ABSOLUTE NUMBER OF PHOTONS PRODUCED BY ALPHA-PARTICLES IN LIQUID AND GASEOUS XENON

The W(s), which is defined as an average energy expended per scintillation photon, was found to be 16.3 +/- 0.3 eV for alpha-particles in liquid xenon, and 49.6 +/- 1.1 eV in gaseous xenon, respectively. These results followed from the number of photoelectrons measured with a VUV sensitive photomultiplier tube, which was used as a photodiode. The number of photoelectrons from the photomultiplier photocathode was measured absolutely with a well calibrated charge sensitive amplifier system as a function of distance between the alpha-source and the photomultiplier photocathode. The detection geometries included both reflective and nonreflective walls. The data were well fitted to corresponding curves obtained with a Monte Carlo simulation, and yielded the total number of scintillation photons.