ELM characteristics and divertor heat loads in ASDEX Upgrade helium discharges

Discharges with helium as working gas are the best candidate for reaching the ELMy H-mode regime during the non-nuclear phase in ITER. Yet, little is known on the ELM regime and target loads expected in He plasmas close to L-H power threshold and with a large fraction of tungsten material in the divertor. In this contribution we analyse the ELM characteristics in a set of ASDEX Upgrade He H-mode pulses with carbon and tungsten target tiles. We find that both larger type-l-like and smaller type-III-like ELM can be obtained similar to the D case. Heat loads are similar for both working gases but with tungsten, and in contrast with carbon target, we observe a strong loads reduction at the inner target with no reversal in the loads asymmetry during ELM. (C) 2010 Elsevier B.V. All rights reserved.