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In the last few years, significant progress has been made in the understanding of H-mode plasmas (e.g. ion temperature profile stiffness, pedestal physics, etc). Based on this improved understanding, a set of rules (models) comprising a physics picture of the H-mode has been implemented in the ASTRA code in order to improve the understanding of experimental observations and ultimately to provide a predictive capability for ITER complementary to the scaling relations. The model has been verified for consistency with experimental observations in ASDEX-UG and JET plasmas. Numerical coefficients for the transport, required because of simplifications or missing quantitative information, are determined for one plasma (e.g. from JET) and then held constant for all others (JET, ASDEX-UP, ITER).After benchmarking the model to experimental results, it was also applied to ITER. It predicts that Q = 10 can be achieved in ITER but only with at least a 50% deep fuelling contribution (inside the H-mode pedestal). However, in existing machines as well as in our model runs for existing machines, gas puffing is sufficient to achieve the observed density pedestal and line average densities. A second important result from the predictive runs for ITER is that electron energy transport in the plasma core, the neoclassical transport in the pedestal and the CX losses at the plasma edge are important constraints for a better performance. Thus future theoretical and experimental work should concentrate on these areas in order to improve our predictions.

͑W7-AS͒. W7-AS ͓G. Grieger et al., Phys. Fluids B 4, 2081 ͑1992͔͒ has demonstrated the feasibility of modular coils and has pioneered the island divertor and the modeling of its three-dimensional characteristics with the EMC3/EIRENE code ͓Y. Feng, F. Sardei et al., Plasma Phys. Controlled Fusion 44, 611 ͑2002͔͒. It has extended the operational range to high density ͑4 ϫ 10 20 m −3 at 2.5 T͒ and high ͗␤͘ ͑3.4% at 0.9 T͒; it has demonstrated successfully the application of electron cyclotron resonance heating ͑ECRH͒ beyond cutoff via electron Bernstein wave heating, and it has utilized the toroidal variation of the magnetic field strength for ion cyclotron resonance frequency beach-wave heating. In preparation of W7-X ͓J. Nührenberg et al., Trans. Fusion Technol. 27, 71 ͑1995͔͒, aspects of the optimization concept of the magnetic design have been successfully tested. W7-AS has accessed the H-mode, the first time in a "non-tokamak" and has extended H-mode operation toward high density by the discovery of the high-density H-mode ͑HDH͒, characterized by H-mode energy and L-mode-level impurity confinement. In the HDH-mode quasisteady state operation is possible close to operational limits without noticeable degradation in the plasma properties. High-␤ phases up to t pulse / E = 65 have been achieved, which can already be taken as an indication of the intrinsic stellarator capability of steady-state operation. Confinement issues will be discussed with emphasis on the similarities to tokamak confinement ͑general transport properties, H-mode transition physics͒ but also with respect to distinct differences ͑no confinement degradation toward operational boundaries, positive density scaling, lack of profile resilience, no distinct isotope effect, H-mode operational window͒. W7-AS turned out to be an important step in the development of the Wendelstein stellarator line towards an independent fusion power plant concept.

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The Demonstration Fusion Power Reactor DEMO is the step foreseen to bridge the gap between ITER and the first commercial fusion power plant. One key element in the European work plan for DEMO is the elaboration of a conceptual design for a suitable core particle fuelling system. First considerations for such a system are presented in this contribution. Following the well-considered ITER solution, most analysis performed in this study assumes conventional pellet technology will be used for the fuelling system. However, taking advantage of the less compressed time frame for the DEMO project, several other techniques thought to bear potential for advanced fuelling performance are considered as well. In a first, basic analysis all actuation parameters at hand and their implications on the fuelling performance were considered. Tentative transport modelling of a reference scenario strongly indicates only particles deposited inside the plasma pedestal allow for efficient fuelling. Shallow edge fuelling results in an unbearable burden on the fuel cycle. Sufficiently deep particle deposition seems technically achievable, provided pellets are launched from the torus inboard at sufficient speed. All components required for a DEMO pellet system capable for high speed inboard pellet launch are already available or can be developed in due time with reasonable efforts. Furthermore, steps to integrate this solution into the EU DEMO model are taken.