Erosion at the inner wall of JET during the discharge campaign 2011-2012 in comparison with previous campaigns

The erosion of Be and W marker layers was investigated using long-term samples during the first ITER-like wall discharge campaign 2011-2012. The markers were mounted in Be coated Inconel tiles between the inner wall guard limiters (IWGL). They were analyzed using Rutherford backscattering (RBS) before and after exposure. All samples showed strong erosion. The results were compared to the data for Be and W erosion rates for the 2005-2009 and the 2001-2004 campaigns, respectively, when JET was operated with a carbon wall. In 2005-2009 Be and C samples were used, and W samples were used in 2001-2004. The mean W erosion rates and the toroidal and poloidal distributions of the W erosion were the same for the 2001-2004 and the 2011-2012 campaigns. The mean erosion rate of Be during the 2011-2012 campaign was smaller by a factor of about two compared to the 2005-2009 campaign and showed a different poloidal distribution. The mean erosion rate of the inner JET ITER-like wall was about 4-5 times smaller than the mean erosion rate of the carbon wall.