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 syste ms to be chosen in the near future. Motivated by the remarkable progre ss in the heating area, but also in view of still existing major issue s with respect to the requirements of ITER, this paper tries to give a fair assessment of the status and perspectives of the four H&CD syste ms presently under discussion: electron cyclotron waves (ECW), ion cyc lotron waves (ICW), lower hybrid waves (LH) and neutral beam injection (NBI). Following a pertaining analysis of an EU ad hoc group it can b e 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. Pa rticular needs or even severe problems arise from both the more string ent technical constraints (e.g. reduced area available for H&CD instal lation, larger plasma distance of H&CD components, radiological implic ations, etc) and the increasing need to also explore steady-state oper ation eventually in 'advanced scenarios' in ITER. Resulting H&CD issue s or problems will be addressed, such as not sufficiently qualified RF sources, problems in connection with the plasma-facing RF-coupling st ructures, or the still unsatisfactory status of negative ion technolog y 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 a nd further steps beyond it.