Progress, since the ITER Physics Basis publication (ITER Physics Basis Editors et al 1999 Nucl. Fusion 39 2137–2664), in understanding the processes that will determine the properties of the plasma edge and its interaction with material elements in ITER is described. Experimental areas where significant progress has taken place are energy transport in the scrape-off layer (SOL) in particular of the anomalous transport scaling, particle transport in the SOL that plays a major role in the interaction of diverted plasmas with the main-chamber material elements, edge localized mode (ELM) energy deposition on material elements and the transport mechanism for the ELM energy from the main plasma to the plasma facing components, the physics of plasma detachment and neutral dynamics including the edge density profile structure and the control of plasma particle content and He removal, the erosion of low- and high-Z materials in fusion devices, their transport to the core plasma and their migration at the plasma edge including the formation of mixed materials, the processes determining the size and location of the retention of tritium in fusion devices and methods to remove it and the processes determining the efficiency of the various fuelling methods as well as their development towards the ITER requirements. This experimental progress has been accompanied by the development of modelling tools for the physical processes at the edge plasma and plasma–materials interaction and the further validation of these models by comparing their predictions with the new experimental results. Progress in the modelling development and validation has been mostly concentrated in the following areas: refinement in the predictions for ITER with plasma edge modelling codes by inclusion of detailed geometrical features of the divertor and the introduction of physical effects, which can play a major role in determining the divertor parameters at the divertor for ITER conditions such as hydrogen radiation transport and neutral–neutral collisions, modelling of the ion orbits at the plasma edge, which can play a role in determining power deposition at the divertor target, models for plasma–materials and plasma dynamics interaction during ELMs and disruptions, models for the transport of impurities at the plasma edge to describe the core contamination by impurities and the migration of eroded materials at the edge plasma and its associated tritium retention and models for the turbulent processes that determine the anomalous transport of energy and particles across the SOL. The implications for the expected performance of the reference regimes in ITER, the operation of the ITER device and the lifetime of the plasma facing materials are discussed.

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Chapter 4: Power and particle control

While covalently bonded materials such as carbon are well known to be eroded by chemical sputtering when exposed to plasmas or low-energy ion irradiation, pure metals have been believed to sputter only physically. The erosion of Be when subject to D bombardment was in this work measured at the PISCES-B facility and modelled with molecular dynamics simulations. During the experiments, a chemical effect was observed, since a fraction of the eroded Be was in the form of BeD molecules. This fraction decreased with increasing ion energy. The same trend was seen in the simulations and was explained by the swift chemical sputtering mechanism, showing that pure metals can, indeed, be sputtered chemically. D ions of only 7eV can erode Be through this mechanism.

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Chemical sputtering of Be due to D bombardment

Zirconium carbide films have been deposited on silicon (100) substrates using direct current magnetron reactive sputtering using CH4 as a carbon source. The films exhibit a typical nanocomposite st ...

Deposition and characterization of reactive magnetron sputtered zirconium carbide films

The plasma facing components, first wall, and blanket systems of future tokamak-based fusion power plants arguably represent the single greatest materials engineering challenge of all time. Indeed, the United States National Academy of Engineering has recently ranked the quest for fusion as one of the top grand challenges for engineering in the 21st century. These challenges are even more pronounced by the lack of experimental testing facilities that replicate the extreme operating environment involving simultaneous high heat and particle fluxes, large time-varying stresses, corrosive chemical environments, and large fluxes of 14-MeV peaked fusion neutrons. Fortunately, recent innovations in computational modeling techniques, increasingly powerful high-performance and massively parallel computing platforms, and improved analytical experimental characterization tools provide the means to develop self-consistent, experimentally validated models of materials performance and degradation in the fusion energy environment. This article will describe the challenges associated with modeling the performance of plasma facing component and structural materials in a fusion materials environment, the opportunities to utilize high-performance computing, and two examples of recent progress.

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Fusion materials modeling: Challenges and opportunities

Nanostructure, mechanical and tribological properties of reactive magnetron sputtered TiCx coatings

Carbon films doped with Ti, V, W, Zr, Cr, and Cu were produced by magnetron sputtering. To predict the film composition, the deposition rates were systematically studied as a function of discharge power and working pressure. The achieved dopant concentrations range from 20 down to 1 at.%. The films are laterally homogeneously doped and show columnar growth. The dopant distribution is not thermally stable. After heating at 1100 K, the carbides TiC, VC, WC, ZrC, and Cr 3 C 2 are definitely present and their grain size is on the nanometre scale. Cu segregates out. There are strong indications of the formation of carbides already during deposition.

Metal-doped carbon films obtained by magnetron sputtering

Two regimes of the chemical erosion of carbon materials under hydrogen bombardment have been separated: (i) the thermally activated regime, Ytherm, with the maximal erosion yield in the temperature range between 550 and 850 K, and (ii) the so-called "surface" regime, Ysurf, at low temperatures (~300 K) and low impact energies ( 1025 D/m2), a reduction of the erosion yield by one order of magnitude is observed for fine-grain carbide-doped graphites. Scanning electron microscopy (SEM) allows to associate these fluence dependencies with the evolution of a rough surface morphology of several µm in the erosion area. For Ytherm an almost complete suppression of the CD4-production yield is observed for Ti-doped C layers. This reduction due to the doping on atomic scale exceeds all previously observed reductions of materials with a coarser dopant distribution. For all investigated carbon materials, the yield below RT does not depend on temperature.

B. Cieciwa

Papers

Metal-doped carbon films obtained by magnetron sputtering

Erosion Processes of Carbon Materials under Hydrogen Bombardment and their Mitigation by Doping

Deuterium-induced chemical erosion of carbon-metal layers

EXAFS study of indium doped magnetic semiconductor CdCr2Se4