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Eliminating line of sight in elliptic guides using gravitational curving

Kleno, Kaspar H.; Willendrup, Peter K.; Knudsen, Erik and Lefmann, Kim LU (2011) International Workshop on Neutron Optics In Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 634. p.100-103
Abstract
Eliminating fast neutrons (lambda < 0.5 angstrom) by removing direct line of sight between the source and the target sample is a well established technique. This can be done with little loss of transmission for a straight neutron guide by horizontal curving. With an elliptic guide shape, however, curving the guide would result in a breakdown of the geometrical focusing mechanism inherent to the elliptical shape, resulting in unwanted reflections and loss of transmission. We present a new and yet untried idea by curving a guide in such a way as to follow the ballistic curve of a neutron in the gravitational field, while still retaining the elliptic shape seen from the accelerated reference frame of the neutron. Analytical calculations... (More)
Eliminating fast neutrons (lambda < 0.5 angstrom) by removing direct line of sight between the source and the target sample is a well established technique. This can be done with little loss of transmission for a straight neutron guide by horizontal curving. With an elliptic guide shape, however, curving the guide would result in a breakdown of the geometrical focusing mechanism inherent to the elliptical shape, resulting in unwanted reflections and loss of transmission. We present a new and yet untried idea by curving a guide in such a way as to follow the ballistic curve of a neutron in the gravitational field, while still retaining the elliptic shape seen from the accelerated reference frame of the neutron. Analytical calculations and ray-tracing simulations show that this method is useful for cold neutrons at guide lengths in excess of 100 m. We will present some of the latest results for guide optimization relevant for instrument design at the ESS, in particular an off-backscattering spectrometer which utilizes the gravitational curving, for 6.66 angstrom neutrons over a guide length of 300m. (C) 2010 Elsevier B.V. All rights reserved. (Less)
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author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
keywords
Neutron guide, ESS, Backscattering spectrometer, Ray-tracing simulations
in
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
volume
634
pages
100 - 103
publisher
Elsevier
conference name
International Workshop on Neutron Optics
external identifiers
  • wos:000290355100022
  • scopus:79952992257
ISSN
0168-9002
DOI
10.1016/j.nima.2010.06.261
language
English
LU publication?
yes
id
6772106a-9bf7-4731-bcdd-6246eebfc93c (old id 1987661)
date added to LUP
2011-06-29 09:16:58
date last changed
2017-08-06 03:56:19
@inproceedings{6772106a-9bf7-4731-bcdd-6246eebfc93c,
  abstract     = {Eliminating fast neutrons (lambda &lt; 0.5 angstrom) by removing direct line of sight between the source and the target sample is a well established technique. This can be done with little loss of transmission for a straight neutron guide by horizontal curving. With an elliptic guide shape, however, curving the guide would result in a breakdown of the geometrical focusing mechanism inherent to the elliptical shape, resulting in unwanted reflections and loss of transmission. We present a new and yet untried idea by curving a guide in such a way as to follow the ballistic curve of a neutron in the gravitational field, while still retaining the elliptic shape seen from the accelerated reference frame of the neutron. Analytical calculations and ray-tracing simulations show that this method is useful for cold neutrons at guide lengths in excess of 100 m. We will present some of the latest results for guide optimization relevant for instrument design at the ESS, in particular an off-backscattering spectrometer which utilizes the gravitational curving, for 6.66 angstrom neutrons over a guide length of 300m. (C) 2010 Elsevier B.V. All rights reserved.},
  author       = {Kleno, Kaspar H. and Willendrup, Peter K. and Knudsen, Erik and Lefmann, Kim},
  booktitle    = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
  issn         = {0168-9002},
  keyword      = {Neutron guide,ESS,Backscattering spectrometer,Ray-tracing simulations},
  language     = {eng},
  pages        = {100--103},
  publisher    = {Elsevier},
  title        = {Eliminating line of sight in elliptic guides using gravitational curving},
  url          = {http://dx.doi.org/10.1016/j.nima.2010.06.261},
  volume       = {634},
  year         = {2011},
}