A semi-empirical formula for HPGe detector efficiency calibration

The precision obtainable by instrumental neutron activation analysis depend s strongly on the quality of the calibration of the gamma-ray spectrometer used for measuring the irradiated samples. Even when relative standardizati on is employed, practical experience has shown the importance of detector c alibration. This is especially relevant when radionuclides of varying activ ities are involved. The problems often encountered are those of intolerable high dead time and the occurrence of summed peaks in the gamma-ray spectra . A simple but accurate semiempirical formula is presented that could effec tively predict the efficiency of a detector at any source-to-detector dista nce. Experimental data obtained at 0, 50, 100, 200 mm source-to-detector di stances are used to demonstrate the usefulness of this formulation. In addi tion, nine elements were analyzed in the NIST Orchard Leaves using absolute standardization including four elements Sm, Ta, Au, and La for which no ce rtified values could be obtained.