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@ARTICLE{Bate:611802,
      author       = {Bate, C. and Kasprzak, K. and Reschke, D. and Steder, L.
                      and Trelle, L. and Weise, Hans and Wiencek, M. and Wolff,
                      Jonas},
      title        = {{C}orrelation of srf performance to oxygen diffusion length
                      of medium temperature heat treated cavities},
      journal      = {Superconductor science and technology},
      volume       = {38},
      number       = {2},
      issn         = {0953-2048},
      address      = {Bristol},
      publisher    = {IOP Publ.},
      reportid     = {PUBDB-2024-05082, arXiv:2407.07779. DESY-24-112},
      pages        = {025003},
      year         = {2024},
      abstract     = {This comprehensive study, being part of the European XFEL
                      $R\&D$ effort, elucidates the influence of medium
                      temperature (mid-T) heat treatments between $250{\deg}C$ and
                      $350{\deg}C$ on the performance of 1.3 GHz superconducting
                      radiofrequency (SRF) niobium cavities. Utilizing a
                      refurbished niobium retort furnace equipped with an
                      inter-vacuum chamber and cryopumps at DESY, we have embarked
                      on an investigation to enhance the state-of-the-art SRF
                      cavity technology. Our research reveals that mid-T heat
                      treatments significantly boost the quality factor ($Q_0$) of
                      the cavities, achieving values between $2\cdot10^{10}$ to
                      $5\cdot10^{10}$ at field strengths around 16 MV/m, while the
                      maximum field strengths are limited to 25-35 MV/m and
                      enhanced sensitivity to trapped magnetic flux is observed.
                      Moreover, we delve into the effects of surface impurity
                      concentration changes, particularly the diffusion of oxygen
                      content, and its impact on performance enhancements. By
                      categorizing treatments based on calculated diffusion
                      lengths using the whole temperature profile, we recognize
                      patterns that suggest an optimal diffusion length conducive
                      to optimizing cavity performance. SIMS results from samples
                      confirm the calculated oxygen diffusion lengths in most
                      instances. Deviations are primarily attributed to grain
                      boundaries in fine-grain materials, necessitating repeated
                      measurements on single-crystal materials to further
                      investigate this phenomenon. Investigations into cooling
                      rates and the resulting spatial temperature gradients across
                      the cavities ranging from 0.04 to 0.2 K/mm reveal no
                      significant correlation with performance following a mid-T
                      heat treatment. However, the increased sensitivity to
                      trapped magnetic flux leads to new challenges in the quest
                      for next-generation accelerator technologies since the
                      requirement for magnetic hygiene gets stricter.},
      cin          = {MSL},
      ddc          = {530},
      cid          = {I:(DE-H253)MSL-20170609},
      pnm          = {621 - Accelerator Research and Development (POF4-621)},
      pid          = {G:(DE-HGF)POF4-621},
      experiment   = {EXP:(DE-H253)SRF-RD-20221201},
      typ          = {PUB:(DE-HGF)16},
      eprint       = {2407.07779},
      howpublished = {arXiv:2407.07779},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:2407.07779;\%\%$},
      UT           = {WOS:001394229800001},
      doi          = {10.1088/1361-6668/ad9fe8},
      url          = {https://bib-pubdb1.desy.de/record/611802},
}