Development of ECRH-based methods for assisted discharge recovery: experiment and simulation

EC assisted plasma initiation has been applied successfully on different tokamaks, providing additional heating during pre-ionization of the prefill gas and during burn-through, although the influence of EC is different on the two phases. In case of ITER First Plasma, burn-through modelling suggests that the power absorption is limited at the second harmonic, even in multi-pass configuration. Clear research question: separate the effect, focusing on burn-through, and confirm predictions. Experiments have been carried out on ASDEX Upgrade: – ECH (X2) used after standard ohmic breakdown to limit the level of stray radiation – injection of neon impurity during pre-fill phase to mimic non-favorable condition such as would be expected in case of impurity influx from the wall – EC successfully sustains the burn-through of pre-filling gas with neon. Data used for modelling.