Applicability of the analytical functions and semi-empirical formulae to the full energy peak efficiency of large volume HPGe gamma detectors

Abstract

The applicability of various analytical functions and semi-empirical formulae proposed for representing the full energy peak efficiency (FEPE) curves of Ge(Li) and HPGe detectors has been studied for 114 cm3 and 157 cm3 HPGe coaxial detectors for gamma ray energies ranging from 244.66 to 1408.03 keV and from 80.997 to 1408.03 keV respectively. One of the functions proposed provides by far the best description of the present data. The most recent function, employed above approximately=110 keV, also gives more or less the same quality of fit. The low-energy (below approximately=110 keV) version of this function reproduces the trend of the 157 cm3 detector data very well below 122.06 keV. This particular function also describes the efficiency of a 38 cm3 Ge(Li) coaxial detector from 319.80 to 2598.80 keV exceedingly well. The semi-empirical formulae of Freeman and Jenkin (1966), Mowatt (1969) and of Vano and co-workers (1975) provide (above 244.66 keV) a very good representation of the present data. In general, the analytical functions describe the data better than the semi-empirical formulae. The present investigation shows that the analytical functions and semi-empirical formulae which represent the FEPE of moderate volume Ge(Li) detectors quite satisfactorily, can also be used for large volume HPGe detectors quite fruitfully, particularly in the energy range 244.66 to 1408.03 keV. This is also true the other way round for a 38 cm3 Ge(Li) detector from 319.80 to 2598.80 keV.