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@ARTICLE{Bentley:201672,
      author       = {Bentley, Phillip M. and Kennedy, Shane J. and Andersen, Ken
                      H. and Martin Rodríguez, Damián and Mildner, David F. R.},
      title        = {{C}orrection of optical aberrations in elliptic neutron
                      guides},
      journal      = {Nuclear instruments $\&$ methods in physics research / A},
      volume       = {693},
      issn         = {0168-9002},
      address      = {Amsterdam},
      publisher    = {North-Holland Publ. Co.},
      reportid     = {FZJ-2015-03966},
      pages        = {268 - 275},
      year         = {2012},
      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.},
      cin          = {ICS-1 / JCNS-1},
      ddc          = {530},
      cid          = {I:(DE-Juel1)ICS-1-20110106 / I:(DE-Juel1)JCNS-1-20110106},
      pnm          = {451 - Soft Matter Composites (POF2-451) / 54G - JCNS
                      (POF2-54G24)},
      pid          = {G:(DE-HGF)POF2-451 / G:(DE-HGF)POF2-54G24},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000311008400035},
      doi          = {10.1016/j.nima.2012.07.002},
      url          = {https://juser.fz-juelich.de/record/201672},
}