Spherical neutron polarimetry with Cryopad-II

Neutron polarimetry (NP), the observation of changes in the neutron spin po larisation vector induced by scattering processes is making progress. In a Spherical version of this method (SNP), routinely available at ILL, the mea surement of the final polarisation vector is made totally independent of th e incident polarisation direction by working in zero field. The zero-field polarimeter Cryopad-II is usually mounted on the IN20 3-axis spectrometer f or inelastic as well as elastic measurements at moderate Q but it was also used very recently on the hot neutron diffractometer D3 in an attempt to do elastic measurements up to large momentum transfer. The most interesting r esults are obtained when measuring the transverse components of the scatter ed polarisation, a completely new possibility. Progress in neutron-scatteri ng theory, triggered by the observation of such components in the inelastic mode, suggests that they are a unique signature of spin-lattice excitation s. (C) 1999 Elsevier Science B.V. All rights reserved.