title: In situ polarized 3He system for the Magnetism Reflectometer at the Spallation Neutron Source.
abstract: We report on the in situ polarized (3)He neutron polarization analyzer developed for the time-of-flight Magnetism Reflectometer at the Spallation Neutron Source at Oak Ridge National Laboratory. Using the spin exchange optical pumping method, we achieved a (3)He polarization of 76% ± 1% and maintained it for the entire three-day duration of the test experiment. Based on transmission measurements with unpolarized neutrons, we show that the average analyzing efficiency of the (3)He system is 98% for the neutron wavelength band of 2-5 Å. Using a highly polarized incident neutron beam produced by a supermirror bender polarizer, we obtained a flipping ratio of >100 with a transmission of 25% for polarized neutrons, averaged over the wavelength band of 2-5 Å. After the cell was depolarized for transmission measurements, it was reproducibly polarized and this performance was maintained for three weeks. A high quality polarization analysis experiment was performed on a reference sample of Fe/Cr multilayer with strong spin-flip off-specular scattering. Using a combination of the position sensitive detector, time-of-flight method, and the excellent parameters of the (3)He cell, the polarization analysis of the two-dimensional maps of reflected, refracted, and off-specular scattered intensity above and below the horizon were obtained, simultaneously.
authors.affiliation: Instrument and Source Design Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393, USA. tongx@ornl.gov
authors.forename: X
authors.initials: X
authors.lastname: Tong
authors.forename: C Y
authors.initials: CY
authors.lastname: Jiang
authors.forename: V
authors.initials: V
authors.lastname: Lauter
authors.forename: H
authors.initials: H
authors.lastname: Ambaye
authors.forename: D
authors.initials: D
authors.lastname: Brown
authors.forename: L
authors.initials: L
authors.lastname: Crow
authors.forename: T R
authors.initials: TR
authors.lastname: Gentile
authors.forename: R
authors.initials: R
authors.lastname: Goyette
authors.forename: W T
authors.initials: WT
authors.lastname: Lee
authors.forename: A
authors.initials: A
authors.lastname: Parizzi
authors.forename: J L
authors.initials: JL
authors.lastname: Robertson