DEVELOPMENT OF INDIUM-LOADED LIQUID SCINTILLATORS WITH LONG ATTENUATION LENGTH

A new indium-loaded liquid scintillator which contains indium up to ∼ 7.5% by weight has been developed. Indium as a form of indium trichloride tetrahydrate was loaded into a xylene-based organic liquid scintillator containing ∼ 30% of surfactant that had a capability to mix polar and nonpolar liquids. The indium-loaded liquid scintillator obtained by this method has an attenuation length of ≥ 150 cm and an energy resolution of ± 13.1% (σ) for 7.1% indium loading (± 11.7% for 5% indium loading) for 477 keV electrons over the entire length of a 1 m test cell with a diameter of 5 cm. A position resolution of ± 4.5 cm was obtained by the timing information from the photomultiplier tubes at each end. Since there are hundreds of surfactants, further improvement of the quality of the indium-loaded liquid scintillator, such as the rate of indium loading, the energy resolution and the attenuation length, would be possible by making different choices and combinations of existing various surfactants. An estimate of an allowable environmental γ-ray background level of this indium-loaded liquid scintillator as a 7Be pep-neutrino detector was also given. © 1990.