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Title: On the limits of spin-exchange optical pumping of {sup 3}He

We have obtained improvement in the {sup 3}He polarization achievable by spin-exchange optical pumping (SEOP). These results were primarily obtained in large neutron spin filter cells using diode bar lasers spectrally narrowed with chirped volume holographic gratings. As compared to our past results with lasers narrowed with diffraction gratings, we have observed between 5% and 11% fractional increase in the {sup 3}He polarization P{sub He}. We also report a comparable improvement in P{sub He} for two small cells, for which we would not have expected an increase from improved laser performance. In particular, prior extensive studies had indicated that the alkali-metal polarization was within 3% of unity in one of these cells. These results have impact on understanding the maximum P{sub He} achievable by SEOP, whether the origin of the improvement is from increased alkali-metal polarization or decreased temperature-dependent relaxation. We conclude that the most likely explanation for the improvement in P{sub He} is increased alkali-metal polarization. We have observed P{sub He} of between 0.80 and 0.85 in several large cells, which marks a new precedent for the polarization achievable by SEOP.
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. University of Maryland, College Park, Maryland 20742 (United States)
  2. (NIST), Gaithersburg, Maryland 20899 (United States)
  3. National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899 (United States)
  4. University of Wisconsin, Madison, Wisconsin 53706 (United States)
  5. Juelich Centre for Neutron Science at FRM 2, Forschungszentrum Juelich GmbH, 85747 Garching (Germany)
Publication Date:
OSTI Identifier:
22306180
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 1; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DIFFRACTION GRATINGS; HELIUM 3; HOLOGRAPHY; LASER RADIATION; NEUTRONS; OPTICAL PUMPING; POLARIZATION; RELAXATION; SPIN; SPIN EXCHANGE; TEMPERATURE DEPENDENCE