Measurement of the ISO series of filtered radiations

The International Standards Organization (ISO) has described the production of a set of filtered X-ray spectra for calibrating protection-level dosemeters and dose ratemeters, and for determining their response as a function of photon energy. These reference radiations cover a range of energies and dose rates determined by the X-ray tube voltage selected and the degree of filtration employed. An accurate set of the filters specified has been manufactured. The spectra have been measured using a high-resolution planar Ge(Li) detector for energies up to 125 keV, and a NaI(Tl) detector for higher energies. The measured pulse-height distributions have been corrected for Compton scattering, escape of K X-rays and transmission through the crystal. The results for mean photon energy and 1st half-value layer have been compared with the ISO values and other sets of results. The comparison shows that some of the ISO values could be improved. (author)