This paper describes the design, construction principles and operations of the distillation and stripping pilot plants tested at the Daya Bay Neutrino Laboratory, with the perspective to adapt these processes, system cleanliness and leak-tightness standards to the final full scale plants to be used for the purification of the liquid scintillator of the JUNO neutrino detector. The main goal of these plants is to remove radio impurities from the liquid scintillator while increasing its optical attenuation length. Purification of liquid scintillator will be performed with a system combining alumina oxide, distillation, water extraction and steam (or N 2 gas) stripping. Such a combined system will aim at obtaining a total attenuation length greater than 20 m @430 nm, and a bulk radiopurity for 238 U and 232 Th in the 10 -15 ÷10 -17 g/g range. The pilot plants commissioning and operation have also provided valuable information on the degree of reliability of their main components, which will be particularly useful for the design of the final full scale purification equipment for the JUNO liquid scintillator. This paper describes two of the five pilot plants since the Alumina Column, Fluor mixing and the Water Extraction plants are being developed by the Chinese part of the collaboration.
OPERA is part of the CNGS project and it is an experiment dedicated to the observation of long-baseline nu(mu) into nu(tau) oscillations through tau appearance. Resistive Plate Chambers (RPCs) with bakelite electrodes are used to instrument the 2 cm gaps between the magnetized iron slabs of the two spectrometers. The RPC installation ended in may 2004 on the first spectrometer and in march 2005 on the second one. Before the installation, every RPC is subjected to a complete test chain in order to reject the poorer quality detectors. The tests are performed in dedicated facilities to ensure the proper RPC gluing, to measure its electrical properties and to verify the response to cosmic rays and the intrinsic noise levels. We have also tested the long term stability of real size OPERA RPC prototypes operated at cosmic ray fluxes for more than one year. On small size prototypes we are performing studies on the gas' mixtures in order to reduce the total charge released in the gas for each detector count. The validation of the installed RPCs has been performed with pure nitrogen. A small part of them has been also tested with the gas mixture Ar/C2H2F4/i - C4H10/SF6 = 75.4/20/4/0.6
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