The strengths, needs and possible drawbacks of different heating and current drive systems in relation to ITER

The final success of the ITER project will be determined decisively by the appropriate combination of plasma heating and current drive systems to be chosen in the near future. Motivated by the remarkable progress in the heating area, but also in view of still existing major issues with respect to the requirements of ITER, this paper tries to give a fair assessment of the status and perspectives of the four H and CD systems presently under discussion: electron cyclotron waves (ECW), ion cyclotron waves (ICW), lower hybrid waves (LH) and neutral beam injection (NBI). Following a pertaining analysis of an EU ad hoc group it can be concluded that all systems, in spite of the remarkable achievements at the various fusion experiments, will not meet all ITER requirements and need further development and investigations in all four cases. Particular needs or even severe problems arise from both the more stringent technical constraints (e.g. reduced area available for H and CD installation, larger plasma distance of H and CD components, radiological implications, etc) and the increasing need to also explore steady-state operation eventually in 'advanced scenarios' in ITER. Resulting H and CD issues or problems will be addressed, such as not sufficiently qualified RF sources, problems in connection with the plasma-facing RF-coupling structures, or the still unsatisfactory status of negative ion technology in the case of NBI. Stationary current drive (with prescribed radial profile and at acceptable efficiency) and the related various control functions seem the greatest challenge for 'advanced' ITER operation and further steps beyond it. (author)