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@PHDTHESIS{Koza:37539,
      author       = {Koza, Yoshie},
      title        = {{P}erformance of {M}etallic and {C}arbon-{B}ased
                      {M}aterials {U}nder the {I}nfluence of {I}ntense {T}ransient
                      {E}nergy {D}eposition},
      volume       = {4137},
      issn         = {0944-2952},
      school       = {Techn. Hochsch. Aachen},
      type         = {Dr. (FH)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-37539, Juel-4137},
      series       = {Berichte des Forschungszentrums Jülich},
      pages        = {II, 140 S.},
      year         = {2004},
      note         = {Record converted from VDB: 12.11.2012; Aachen, Techn.
                      Hochsch., Diss., 2004},
      abstract     = {Intense energy is deposited on localized areas of the
                      plasma facing materials under transient thermal loads such
                      as edge localized modes (ELMS), plasma disruptions or
                      vertical displacement events (VDEs) in a magnetic confined
                      fusion reactor. Crack formation, thermal erosion and
                      redeposition mainly take place under these conditions and
                      may cause catastrophic damage in the materials. Dust
                      formation associated with evaporation and liquid or solid
                      particles emission are also serious issues to influence
                      plasma contamination. In order to estimate the lifetime of
                      the components during above mentioned events (ELMS,
                      disruptions, VDEs), the thermal erosion mechanisms and
                      performance of carbon-based and high Z materials have been
                      investigated using energetic electron beam facilities.
                      Moreover, a thorough calibration of an electron beam in the
                      high heat flux facility JUDITH was done. For the evaluation
                      of erosion data obtained in different test facilities
                      several factors have to be taken into account. Different
                      material erosion processes at identical heat loads induced
                      by different facilities take place due to different beam
                      generation and beam modes (static/scanned beam). The
                      different degradation processes were created by different
                      surface tensions and vapor recoil pressures at local spots
                      in the loaded area. Molten and re-solidified material
                      remained within the loaded area by fast scanning of the
                      electron beam in JUDITH, which leaded to a rippling surface.
                      Erosion scenarios have been elucidated on pure W and
                      carbon-based materials. For W, the thermal erosion is
                      initiated by convection of melt, strong evaporation or
                      boiling processes. Moreover the formation of a vapor cloud
                      was observed in the simulation experiments indicating vapor
                      shielding on the surface. From screening tests on different
                      high Z materials, pure Wwas found to show the highest
                      resistance against thermal shock under plasma disruption
                      conditions and are suitable for the components in Tokamak
                      fusion reactors. A castellated structure was found to help
                      reducing crack formation compared to monolithic structure.
                      For carbon-based materials (isotropic graphite,
                      $\underline{c}$arbon $\underline{f}$iber
                      $\underline{c}$omposites (CFCs), Si-doped CFC), material
                      erosion in different particle emission regimes, and
                      characterization of emitted particles have been studied.
                      "Small" and "Big" particle emission regimes have been
                      identified under brittle destruction, which represents the
                      combined action of sublimation, crack formation and ejection
                      of solid particles. These regimes were related to the
                      ejected particle size and maximum erosion depth. The
                      resulting erosion patterns on the test samples and the
                      morphology of the ejected particles differ significantly for
                      the three materials. For both carbon and tungsten,
                      preheating of samples before loading enhances material
                      damages such as weight loss and crater formation.},
      cin          = {IWV-2},
      cid          = {I:(DE-Juel1)VDB2},
      pnm          = {Kernfusion und Plasmaforschung},
      pid          = {G:(DE-Juel1)FUEK250},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/37539},
}