Enhancing neutron beam production with a convoluted moderator

E. B. Iverson; D. V. Baxter; G. Muhrer; S. Ansell; R. Dalgliesh; F. X. Gallmeier; H. Kaiser; W. Lu

doi:10.1016/j.nima.2014.04.047

Enhancing neutron beam production with a convoluted moderator

E. B. Iverson, D. V. Baxter, G. Muhrer, S. Ansell, R. Dalgliesh, F. X. Gallmeier, H. Kaiser, W. Lu

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

16 Scopus citations

Abstract

We describe a new concept for a neutron moderating assembly resulting in the more efficient production of slow neutron beams. The Convoluted Moderator, a heterogeneous stack of interleaved moderating material and nearly transparent single-crystal spacers, is a directionally enhanced neutron beam source, improving beam emission over an angular range comparable to the range accepted by neutron beam lines and guides. We have demonstrated gains of 50% in slow neutron intensity for a given fast neutron production rate while simultaneously reducing the wavelength-dependent emission time dispersion by 25%, both coming from a geometric effect in which the neutron beam lines view a large surface area of moderating material in a relatively small volume. Additionally, we have confirmed a Bragg-enhancement effect arising from coherent scattering within the single-crystal spacers. We have not observed hypothesized refractive effects leading to additional gains at long wavelength. In addition to confirmation of the validity of the Convoluted Moderator concept, our measurements provide a series of benchmark experiments suitable for developing simulation and analysis techniques for practical optimization and eventual implementation at slow neutron source facilities.

Original language	English
Pages (from-to)	31-41
Number of pages	11
Journal	Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume	762
DOIs	https://doi.org/10.1016/j.nima.2014.04.047
State	Published - Oct 21 2014
Externally published	Yes

Funding

Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory , managed by UT-Battelle, LLC, for the U. S. Department of Energy. Work performed at Oak Ridge National Laboratory is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. Construction of LENS was supported by the National Science Foundation Grants DMR-0220560 and DMR-0320627 , the 21st Century Science and Technology fund of Indiana, Indiana University, and the Department of Defense. Operation of LENS is supported by Indiana University , and the experiments described in this paper were supported with funds from the US Department of Energy. This work was supported by Readiness in Technical Base and Facilities (RTBF) which is funded by the Department of Energy׳s Office of National Nuclear Security Administration . It has benefited from the use of the Manuel Lujan, Jr. Neutron Scattering Center at Los Alamos National Laboratory, which is funded by the Department of Energy׳s Office of Basic Energy Sciences . Los Alamos National Laboratory is operated by Los Alamos National Security LLC under DOE Contract DE-AC52-06NA25396 .

Funders	Funder number
Department of Energy׳s Office of Basic Energy Sciences
U. S. Department of Energy
US Department of Energy
UT-Battelle	DE-AC05-00OR22725
National Science Foundation	DMR-0220560, DMR-0320627
U.S. Department of Defense
U.S. Department of Energy	DE-AC52-06NA25396
National Nuclear Security Administration
Oak Ridge National Laboratory
Indiana University
Los Alamos National Laboratory

Keywords

Grooved moderator
Neutron beam production
Neutron moderation
Neutron source

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10.1016/j.nima.2014.04.047

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title = "Enhancing neutron beam production with a convoluted moderator",

abstract = "We describe a new concept for a neutron moderating assembly resulting in the more efficient production of slow neutron beams. The Convoluted Moderator, a heterogeneous stack of interleaved moderating material and nearly transparent single-crystal spacers, is a directionally enhanced neutron beam source, improving beam emission over an angular range comparable to the range accepted by neutron beam lines and guides. We have demonstrated gains of 50% in slow neutron intensity for a given fast neutron production rate while simultaneously reducing the wavelength-dependent emission time dispersion by 25%, both coming from a geometric effect in which the neutron beam lines view a large surface area of moderating material in a relatively small volume. Additionally, we have confirmed a Bragg-enhancement effect arising from coherent scattering within the single-crystal spacers. We have not observed hypothesized refractive effects leading to additional gains at long wavelength. In addition to confirmation of the validity of the Convoluted Moderator concept, our measurements provide a series of benchmark experiments suitable for developing simulation and analysis techniques for practical optimization and eventual implementation at slow neutron source facilities.",

keywords = "Grooved moderator, Neutron beam production, Neutron moderation, Neutron source",

author = "Iverson, {E. B.} and Baxter, {D. V.} and G. Muhrer and S. Ansell and R. Dalgliesh and Gallmeier, {F. X.} and H. Kaiser and W. Lu",

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doi = "10.1016/j.nima.2014.04.047",

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AU - Iverson, E. B.

AU - Baxter, D. V.

AU - Muhrer, G.

AU - Ansell, S.

AU - Dalgliesh, R.

AU - Gallmeier, F. X.

AU - Kaiser, H.

AU - Lu, W.

PY - 2014/10/21

Y1 - 2014/10/21

N2 - We describe a new concept for a neutron moderating assembly resulting in the more efficient production of slow neutron beams. The Convoluted Moderator, a heterogeneous stack of interleaved moderating material and nearly transparent single-crystal spacers, is a directionally enhanced neutron beam source, improving beam emission over an angular range comparable to the range accepted by neutron beam lines and guides. We have demonstrated gains of 50% in slow neutron intensity for a given fast neutron production rate while simultaneously reducing the wavelength-dependent emission time dispersion by 25%, both coming from a geometric effect in which the neutron beam lines view a large surface area of moderating material in a relatively small volume. Additionally, we have confirmed a Bragg-enhancement effect arising from coherent scattering within the single-crystal spacers. We have not observed hypothesized refractive effects leading to additional gains at long wavelength. In addition to confirmation of the validity of the Convoluted Moderator concept, our measurements provide a series of benchmark experiments suitable for developing simulation and analysis techniques for practical optimization and eventual implementation at slow neutron source facilities.

AB - We describe a new concept for a neutron moderating assembly resulting in the more efficient production of slow neutron beams. The Convoluted Moderator, a heterogeneous stack of interleaved moderating material and nearly transparent single-crystal spacers, is a directionally enhanced neutron beam source, improving beam emission over an angular range comparable to the range accepted by neutron beam lines and guides. We have demonstrated gains of 50% in slow neutron intensity for a given fast neutron production rate while simultaneously reducing the wavelength-dependent emission time dispersion by 25%, both coming from a geometric effect in which the neutron beam lines view a large surface area of moderating material in a relatively small volume. Additionally, we have confirmed a Bragg-enhancement effect arising from coherent scattering within the single-crystal spacers. We have not observed hypothesized refractive effects leading to additional gains at long wavelength. In addition to confirmation of the validity of the Convoluted Moderator concept, our measurements provide a series of benchmark experiments suitable for developing simulation and analysis techniques for practical optimization and eventual implementation at slow neutron source facilities.

KW - Grooved moderator

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KW - Neutron moderation

KW - Neutron source

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ER -

Enhancing neutron beam production with a convoluted moderator

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