Erosion at the inner wall of JET during the discharge campaigns 2001–2009

Abstract

The erosion of Be, C, Ni and W marker layers was investigated with long-term samples exposed during the discharge periods 2001-2004 and 2005-2009. The markers were mounted in carbon wall tiles between the inner wall guard limiters (IWGLs) and at positions between the lower end of the IWGLs and the inner divertor entrance. They were analyzed using ion beam analysis techniques before and after exposure. All samples showed strong erosion of all elements. The erosion is predominantly due to neutral particles created by charge-exchange (CX) collisions. The erosion of carbon was about 8×10 19 atoms/cm 2 (about 8 µm) during the 2005-2009 campaign, which gives a total erosion of carbon from the recessed areas between the IWGLs of about 230 g: The inner wall is therefore an important net carbon source. The erosion of the four different elements allows a rough reconstruction of the energy spectrum of the eroding CX neutrals.