Progress in ICRH and lower hybrid launcher development

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Abstract
Radio frequency methods of heating and noninductive current drive have become well established and are likely to be part of any next-step Tokamak programme. The author reviews the development of antennae for ion cyclotron heating and developments to enhance the effectiveness of fast wave current drive systems. The performance achieved by systems enables the provision of an ICRH system for next step devices within the existing technology limits. The main lower hybrid current drive systems are also reviewed. Present operating limits suggest that the design power density at the grill in large multijunction launchers must be somewhat reduced due to peaking of the electric field. The resulting launcher for a next step machine based on present technology is a large is a large and highly complex device. Development of proposals such as the rod array or the hyperguide, in parallel with necessary improvements in the current drive efficiency would make lower hybrid a more attractive method of noninductive current drive for the next step machines.