Measurements of short-lived photofission product yields using a rapid transfer system*

Photon-induced fission product yield (FPY) studies were conducted on the three major actinide isotopes: $^{\mathrm{235}}$U, $^{\mathrm{238}}$U, and $^{\mathrm{239}}$Pu. Fission was induced at the Triangle Universities Nuclear Laboratory's High Intensity $\gamma $-ray Source using monoenergetic $\gamma $-rays of E$_{\mathrm{\gamma }} \quad =$ 11.2 and 13.0 MeV. To measure the short-lived FPYs, a RApid Belt-driven Irradiated Target Transfer System (RABITTS) was used. The RABITTS is a fully automated 1 m track system which performs cyclic activation by moving the target between irradiation and counting positions. Following $\gamma $-ray activation, the target was rapidly (0.4 s) transferred to two well-shielded Highly Purity Germanium detectors, which measure the induced activity. The irradiation-counting cycle was repeated until the summed data are sufficient for statistical analysis. The counting data was used to validate the half-lives for most identified fission products. More than 40 fission products with half-lives ranging from 1 s to 240 s were uniquely identified, and their yield values computed. The results are compared with previous photon and neutron induced FPY measurements.