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Polarized 3 He Neutron Spin Filter Development at ORNL

Polarized 3 He Neutron Spin Filter Development at ORNL. Hal Lee, Dennis Rich Instrument Development Group, Neutron Facilities Development Division Oak Ridge National Laboratory Oak Ridge, TN 37831, USA. What we have done in the past.

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Polarized 3 He Neutron Spin Filter Development at ORNL

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  1. Polarized 3He Neutron Spin Filter Development at ORNL Hal Lee, Dennis Rich Instrument Development Group, Neutron Facilities Development Division Oak Ridge National Laboratory Oak Ridge, TN 37831, USA

  2. What we have done in the past • Together with Hamilton College (Gordon Jones), NIST, and IUCF, we developed some useful techniques to use SEOP type polarized 3He neutron spin filter • On-beam continuous optical pumping to keep the polarization stable • Use adiabatic fast passage to flip the 3He polarization. • Carry out experiments using a roll-on/roll-off polarizer on the Single Crystal Diffractometer at the Intense Pulsed Neutron source, Argonne National Laboratory. • We developed a polarized 3He analyzer for use on the Magnetism Reflectometer, Spallation Neutron Source • Covers 10” diameter cross-section area. • On-beam optical pumping • AFP flipping of the 3He polarization • Cell made by NIST tested in laboratory to reach 74.5% 3He polarization • Test at HFIR planned for November. Test on line planned for January (laser safety delay).

  3. Detector Polarized 3He Neutron Spin Filter Polarized Neutrons Unpolarized Neutrons Sample (CoFe Analyzer) 1 flip /10 min 1 filp/2 min * Laser & optics Polarizer with online pumping and AFP flipping • We have been working with the polarized 3He community (Hamilton, NIST, LENS) to develop the use of polarized 3He in neutron scattering. Some highlights: • used polarized neutrons on a pulsed source scattering instrument beyond reflectometer - SCD, IPNS; • used online continuous optical pumping to maintain a stable polarization in scattering experiment; • tested using AFP to flip the 3He polarization to make a spin filter-flipper. • G.L. Jones, et. al., Physica B 356, 86-90 (2005). • G.L. Jones, et. al., Proceedings of ICANS-XVII, Vol. III, 838-843 (2006).

  4. What we have done in the past • Together with Hamilton College (Gordon Jones), NIST, and IUCF, we developed some useful techniques to use SEOP type polarized 3He neutron spin filter • On-beam continuous optical pumping to keep the polarization stable • Use adiabatic fast passage to flip the 3He polarization. • Carry out experiments using a roll-on/roll-off polarizer on the Single Crystal Diffractometer at the Intense Pulsed Neutron source, Argonne National Laboratory. • We developed a polarized 3He analyzer for use on the Magnetism Reflectometer, Spallation Neutron Source • Covers 10” diameter cross-section area. • On-beam optical pumping • AFP flipping of the 3He polarization • Cell made by NIST tested in laboratory to reach 74.5% 3He polarization • Test at HFIR planned for November. Test on line planned for January (laser safety delay).

  5. Polarized 3He based analyzer for Magnetism Reflectometer Laser optics 3He neutron spin filter Neutrons Cell Chianti 3He polarization PHe = 74.5% Pressure = 1.82 bar (n=4.46 x 1019 cm-3) ø11.7 cm ID, l = 8.1 cm 1-2 days to polarized to 74.5% Test at Indiana Univeristy Cyclotron Facility We only polarized the cell at 170ºC for 18 hours, the 3He polarization reached 23%. The result is consistent with the test at NIST where the cell was polarized at 200ºC for 2-3 days.

  6. What we are doing now • 3He Filling Station Development: We are constructing a filling station that can • Prepare 2 sealed cells simultaneously • Fill an additional valved optical pumping cell for R&D and polarized 3He gas production. • Wide-angle analyzer (ORNL): • Our glass shop has made a prototype wide angle quartz cell. • ID=6”/150mm, OD=12”/300mm, Arc=45º, H=3”/75mm, Wall=3-5 mm. • The cell is being prepared for testing at ILL. • Additional information - Wide-angle analyzer (NIST): • NIST purchased a quartz cell: ID=140 mm, OD=300mm, Arc=120º, H=80mm, Wall=3/16”/5mm. • The cell was filled as a hybrid sealed cell for direct optical pumping • The cell turns an amber color at 220ºC • Laser Optics: • In the past, we modified the Littrow cavity for high-power laser. • We will be testing laser stack narrowed by volume Bragg grating.

