% 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”.

@PHDTHESIS{Loewenhoff:127417,
      author       = {Loewenhoff, Thorsten Werner},
      title        = {{C}ombined {S}teady {S}tate and {H}igh {C}ycle {T}ransient
                      {H}eat {L}oad {S}imulation with the {E}lectron {B}eam
                      {F}acility {JUDITH} 2},
      volume       = {173},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2012-00414},
      isbn         = {978-3-89336-869-3},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {120 p.},
      year         = {2013},
      note         = {RWTH Aachen, Diss., 2012},
      abstract     = {The increasing world energy needs lead to strong efforts in
                      today's energy $R\&D$ trying to open up new energy
                      resources. One possible option to access energy in large
                      scale power plants is to use the process of nuclear fusion
                      to generate heat and, from that, electricity with
                      conventional steam turbine technology. However, the
                      realisation is technologically and scientifically very
                      challenging. The heat fluxes that load the inner walls of a
                      fusion device, especially the most severely loaded part, the
                      divertor, are one of the issues currently being under
                      investigation. A distinction is made between steady state
                      heat loads (SSHLs) that are continuously active during
                      operation and transient heat loads (THLs) that are
                      superimposed short-time events. The potentially most harmful
                      THLs during normal operation are type I Edge Localised Modes
                      (ELMs). They are estimated to have a power density of 1 - 10
                      GW/m² for 0.2 - 0.5 ms duration in the upcoming next step
                      fusion experiment ITER. Because of high pulse repetition
                      frequency more than 1,000,000 ELM events are expected during
                      the foreseen lifetime of divertor components. However, only
                      data regarding behaviour of materials for a low number of
                      pulses (typically 100 - 1000) exists. This work describes
                      the development of a procedure to simulate THLs at high
                      repetition frequency using an electron beam facility and the
                      tests done on tungsten and carbon-based (carbon fibre
                      composite, CFC) plasma facing materials. The developed
                      procedure uses a pulse frequency of 25 Hz, hence actively
                      cooled components are necessary and were designed. A novel
                      electron beam guidance procedure, called circular loading
                      method, was a result of the developmental process. It was
                      used for all later tests because it provides a stabilisation
                      of the applied power density against test parameter
                      fluctuations (e.g. vacuum quality). The electron beam
                      guidance is flexible enough to provide a SSHL pattern during
                      the interpulse time (between two successive THLs)
                      additionally to the THL pulses. This allowed to influence
                      the base temperature of the sample surface. The material
                      tests were done with pulse numbers of 100 - 1,000,000 and
                      absorbed power densities of up to 0.55 GW/m² and 0.68
                      GW/m² per pulse for tungsten and CFC materials
                      respectively. The surface base temperature was predicted by
                      finite element analyses and monitored by pyrometer
                      measurements. Damage thresholds of the investigated tungsten
                      and CFC were found to be < 0.27 GW/m² and < 0.68 GW/m²
                      respectively. Below these power densities no
                      damage/degradation was found for pulse numbers up to
                      1,000,000 (tungsten) or 100,000 (CFC). Tungsten showed long
                      term fatigue, which did not occur in CFC. Although it was
                      expected that tungsten would be more resistant at higher
                      base temperatures due to higher ductility, it was found to
                      show earlier degradation at higher temperatures. It is
                      proposed that an increased ductility leads to stronger
                      fatigue damage.},
      keywords     = {Dissertation (GND)},
      cin          = {IEK-2},
      cid          = {I:(DE-Juel1)IEK-2-20101013},
      pnm          = {133 - Fusion technology for ITER (POF2-133)},
      pid          = {G:(DE-HGF)POF2-133},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:hbz:82-opus-43133},
      url          = {https://juser.fz-juelich.de/record/127417},
}