd-doped Water Detector
我们提出了一个测量的相关中子捕获率的手表男孩探测器，部署在深度约390米水当量（m.w.e.）。Kimballton Underground Research Facility（KURF）WATCHBOY由一个2吨重的圆柱形水靶组成，其中掺杂了0.1%的钆，周围有一个40吨重的无掺杂水密封屏蔽层。我们提出了一个比较我们的结果与预期的相关中子捕获率所产生的高能中子入射在外面的手表屏蔽，预测的混合FLUKA/GEANT 4为基础的模拟。模拟中使用的入射中子能量分布是由快中子谱仪，1.8吨多重和反冲谱仪（MARS）探测器，在同一深度测量的。我们发现，测量的两个相关的中子的探测率是一致的模拟预测。这一结果为MARS使用的探测技术提供了额外的信心，因此也为在三个不同深度测量的MARS光谱提供了信心。快中子通量和能谱的确认是重要的，因为它有助于验证用于预测不同覆盖层下快中子通量的标度模型。
