Wall Conditioning of JET with the ITER-Like Wall
The initial conditioning cycle of JET ILW is analysed and compared with restart and operation in 2008 with a carbon dominated wall. Comparable water and oxygen decay times are observed during bake-out in both cases. Despite a 2.10-3 mbar·l/s leak rate during plasma operation, lower O levels are measured with the ILW. However, no wall conditioning has been necessary after plasma restart, which dramatically contrasts with 2008. Higher O levels measured after nights or week-ends, BeO layers being formed and re-eroded, do not impact plasma operation and performance with the ILW. First results on isotopic wall changeover by GDC on the ILW six months of the first D2 campaign evidence a reservoir of about 3.1022 atoms, i.e. ten time lower than in carbon PFCs. A study in JET of the glow discharge current distribution for different ratios of the ionization mean free paths to the vessel dimensions seems to indicate sufficient toroidal and poloidal homogeneity in ITER.