Prompt fission neutron spectra in the ²³⁵U(n,f) reaction

Prompt fission neutron spectra (PFNS) are crucial to any neutronic simulation of critical nuclear systems. An experimental setup dedicated to the measurements of PFNS of very high accuracy was developed at the Los Alamos Neutron Science Center (LANSCE) some ten years ago. It allows for the measurement of PFNS for neutron induced fission at the Weapon Neutron Research (WNR) neutron source of the LANSCE. A measurement of the PFNS from the 235 U(n,f) reaction was realized recently and is currently analyzed. Preliminary results are presented here and are compared to present nuclear data evaluations.