Micro in situ 3He Polarizer for Dimensional Extreme Magnetic Neutron Diffractometer at the High Flux Isotope Reactor

Abstract

Abstract A new micro in situ polarized 3He neutron spin filter has been custom built for use as a neutron polarizer on the Dimensional Extreme Magnetic Neutron Diffractometer (DEMAND) at the High Flux Isotope Reactor (HFIR). The 3He is polarized via spin-exchange optical pumping with a high-power fiber-coupled laser. The 3He neutron spin filter polarizer is designed to be compact in size with the length along the neutron beam only 30 cm because of the limited space available on the beamline. The polarizer is used for the shorter wavelength neutrons (1.005 Å and 1.546 Å) at DEMAND. A 3 bar 3He cell was filled to provide enough opacity so that good neutron polarization can be attained. At DEMAND the polarizer is mounted on an Automated Polarizer Changeover system (APCS) enabling quick switching between polarized and unpolarized neutron diffraction.