Experimental demonstration of focusing performance of an ellipsoidal neutron mirror

The focusing performance of an ellipsoidal neutron mirror was experimentally demonstrated using BL06 beam line at J-PARC/MLF. The mirror, which was made with electroless nickel-phosphorus (NiP) plated material, has sub-micrometer from accuracy and sub-nanometer surface roughness. The results show that a circular focusing spot, of which size at full width at half maximum (FWHM) is almost equivalent to the size of pinhole, was realized with little diffuse scattering. The beam shapes at different mirror-center-to-detector distance (MDD) was examined and the FWHM values of beam profiles show in a good coincidence with those calculated by geometry optics. Some issues regarding reflectivity and focusing gain were briefly discussed. (author)