Absolute light yield measurements on BaF/sub 2/ crystals and the quantum efficiency of several photomultiplier tubes

The quantum efficiency curves of five Philips XP2020Q photomultiplier tubes (PMTs), one Hamamatsu R2059 PMT, and a Na-salicylate coated glass window are determined using a calibrated Thorn EMI 9426 PMT as a reference. The QE of XP2020Q PMTs at wavelengths smaller than 230 nm appears much better than the values specified by the manufacturer. Consequently, the often reported photon yield of 2000 photons/MeV for the fast component of the scintillation pulses from pure BaF/sub 2/ crystals determined with this tube is overestimated. The authors' results, obtained by means of calibrated equipment and using 662-keV gamma -rays, yield a value of 1400 photons/MeV.<
>