Neutron tomography experiments for the study of trapped flux distributions in high-Tc superconducting ceramics

We describe a new version of Neutron Spin Echo, for the study of magnetic flux in high-Tc superconductors, which is based on the evolution of the echo group in the specimen which is installed in the third precession region. The polarization of the transmitted beam reflects the spin rotation in the internal field which can be found by Fourier transforming the data. It is required for example, in research on the flux self-organization in the critical state. Experiments on Y-Ba-Cu-O ceramics are discussed. (orig.)