Zn Yields for Fission Spectrum Neutrons

Electron beams in the tens of MeV range provide opportunities to perform post detonation nuclear forensics research. In a nuclear detonation, neutrons will activate bomb components and materials in the environment, potentially revealing both the flux and the energy spectrum of the neutrons. In a ²³⁹Pu based device, the plutonium is typically alloyed with gallium which will experience a high flux of fast neutrons in the event of a detonation. We will report on measurements performed at the Idaho State University Idaho Accelerator Center of (n,p) reactions on two different isotopes of gallium. Fission spectrum neutrons were generated with a 39 MeV electron beam incident on a tungsten bremsstrahlung radiator, which also served as a photo-neutron production target. Activation spectra from ⁷¹Ga(n,p)^71mZn and ⁶⁹Ga(n,p)^69mZn measurements with a high purity germanium detector will be presented demonstrating the feasibility of measuring the ratio of these cross sections for fission spectrum neutrons.