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

We have studied the electron extraction from a CsI photocathode into g aseous (0-55 atm) and liquid Xe, Kr, and Ar. Two experimental setups w ere used. In the first one the photocathode was irradiated with a UV l amp and the photocurrent was directly measured. In the liquid phase, t he 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 th an 50 atm, we observed that the QE increased with increasing pressure and gave a value higher than that measured in vacuum. In the second se tup, 5.5 MeV alpha particles were used as the source of ionization and scintillation in the liquids, and both the charge and scintillation s ignals were measured. From the scintillation signal, the intrinsic ene rgy resolution was measured to be 2.8%, 5.2% and 8.4% FWHM, respective ly, in LXe, LKr and LAr. Stable operation was demonstrated for all thr ee cryogenic liquids.