Solid Deuterium Surface Degradation at Ultracold Neutron Sources

Alexander Anghel; Thomas L. Bailey; George Bison; Bertrand Blau; Leah J. Broussard; Stephen M. Clayton; Christopher Cude-Woods; Manfred Daum; Ayman I. Hawari; Nora Hild; Paul R. Huffman; Takeyasu M. Ito; Klaus Kirch; E. Korobkina; Bernhard Lauss; Kent Leung; E. M. Lutz; Mark Makela; G. Medlin; C. L. Morris; Robert W. Pattie; Dieter Ries; Alexander Saunders; Phillip Schmidt-Wellenburg; Vadim Talanov; Albert R. Young; Bernard Wehring; C. White; Michael Wohlmuther; Geza Zsigmond

doi:10.1140/epja/i2018-12594-2

Solid Deuterium Surface Degradation at Ultracold Neutron Sources

Alexander Anghel
, Thomas L. Bailey
, George Bison
, Bertrand Blau
, Leah J. Broussard
, Stephen M. Clayton
, Christopher Cude-Woods
, Manfred Daum
, Ayman I. Hawari
, Nora Hild
, Paul R. Huffman
, Takeyasu M. Ito
, Klaus Kirch
, E. Korobkina
, Bernhard Lauss
, Kent Leung
, E. M. Lutz
, Mark Makela
, G. Medlin
, C. L. Morris

Robert W. Pattie, Dieter Ries, Alexander Saunders, Phillip Schmidt-Wellenburg, Vadim Talanov, Albert R. Young, Bernard Wehring, C. White, Michael Wohlmuther, Geza Zsigmond

Paul Scherrer Institut
North Carolina State University
Los Alamos National Laboratory
ETH Zurich
University of Mainz

Research output: Contribution to journal › Article › peer-review

Abstract

<div class="line" id="line-31"> Solid deuterium (sD  <img src="https://epja.epj.org/articles/epja/abs/2018/09/10050_2018_Article_12594/10050_2018_Article_12594_tex_eq1.png"/>  is used as an efficient converter to produce ultracold neutrons (UCN). It is known that the sD  <img src="https://epja.epj.org/articles/epja/abs/2018/09/10050_2018_Article_12594/10050_2018_Article_12594_tex_eq1.png"/> 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  <img src="https://epja.epj.org/articles/epja/abs/2018/09/10050_2018_Article_12594/10050_2018_Article_12594_tex_eq1.png"/>  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  <img src="https://epja.epj.org/articles/epja/abs/2018/09/10050_2018_Article_12594/10050_2018_Article_12594_tex_eq1.png"/>  . We show that, in addition to the quality of the bulk sD  <img src="https://epja.epj.org/articles/epja/abs/2018/09/10050_2018_Article_12594/10050_2018_Article_12594_tex_eq1.png"/>  , 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  <img src="https://epja.epj.org/articles/epja/abs/2018/09/10050_2018_Article_12594/10050_2018_Article_12594_tex_eq1.png"/>  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  <img src="https://epja.epj.org/articles/epja/abs/2018/09/10050_2018_Article_12594/10050_2018_Article_12594_tex_eq1.png"/>  frost formation on initially transparent sD  <img src="https://epja.epj.org/articles/epja/abs/2018/09/10050_2018_Article_12594/10050_2018_Article_12594_tex_eq1.png"/>  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. </div>

Original language	American English
Journal	European Physical Journal A
Volume	54
DOIs	https://doi.org/10.1140/epja/i2018-12594-2
State	Published - Aug 28 2018
Externally published	Yes

