The importance of the adiabatic condition on polarized neutron imaging

Abstract

Polarized neutron imaging has many applications through characterization of magnetic fields generated from currents or magnetic moments. If local magnetic field directions change slowly relative to its precession frequency, the angle between neutron polarization vector and the local field vector remains constant. Conversely, if the fields change rapidly relative to the precession frequency, this angle may vary. The transition between these scenarios follows the adiabatic condition. In this study, we analyze the effects of the adiabatic condition on a polarized neutron image. Two case studies are used for illustrating possible scenarios. The first case shows how an external field, due to the adiabatic condition, influences the symmetry of a polarized neutron image of a current carrying solenoid. The second case study shows how the adiabatic coupling of the beam polarization could lead to the loss of contrast in a polarized neutron image while studying field penetration in type II superconductors. Both case studies serve to highlight the importance of taking this phenomenon into account while interpreting polarized neutron imaging data given the rising importance of the technique as a characterization method in magnetism and superconductivity research.