The provision of a particle and power exhaust solution which is compatible with first-wall components and edge-plasma conditions is a key area of present-day fusion research and mandatory for a successful operation of ITER and DEMO. The work package plasma-facing components (WP PFC) within the European fusion programme complements with laboratory experiments, i.e. in linear plasma devices, electron and ion beam loading facilities, the studies performed in toroidally confined magnetic devices, such as JET, ASDEX Upgrade, WEST etc. The connection of both groups is done via common physics and engineering studies, including the qualification and specification of plasma-facing components, and by modelling codes that simulate edge-plasma conditions and the plasma-material interaction as well as the study of fundamental processes. WP PFC addresses these critical points in order to ensure reliable and efficient use of conventional, solid PFCs in ITER (Be and W) and DEMO (W and steel)

Since the installation of an ITER-like wall, the JET programme has focused on the consolidation of ITER design choices and the preparation for ITER operation, with a specific emphasis given to the bulk tungsten melt experiment, which has been crucial for the final decision on the material choice for the day-one tungsten divertor in ITER. Integrated scenarios have been progressed with the re-establishment of long-pulse, high-confinement H-modes by optimizing the magnetic configuration and the use of ICRH to avoid tungsten impurity accumulation. Stationary discharges with detached divertor conditions and small edge localized modes have been demonstrated by nitrogen seeding. The differences in confinement and pedestal behaviour before and after the ITER-like wall installation have been better characterized towards the development of high fusion yield scenarios in DT. Post-mortem analyses of the plasma-facing components have confirmed the previously reported low fuel retention obtained by gas balance and shown that the pattern of deposition within the divertor has changed significantly with respect to the JET carbon wall campaigns due to the absence of thermally activated chemical erosion of beryllium in contrast to carbon. Transport to remote areas is almost absent and two orders of magnitude less material is found in the divertor.

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Combined Magnetron Sputtering and Ion Implantation (CMSII) is a deposition technique involving simultaneously magnetron sputtering and high energy ion bombardment of the coating during its growth. A high voltage pulse discharge (U = 40 kV, τ = 20 µs, f = 25 Hz) is superposed over the magnetron deposition and by this way, positive ions are accelerated to the components to be coated, bombarding initially the substrate and then the coating itself. In the framework of the ITER-like Wall Project this method was applied to produce nanostructured W coatings on the CFC (Carbon Fibre Composite) substrate. These coatings have been characterized in terms of adhesion, thickness, structure and resistance to high thermal loads (up to 23.5 MW/m 2). Based on the results of these tests, which are presented in this paper, CMSII technology was selected for coating about 1,100 tiles with 10 µm tungsten layer for the JET first wall and divertor.

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