The role of ELM's and inter-ELM phases in the transport of heavy impurities in JET

A series of dedicated experiments have started at JET in order to study in detail the way type 1 ELM's and intra-ELM periods determine the transport of heavy impurities at the edge of the plasma. For the purpose, trace amounts of extrinsic Mo, Kr and Ne have been injected in 10-12 MW NBI heated elmy H-mode discharges, and the evolution of their content in the plasma has been analyzed. Spontaneous ELM's have been compared with ELM's triggered by vertical kicks. The main results are: the ELM process reduces the content of all impurities regardless of their masses and the finding applies to W as well. Natural and kicks-induced ELM's behave similarly with respect to the impurity expulsion. Simulation of the impact of a single ELM on Mo injected via Laser Blow Off appears to be a good tool to investigate the nature of the ELM induced transport.