Neutron polarimetry

Zero-field neutron polarimetry is a technique which has recently been developed to allow spherical polarization analysis to be carried out in a neutron scattering experiment. The incident beam polarization can be set to any desired direction and the magnitude and direction of the polarization of the scattered beam determined. The polarimeter exploits the Meissner effect to separate the magnetic fields of the active elements. A precision of ca . 2° in the polarization direction can be obtained with the prototype. Expressions are given for the change in polarization to be expected in diffraction experiments on various types of magnetic structure and the effect of magnetic domains is discussed. Some examples of the application of the technique to magnetic structure determination are given. Effects due to breakdown of the kinematical approximation have been demonstrated. Some ideas for a second generation polarimeter are outlined and new areas of application proposed.