Detection of γ-rays with a 3.5 1 liquid xenon ionization chamber triggered by the primary scintillation light

A gridded ionization chamber with a drift length of 4.5 cm and a total volume of 3.5 1, was operated with high-purity liquid xenon and extensively tested with gamma-rays from Cs-137, Na-22 and Co-60 radioactive sources. An electron lifetime in excess of I ins was inferred from two independent measurements. The electric Field dependence of the collected charge and energy resolution was studied in the range 0.1-4 kV/cm, for different gamma-ray energies, With an electric field of 4 kV/cm, the spectral performance of the detector is consistent with an energy resolution of 5.9% at 1 MeV, scaling with energy as E-0.5 The chamber was also used to detect the primary scintillation light produced by gamma-ray interactions in liquid xenon. The light signal was successfully used to trigger the acquisition of the charge signal with a FADC readout. A trigger efficiency of similar to85% was measured at 662 keV. (C) 2002 Elsevier Science B.V. All rights reserved.