1. Mixed materials in JET 2006 J P Coad Present JET situation Deposited films at the inner divertor (plasma-facing surfaces) Films deposited in shadowed areas Conclusions

2. Deposition at inner divertor Impurities from main chamber (and outer divertor) arrive at inner divertor tiles 1 and 3 Carbon re-eroded by chemical sputtering leaving film rich in Be and other metals Carbon migrates to sloping part of tile 4, then can be ejected into shadowed region when plasma power is on tile 4 SIMS profiles sample 3/8 exposed 1998-2001 One outstanding puzzle: Inner layer (to right of line): High Be (+ other metals) Lower D Outer layer: (to left of line) Lower Be (+ Ni) High D 13 C at very surface Tile 1 Tile 3 Tile 4 Task Force E JET

3. Analysis of samples removed in 2004 SIMS profiles sample 3/8 exposed 1998-2004 Inner part (to right of line): similar to film deposited 1998- 2002 Outer part: (to left of line) High Be + other metals (e.g. Ni) except close to surface Little 13 C at surface Tile 1 Tile 3 Tile 4 Task Force E JET Film deposited 2001-2004 also has high Be/C ratio, although operations were at 200°C He-fuelled campaign must be responsible for outer layer from 1999-2001 Film structure may be different allowing trapping of large amount of D

4. 3µm W deposit CFC W W Sections from JET MkII-SRP divertor tiles J Likonen P1-18 Task Force E JET

5. RBS of tile 3 removed in 2004 compared with one from 2001 Much more Be and other metals in 2004 Much more D and 13 C in 2001

6. NRA of tile 3 removed in 2004 compared with one from 2001 Much more Be in 2004 Much more D in 2001 and 13 C also detectable

7. Conclusions Thick deposits are found at JET inner divertor that are (mostly) mixtures of C, Be, O and D Although can have Be/C ~1, suggesting carbide, no evidence of the chemical state of the Be. Also oxygen - from plasma or atmosphere? XPS (and AES) can provide such information (e.g. Be carbide and oxide identified in JET in 1989 - Coad PSI 1990) Profiling through films possible by ball-cratering or sputtering - also to remove surface layer - (each have danger of altering the real chemical state). Plans under TFFT to involve SCK/CEN (Mol) in XPS/AES work (V Philipps also in contact?) General paucity of data on the films - electrical resistivity, thermal conductivity, density, structure, hardness?