Basic Research for a Large Liquid Scintillator Detector

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This study aims to measure the basic properties of liquid scintillator for a large liquid scintillator detector, which Tohoku university group is planning to build for studying the neutrino oscillation. To build such a detector, we need a large amount of the very expensive liquid scintillation. Oneway to reduce the cost of the detector is to dilute the scintillator with solvent such as mineral oil. However, no information for the properties of such a mixed liquid scintillator. Thus, we made a test detector of 2.5cm*7cm phi to measure the absorption length of the liquid scintillator with two phototubes. We use NE224 and 0.976MeV conversion electrons from ^<207>Bi for this test.The test detector was designed to avoid the light reflection from the tube wall by putting shielding rings. After examining the stability of the phototubes, we obtained the absorption length (mu) of NE224mu=5.8(]SY.+-。[)0.9m.Since no information is available for the absorption length of NE224, we repeated the measurements and found that the measured values are consistent with each other.For mixing mineral oil to liquid scintillator, we need to study and establish the mixing method before measuring the absorption length of mixture. Finally, we thank the Ministry of Education, Science, Sports and Culture that we could establish the method of measuring absorption length of liquid scintillator through this Grant-in-Aid.