1 / 17

Using polarized 3 He spin filter at the SNS - Update on current development

Using polarized 3 He spin filter at the SNS - Update on current development. W.T. Hal Lee Spallation Neutron Source. OUTLINE. March ’06 Experiment at SCD, IPNS 3He analyzer for use on the Magnetism Reflectometer A plausible setup on HYSPEC. March ’06 Experiment at SCD, IPNS

chesmu
Download Presentation

Using polarized 3 He spin filter at the SNS - Update on current development

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Using polarized 3He spin filter at the SNS - Update on current development W.T. Hal Lee Spallation Neutron Source

  2. OUTLINE • March ’06 Experiment at SCD, IPNS • 3He analyzer for use on the Magnetism Reflectometer • A plausible setup on HYSPEC

  3. March ’06 Experiment at SCD, IPNS Polarized neutron diffraction study of the ferromagnetic semiconductor Yb14MnSb11 V.O. Garlea1, G.L. Jones2, B. Collett2, W.C. Chen3,5, T.R. Gentile3, P.M.B. Piccoli4, M.E. Miller4, A.J. Schultz4, H.Y. Yan5, X. Tong5, M. Snow5, B.C. Sales1, S.E. Nagler1, W.T. Lee6, C. Hoffmann6 1HFIR, Oak Ridge National Laboratory, Oak Ridge, TN 378312 Hamilton College, Clinton, NY 13323 3 NIST Center for Neutron Research, Gaithersburg, MD 20899 4 IPNS, Argonne National Laboratory, Argonne, IL 60439 5 IUCF, Indiana University, Bloomington, IN 47405 6 SNS, Oak Ridge National Laboratory, Oak Ridge, TN 37831

  4. 2 AFP/10 min 2 AFP/4 min Previously… • In 2004, we tested online continuous optical pumping that kept the 3He polarization stable for days using a compact online system. • In 2005, an improved setup optimized at the instrument resulted in close to the highest 3He polarization archived in a prior off-line test – and remained stable for days. • In 2005, we tested fast-switching of 3He polarization by adiabatic fast passage (AFP). We repeatedly switch between spin+ & spin- neutron filtering modes without using a neutron spin flipper.

  5. Experiment setup at SCD, IPNS 2005 Detector 3He cell inside B-field & AFP coil Polarized Neutron Unpolarized Neutron Co Fe Analyzer 2006 * Polarized Neutron Polarizer (light) Laser Co Fe Analyzer Sample magnet refrigurator

  6. Experiment setup at SCD, IPNS Detectors Neutrons Sample magnet Laser 3He polarization: 60% • Online continuous optical pumping • AFP 3He polarization switching • Cold sample to 6K • 3kG sample field

  7. Snap shot of the scattering experiment The experiment: Measure magnetic moments on Mn & Sb Spin+ Spin - Many of the peaks are magnetic Data analysis is underway… We have made the transition from developing a 3He polarizer to carrying out polarized neutron scattering measurements.

  8. Construction of a 3He-based neutron polarization analyzer for use at the Magnetism Reflectometer W. T. Hal Lee, SNS T. Gentile, W.C. Chan, NIST G. L. Jones, Hamilton College

  9. 3He analyzer for Magnetism Reflectometer Laser optics Coils & Shield Oven Neutron Beam 3He • Operates at neutron wavelengths from 1.8 Å to 6 Å • Online continuous optical pumping during experiment to maximize and maintain a non-decaying 3He polarization. • The analyzer cell is in a uniform holding field enclosed in m-metal magnetic shielding to mitigate external magnetic interference. • Use adiabatic-fast-passage for both NMR polarization monitoring and 3He polarization flipping. This will enable the system to analyze spin-up and spin-down neutrons with fast-switching from one mode to the other. • The system is located inside the detector housing. All operations will occur online

  10. 3He analyzer for Magnetism Reflectometer “Chianti”: Max 3He polarization=74.5% for 53 W of narrowed lightT1=270 h Pressure = 1.82 bar 11.7 cm ID, 8.1 cm inside length12.9 cm OD, 10 cm outside length, 4 cm tip-off length

  11. 3He analyzer for Magnetism Reflectometer Reflective Grating Laser Polarizing Beam Splitter Cube l4 l2 Grating Output to 3He cell Laser Beam Split At 60 W, with 20 W feedback and 40 W output, At 794.7 nm, Narrowed peak intensity = 2.25 x total un-narrowed peak intensity

  12. Individual components tested. Polarizing 3He test in April Laser optics Coils & Shield Oven Neutron Beam 3He

  13. A plausible scheme for 3He-based neutron polarization analyzer for HYSPEC W. T. Hal Lee, SNS M. Hagen, SNS L. Passell, BNL

  14. 3He analyzer for HYSPEC Gas return Local filling A SEOP based filling station Sample Polarizing Polarized gas supply 3He cell Coil Optical pumping may be difficult due to the shape of the cell. Refilling may be the solution. Filling station example: Max 3He polar. =0.75, optimized at 1.5 Å. T1=200 hours, refill 75% volume every 5 hours. (Plot: for 2 Å neutrons)

  15. HYSPEC 2 pairs of coils with diameter 400 mm & 350 mm separated by 400 mm. By applying appropriate currents to the coils, field uniformity similar to a pair of 400 mm diameter Helmholtz coils can be obtained.

  16. SNS Instrument Layout 2 - Backscattering Spectrometer Field Sensitive 3He filter, magnet magnet 1A – Vacant 17 - SEQUOA 18 - ARCS 1B - NOMAD 16 Vacant SERGIS 3 - SNAP 14A, 14B, 15 SESANS HYSPEC NSE 4A - Magnetism Refl. m-SANS 13 - Fundamental Physics 4B - Liquids Refl. Mandi 5 - CNCS Vision New concept 6 - SANS 12 - SCD 7 – Vacant 11B – Vacant 8 – Vacant 11A – POWGEN3 9 - VULCAN 10 – Vacant

  17. Self-shielded split-pair 10 Tesla superconducting magnet study - Results • Substantial reduction of fringe field in both radial and axial directions • Shielding factor 40-50

More Related