Performance of a cooled sapphire and beryllium assembly for filtering of thermal neutrons

Tennant, D. C.

doi:10.1063/1.1140212

Cited by 24 publications

(18 citation statements)

References 1 publication

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“…On Rita the fast neutron flux from the source has been reduced a factor of four by a 7.5 cm sapphire [3,4] single crystal. In front of the monochromator, a tunable bandpass filter for the suppression of higher (or lower) order neutrons is installed [ 5 ] .…”

Section: The Front End Of Ritamentioning

confidence: 99%

The RITA spectrometer at risø

et al. 1996

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Section: The Front End Of Ritamentioning

confidence: 99%

The RITA spectrometer at risø

et al. 1996

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“…Though we believe this to be a good approximation, we would only be able to verify the correction by redoing the experiment using a polycrystalline corundum reflector-filter of equal dimension and density as the single crystal reflector-filter. The apparent gain factor a short wavelength, significantly higher than the transmission of a comparable filter (as opposed to a reflector-filter), for which values from the literature range over 0.15-0.35 [19][20][21][22]. The significant variation in the literature is not something we can address at this point, but our apparent gain factor λ ( ) G y 0 is larger yet, indicating that the reflector-filter does indeed boost the intensity within the moderator and at the moderator surface by a significant amount.…”

Section: Spectral Gainmentioning

confidence: 97%

Demonstration of a single-crystal reflector-filter for enhancing slow neutron beams

Muhrer

Schönfeldt

Iverson

et al. 2016

Nuclear Instruments and Methods in Physics Research Section A:

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a b s t r a c tThe cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystal reflector-filter at a reflected neutron source and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. This finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.

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“…The possible choices considered for this purpose included silicon, quartz, sapphire, bismuth, and lead. A 2.5-in diameter single crystal sapphire was selected as a fast neutron filter due to its proven quality as a filter at room temperature as opposed to cryogenically cooled silicon and quartz [3], [4]. Also, the transmission characteristics of sapphire are not expected to be altered even after years of exposure in the neutron beam.…”

Section: B Design Performance Using Simulationsmentioning

confidence: 99%

Design and Performance of a Thermal Neutron Imaging Facility at the North Carolina State University PULSTAR Reactor

Mishra

Hawari

Gillette

2006

IEEE Trans. Nucl. Sci.

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A thermal neutron imaging facility has been set up at the North Carolina State University PULSTAR reactor. The PULSTAR is an open pool light water moderated 1 MWth research reactor with six beam tubes. The present facility is set up on beam tube # 5 of the reactor. The facility is intended to have radiographic and tomographic capabilities. The design of the neutron collimator was performed using MCNP5. The collimator includes a 4-in bismuth filter followed by a 6-in single-crystal sapphire filter. Thermal neutron scattering cross-section libraries for sapphire and bismuth were generated and used in the MCNP simulation of the system. Based on the current design, the L/D of the facility ranges between 100 and 150. The neutron flux at the image plane can be varied from 1 8 10 6 to 7 10 6 n/cm 2 s with a Cd-ratio of 450. The resolution of the system for different imaging media was also estimated and found to be 33 m for conventional radiography film and 110 m for digital image plates. Initial measurements, using ASTM standards, show that the imaging facility achieves a beam quality classification of I A .

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Performance of a cooled sapphire and beryllium assembly for filtering of thermal neutrons

Cited by 24 publications

References 1 publication

The RITA spectrometer at risø

The RITA spectrometer at risø

Demonstration of a single-crystal reflector-filter for enhancing slow neutron beams

Design and Performance of a Thermal Neutron Imaging Facility at the North Carolina State University PULSTAR Reactor

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