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The Jiangmen Underground Neutrino Observatory (JUNO) is a large-scale neutrino detector with 20 kton high transparency liquid scintillator (LS). To increase the attenuation length of LS, alumina absorption columns are used to purify the optical impurities in Linear Alkyl Benzene (LAB), the raw material of LS. Prototypes of absorption columns were constructed to test absorption material and parameters that could affect the purification efficiency including column height-diameter ratio and flow rate. Meanwhile, the pilot plant of alumina purification system was built in the Daya Bay Neutrino Laboratory to test the design and operation process, provide parameter reference for the design of JUNO purification system. The alumina purification pilot plant can increase the attenuation length of LAB from 20 m to more than 24 m without introducing radioactive background at 1 0 − 15 g/g level. The pilot plant of alumina purification system can meet the JUNO requirements in LS optical purification. [ABSTRACT FROM AUTHOR]

The Jiangmen Underground Neutrino Observatory (JUNO) uses 20k tons of liquid scintillator (LS) to detect neutrinos. The content of radioactive substances in the liquid scintillator will affect the experimental results. JUNO will use counter current water extraction to reduce the radioactive metal ions inside the LS. In this article, factors that affect the final water extraction like the partition coefficient, the optimal mass transfer droplet size, the flow rate ratio, theoretical stage and different working mode (LS as continuous phase or dispersed phase) have been studied. We built counter current extraction prototype in the laboratory and a pilot plant in Daya Bay. We study the factors above, and gain engineering experience that worth sharing. [ABSTRACT FROM AUTHOR]

The Jiangmen Underground Neutrino Observatory (JUNO), a multi-purpose neutrino experiment, will use 20 kt liquid scintillator (LS). To achieve the physics goal of determining the neutrino mass ordering, 3% energy resolution at 1 MeV is required. This puts strict requirements on the LS light yield and the transparency. Four LS purification steps have been designed and mid-scale plants have been built at Daya Bay. To examine the performance of the purified LS and find the optimized LS composition, the purified LS was injected to the antineutrino detector 1 in the experimental hall 1 (EH1-AD1) of the Daya Bay neutrino experiment. To pump out the original gadolinium loaded LS and fill the new LS, a LS replacement system has been built in EH1 in 2017. By replacing the Gd-LS with purified water, then replacing the water with purified LS, the replacement system successfully achieved the designed goal. Subsequently, the fluorescence and the wavelength shifter were added to higher concentrations via the replacement system. The data taken at various LS compositions helped JUNO determine the final LS cocktail. Details of the design, the construction, and the operation of the replacement system are reported in this paper. [ABSTRACT FROM AUTHOR]