"Apart from deposition of thick layers on plasma-exposed surfaces   co-deposition in narrow gaps of castellated structures is a major concern    . Especially the side walls of gaps are expected to be the main deposition areas     . Also deposition far away from the first wall in socalled remote locations may contribute significantly to the total fuel build-up (see  and references therein). "
[Show abstract][Hide abstract] ABSTRACT: Carbon removal in the so-called remote areas, where no energetic species can reach the surface, is investigated with low-temperature glow discharges in pure oxygen. Plasma-deposited amorphous hydrogenated carbon thin films are used as a model system for redeposited films. Erosion measurements are performed on flat substrates as well as on two different three-dimensional (3D) test structures. One design consists of 19mm deep gaps with widths ranging from 0.5 to 4mm to simulate ITER tile gaps. A second design consists of a flat box-like structure where particles can enter only through a narrow slit. Measurements are performed for substrate temperatures ranging from 290 to 580 K. Erosion rates follow an Arrhenius-type dependence on substrate temperature with an effective activation energy of 0.25 eV. While at room temperature the surface loss probability of the dominant eroding species is 50% it becomes smaller at elevated temperatures. At elevated temperatures, the films are not only removed faster but simultaneously erosion penetrates deeper into the gaps.
Physica Scripta 12/2009; T138:014009. DOI:10.1088/0031-8949/2009/T138/014009 · 1.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The sessions of experiments EX/D, EX/S and EX/W covering (D) Plasma–material interactions, Divertors, Limiters, SOL, (S) Stability, (W) Wave–plasma interactions, Current drive, Heating and Energetic particles are summarized in this paper. These general topics are divided into two categories, which are (1) ITER oriented and (2) ITER/DEMO oriented corresponding to the subject of each topic and considering the road map of fusion research. Topics in the ITER oriented category are strongly linked to the present direction of the fusion research for ITER, namely tokamak research, whereas issues in the ITER/DEMO oriented category are generally common issues for both tokamaks and helical devices.
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