Quenching of undesired fluorescence in a liquid scintillator particle detector

The efficiency of quenching the fluorescence light in pseudocumene (PC) by the addition of pyridyl and phthalate derivatives (quenchers) has been studied both by ultraviolet excitation of PC and by using ionizing particles. The results show that a controlled reduction of the PC fluorescence is easily achieved by the addition of quencher in concentrations of a few grams per litre. The scintillation light can be quenched to a level where the Cherenkov light remains the only detectable signal when ionizing particles deposit energy in the solvent. While these data are of particular interest for the design of the Borexino buffer, more general applications of these results are envisaged and discussed.