PRECISION NEUTRON-INTERFEROMETRIC MEASUREMENT OF THE COHERENT NEUTRON-SCATTERING LENGTH IN SILICON

The neutron-interferometry (NI) technique provides a precise and direc t way to measure the bound, coherent scattering lengths b of low-energ y neutrons in solids, liquids, or gases. The potential accuracy of NI to measure b has not been fully realized in past experiments, due to s ystematic sources of error. We have used a method which eliminates two of the main sources of error to measure the scattering length of sili con with a relative standard uncertainty of 0.005%. The resulting valu e, b=4.1507(2) fm, is in agreement with the current accepted value, bu t has an uncertainty five times smaller. [S1050-2947(98)04808-2].