Power Load Studies in JET and ASDEX Upgrade with Full-W Divertors

For the design and the operation of large fusion devices a detailed understanding of the power exhaust processes is necessary. This paper will give an overview of the current research on the divertor power load mechanisms. The results shown are obtained in JET with the ITER like wall and ASDEX Upgrade with tungsten coated plasma facing components. The challenges of infrared thermography on an ITER like bulk tungsten divertor are presented. For the steady state heat load, the power fall-off length q in JET-ILW is compared to an empirical scaling found in JET and ASDEX Upgrade with carbon plasma facing components. A first attempt to scale the divertor broadening S in ASDEX Upgrade with tungsten plasma facing components is shown. The ELM duration tELM in JET-C and JET-ILW is compared. For similar pedestal conditions (Te,ped and ne,ped), similar ELM durations are found in JET-C and JET-ILW. For higher ne,ped at the same pedestal pressure pe,ped, longer ELM durations are found in JET-ILW. The pedestal pressure pe,ped is found to be a good qualifier for the ELM energy fluency in both JET-C and JET-ILW. Improved diagnostic capabilities reveal ELM substructures on the divertor target occurring a few milliseconds before the ELM crash.
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