ELECTRON EXTRACTION FROM A CSI PHOTOCATHODE INTO CONDENSED XE, KR, AND AR

We have studied the electron extraction from a CsI photocathode into gaseous (0-55 atm) and liquid Xe, Kr, and Ar. Two experimental setups were used. In the first one the photocathode was irradiated with a UV lamp and the photocurrent was directly measured. In the liquid phase, the QE was 2-3 times higher than that in vacuum for LXe and LKr. In LAr, 50% of the vacuum value was achieved. For Xe at a pressure higher than 50 atm, we observed that the QE increased with increasing pressure and gave a value higher than that measured in vacuum. In the second setup, 5.5 MeV alpha particles were used as the source of ionization and scintillation in the liquids, and both the charge and scintillation signals were measured. From the scintillation signal, the intrinsic energy resolution was measured to be 2.8%, 5.2% and 8.4% FWHM, respectively, in LXe, LKr and LAr. Stable operation was demonstrated for all three cryogenic liquids.