TIGHT ASPECT RATIO TOKAMAKS - THEORY AND EXPERIMENT

The START (Small Tight Aspect Ratio Tokamak) experiment became operati onal in January 1991 at AEA Fusion Culham Laboratory. It is the only t okamak producing hot plasmas at aspect ratios as low as A = R/a approx imately 1.3, and is providing valuable insight into the physical proce sses (such as toroidicity and trapping) involved at low aspect ratio. Three topics are discussed in this paper: equilibrium properties, incl uding evidence of neo-classical and bootstrap effects; energy confinem ent studies; and MHD properties, including possible explanations for t he apparent absence of the major disruption at low A.