Divertor power deposition and target current asymmetries during type-I ELMs in ASDEX Upgrade and JET

Analysis of the type-I ELM power load asymmetries using infra-red thermography and target current measurements is performed ASDEX Upgrade Upper Single Null and JET DOC-L 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 a net negative charge flows into the outer target and a net positive charge into the inner target 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, E_outer - E_inner, is well correlated with the measured charge flowing through the targets due to the ELM. A comparison to JET data shows that in both devices the maximum asymmetry in energy load corresponds to values of E_inner/E_outer ≈ 2.