IMPROVEMENT POSITRON-ANNIHILATION LIFETIME SPECTROMETER BY USING THE FAST DECAY COMPONENT IN BAF2 LUMINESCENCE

Application of our BaF//2 detector to positron annihilation lifetime spectrometer (PALS) can improve the time resolution from FWHM equals 270 ps to FWHM equals 190 ps or increase the counting rate by ten times. The energy resolution and the timing resolution of BaF//2 detector depend on the number of photoelectrons, converted by the scintillation light, from the photocathode of the photomultiplier. The photoelectron yield of the BaF//2 detector has been measured by means of these method of comparing with the pulse amplitude of the single electron emitted by the photocathode of the photomultiplier. The results of the measurement are given.