Dynamics of Erosion and Deposition in Tokamaks

In recent years, a general understanding has been reached about the major pathways of material migration in divertor tokamaks. The main chamber wall has been identified as the major source of material erosion. The eroded material is transported by the scrape-off layer flows, in the case of the ion B¥B drift pointing towards the X-point, predominately towards the inner divertor leg, where it is deposited in the form of amorphous layers. On JET it has been found that the presence of deposited layers determines the dynamic characteristics of further re-distribution of carbon, in particular towards remote areas. The transport from the strike point to the deposition location is mainly line-of-sight. The amount of eroded carbon depends on the surface type, with lower rates for the bare CFC and higher rates for deposited layers. The erosion rates in the inner divertor increase non-linearly with increasing ELM energies. Preprint of Paper to be submitted for publication in Proceedings of the 18th Plasma Surface Interactions in Controlled Fusion Devices Toledo, Spain ( 26th May 2008 - 30th May 2008)
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