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@INPROCEEDINGS{Eisenhut:867785,
      author       = {Eisenhut, S. and Klaus, M. and Baggemann, J. and Rücker,
                      U. and Beßler, Y. and Haberstroh, C. and Cronert, T. and
                      Gutberlet, T. and Brückel, T. and Lange, C.},
      title        = {{C}ryostat for the provision of liquid hydrogen with
                      variable ortho-para-ratio for a low-dimensional cold neutron
                      moderator},
      reportid     = {FZJ-2019-06395},
      year         = {2019},
      abstract     = {A significant contribution to the enhancement of the
                      neutron brilliance achievable with Compact
                      Accelerator-driven Neutron Sources (CANS) can be made by an
                      optimized cold moderator design. When using liquid para-H2
                      as the moderating medium, the concept of low-dimensional
                      cold moderators can be employed to increase the neutron
                      brightness (as currently foreseen at the European Spallation
                      Source ESS). Para-H2 shows a drop in the scattering cross
                      section by about one order of magnitude around 15 meV,
                      resulting in large deviation between the mean free paths of
                      thermal and cold neutrons. Taking advantage of this effect,
                      the cold moderator geometry can be optimized to allow the
                      intake of thermal neutrons through a relatively large
                      envelope surface and then extracting them in an efficient
                      way towards the neutron guides. One drawback of this
                      solution is the lack of thermalization of the cold neutrons.
                      In the context of the HBS (High Brilliance Source) project,
                      efforts are made to overcome this problem by increasing the
                      scattering cross section of the H2 in a defined way. The
                      idea is to admix small amounts of ortho-H2, which maintains
                      its large scattering cross section in the region below 15
                      meV. Like this, the neutron spectrum can be shifted towards
                      lower energies and adjusted for the needs of the respective
                      instrument. In a cooperation between TU Dresden and FZ
                      Jülich, an experimental setup has been created to proof the
                      feasibility of this concept. The main component of the
                      experimental setup is a LHe-cooled flow cryostat that
                      enables the separate condensation of a para-H2 and a
                      normal-H2 flow and a subsequent mixing of the two in precise
                      proportions. The resulting LH2 mixture at 17 – 20 K is fed
                      into a small cold moderator vessel (approx. 200 ml). In this
                      work, the current status of the setup is presented. The
                      construction and commissioning of the mixing cryostat have
                      been completed and extensive test runs show that different,
                      stable ortho-para-H2 mixtures can be produced and monitored.
                      Currently, preparations for first measurements of the
                      resulting neutron spectra are being prepared at
                      Forschungszentrum Jülich.},
      month         = {Dec},
      date          = {2019-12-16},
      organization  = {Workshop SCANS – A Compact
                       Accelerator-Driven Neutron Source for
                       Scandinavia?, Institute for Energy
                       Technology, Kjeller (Norway), 16 Dec
                       2019 - 17 Dec 2019},
      subtyp        = {Invited},
      cin          = {JCNS-2 / PGI-4 / JARA-FIT / JCNS-HBS / ZEA-1},
      cid          = {I:(DE-Juel1)JCNS-2-20110106 / I:(DE-Juel1)PGI-4-20110106 /
                      $I:(DE-82)080009_20140620$ / I:(DE-Juel1)JCNS-HBS-20180709 /
                      I:(DE-Juel1)ZEA-1-20090406},
      pnm          = {144 - Controlling Collective States (POF3-144) / 524 -
                      Controlling Collective States (POF3-524) / 6212 - Quantum
                      Condensed Matter: Magnetism, Superconductivity (POF3-621) /
                      6213 - Materials and Processes for Energy and Transport
                      Technologies (POF3-621) / 6G4 - Jülich Centre for Neutron
                      Research (JCNS) (POF3-623)},
      pid          = {G:(DE-HGF)POF3-144 / G:(DE-HGF)POF3-524 /
                      G:(DE-HGF)POF3-6212 / G:(DE-HGF)POF3-6213 /
                      G:(DE-HGF)POF3-6G4},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/867785},
}