Realtime Measurement of pp and ^7Be Solar Neutrinos

研究和开发了具有带电电流相互作用的低能太阳中微子的实时测量方法。^<160>的Gd原子非常适合这一目的，因为它具有非常低的能量反应阈值，可以进行pp中微子探测，并且具有非常典型的三重符合信号，有助于抑制背景。在本研究中，重点是将钆溶解到快速液体闪烁体中，以实现必不可少的三重重合。对负载钆液体闪烁体进行了性能测试，并进行了作为低能太阳中微子探测器的可行性测试。对溶剂和钆化合物进行了广泛的调查，发现PsuedoCumene(60%)，洗涤剂NS210（40%）和Gd(NO_3)_36H_2O的良好组合可以保持高达8重量%的钆。负载钆的液体闪烁体在5wt %时的性能为；衰减时间2ns， 3500光子/MeV，有效透射率39 cm， 7.8MeV α猝灭7.4，α分辨率95%，适用于低能太阳中微子观测。对1m^3大小的探测器的模拟表明，即使选择标准对有问题的^<152>Gd α衰变的错误识别概率小于0.05%，对^7Beneutrino信号的三倍符合识别效率为65%，对pp中微子的三倍符合识别效率为63%。这个闪烁体的成本仅为其他竞争项目的十分之一。因此，成功地研制出了极具竞争力的含钆液体闪烁体。

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.