TIGHT ASPECT RATIO TOKAMAKS - THEORY AND EXPERIMENT

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