1. P. Coad, J. Likonen, H. Bergsåker, M. Rubel, I. Uytdenhouwen, A. Widdowson JET mixed Be/C/O layers SEWG meeting on mixed materials, 9.-10.7.2007, JET

2. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 2 Dump plate, saddle coil protection tiles: Main erosion source? OPL: erosion divertor: deposition (inboard) erosion (outboard) IWGL: erosion deposition Erosion/deposition at JET

3. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 3 Inner divertor: heavy deposition Outer divertor: erosion SIMS depth profiles from centre of lower inner divertor wall tile: High vessel temperature Be/C > 1 Deposit: thickness ~8 m 3/3 Erosion/deposition at JET (MkIIA)

4. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 4 Micrometer and SIMS results Inner wall: thickness increase towards the bottom at inner divertor wall (points 1-8), reaching a maximum of about 90 m SIMS gives somewhat smaller values Floor: thick powdery deposits at points 10 and 16 Outer wall: small amounts of erosion/deposition Erosion/deposition at divertor (MkIIGB) 1 6/16/7 1 1 4 7 13 14 24 19

5. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 5 Inner divertor: heavy deposition SIMS depth profiles from bottom of upper inner divertor wall tile: Deposit: 2 layers (thickness ~11 m). Surface layer: mostly D, C and Be Film underneath the surface layer: rich in Be Vessel temperature decreased in Dec. 2000 Deposition at inner divertor (MkIIGB) bulk CFCBe-richC- 1/1 Re

6. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 6 layerD (at%) Be (at%) 12 C (at%) 13 C (at%) O (at%) 1124312825 23055210 35204121 layerD (at%) Be (at%) 12 C (at%) 13 C (at%) O (at%) 1266501325 22885510 312116410 Composition of deposits (MkIIGB) RBS spectrum and SIMNRA simulation from the bottom of tile 1

7. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 7 t Surface analysis (SIMS, RBS, TOF- ERDA), inner divertor: Be 22 g t Assume that Be/C ratio (7%) arriving in the divertor is the same as the Be/C ratio in the main chamber (Be/C ratio on IWGL tiles is ~8%). C: 420 g Amount of deposited C: t Tiles 1, 3 and 4: 310 g (SIMS, RBS) t Louvres: 20 - 60 g (QMB and deposition monitor sample) t Septum: 10 g (RBS) t Total: 340 - 380 g t Good agreement between surface analyses and optical spectroscopy Be accumulation and C deposition (MkIIGB)

8. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 8 Inner divertor: heavy deposition SIMS depth profiles from bottom of upper inner divertor wall tile: Low vessel temperature Deposit: Be/C high Duplex structure of deposits on MkIIGB tiles due to He-phase at the end of C4 campaign 1/2 Deposition at inner divertor (MkIISRP) bulk CFC depositW marker

9. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 9 layerD (at%) Be (at%) 12 C (at%) 13 C (at%) O (at%) 116561511 219105018 311203928 layerD (at%) Be (at%) 12 C (at%) 13 C (at%) O (at%) 1122243320 26145420 31156213 Composition of deposits, RBS (MkIISRP) RBS spectrum and SIMNRA simulation from the bottom of tile 1 Cr O 13 C 12 C Be D

10. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 10 layerD (at%) Be (at%) 12 C (at%) 13 C (at%) O (at%) 1180.557915 21636813 31536813 Composition of deposits, floor (MkIISRP) 12 C 13 C O Be D RBS SIMS

11. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 11 Erosion/deposition at JET Inner divertorOuter divertor MkIIAHeavy deposition, Be/C ratio highErosion (no markers) MkIIGBHeavy deposition, films have duplex structure (C- and Be-rich layers), no Be on floor tile, deposited C quantified Erosion (markers eroded completely) MkIISRPHeavy deposition, Be/C ratio high, some Be on floor tile Erosion/deposition (due to rev B campaign?) see our review paper Coad et al.: Overview of material re-deposition and fuel retention studies at JET with the gas box divertor, Nucl. Fus. 46 (2006) 350.

12. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 12 Nature of the films t All analysis is done ex-situ and this may introduce much of the observed oxygen and affects H/D/T levels t We have a good idea of the atomic Be/C composition, but no idea of the chemical composition. For example it is sometimes assumed that the Be/C is beryllium carbide – is this really true? t XPS/AES can demonstrate the chemical state, but only analyses a few monolayers at the surface, so needs to be combined with profiking in some way t Carbides may be detected by XRD, if present t There are many other film properties that would be of interest, such as density, electrical and thermal coefficients, thermal desorption etc

13. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 13 Erosion/deposition at JET divertor deposit 3µm W CFC W W

14. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 14 Micro beam analysis (MkIIGB) 2D image for D and Be on sample 3/1 Concentration profiles of Be and D on sample 3/1, taken from tile 3, exposed in JET 1999-2001.

15. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 15 XPS analysis of tile sample 1-5 before and after sputter cleaning Before After

16. Sample 1-5, rough quantification Ni3s or Carbide ?

17. Conclusions Most important deposition in JET occurs at the inner divertor The deposits left on tiles 1 and 3 are mixtures of C & Be (+ other metals), most C migrates to inner divertor corner Almost nothing is known about the chemical state or physical properties of the films