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@PHDTHESIS{Spilker:829762,
      author       = {Spilker, Benjamin},
      title        = {{T}he {I}mpact of {T}ransient {T}hermal {L}oads on
                      {B}eryllium as {P}lasma {F}acing {M}aterial},
      volume       = {371},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2017-03396},
      isbn         = {978-3-95806-227-6},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {XII, 134 S.},
      year         = {2017},
      note         = {RWTH Aachen, Diss., 2017},
      abstract     = {The rising global energy consumption requires a broad
                      research and development approach in the field of energy
                      technology. Besides renewables, nuclear fusion promises an
                      efficient, CO$_{2}$ free, no long-term radioactive waste
                      producing, and safe energy source using only deuterium and
                      lithium as primary resources, which are widely abundant.
                      However, several technical challenges have to be overcome
                      before a nuclear fusion power plant can be built. For this
                      purpose, the experimental reactor ITER is currently under
                      construction in France. ITER is intended to demonstrate the
                      scientific and technological feasibility of net energy
                      generation via nuclear fusion. The most heavily loaded
                      components inside a fusion reactor, which are directly
                      facing the fusion plasma, have to be armoured with well
                      suited materials, which need to be able to withstand the
                      high thermal and particle loads for an economically
                      reasonable lifetime. For ITER, beryllium is chosen as plasma
                      facing material for the largest fraction of the inner vacuum
                      vessel, the so called first wall. Tungsten will be applied
                      in the bottom region of the vacuum vessel, the so called
                      divertor, which acts as the exhaust system of the machine.
                      The choice of beryllium as plasma facing material was driven
                      by its outstanding advantages, e.g. the low atomic number
                      assures that eroded wall material does not strongly decrease
                      the fusion plasma performance, while it combines a high
                      thermal conductivity with low chemical sputtering
                      characteristics. However, the relatively low melting
                      temperature of beryllium of 1287 °C comprises the risk of
                      amour damage by melting during transient plasma events, such
                      as edge localized modes or plasma disruptions. Even when
                      mitigated, these events put tremendous power densities in
                      the GW m$^{-2}$ range with durations in the ms scale onto
                      the plasma facing materials. Hence, the performance of the
                      ITER reference beryllium grade S-65 under transient thermal
                      loads was studied within this work. Thereby, the focus was
                      set on the understanding of the different damage mechanisms
                      and melting behaviour of beryllium in order to contribute to
                      more reliable performance and lifetime estimations under
                      ITER operational conditions. The transient thermal loads
                      were experimentally simulated in the electron beam
                      facilities JUDITH 1 and JUDITH 2. In the course of the
                      experiments, the absorbed power density, pulse duration,
                      base temperature, number of pulses, and the surface
                      qualities of beryllium specimens were varied to cover a
                      broad range of relevant loading scenarios. With the
                      generated data, a damage map was created showing the surface
                      damages to be expected originating from transient thermal
                      loads with varying absorbed power densities and base
                      temperatures. Furthermore, the damage, cracking, and melting
                      thresholds of beryllium were determined. These thresholds
                      mark the parameter range, in which ITER can be operated
                      without inducing the respective damage type to the first
                      wall. Furthermore, the performance of dierent surface
                      qualities under transient thermal loading was compared in
                      order to determine the optimal surface treatment for the
                      beryllium armour tiles. As a result, the polished and the as
                      received electric discharge machining cut surface qualities
                      exhibited the best performance, while all ground surfaces
                      were severely damaged after 1000 pulses. Hence, grinding of
                      the [...]},
      cin          = {IEK-2},
      cid          = {I:(DE-Juel1)IEK-2-20101013},
      pnm          = {899 - ohne Topic (POF3-899)},
      pid          = {G:(DE-HGF)POF3-899},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/829762},
}