Accurate efficiency calibration of a low-energy HPGe detector using a monochromatic x-ray source

HPGe detector efficiency has been calibrated using complementary methods involving radioactive x-ray standards, reference synchrotron flux (Super ACO, LURE, France) and a monochromatic x-ray source (SOLEX), combined with Monte Carlo simulation. In the study described here, SOLEX was used to determine the thickness of detector components that create absorption sites in front of the active zone of the detector, by energy scanning in the vicinity of their K and L binding energies. The layers of aluminium (infrared shielding), nickel (electrical contact) and germanium (dead layer) have been measured. This approach ensures accurate determination of the thickness of each component and enables the detector efficiency calculation by Monte Carlo simulation. Differences between simulated data and experimental efficiency values are about 1-5% at energies above 1400 eV and reach 20% at lower energies. (authors)