A new technique has recently been described for the absolute calibration of intense sources of pulsed radiation in the 0.2-1-MeV range of photon energies. An x-ray activation technique, it depended upon the storage of samples of the irradiating spectrum in the form of populations of nuclei excited to isomeric states with lifetimes of seconds to hours. Accuracy was dependent upon the precision assumed for tabulated values of nuclear parameters. Described here is an extension of this technique to the larger range of photon energies, 0.2-1.5 MeV and to intensities from 1012 keV/keV to 10 16 keV/keV using the target nuclei 7 9Br and 77Se. In this work self-consistency of the nuclear parameters was directly determined. Important changes were found to be necessary for improved accuracy, particularly over the larger ranges of experimental variables being considered. Values of the now-consistent set of nuclear parameters are reported.
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