Electron Bernstein wave (EBW) assisted plasma current start-up has been demonstrated for the first time in a tokamak. It was shown that plasma currents up to 17 kA can be generated noninductively by 100 kW of RF power injected. With optimized vertical field ramps, plasma currents up to 33 kA have been achieved without the use of solenoid flux. It is shown that the plasma formation and current generation are governed predominantly by EBW current drive. Experimental results are consistent with ray-tracing and quasilinear Fokker-Planck modeling.

Tokamak Energy Ltd, UK, is developing spherical tokamaks using high temperature superconductor magnets as a possible route to fusion power using relatively small devices. We present an overview of the development programme including details of the enabling technologies, the key modelling methods and results, and the remaining challenges on the path to compact fusion.

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