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The Jiangmen Underground Neutrino Observatory (JUNO) is a state-of-the-art liquid scintillator-based neutrino physics experiment under construction in South China. To reduce the background from external radioactivities, a water Cherenkov detector composed of 35 kton ultra-pure water and 2,400 20-inch photomultiplier tubes is developed. Even after specialized treatment, ultra-pure water still contains trace levels of radioactive elements that can contribute to the detector background. Among which 222Rn is particularly significant. To address this, an online radon removal system based on the JUNO prototype has been developed. By integrating micro-bubble generators to enhance degasser's radon removal efficiency, the radon concentration in water can be reduced to 1 mBq/m3 level, meeting the stringent requirements of JUNO. Additionally, a highly sensitive online radon concentration measurement system capable of detecting concentrations ∼ 1 mBq/m 3 has been developed to monitor the radon concentration in water. In this paper, the details regarding both systems will be presented. [ABSTRACT FROM AUTHOR]

Due to the shortage of the 3He gas and its rapidly increasing price, scintillator detectors, the advantages of which are high spatial resolution and capability of detection in real time, become widely used in many neutron instruments. In this work, a position-sensitive neutron detector consisting of a 6LiF/ZnS scintillation screen and a silicon photomultiplier array linked to a capacitive network to detect the positions of incident neutrons, is constructed and tested. To evaluate the detector performance, a series of neutron beam experiments with the detector prototype were performed in the BL20 at the China Spallation Neutron Source. The spatial resolution was measured, and the energy-selective neutron imaging and Bragg edge measurements of a 316L stainless steel sample were performed. A sub-millimeter spatial resolution could be obtained for the detector prototype under study. The detector with such a high spatial resolution is promising for applications in neutron scattering experimental installations, especially for neutron single-crystal diffractometers. [ABSTRACT FROM AUTHOR]

A 128-channel positron detection system will be constructed at Experimental Muon Source (EMuS) of China Spallation Neutron Source (CSNS) to conduct muon spin rotation/relaxation/resonance ($\mu $ SR) measurements. Each detector channel consists of a scintillator, a light guide, and a photomultiplier tube (PMT). The long light guide is bent to an “L” shape to propagate optical photons from the scintillator to the PMT. A series of Geant4 simulations and experiments has been performed to optimize the light collection performance of the L-bent detector. Geometry deformation induced by the bending process has been well modeled. Simulation results agree with the experimental tests. Accordingly, a novel hybrid wrapping method (scintillator with polytetrafluoroethylene (PTFE) and light guide with aluminum tape) has been developed to improve the amplitude of detector signals greatly. Compared to wrapping the detector with merely PTFE tapes or aluminum tapes, this method leads to an enhancement in light collection efficiency of 73% or 14%, respectively. Two optimally manufactured prototype detectors using the novel wrapping method have been tested at the ISIS Muon Facility. The beam tests demonstrated that the L-bent detectors can precisely measure the behavior of muon spins inside samples. Therefore, the L-bent detector design is competent for $\mu $ SR applications at CSNS/EMuS. [ABSTRACT FROM AUTHOR]

The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose, large size, liquid scintillator experiment under construction in China. JUNO will perform leading measurements detecting neutrinos from different sources (reactor, terrestrial and astrophysical neutrinos) covering a wide energy range (from 200 keV to several GeV). This paper focuses on the design and development of a test protocol for the 20-inch PMT underwater readout electronics. The protocol has been employed for 10 months during the mass production and validation of all the electronics that will be installed in JUNO. A total number of 6950 electronic boards were tested with an acceptance yield of 99.1 %. [ABSTRACT FROM AUTHOR]

Two inorganic scintillator detectors consisting of Yb:YAG scintillators and photomultiplier tubes, and an oscilloscope were used to studied the neutron sensitivities of Yb:YAG scintillators at the China Spallation Neutron Source (CSNS) Back-n white neutron source. The relative neutron sensitivity curves of two Yb:YAG scintillators in the energy region between 0.5 and 20 MeV were obtained for the first time. As the measured relative neutron sensitivity curves of Yb:YAG scintillators cannot be verified by the Monte Carlo method and there was no referable data, the neutron sensitivity curve of a ST401 scintillator was also studied in the same method and a Geant4 simulation of ST401 scintillator was conducted to verify the experiment method in this paper. The result showed that the experimental and simulation results were approximately consistent between 17–20 MeV, and agreed well between 1–17 MeV. A comparison between the experimental result and references of ST401 scintillator was also applied and the result showed that the curve tendency of the experimental result and references was matched. The above results imply that the measured relative neutron sensitivity curves and the experimental method used herein were reliable. It also demonstrated the feasibility of studying the neutron sensitivity of inorganic scintillator based on the white neutron source. [ABSTRACT FROM AUTHOR]