Spherical tokamaks: Present status and role in the development of fusion power

The spherical tokamak (ST) has triggered a fast-growing activity world-wide on account of its promising potential and its strong physics overlap with conventional tokamaks, including ITER. There has long been a view that it could have a key role as a component test facility, to complement ITER, IFMIF, and DEMO, and there are also interesting possibilities as an option for the fusion power source of an electricity plant. The experimental base is now considerably advanced from the time when these ideas were first raised, with the advent of the MA scale machines MAST and NSTX, and a growing theoretical and modelling base. Here, we describe the status of development on the key engineering and physics issues of the ST, considering in particular application to a component test facility and input to an accelerated programme towards deployed fusion power plants, the so-called “fast track”.