Keywords

Deuterium
Solid
Surface Degradation
Ultracold Neutron Sources

Disciplines

Atomic, Molecular and Optical Physics
Physics

Access to Document

10.1140/epja/i2018-12594-2License: Unspecified

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Cite this

Anghel, A., Bailey, T. L., Bison, G., Blau, B., Broussard, L. J., Clayton, S. M., Cude-Woods, C., Daum, M., Hawari, A. I., Hild, N., Huffman, P. R., Ito, T. M., Kirch, K., Korobkina, E., Lauss, B., Leung, K., Lutz, E. M., Makela, M., Medlin, G., ... Zsigmond, G. (2018). Solid Deuterium Surface Degradation at Ultracold Neutron Sources. European Physical Journal A, 54. https://doi.org/10.1140/epja/i2018-12594-2

Anghel, A, Bailey, TL, Bison, G, Blau, B, Broussard, LJ, Clayton, SM, Cude-Woods, C, Daum, M, Hawari, AI, Hild, N, Huffman, PR, Ito, TM, Kirch, K, Korobkina, E, Lauss, B, Leung, K, Lutz, EM, Makela, M, Medlin, G, Morris, CL, Pattie, RW, Ries, D, Saunders, A, Schmidt-Wellenburg, P, Talanov, V, Young, AR, Wehring, B, White, C, Wohlmuther, M & Zsigmond, G 2018, 'Solid Deuterium Surface Degradation at Ultracold Neutron Sources', European Physical Journal A, vol. 54. https://doi.org/10.1140/epja/i2018-12594-2

@article{da4b34eff2004288bb327b7a608d14fe,

title = "Solid Deuterium Surface Degradation at Ultracold Neutron Sources",

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 = "Deuterium, Solid, Surface Degradation, Ultracold Neutron Sources",

author = "Alexander Anghel and Bailey, \{Thomas L.\} and George Bison and Bertrand Blau and Broussard, \{Leah J.\} and Clayton, \{Stephen M.\} and Christopher Cude-Woods and Manfred Daum and Hawari, \{Ayman I.\} and Nora Hild and Huffman, \{Paul R.\} and Ito, \{Takeyasu M.\} and Klaus Kirch and E. Korobkina and Bernhard Lauss and Kent Leung and Lutz, \{E. M.\} and Mark Makela and G. Medlin and Morris, \{C. L.\} and Pattie, \{Robert W.\} and Dieter Ries and Alexander Saunders and Phillip Schmidt-Wellenburg and Vadim Talanov and Young, \{Albert R.\} and Bernard Wehring and C. White and Michael Wohlmuther and Geza Zsigmond",

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doi = "10.1140/epja/i2018-12594-2",

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T1 - Solid Deuterium Surface Degradation at Ultracold Neutron Sources

AU - Anghel, Alexander

AU - Bailey, Thomas L.

AU - Bison, George

AU - Blau, Bertrand

AU - Broussard, Leah J.

AU - Clayton, Stephen M.

AU - Cude-Woods, Christopher

AU - Daum, Manfred

AU - Hawari, Ayman I.

AU - Hild, Nora

AU - Huffman, Paul R.

AU - Ito, Takeyasu M.

AU - Kirch, Klaus

AU - Korobkina, E.

AU - Lauss, Bernhard

AU - Leung, Kent

AU - Lutz, E. M.

AU - Makela, Mark

AU - Medlin, G.

AU - Morris, C. L.

AU - Pattie, Robert W.

AU - Ries, Dieter

AU - Saunders, Alexander

AU - Schmidt-Wellenburg, Phillip

AU - Talanov, Vadim

AU - Young, Albert R.

AU - Wehring, Bernard

AU - White, C.

AU - Wohlmuther, Michael

AU - Zsigmond, Geza

PY - 2018/8/28

Y1 - 2018/8/28

N2 - 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.

AB - 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.

KW - Deuterium

KW - Solid

KW - Surface Degradation

KW - Ultracold Neutron Sources

U2 - 10.1140/epja/i2018-12594-2

DO - 10.1140/epja/i2018-12594-2

M3 - Article

VL - 54

JO - European Physical Journal A

JF - European Physical Journal A

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