EFDA-JET-CP(06)02/09
Divertor Power Deposition and Target Current Asymmetries during Type-I ELMs in JET and ASDEX Upgrade
Analysis of the type-I ELM power load asymmetries using infra-red thermography and target current measurements is performed in JET DOC-L and ASDEX Upgrade Upper Single Null Type-I ELMy H-Mode discharges with 'normal' and 'reversed' field direction, i.e. with the ion B¥B drift direction pointing towards the active X-point and the ion B¥B drift direction pointing away from the active X-point, respectively. The ELM power load towards the inner target plate is found to be larger as towards the outer target with 'normal' field direction and vice versa with 'reversed' field. Current measurements are performed in ASDEX Upgrade providing information that the inner target receives a net positive and the outer target a net negative charge during the ELM in 'normal' field and vice versa for discharges with 'reversed' field. The difference between the ELM energy load on the inner and outer target, Eouter - Einner, is well correlated with the net charge due to the ELM giving a net charge of 5As for a value of 5kJ for Eouter - Einner. A comparison to JET data shows that in both devices the maximum difference for values on Eouter - Einner for 'normal' field direction, as foreseen in ITER, corresponds to values of Eouter - Einner = 2.