“…Moreover, having determined the detection efficiency in this way, the K x-ray singles counting rates from the sources of 113 Sn, 137 Cs, 2 03 Hg, 243 Am, 249 Cf, etc. used in the CEX method then give the absolute K x-ray emission rates from these sources, so that they can be used in turn to calibrate other detectors in the singles mode.…”