SIMPLE AND ACCURATE CALIBRATION TECHNIQUE FOR MEASURING GAMMA-RAY ENERGIES AND GE(LI)DETECTOR LINEARITY

A technique for precise calibration of Ge(Li) γ-ray spectrometers, which is particularly useful in studies of decay schemes, has been developed. The differential response of a multichannel analyzer is measured with a sliding pulse generator whose incremental nonlinearity is 0.005-0.01%. The integral of this response with respect to counts is a linear function of energy. With the use of two known γ-ray lines the calibration constant in counts/keV, and in turn, the energies corresponding to unknown γ-ray peaks can be determined. The technique is simple, fast and virtually automatic. The method was evaluated by measuring γ-ray energies (0.27-2.75 MeV) from ten sources. The results obtained agree with published values to within the measurement uncertainty of 40-110 eV. The accuracy of the technique depends on the linearity of the sliding pulser and the Ge(Li) detector. From a spectrum of 66Ga, measured energy intervals of 2m0c2 were examined as a function of γ-ray energy. The standard deviation of the eight 2m0c2 intervals was only 0.08 keV. It is therefore concluded that between 1 and 5 MeV the incremental non-linearity of the coaxial Ge(Li) detector is less than ±0.1 keV. Measurement uncertainties due to errors in the calibration standards, peak location, and the number of counts/channel in the differential response are discussed. © 1969.