High accuracy measurements and Monte Carlo calculations of the relative efficiency curve of an HPGe detector from 433 to 2754 keV

The relative full-energy peak efficiency curve of a 280-cm3 coaxial HPGe detector was determined to an accuracy of about 0.1% over the energy range from 433 to 2754 keV from pairs of gamma-ray lines whose emission probabilities are very accurately known. The curve was extended from previous studies by the addition of lines from 108mAg and 24Na. Ratios of full- energy peak efficiencies were also determined by Monte Carlo calculations using the CYLTRAN code. The measured ratios and the Monte Carlo values were in excellent agreement (0.03–0.19%). The relative efficiency was defined by a pair of functions, one for 433–1332 and one for 614–2754 keV. Monte Carlo values were used to supplement the measured values, resulting in a more accurate fit. The stability of the relative efficiency curve for a 94-cm3 HPGe detector was studied and it was found that there was no statistically significant change over a period of 3 years.