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@INPROCEEDINGS{Schwab:877651,
      author       = {Schwab, A. and Baggemann, Johannes and Zakalek, P. and
                      Rücker, U. and Li, Jingjing and Gutberlet, T. and Brückel,
                      T.},
      title        = {{A} compact solid methane moderator system for the
                      {J}ülich {H}igh {B}rilliance {N}eutron {S}ource ({HBS})
                      prototype},
      reportid     = {FZJ-2020-02364},
      year         = {2020},
      abstract     = {During the last year two cryogenic moderators for the
                      Jülich High Brilliance Neutron Source (HBS) project were
                      tested at the COSY facility at the Jülich Research Centre.
                      Time-of-flight spectra were measured for solid mesitylene at
                      different temperatures (24 K to 300 K) and liquid hydrogen
                      for different ortho-para-ratios $(25\%$ to approx. $100\%$
                      p-H2). An attempt to increase the cold neutron brilliance
                      exists in lowering the temperature of the moderating
                      material even below 20 K, a commonly used minimum
                      temperature for solid cryogenic moderator materials. At
                      temperatures below 20 K and corresponding energies, energy
                      transfer mostly takes place by excitations of vibrational
                      and rotational movements of the lattice molecules.
                      Therefore, an effective cryogenic moderator has to allow
                      sufficient low-energy modes. Solid methane shows a phase
                      change below approximately 21 K from phase I to phase II,
                      which leads to a change of free molecular rotations to
                      three-fourths of hindered rotations. Due to energy transfer
                      by inducing librational movements of the hindered molecules
                      even down to low temperatures, methane in phase II is one of
                      the most effective candidates for increasing the cold
                      neutron brilliance. Simulations on different methane
                      thicknesses and geometries were performed to find an
                      effective way of dimensioning the phase II methane moderator
                      to maximize cold neutron brightness while keeping the
                      moderator vessel as compact as possible. Using a reentrant
                      hole for extracting cold neutrons from the center of the
                      moderator volume, as suggested in literature, didn’t prove
                      profitable. A preliminary design for a new cryogenic system
                      for using solid methane at an HBS prototype is currently
                      being carried out. Besides different measures to keep the
                      heat load onto the cold moderator as low as possible, one
                      also has to examine possible dangers in using solid methane
                      being irradiated for extended periods of time while at the
                      same time keeping those periods of time as long as
                      possible.},
      month         = {Jun},
      date          = {2020-06-22},
      organization  = {The Japanese RIKEN Center for Advanced
                       Photonics (RAP) and the Jülich Centre
                       for Neutron Science (JCNS) fourth joint
                       workshop on compact accelerator-driven
                       neutron sources (CANS) special webinar,
                       Forschungszentrum Jülich (Germany), 22
                       Jun 2020 - 24 Jun 2020},
      subtyp        = {Invited},
      cin          = {JCNS-2 / PGI-4 / JARA-FIT / JCNS-HBS},
      cid          = {I:(DE-Juel1)JCNS-2-20110106 / I:(DE-Juel1)PGI-4-20110106 /
                      $I:(DE-82)080009_20140620$ / I:(DE-Juel1)JCNS-HBS-20180709},
      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/877651},
}