Polarized neutron imaging at the CONRAD instrument at Helmholtz Centre Berlin

Neutrons are highly sensitive to magnetic fields because of their intrinsic magnetic moment. At the same time, their zero net electrical charge allows them to penetrate thick layers of matter. In combination with standard radiographic and tomographic imaging techniques, these properties have been exploited to visualize magnetic fields in free space and within the bulk of solid, massive, opaque samples. In this paper, the basic principle of this new technique and its realization at the CONRAD instrument at the Helmholtz Centre Berlin (formerly Hahn-Meitner Institute Berlin) are explained. Two application examples will be given: the visualization of the magnetic field around a permanent magnet and the investigation of the displacement of the current density from the core of a conductor to the surface (the skin effect).