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@INPROCEEDINGS{Dhillon:631514,
      author       = {Dhillon, Aman Kumar and Barbanotti, Serena and Bozhko, Yury
                      and Jensch, Kay and Ramalingam, Rajinikumar and Abassi, Emna
                      and Schnautz, Tobias},
      title        = {{M}odelling two-phase {H}e {II} flow for heat load limits
                      in {XFEL} {C}ryomodules for {CW} operation},
      journal      = {IOP conference series / Materials science and engineering},
      reportid     = {PUBDB-2025-02026},
      pages        = {1-9},
      year         = {2025},
      note         = {online first},
      abstract     = {The European XFEL (EuXFEL) is under consideration for a
                      High Duty Cycle (HDC) upgrade to enhance the user’s
                      operational range by enabling short pulse, long pulse, and
                      Continuous Wave (CW) operation. Therefore, the EuXFEL shall
                      be extended by new CW optimized cryomodules (CMs) that will
                      be installed at the beginning of the EuXFEL linac. These new
                      CMs will be followed by the already existing CMs, which have
                      to be operated at respectively higher 2 K dynamic heat loads
                      at various operating modes. One of the key challenges for
                      this upgrade is the design of the CW-optimized CMs.
                      Furthermore, the heat load limit of the existing EuXFEL CMs
                      has to be identified with respect to operational stability.
                      Measures must be implemented to increase the heat load limit
                      to meet the requirements of the HDC upgrade. Referring to
                      operational stability, the flow conditions in the two-phase
                      pipe within the CMs play a critical role to prevent
                      vibrations and microphonic effects with undesirable impacts
                      on RF operation. To address these challenges, a simulation
                      model has been developed to analyze the two-phase flow
                      behavior of superfluid helium in EuXFEL-like CMs installed
                      on the cryomodule test stands in the Accelerator Module Test
                      Facility (AMTF). This model incorporates the Taitel-Dukler
                      criterion to evaluate the transition from stratified smooth
                      to stratified wavy flow in the two-phase pipe under varying
                      heat loads. The findings provide path for the CW optimized
                      CM design and JT valve arrangement, ensuring stable
                      operation under increased heat loads. Validation tests
                      planned at AMTF will further establish the predictive
                      accuracy of the model and support its future use in XFEL HDC
                      upgrades.},
      month         = {May},
      date          = {2025-05-18},
      organization  = {Cryogenic Engineering Conference $\&$
                       International Cryogenic Materials
                       Conference, Reno (USA), 18 May 2025 -
                       22 May 2025},
      cin          = {MKS1},
      cid          = {I:(DE-H253)MKS1-20210408},
      pnm          = {621 - Accelerator Research and Development (POF4-621)},
      pid          = {G:(DE-HGF)POF4-621},
      experiment   = {EXP:(DE-H253)XFEL(machine)-20150101},
      typ          = {PUB:(DE-HGF)16 / PUB:(DE-HGF)8},
      url          = {https://bib-pubdb1.desy.de/record/631514},
}