Polarized-neutron reflections: a new technique used to measure the magnetic field penetration depth in superconducting niobium

An absolute determination of the superconducting penetration length in niobium has been carried out by a novel technique, in which the reflectivity of a polarized-neutron beam from a polished surface is measured. The result thus obtained, ..lambda..(0) = 410 +- 40 A, is in substantial agreement with the earlier work.