Advantages of the Spherical Tokamak

These fall into two categories: the simplicity of the ST compared with the conventional tokamak, and improvements due to the novel physics properties of low aspect ratio. Numerical equilibrium studies show that spherical tokamak plasmas are naturally elongated and D-shaped and moreover have a natural system for power and particle exhaust, an advantage for an eventual power plant. Significantly, it is found that the toroidal magnetic field (supplied by the centre column) required for plasma stability is a factor 10 less for the ST than for the conventional case - implying a substantial gain in efficiency. Further advantages are implied by theories of particle behaviour at low aspect ratio, suggesting improved plasma heating and other benefits.

Central solenoid being loaded into START