Measurement of the absolute neutron beam polarization from a supermirror polarizer and the absolute efficiency of a neutron spin rotator for the NPDGamma experiment using a polarized 3He neutron spin-filter

M. M. Musgrave, S. Baeßler, S. Balascuta, L. Barrón-Palos, D. Blyth, J. D. Bowman, T. E. Chupp, V. Cianciolo, C. Crawford, K. Craycraft, N. Fomin, J. Fry, M. Gericke, R. C. Gillis, K. Grammer, G. L. Greene, J. Hamblen, C. Hayes, P. Huffman, C. JiangS. Kucuker, M. McCrea, P. E. Mueller, S. I. Penttilä, W. M. Snow, E. Tang, Z. Tang, X. Tong, W. S. Wilburn

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Accurately measuring the neutron beam polarization of a high flux, large area neutron beam is necessary for many neutron physics experiments. The Fundamental Neutron Physics Beamline (FnPB) at the Spallation Neutron Source (SNS) is a pulsed neutron beam that was polarized with a supermirror polarizer for the NPDGamma experiment. The polarized neutron beam had a flux of ∼109 neutrons per second per cm2 and a cross sectional area of 10 × 12 cm2. The polarization of this neutron beam and the efficiency of a RF neutron spin rotator installed downstream on this beam were measured by neutron transmission through a polarized 3He neutron spin-filter. The pulsed nature of the SNS enabled us to employ an absolute measurement technique for both quantities which does not depend on accurate knowledge of the phase space of the neutron beam or the 3He polarization in the spin filter and is therefore of interest for any experiments on slow neutron beams from pulsed neutron sources which require knowledge of the absolute value of the neutron polarization. The polarization and spin-reversal efficiency measured in this work were done for the NPDGamma experiment, which measures the parity violating γ-ray angular distribution asymmetry with respect to the neutron spin direction in the capture of polarized neutrons on protons. The experimental technique, results, systematic effects, and applications to neutron capture targets are discussed.

Funding

We would like to thank the ORNL glass shop and the University of Tennessee machine shop for their valuable contributions. We also thank the management and staff of the Spallation Neutron Source for providing their support and for keeping the neutron source reliably running. We gratefully acknowledge the support of the US Department of Energy Office of Nuclear Physics (Grants No. DE-FG02-03ER41258, DE-SC0008107, and DE-SC0014622), the US National Science Foundation (Grants No. PHY-1306942, PHY-1614545, NSF-0855610, and NSF-1205833), the Indiana University Center for Spacetime Symmetries, the Natural Sciences and Engineering Council of Canada (NSERC) (Grant No. SAPPJ 341289-2013), and the Canada Foundation for Innovation (CFI). We would like to thank the ORNL glass shop and the University of Tennessee machine shop for their valuable contributions. We also thank the management and staff of the Spallation Neutron Source for providing their support and for keeping the neutron source reliably running. We gratefully acknowledge the support of the US Department of Energy Office of Nuclear Physics (Grants No. DE-FG02-03ER41258 , DE-SC0008107 , and DE-SC0014622 ), the US National Science Foundation (Grants No. PHY-1306942 , PHY-1614545 , NSF-0855610 , and NSF-1205833 ), the Indiana University Center for Spacetime Symmetries , the Natural Sciences and Engineering Council of Canada (NSERC) (Grant No. SAPPJ 341289-2013 ), and the Canada Foundation for Innovation (CFI) .

FundersFunder number
Indiana University Center for Spacetime Symmetries
US Department of Energy Office of Nuclear Physics
US National Science Foundation
National Science Foundation1205833, 0855610, PHY-1614545, NSF-0855610, PHY-1306942, 1306942, NSF-1205833
U.S. Department of EnergyDE-FG02-03ER41258, DE-SC0008107, DE-SC0014622
Natural Sciences and Engineering Research Council of CanadaSAPPJ 341289-2013
Canada Foundation for Innovation

    Keywords

    • NPDGamma
    • Polarimetry
    • Polarized He
    • Polarized neutrons
    • Spin-exchange optical pumping

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