High Efficiency Fission Tagged U235 Gamma Ray Data

Fission gamma ray data is important for identifying nuclear material. In this work we are examining gamma rays from U-235 fission using an ionization chamber for fission tagging. A U-235 fission target was placed inside of the Total Kinetic Energy (TKE) double Frisch-gridded ionization chamber and bombarded with incident neutrons to induce fission. The two emitted fission fragments ionize the gas in the two sides of the chamber. Electrons in the ionized gas, under an E field, generate signals on the anodes and Frisch grids These signals can be used for identification or, in our work, for gating on fissions. A LaBr3 detector was used beside the TKE chamber for gamma measurements. LANSCE provides a t0 signal for each beam pulse, at 20 Hz, allowing us to examine gamma spectra as a function of time. We are able to use this setup to gather the energies of both fragments in binary fission simultaneously, allowing us to extract mass information to correlate wit the gammas. This data will help in many areas, including stockpile stewardship, fission theory, and nuclear safeguards.