Wide Angle Spherical Neutron Polarimetry at Oak Ridge National Laboratory

Abstract

Spherical Neutron Polarimetry (SNP) analyzes complex magnetic structures through distinguishing contributions from nuclear-magnetic interference and chiral structure in addition to nuclear magnetic scattering separation. This analysis is achieved through determining all components in the polarization transfer process. Currently, wide-angle SNP is being realized at Oak Ridge National Laboratory (ORNL) for multiple beamlines including: the polarized tripleaxis spectrometer (HB-1) and general-purpose small angle neutron scattering instrument (CG-2) at the High Flux Isotope Reactor (HFIR), as well as the hybrid spectrometer (HYSPEC) at the Spallation Neutron Source (SNS). The SNP device consists of three units: incoming/outgoing neutron polarization, sample environment and a zero-field chamber. The incoming/outgoing neutron polarization regions use high-T_c superconducting YBCO films and mu-metal to achieve full control of neutron polarization. The sample environment is an evaporation refrigerator with a customized tail piece placed into the zero-field chamber. The device has been fully assembled and tested at the University of Missouri Research Reactor (MURR).