Evaluation of high-energy delayed gamma-ray spectra dependence on interrogation timing patterns

Rodriguez, D. ; Bogucarska, T.*; Koizumi, Mitsuo ; Lee, H.-J.; Pedersen, B.*; Rossi, F. ; Takahashi, Tone; Varasano, G.*

Under the MEXT subsidy to strengthen nuclear security related research, the ISCN is developing delayed gamma-ray spectroscopy (DGS) for nuclear safeguards. Here we present results from experiments using the PUNITA instrument in collaboration with JRC-Ispra to evaluate the gamma-ray spectral dependence on interrogation time patterns and number of cycles. Specifically, we investigated the observable gamma rays useful to quantify the Pu and U contributions. Of the time patterns tested in this study, we determined that irradiating the sample for 60- followed by a gamma-ray measurement of 60- was the best for a comparable one-hour total interrogation time.