  7. Fill Cell – Fill One, Bake the other System bake out Fill Cell – Empty excess Helium-3 Fill Cell – Empty excess Nitrogen Gas lines - simplified schematic Fill Cell – Empty Excess Helium-4 Fill Cell – Fill Helium-4 Cell bake out Cell bake out Fill Cell – Fill Nitrogen Fill Cell – Fill Helium-3 To turbo pump To turbo pump To turbo pump To turbo pump To turbo pump To turbo pump To turbo pump To turbo pump To turbo pump To turbo pump To turbo pump Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Getter Getter Getter Getter Getter Getter Getter Getter Getter Getter N2 Getter Regulator N2 N2 N2 N2 N2 N2 N2 N2 N2 Regulator Regulator Regulator Regulator Regulator Regulator Regulator Regulator N2 Regulator Regulator Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Getter Getter Getter Getter Getter Getter Getter Getter Getter Getter Getter Regulator 3He Regulator Regulator Regulator Regulator Regulator Regulator Regulator Regulator 3He 3He 3He 3He 3He 3He 3He 3He Regulator 3He Regulator 3He Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Baratron Getter Getter Getter Getter Getter Getter Getter Getter Getter Getter Getter Regulator 4He Regulator Regulator Regulator Regulator Regulator Regulator Regulator Regulator 4He 4He 4He 4He 4He 4He 4He 4He Regulator 4He Regulator 4He To dry pump To dry pump To dry pump To dry pump To dry pump To dry pump To dry pump To dry pump To dry pump To dry pump To dry pump 3He Filling Station

  8. 3He Filling Station

  9. What we are doing now • 3He Filling Station Development: We are constructing a filling station that can • Prepare 2 sealed cells simultaneously • Fill an additional valved optical pumping cell for R&D and polarized 3He gas production. • Wide-angle analyzer (ORNL): • Our glass shop has made a prototype wide angle quartz cell. • ID=6”/150mm, OD=12”/300mm, Arc=45º, H=3”/75mm, Wall=3-5 mm. • The cell is being prepared for testing at ILL. • Additional information - Wide-angle analyzer (NIST): • NIST purchased a quartz cell: ID=140 mm, OD=300mm, Arc=120º, H=80mm, Wall=3/16”/5mm. • The cell was filled as a hybrid sealed cell for direct optical pumping • The cell turns an amber color at 220ºC • Laser Optics: • In the past, we modified the Littrow cavity for high-power laser. • We will be testing laser stack narrowed by volume Bragg grating.

  10. Wide Angle Analyzer Cell – ORNL, NIST Our first test cell. To be Cs coated, filled, and tested at ILL. No stress point found under polarized light NIST attempt to directly pump the wide-angle cell: Potassium reacts with quartz glass at >200ºC? Preliminary test shows the passage of 794.7 nm light is not affected by the coloring.

  11. What we are doing now • 3He Filling Station Development: We are constructing a filling station that can • Prepare 2 sealed cells simultaneously • Fill an additional valved optical pumping cell for R&D and polarized 3He gas production. • Wide-angle analyzer (ORNL): • Our glass shop has made a prototype wide angle quartz cell. • ID=6”/150mm, OD=12”/300mm, Arc=45º, H=3”/75mm, Wall=3-5 mm. • The cell is being prepared for testing at ILL. • Additional information - Wide-angle analyzer (NIST): • NIST purchased a quartz cell: ID=140 mm, OD=300mm, Arc=120º, H=80mm, Wall=3/16”/5mm. • The cell was filled as a hybrid sealed cell for direct optical pumping • The cell turns an amber color at 220ºC • Laser Optics: • In the past, we modified the Littrow cavity for high-power laser. • We will be testing laser stack narrowed by volume Bragg grating.

  12. Polarizing Beam Splitter Cube Reflection Grating Laser l2 l/4 3He cell Magnetic field Laser optics Modified Littrow cavity (Hal Lee, manuscript to Journal of Applied Physics) Laser Stack with volume Bragg grating Volume Bragg grating feedback narrows the bandwidth to 0.5 nm FWHM. We purchased a 150W 794.7 nm stack from LaserTel. An example below: 780 nm, 500 W, 0.5 nm FWHM laser stack from LaserTel (60 amp, 18 V, 50% efficiency).

  13. Acknowledgement IUCF Indiana Univ. Hai Yan Yan Tony Xin Tong Peter Chenyang Jiang W. Mike Snow Hamilton College Gordon L. Jones Freddie Dias Brian Collett Jonathan Wexler ILL Ken Andersen Eddy Lelievre-Berna David Jullien Pascal Mouveau Earl Babcock ORNL Mark Hagen Bill Leonhardt Christina Hoffmann Jack Thomison NIST Tom Gentile Wang Chun Chen ISIS Steve Parnell Steven Boag Chris Frost ANL Paula M. B. Piccoli Martha E. Miller Art Schultz Univ. of New Hampshire Bill Hersman

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