Oxygen contamination in liquid argon: combined effects on ionization electron charge and scintillation light

A dedicated test of the effects of Oxygen contamination in liq. Argon has been performed at the INFN-Gran Sasso Lab. (LNGS, Italy) within the WArP R&D program. Two detectors have been used: the WArP 2.3 It prototype and a small (0.7 It) dedicated detector, coupled with a system for the injection of controlled amts. of gaseous Oxygen. O2 contamination in LAr leads to depletion of both the free electron charge (via attachment process) and the scintillation light (via quenching and absorption mechanisms) available for ionization signal detection