Neutron Interferometric Determination of the Coherent Scattering Length of Natural Uranium

A very accurate determination of the neutron coherent scattering length of natural uranium $b_{\mathrm{U}}$ was carried out with the neutron interferometer installed at the high-flux reactor of the Institut Laue-Langevin, Grenoble. A recently developed technique was used including the rotation of a parallel-sided Al phase shifter with and without the presence of the uranium sample in one path of the neutron beam. From the observed phase shift between the two interferograms the value $b_{\mathrm{U}}=8.417\mathrm{}\pm 0.005$ fm was obtained.