Precise measurement of attenuation length of the JUNO liquid scintillator
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ORIGINAL PAPER
Precise measurement of attenuation length of the JUNO liquid scintillator Xiang-Wei Yin1,2,3 · Tao Hu1,2,3 · Bo-Xiang Yu1,2,3 · Wei Hu1,2,3 · Wen-Qi Yan1,2,3 · Jie-Chen Jiang1,2,3 · Li Zhou1,2,3 · Xiao Cai1,2,3 · Li-Jun Sun1,2,3 · Jian Fang1,2,3 · Yu-Guang Xie1,2,3 Received: 21 March 2020 / Revised: 28 May 2020 / Accepted: 14 June 2020 © Institute of High Energy Physics, Chinese Academy of Sciences 2020
Abstract Introduction The Jiangmen Underground Neutrino Observatory has critical requirements on quality of the liquid scintillator, one of which is long attenuation length. Purpose A system with a height of 3 m is used to precisely measure the attenuation length of the liquid scintillators. Methods The light generated by a LED is transmitted through an optical fiber. After being focused, filtered and collimated, the light enters the test tube with the liquid scintillator and is detected by the PMT. The stepping motor is controlled by the Labview program to adjust the level of the liquid scintillator, and the emitted light intensity of different liquid levels can be obtained to fit the attenuation length. In addition, the systematic errors have been studied, which includes the measurement error of the emitted light intensity and the error caused by the movement of light spot, and the latter is responded to the non-uniformity of the PMT photocathode. Meanwhile, analytical methods were improved. Results The system can measure the attenuation length stably and a small error was obtained, including statistical error and systematic error (0.69–23.70 m). Keywords Precise measurement · Liquid scintillator · Attenuation length
Introduction The Jiangmen Underground Neutrino Observatory(JUNO) [1] is a multi-purpose underground experiment, which includes neutrino mass hierarchy and lepton CP-violating phase [2]. The diameter of the center detector is 35.4 m, including 20,000 tons of liquid scintillator and energy resolution is designed to be 3% @1 MeV [3], corresponding to at least 1100 photoelectrons per MeV of deposited energy. It has various critical requirements for the scintillator, such as the low radioactive background, high light yield and long attenuation length. Specifically, the attenuation length of the liquid scintillator is required to be larger than 20 m@430 nm.
B
Bo-Xiang Yu [email protected]
1
State Key Laboratory of Particle Detection and Electronics, Beijing 100049, China
2
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
3
University of Chinese Academy of Sciences, Beijing 100049, China
So precise measurement of the attenuation length of liquid scintillator is necessary. There are two measurement systems, the height of previous system is 1.5 m, corresponding the effective height 1.4 m, and the new system is 3.0 m, corresponding to the effective height 2.8 m. As shown in Fig. 1, (Formula 14, 16 and 15 represent blue, red and black curves, respectively; a = 0.06%, b = 0.3%)with other factors (the emitted light intensity and the error caused by the m
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