[A new method of measuring the system intrinsic variance of scintillation detectors (author's transl)]

A new method is described for the measurement of the system intrinsic variance of scintillation detectors. The system intrinsic variance can be obtained by subtracting the component of photomultiplier variance from the total (observed) variance of detector pulse amplitude; the former component has usually been determined by the use of a light pulser. In the present method, two photomultiplier tubes are optically coupled to a scintillator which is irradiated by a collimated beam of gamma-rays, and the system intrinsic variance is determined from the analysis of mutual correlation of pulse amplitude between the outputs of these two photomultiplier tubes. The method does not need the use of a light pulser, and is able to discriminate the effect of multiple interaction of gamma-rays in the scintillator. A preliminary experiment with a cylindrical NaI(Tl) crystal (4 cmphi X 10 cm) has been performed for a range of gamma-ray energy from 60 keV to 835 keV. The result is well consistent with ones reported by other authors using light pulsers.