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Selected Works of Robert W. Pattie Jr.
Article
Solid Deuterium Surface Degradation at Ultracold Neutron Sources
European Physical Journal A (2018)
  • Alexander Anghel, Paul Scherrer Institut
  • Thomas L. Bailey, North Carolina State University
  • George Bison, Paul Scherrer Institut
  • Bertrand Blau, Paul Scherrer Institut
  • Leah J. Broussard, Los Alamos National Laboratory
  • Stephen M. Clayton, Los Alamos National Laboratory
  • Christopher Cude-Woods, Los Alamos National Laboratory
  • Manfred Daum, Paul Scherrer Institut
  • Ayman I. Hawari, North Carolina State University
  • Nora Hild, ETH Zurich
  • Paul R. Huffman, North Carolina State University
  • Takeyasu M. Ito, Los Alamos National Laboratory
  • Klaus Kirch, ETH Zurich
  • E. Korobkina, North Carolina State University
  • Bernhard Lauss, Paul Scherrer Institut
  • Kent Leung, North Carolina State University
  • E. M. Lutz, North Carolina State University
  • Mark Makela, Los Alamos National Laboratory
  • G. Medlin, North Carolina State University
  • C. L. Morris, Los Alamos National Laboratory
  • Robert W. Pattie, Los Alamos National Laboratory
  • Dieter Ries, University of Mainz
  • Alexander Saunders, Los Alamos National Laboratory
  • Phillip Schmidt-Wellenburg, Paul Scherrer Institut
  • Vadim Talanov, Paul Scherrer Institut
  • Albert R. Young, North Carolina State University
  • Bernard Wehring, North Carolina State University
  • C. White, North Carolina State University
  • Michael Wohlmuther, Paul Scherrer Institut
  • Geza Zsigmond, Paul Scherrer Institut
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Abstract
Solid deuterium (sD  is used as an efficient converter to produce ultracold neutrons (UCN). It is known that the sD must be sufficiently cold, of high purity and mostly in its ortho-state in order to guarantee long lifetimes of UCN in the solid from which they are extracted into vacuum. Also the UCN transparency of the bulk sD  material must be high because crystal inhomogeneities limit the mean free path for elastic scattering and reduce the extraction efficiency. Observations at the UCN sources at Paul Scherrer Institute and at Los Alamos National Laboratory consistently show a decrease of the UCN yield with time of operation after initial preparation or later treatment (“conditioning”) of the sD  . We show that, in addition to the quality of the bulk sD  , the quality of its surface is essential. Our observations and simulations support the view that the surface is deteriorating due to a build-up of D  frost-layers under pulsed operation which leads to strong albedo reflections of UCN and subsequent loss. We report results of UCN yield measurements, temperature and pressure behavior of deuterium during source operation and conditioning, and UCN transport simulations. This, together with optical observations of sD  frost formation on initially transparent sD  in offline studies with pulsed heat input at the North Carolina State University UCN source, results in a consistent description of the UCN yield decrease.
Keywords
  • Solid,
  • Deuterium,
  • Surface Degradation,
  • Ultracold Neutron Sources
Disciplines
Publication Date
August 28, 2018
DOI
10.1140/epja/i2018-12594-2
Publisher Statement
This document is an author manuscript from arXiv. The publisher's final edited version of this article is available at European Physical Journal A.
Citation Information
Alexander Anghel, Thomas L. Bailey, George Bison, Bertrand Blau, et al.. "Solid Deuterium Surface Degradation at Ultracold Neutron Sources" European Physical Journal A Vol. 54 (2018) p. 148 ISSN: 1434-6001
Available at: http://works.bepress.com/robert-pattie/3/