Accurate measurement of the standard U-235(n,f) cross section from thermal to 170 keV neutron energy

Abstract

An accurate measurement of the U-235(n,f) cross section from thermal to 170 keV of neutron energy has recently been performed at n_TOF facility at CERN using Li-6(n,t)He-4 and B-10(n,alpha)Li-7 as references. This measurement has been carried out in order to investigate a possible overestimation of the U-235 fission cross section evaluation provided by most recent libraries between 10 and 30 keV. A custom experimental apparatus based on in-beam silicon detectors has been used, and a Monte Carlo simulation in GEANT4 has been employed to characterize the setup and calculate detectors efficiency. The results evidenced the presence of an overestimation in the interval between 9 and 18 keV and the new data may be used to decrease the uncertainty of U-235(n,f) cross section in the keV region.