Use of tunable monochromatic X-ray sources for metrological studies in the low-energy range at the Laboratoire National Henri Becquerel

In the frame of the French Metrology Institute, the Laboratoire National Henri Becquerel (LNHB) performs accurate measurements of photon emission intensities in order to improve the knowledge of radionuclides decay scheme. This is achieved using semiconductor detectors, however, in the low-energy range (E < 20 keV) their efficiency calibration is not straightforward. Moreover, their energy resolution and the detailed shape of their response function are parameters of interest for accurate processing of low-energy X-ray spectra. For these purposes, and in complement to the use of classical calibration method using standard radionuclides, an original method for detectors characterization have been developed using tunable monochromatic radiation. The tunable radiation makes possible examining and identifying the different features of X-ray spectra by fine scanning at the binding energies of the detector materials, thus improving the knowledge of the detector response function and the subsequent processing of complex X-ray spectra. Since 2001, the SOLEX source (Source Of Low Energy X-rays) has been installed at LNHB and provides tunable monochromatic radiation in the 1-20 keV energy range. This facility has been applied to the measurement of photon emission intensities and attenuation coefficients of materials (Al, Cu) in the low-energy range. In the next future, the SOLEIL synchrotron facility will be equipped with a metrology beam line that will be partially managed by LNHB: this will allow subsequent development of such metrological studies with enhanced performances.