Low voltage start-up in the CLEO Tokamak using ECRH

Studies of ECRH-assisted start-up in the CLEO Tokamak have resulted in the production of well-controlled discharges with I p approximately 13 kA, n e approximately 5*10 18 m -3 in the presence of a loop voltage V l <2 V throughout. The average loop voltage during the start-up phase is approximately 1.1 V, corresponding to an electric field E approximately 0.19 V m -1 , and results in an average rate of current rise of dI p /dt approximately 0.44 MA s -1 . Calculated over the whole of the current rise there is a approximately 50% reduction in volt-second consumption when compared with the best case in the absence of RF power. It is estimated that during the plasma current rise approximately 30-50% of the electromagnetic energy input from the poloidal field system is converted to stored magnetic energy.