METAL CAPILLARIES FOR NEUTRON LENSES

The use of metal reflective surfaces should greatly improve the transm ission of neutron focusing devices based on glass polycapillary lenses because the longer scattering lengths of many metals allow greater cr itical angles compared to glass, The neutron transmission of single ch annel metal capillaries has been studied using cold neutron beams and an imaging neutron detector. Metal capillaries obtained from commercia l sources have been studied both as supplied and as treated by chemica l flow or electropolishing techniques to compare the transmission perf ormance as a function of the smoothness of the metal surface. The refl ectivities calculated from the experimental transmissions vary as a fu nction of internal diameter and of capillary length, but are not sensi tive to the various surface treatments studied here. None of the metal capillaries have reflectivities as good as the glass capillaries curr ently being used.