Advanced

Correction of optical aberrations in elliptic neutron guides

Bentley, Phillip LU ; Kennedy, Shane J.; Andersen, Ken LU ; Rodriguez, Damian Martin and Mildner, David F. R. (2012) In Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment 693. p.268-275
Abstract
Modern, nonlinear ballistic neutron guides are an attractive concept in neutron beam delivery and instrumentation because they offer increased performance over straight or linearly tapered guides. However, like other ballistic geometries they have the potential to create significantly non-trivial instrumental resolution functions. We address the source of the most prominent optical aberration, namely coma, and we show that for extended sources the off-axis rays have a different focal length from on-axis rays, leading to multiple reflections in the guide system. We illustrate how the interplay between coma, sources of finite size, and mirrors with non-perfect reflectivity can therefore conspire to produce uneven distributions in the neutron... (More)
Modern, nonlinear ballistic neutron guides are an attractive concept in neutron beam delivery and instrumentation because they offer increased performance over straight or linearly tapered guides. However, like other ballistic geometries they have the potential to create significantly non-trivial instrumental resolution functions. We address the source of the most prominent optical aberration, namely coma, and we show that for extended sources the off-axis rays have a different focal length from on-axis rays, leading to multiple reflections in the guide system. We illustrate how the interplay between coma, sources of finite size, and mirrors with non-perfect reflectivity can therefore conspire to produce uneven distributions in the neutron beam divergence, a source of complicated resolution functions. To solve these problems, we propose a hybrid elliptic-parabolic guide geometry. Using this new kind of neutron guide shape, it is possible to condition the neutron beam and remove almost all of the aberrations, whilst providing the same performance in beam current as a standard elliptic neutron guide. We highlight the positive implications for neutron scattering instruments that this new shape can bring. (c) 2012 Elsevier B.V. All rights reserved. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Neutron guide, Elliptic, Parabolic, Ballistic, Conic section
in
Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment
volume
693
pages
268 - 275
publisher
Elsevier
external identifiers
  • wos:000311008400035
  • scopus:84865341225
ISSN
0167-5087
DOI
10.1016/j.nima.2012.07.002
language
English
LU publication?
yes
id
a2a159fa-b4ec-4392-bde1-ad438e3af2c6 (old id 3382455)
date added to LUP
2013-01-30 14:32:09
date last changed
2017-07-23 03:59:41
@article{a2a159fa-b4ec-4392-bde1-ad438e3af2c6,
  abstract     = {Modern, nonlinear ballistic neutron guides are an attractive concept in neutron beam delivery and instrumentation because they offer increased performance over straight or linearly tapered guides. However, like other ballistic geometries they have the potential to create significantly non-trivial instrumental resolution functions. We address the source of the most prominent optical aberration, namely coma, and we show that for extended sources the off-axis rays have a different focal length from on-axis rays, leading to multiple reflections in the guide system. We illustrate how the interplay between coma, sources of finite size, and mirrors with non-perfect reflectivity can therefore conspire to produce uneven distributions in the neutron beam divergence, a source of complicated resolution functions. To solve these problems, we propose a hybrid elliptic-parabolic guide geometry. Using this new kind of neutron guide shape, it is possible to condition the neutron beam and remove almost all of the aberrations, whilst providing the same performance in beam current as a standard elliptic neutron guide. We highlight the positive implications for neutron scattering instruments that this new shape can bring. (c) 2012 Elsevier B.V. All rights reserved.},
  author       = {Bentley, Phillip and Kennedy, Shane J. and Andersen, Ken and Rodriguez, Damian Martin and Mildner, David F. R.},
  issn         = {0167-5087},
  keyword      = {Neutron guide,Elliptic,Parabolic,Ballistic,Conic section},
  language     = {eng},
  pages        = {268--275},
  publisher    = {Elsevier},
  series       = {Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment},
  title        = {Correction of optical aberrations in elliptic neutron guides},
  url          = {http://dx.doi.org/10.1016/j.nima.2012.07.002},
  volume       = {693},
  year         = {2012},
}