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Work is in progress to completely replace, in 2008/9, the existing JET CFC tiles with a configuration of plasma facing materials consistent with the ITER design. The ITER-like Wall (ILW) will be created with a combination of beryllium (Be), tungsten (W), W-Coated CFC and Be-Coated inconel tiles, with the material depending on the local anticipated heat flux and geometry. It is part of an integrated package of JET enhancements whose aim is to develop an understanding of the ITER materials issues and develop the techniques required to operate with inductive and advanced scenarios as close as possible to ITER parameters. Over 4000 tiles will be replaced and the ILW will accommodate additional heating up to at least 50 MW for 10 s. This paper describes the scientific background to the project, the technical objectives, the material configuration selected, the R&D behind the practical realisation of the objectives and the generic problems associated with the Be tiles (power handling capacity and disruption induced eddy currents). One of the objectives is to maintain or improve the existing CFC tile power handling performance which has been achieved in most cases by hiding bolt holes, optimising tile size and profile and introducing castellations on plasma facing surfaces.

Key word codes: C0600, T1000, P0500, D0500, F0400Experiments with tungsten plasma facing components (PFCs) are performed in the ASDEX Upgrade divertor tokamak and the area covered by W-PFCs has been increased steadily since 1999 reaching 85% for the 2005/2006 campaign. The configurations chosen are W coatings on graphite and CFC. The different locations are subject to different power loads and erosion yields. This is taken into account by selecting different thicknesses in the W-coating manufactured either by physical vapour deposition or vacuum plasma spraying. Power loads in excess of 15 MW/m 2 can be handled in this way. The experiments on ASDEX Upgrade show that plasma operation is feasible with walls and divertor surfaces mostly covered with tungsten, but also reveal critical issues: Fast particles from plasma heating can play a crucial role in W erosion and particle transport must be kept high enough to overcome high impurity content and to prevent central impurity accumulation.

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Operation with all tungsten plasma facing components has become routine in ASDEX Upgrade. The conditioning of the device is strongly simplified and short glow discharges are used only on a daily basis. The long term fuel retention was reduced by more than a factor of 5 as demonstrated in gas balance as well as in post mortem analyses. Injecting nitrogen Preprint submitted to Elsevier 23 November 2012for radiative cooling, discharges with additional heating power up to 23 MW have been achieved, providing good confinement (H98 y2 = 1), divertor power loads around 5 MW m −2 and divertor temperatures below 10 eV. ELM mitigation by pellet ELM pacemaking or magnetic perturbation coils reduces the deposited energy during ELMs, but also keeps the W density at the pedestal low. As a recipe to keep the central W concentration sufficiently low, central (wave) heating is well established and low density H-Modes could be re-established with the newly available ECRH power of up to 4 MW. The ICRH induced W sources could be strongly reduced by applying boron coatings to the poloidal guard limiters.