Enhancing Neutron Beam Production with a Convoluted Moderator

Journal Article · Wed Oct 01 00:00:00 EDT 2014 · Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment

DOI:https://doi.org/10.1016/j.nima.2014.04.047· OSTI ID:1143543

Iverson, Erik B ^[1]; Baxter, David V ^[2]; Muhrer, Guenter ^[3]; Ansell, Stuart ^[4]; Gallmeier, Franz X ^[1]; Dalgliesh, Robert ^[4]; Lu, Wei ^[1]; Kaiser, Helmut ^[2]

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1. ORNL
2. Center for the Exploration of Energy and Matter, Indiana University
3. Los Alamos National Laboratory (LANL)
4. ISIS Facility, Rutherford Appleton Laboratory (ISIS)

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 effectiveness 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.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
• Sponsoring Organization: USDOE Laboratory Directed Research and Development (LDRD) Program
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1143543
• Journal Information: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 762; ISSN 0168-9002
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

Neutron moderation
Neutron beam production
Neutron source
Grooved moderator