EXPERIMENTAL INVESTIGATION OF SCINTILLATION COUNTER EFFICIENCY

The efficiency of cylindrical NaI(Tl) crystals, irradiated by point sources of Tl/sup 204/, Hg/sup 203/, Sn/sup 113/, Cs/sup 137/, and Co /sup 60/ calibrated in an air-equivalent ionization chamber, was investigated and correlated with radium. Curves plotted for various size crystals and discrimination levels show that efficiency is determined mainly by photomultiplier performance and by the sensitivity of the scheme rather than by the dimensions of the crystals. (R.V.J.)