The experimental results coming from an intense R&D study about the possibility of detecting the light produced by the liquid argon scintillation certify the use of glass-window photomultiplier tubes.The devices,working in cryogenic liquid,are made sensitive to the VUV photons by means of a wavelength shifter coating.This is a useful detection method to provide an effective way for the absolute time measurement and trigger of ionizing events occurring in Time Projection Chambers.2003 Elsevier Science B.V. All rights reserved.