The EUROMET project 428 examines efficiency transfer results for Ge gamma-r
ay spectrometers when the efficiency is known for a reference point source
geometry. For this, different methods are used, such as Monte Carlo simulat
ion or semi-empirical computation. The exercise compares the application of
these methods to the same selected experimental cases to determine the usa
ge limitations versus the requested accuracy. For carefully examining these
results and trying to derive information for improving the computation cod
es, this study was limited to a few simple cases. The first part concerns t
he simplest case of geometry transfer, i.e., using point sources for 3 sour
ce-to-detect or distances: 2, 5 and 20 cm; the second part deals with trans
fer from point source geometry to cylindrical geometry with three different
matrices. The general conclusion is that the deviations between the comput
ed results and the measured efficiencies are mostly within 10%, The quality
of the results is rather inhomogeneous and shows that these codes cannot b
e used directly for metrological purposes. However, most of them are operat
ional for routine measurements when efficiency uncertainties of 5-10% can b
e sufficient. (C) 2001 Elsevier Science Ltd. All rights reserved.