An overview of erosion-deposition studies for the JET Mk II high delta divertor

Post-mortem analyses of tiles removed from the JET MkII HD divertor in 2007 are presented. The results indicate an increase in deposition at the outer plasma-shadowed region of the divertor, not seen prior to 2004 and indicate a shift away from the asymmetric picture of net deposition at the inner divertor compared with no overall deposition or erosion at the outer divertor. Surface analysis of the inner and outer vertical divertor tiles is largely the same as observed previously; however, a notable increase in Be composition on the inner and outer floor tiles is observed. An attempt has been made to correlate these data with campaign-averaged plasma configurations and spectroscopy results. While some changes in deposition/erosion characteristics can be explained, further detailed analysis of diagnostics and especially of time-resolved data, such as from rotating collector and quartz microbalance diagnostics, is required.