The ST25 Tokamak for rapid technological development

The ST25 tokamak is a new table-top tokamak, of major radius 25 cm and aspect ratio 2, and hence (marginally) a `spherical' tokamak (ST). It was designed specifically to test out the feasibility of a fully superconducting device made entirely from High Temperature Superconductor (HTS) and hence be the first tokamak to demonstrate the practicality of this new medium. As a prerequisite a version with simple copper coils wound from cable has been assembled to establish operating conditions such as good vacuum, gas handling, wall conditioning, control and data acquisition etc. This has proved a valuable facility in its own right and rather than stripping off the copper coils to replace with cryostats, it will be retained and indeed upgraded, and a new vessel (denoted ST25HTS) is under construction, and will be equipped with HTS coils. Details are given of the existing copper-coil ST25, its upgrade, and the new superconducting tokamak ST25HTS.