RF heating in stellarators

Nuclear fusion research has made considerable progress using tokamaks, and detailed design for a reactor-sized tokamak, ITER, is now under way. On the other hand, the stellarator has been considered to be alternative to the tokamak and there has been considerable progress recently. Plasma heating has been the most important theme of investigation in stellarator research as well as in tokamak research. This paper refers to a few key aspects of stellarator plasma heating in the existing experiments CHS and W7-AS. Efforts to understand the physical meaning of the experimental results in terms of neoclassical theory are also introduced. Throughout this review, the particular importance of particle orbits will be emphasized and the performance of plasma heating in the coming next-generation devices such as LHD and W7-X will be estimated according to the model employed. (author)