Realtime Measurement of pp and ^7Be Solar Neutrinos

研究和发展了一种利用带电电流相互作用实时测量低能太阳中微子的方法。^<160>Gd原子非常适合用于此目的，因为其非常低的能量反应阈值使得能够进行pp中微子检测，并且具有非常特征的三重符合信号，可用于背景抑制。本研究的重点是将钆溶解到快速液体闪烁体中，以获得不可缺少的三重符合。同时，还对钆闪烁体进行了性能测试和作为低能太阳中微子探测器的可行性试验。通过对溶剂和钆化合物的广泛考察，发现了一种优良的组合，即假枯烯（60%）、洗涤剂NS 210（40%）和Gd（NO_3）_36H_2O，其可容纳高达8wt%的钆。实验测得5wt%钆闪烁体的衰减时间为2ns，有效光透射率为39cm，在7.8MeV时α猝灭为7.4，α二次猝灭率为95%，适用于低能太阳中微子观测。对1 m^3大小的探测器进行的模拟表明，即使在对有问题的^ Gd α衰变的错误识别概率小于0.05%的选择标准下，^7 β中微子信号的三重符合识别效率为65%，pp中微子的三重符合识别效率为63%<152>。这种闪烁体的成本仅为其他竞争产品的十分之一。因此，非常有竞争力的钆负载液体闪烁体已被成功开发。

Research and development for a realtime measurement of low energy solar neutrinos with charged current interaction has been performed. The ^<160>Gd atom is quite suitable for this purpose because of its very low energy reaction threshold enabling pp neutrino detection and of very characteristic three fold coincidence signal useful for background rejection. In this research, it was focused on solving Gadolinium into fast liquid scintillator so that indispensable three fold coincidence can be achieved. Performance measurement of the Gadolinium loaded liquid scintillator and feasibility test as low energy solar neutrino detector are also carried out. Performing wide survey of solvents and Gadolinium compounds, an excellent combination of PsuedoCumene (60 %), detergent NS210 (40 %) and Gd(NO_3)_36H_2O was found that it can hold Gadolinium up to 8 weight %. The performance of the Gadolinium loaded liquid scintillator at 5wt % was measured to be ; 2ns as decay time, 3500photons/MeV, effective light transmission 39 cm, alpha quench 7.4 at 7.8MeV and alpha dicrimination 95 % resulting applicable to the low energy solar neutrino observation. A simulation of 1m^3 size detector provided efficiencies of three fold coincidence identification to be 65 % for ^7Beneutrino signal and 63 % for pp neutrino even with a selection criteria that has less than 0.05 % misidentification probability to the problematic ^<152>Gd alpha decay. This scintillator costs only one tenth in relative to the other competing developments. Thus, the very competitive Gadolinium loaded liquid scintillator has been successfully developed.