Experimental investigation on the role of external actuators in the success of AC discharges in the ISTTOK Tokamak
In ISTTOK AC discharges at 4 kA plasma current up to 1s duration have been successfuly obtained (corresponding to 20 full plasma current cycles of 50 ms). The relatively long plasma discharges allow for performing more representative experiments in test materials for possible use in plasma facing components (e.g. Ga and Tn). The success of AC discharges at 4 kA plasma current depends on the fine tune (mostly empirical) balance of external factors such as background pressure, gas puff and external magnetic field, to mention a few. In this talk we present the results of the experiments conducted in order to reveal the role of such control parameters and provide some clues on their possible interplay aiming at providing the basis to support a better understanding of the underlying physics. Particular atention will be given to the results obtained with the heavy ion beam diagnostic (HIBD) that can follow the evolution of ‘plasma pressure like’ profiles and reveal some subtil phenomena.