Way forward for the spherical tokamak

The low aspect ratio or spherical tokamak offers the prospect of burning plasmas in a compact simple system at a lower cost than in conventional tokamaks. The promising results obtained on START and other small spherical tokamaks have led to the approval of higher current devices at the MA level where the key issues of operational limits, confinement, plasma exhaust and steady state potential can be tested under more demanding conditions. From such devices it is a comparatively small step to a burning plasma and such devices have already been proposed. The compact nature of the spherical tokamak and its steady state potential make it ideally suited as a component test facility and also as a low cost, small unit size power plant capable of advancing the timetable for fusion exploitation.