Introduction Tokamak research is advancing toward the ultimate goal of obtaining economic power from fusion, with emphasis on the JET-ITER route which should supply vital experience of ignited plasmas. At the same time, so-called advanced tokamak scenarios are being explored in order to develop the economic and practical aspects of fusion power. One form of concept improvement, the low aspect-ratio or 'spherical' tokamak (ST), is showing particular promise.
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