EFFECT OF CASCADE COINCIDENCES ON THE EFFICIENCY CALIBRATION OF A GAMMA-X DETECTOR

The sensitivity on n-type gamma-X detectors for low-energy X- and gamm a-rays calls for coincidence corrections in the efficiency calibration that do not apply to the calibration of p-type detectors. Corrections were calculated for the effect of cascade coincidences between gamma- rays, X-rays, annihilation radiation, and bremsstrahlung, for 15 radio nuclides frequently used for efficiency calibration. Experimental resu lts are presented for a gamma-X detector with 37% relative efficiency at distances from 0.9 to 17.5 cm. After coincidence correction smooth efficiency curves were found for the energy range 12 to 2750 keV, even for the position closest to the detector.