Surrogate Reaction Measurements of Fission $\gamma $-ray Spectra with Liberace and STARS.

Very few high-resolution measurements have been made of the prompt $\gamma $-ray spectrum following non-spontaneous fission. However, this information is useful for stockpile stewardship and can also provide a wealth of information about the fission process. Recent experiments using STARS+LIBERACE at the 88-Inch cyclotron designed to determine surrogate neutron-induced cross sections in the Uranium isotopic chain have also produced a wide range of triple-coincident particle-fission-$\gamma $ data which can be used to determine fission $\gamma $-ray spectra for $^{234-238}$U and $^{235,238}$Np compound nuclei. In this talk we will present the spectra from these different systems and compare $\gamma $-ray spectra from different ``chance'' fission channels over a wide range of isotopes and energies. This work was sponsored by UC-LLNL under Contract No. W-7405-Eng-48 and Grant Nos. DE-FG-05NA25929, DE-FG52-06NA26206, and DE-FG02-05ER41379.