The physics and technology basis of ITER and its mission on the path to demo

Summary form only given. The paper will give a very brief introduction to magnetic fusion and the presently available facilities (physics and technology) which were and are essential to develop the physics and technology basis for ITER. In the next section ITER´s mission as well as the mission of planned satellite facilities will be briefly described. The core of the paper will then concentrate on the physics and technology basis of ITER and demonstrate on a few examples the very significant developments which had to be successfully performed in physics and technology to make the construction of ITER viable and feasible. These include in the area of Physics: (a) The improved understanding of energy and particle confinement in a tokamak which permitted the design of a machine with limited performance margin (cost effective) (b) Realization of the impact of magnetic ripple on confinement and its mitigation by ferromagnetic inserts (c) An emerging understanding of instabilities and of conceptual ways of stabilizing them (e.g. ELMs, RWM, etc) (d) The development of radiative divertor regimes which are essential for operating a reactor class tokamak These include in the area of Technology: (a) A very significant advance in the development of large high field superconducting magnets which are essential for a reactor class machine like ITER or later DEMO (b) The development of divertor high heatflux components which can handle at the same time 20 MWm^-2 and have enough sacrificial material to withstand many disruptions with energy loads of up to 100 MJm^-2 (c) The development of H&CD (negative NBI, ECH, ICRH, LH) and of diagnostic systems suitable for a reactor class machine (high parallel power flux along fieldlines, nuclear environment, etc) (d) The development of the D-T fuel cycle technology (fuelling, pumping, T-plant) suitable for circulating and handling several kg of T. (e) The development of remote maintenance technologies for all in ves- el components and the hot cell In a brief final section the remaining scientific and technical challenges for making the next step after successfully operating ITER, namely to built a demonstration fusion reactor (DEMO) which will deliver significant amount of electricity into the grid with an availability > 50% will be described.