Measurements of beta-delayed neutrons from photofission of ²³⁸U

Many fission products emit neutrons following β^- decay, seconds to minutes after fission has occurred. Because of this unique signature, β-delayed neutrons play an important role in applications such as nuclear security and reactor modeling. Photofission of ²³⁸U may be used as a surrogate reaction to probe the β-delayed neutron spectra of the neutron-induced fission of ²³⁷U, which is difficult to experimentally measure. Fission is induced using mono-energetic γ-rays produced by Compton backscattering of free-electron laser light at HIγS. The ²³⁸U target is transported by a rabbit system from an in-beam irradiation position to the center of a moderated array of ³He neutron detectors, where the time spectra of β-delayed neutrons is measured. Preliminary results will be presented, and comparisons will be made to previous measurements using bremsstrahlung beams [1].

 

[1] D. Doré et al., J. Phys.: Conf. Ser. 41, 025 (2006).