Development of Water-Based Liquid Scintillator for Elementary-Particle, Nuclear and Cosmic-Ray Experimental

本研究的目的是开发水基液体闪烁体，以解决油基液体闪烁体的各种问题。在这项研究中，含有苯环的分子被溶解在水和氟中，以便在带电粒子通过液体时获得荧光。含有苯环的分子有两种，可以溶解在水中。一种是含苯环的表面活性剂，另一种是水溶性芳香族液体。将不同种类的这类分子与不同浓度组合的PPO、bi-MSB等荧光剂混合在水中，用^&lt；60&gt；公司的γ-射线测量其光输出。如果样品有显著的光输出，则进一步研究其光衰减长度、闪点和稳定性。将表面活性剂和氟溶解于水中，可制得水含量82%、出光量7.2%、光衰减长度77cm420 nm光的不可燃液体闪烁体，或水含量81%、出光量4.0%、光衰减长度220cm.这些光输出足以用于原子核实验和处理高电离粒子的基本粒子实验。另一方面，在加速试验中，这些液体闪烁体在8个月的等效期后表现出老化性能。这仍然是一个遗留问题。一个中微子实验正在设计中，这种水基液体闪烁体是使用的候选之一。

The aim of this research is to develop water-based liquid scintillator to solve various issues associated with the oil based liquid scintillators. In this research, molecules which contains benzene circle are dissolved in water as well as fluors in order to obtain fluorescence when a charged particle passes through the liquid. There are two kinds of molecules which contain the benzene circle and can be dissolved in the water. One is surfactant with the benzene circle and the other is water-solvable aromatic liquid. Various kinds of such molecules were listed up and mixed in water together with fluors such as PPO and bis-MSB with various combinations of concentrations and its light output was measured using γ-rays from ^<60>Co. If a sample showed a significant light output, its light attenuation length, flash point and stability were further investigated. We could make noninflammable liquid scintillators with 82% of water content, 7.2% Anthracene of light output and 77cm of light attenuation length for 420nm wavelength light, or 81% water content, 4.0% Anthracene of light output and 220cm of light attenuation length, by dissolving surfactant and fluors in water. These light outputs are high enough for nuclear experiments and elementary particle experiments which deal with high ionizing particles. On the other hand it turned out these liquid scintillators show aging properties after 8months equivalent period in acceleration tests. This is still a remaining issue. A neutrino experiment is being designed in which this water-based liquid scintillator is one of the candidates to be used.