% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@INPROCEEDINGS{Rcker:906990,
      author       = {Rücker, U. and Zakalek, P. and Li, Jingjing and Voigt, J.
                      and Shabani, D. and Böhm, S. and Mauerhofer, E. and
                      Gutberlet, T. and Brückel, Th.},
      title        = {{O}ptimized thermal moderators for {C}ompact
                      {A}ccelerator-driven {N}eutron {S}ources},
      reportid     = {FZJ-2022-01802},
      year         = {2022},
      abstract     = {Compact Accelerator-driven Neutron Sources (CANS) have the
                      advantage (compared to researchreactors or spallation
                      sources) that the primary neutrons are emitted from a volume
                      well below 1 dm3.The thermal moderator is used to change the
                      energy of the primary neutrons (typically in the MeVrange)
                      down to the 100 meV range, where they are useful for the
                      structural investigation of matter.This moderation process
                      takes place by multiple scattering events with the nuclei of
                      the moderatormaterial(s). To be able to extract neutron
                      beams efficiently from the thermal moderator, it isimportant
                      not to dilute the primary neutron cloud too much, but to
                      keep it confined and dense forthe time of the neutron pulse
                      length desired.The different materials useful for building a
                      moderator-reflector assembly around a target of a CANSdiffer
                      in their absorption probability, scattering power, and
                      energy transfer during a single neutronscattering event. The
                      scattering leads to energy loss and confinement (by a
                      randomized flight directionof the neutron after the
                      scattering), while absorption and diffusion out of the
                      moderator -reflectorregion are the main mechanisms of
                      intensity decay. Some typical materials are e.g. light water
                      orpolyethylene as hydrogen rich materials that lead to fast
                      energy transfer (complete thermalizationwithin 7 μs) and a
                      good confinement of the thermal neutron cloud (about 8 cm
                      FWHM), but thethermal neutrons decay with a time constant
                      below 200 μs due to the nuclear absorption by thehydrogen
                      nuclei. Beryllium or lead show a much weaker scattering
                      probability and a lower energytransfer, which lead to slower
                      moderation, a larger size of the thermal neutron cloud, but
                      a longerlifetime due to an absorption probability that is
                      several orders of magnitude lower.We try to optimize the
                      geometry and the combination of materials in a way to be
                      able to provide theextraction of several neutron beams from
                      a single moderator-reflector assembly with a suitable
                      pulsetime structure either for thermal neutron instruments
                      or for feeding cold neutron sources insertedinto the thermal
                      moderator assembly.},
      month         = {Mar},
      date          = {2022-03-28},
      organization  = {International Symposium UCANS9, online
                       by RIKEN, Japan (online event), 28 Mar
                       2022 - 31 Mar 2022},
      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          = {632 - Materials – Quantum, Complex and Functional
                      Materials (POF4-632) / 6G4 - Jülich Centre for Neutron
                      Research (JCNS) (FZJ) (POF4-6G4)},
      pid          = {G:(DE-HGF)POF4-632 / G:(DE-HGF)POF4-6G4},
      typ          = {PUB:(DE-HGF)1},
      url          = {https://juser.fz-juelich.de/record/906990},
}