Erosion at the vessel walls of JET

Erosion at the JET vessel wails has been investigated by means of carbon long term samples (LTS), partly covered with 530 nm Al and 750 nm Ni as well as implanted with Mo markers in a depth of 380 nm. The samples were exposed to JET plasmas between April-June 1995 (about 940 discharges). Upon removal, the surface layers of the LTS were analyzed with MeV ion beam techniques. On the inner torus walls, net erosion is found with an average of about 1.2 x 10(15) Al-atoms/cm(2) and 9.4 x 10(14) Ni-atoms/cm(2) per JET discharge, respectively. The erosion of carbon was > 3.9 x 10(15) C-atoms/cm(2) per JET discharge. The erosion is due to sputtering by energetic charge-exchange neutrals emitted from the plasma during the discharge and He glow discharge cleaning between the discharges.