Efficiency calibration of a Si(Li) detector in the low-energy region using electron bremsstrahlung

In the low-energy region the determination of the detector efficiency is complicated by the fact of nonavailability of certificated calibration sources. To solve this problem the use of electron bremsstrahlung for determining the relative photon detection efficiency of a Si(Li) detector in the low-energy range 0.5–19 keV is proposed. The calibration is based on energy dispersive measurements of electron bremsstrahlung emitted by an X-ray tube. Model spectra are computed from thick-target bremsstrahlung spectra in a semiclassical approximation and from a physical model for the detector response. Model spectra are fitted to the measured spectra using a parametric adaptor term. Thereby, the error of the determined detector efficiency is approximately 5%.