J.P. Coad 1 H Workshop, Salamanca 3 June 2008 Local deposition of 13C tracer at the JET MkII-SRP outer divertor J Paul Coad Hydrogen Workshop, Salamanca, 2-3 June 2008

J.P. Coad 2 H Workshop, Salamanca 3 June 2008 Local deposition of 13 C tracer at the JET MkII-SRP outer divertor J. P. Coad a,, L. K. Aho-Mantila b, M. I. Airila b, D. E. Hole c, J. Likonen d, A. Widdowson a and JET- EFDA Contributors[1 ][1 ] JET-EFDA Culham Science Centre OX14 3DB, Abingdon, UK a UKAEA/EURATOM Fusion Association, Culham Science Centre, Abingdon, OX14 3DB, U.K. b Association EURATOM-Tekes, Helsinki University of Technology TKK, PO Box 4100, 02015, TKK, Espoo, Finland d Dept. of Engineering and Design, University of Sussex, Brighton, BN1 9QH, East Sussex, UK e Association EURATOM-Tekes, VTT, PO Box 1000, VTT, Espoo, Finland [1][1] See the Appendix of M.L. Watkins et al., Fusion Energy 2006 (Proc. 21st Int. Conf. Chengdu) IAEA, (2006) Introduction 13 C puffing experiment in 2004 Local deposition near the puffing port General considerations of shadowing in the JET divertor Mk I divertor Mk II divertors present time Conclusions

J.P. Coad 3 H Workshop, Salamanca 3 June C-methane puffing experiment in similar pulses on last day of operation ELMy H-mode discharges:- B T 1.2T, I P 1.2 MA, ~7.5 MW additional heating Total of molecules 13 C- methane puffed in outer divertor from 48 locations Approximate line of W-stripe is shown as white dashes

J.P. Coad 4 H Workshop, Salamanca 3 June 2008 Field line plot showing strike points and SOL region for the 13 C- puffing experiment Occasional sweeps of strike- point position for Langmuir probe data Collector probe on reciprocating probe in SOL at top of machine

J.P. Coad 5 H Workshop, Salamanca 3 June 2008 Tile 1 Tile 3 Tile 4 Tile 8 Tile 7 Tile6 Amounts of 13 C measured on divertor tiles by SIMS and IBA Note: Measurements have been extrapolated, assuming toroidal symmetry Tile 13 C amount(%) 1 2.2% 3 0.7% 4 3.2% SRP 1.8% 6 2.5% % 8 0.9% Total 27.0% SRP Shadowing edge

J.P. Coad 6 H Workshop, Salamanca 3 June 2008 J Strachan et al Modelling of SIMS and IBA data

J.P. Coad 7 H Workshop, Salamanca 3 June 2008 G7B a 1a

J.P. Coad 8 H Workshop, Salamanca 3 June (max) x10 18 atoms/cm x10 18 atoms/cm x10 18 atoms/cm x10 18 atoms/cm x10 18 atoms/cm 2 Total number deposited 13 C in this area is ~215 x10 18 atoms Tungsten stripe 13 C injection 20mm Cores cut for SIMS analysis Deposition in shadow on tile 14OW G7B

J.P. Coad 9 H Workshop, Salamanca 3 June mm C Be O 12 C

J.P. Coad 10 H Workshop, Salamanca 3 June C deposition on 2ON G7A

J.P. Coad 11 H Workshop, Salamanca 3 June 2008 D and 13 C concentrations Distance on tile (poloidally), mm Count rate Ion Beam Analysis (Nuclear Reaction Analysis) data across tile depend on where line is relative to injection point

J.P. Coad 12 H Workshop, Salamanca 3 June C and 13 C concentrations Distance on tile (poloidally), mm Count rate IBA data show film in shadowed region is almost pure 13 C (plus a lot of H)

J.P. Coad 13 H Workshop, Salamanca 3 June 2008 Deposition at the JET Mk I divertor JET MkI divertor operated , first with C, then Be tiles Pairs of tiles were mounted on water- cooled poloidal bars, 196 bars toroidally. There was a gap between each bar. Tiles were in a “roof- top” arrangement

J.P. Coad 14 H Workshop, Salamanca 3 June 2008 Cross-section of tiles of the JET Mk I divertor, and deposition at the outer strike zone Exposed part of each tile in strike zone eroded local re-deposition in the shadowed area

J.P. Coad 15 H Workshop, Salamanca 3 June 2008 Subsequent JET divertors have used large format tiles mounted to solid carriers, in turn mounted on a water- cooled support structure Pumping is only through the corners of the divertor, heavy deposition in these regions No significant deposition in areas shadowed toroidally on tiles

J.P. Coad 16 H Workshop, Salamanca 3 June 2008 Tritium remaining in the JET vessel after DTE1 in 1997 Rest of T assumed to be in flakes at bottom of vessel Collected from the louvres and divertor floor R-D Penzhorn, N Bekris, FZK, Karlsruhe

J.P. Coad 17 H Workshop, Salamanca 3 June 2008 G7B a 1a

J.P. Coad 18 H Workshop, Salamanca 3 June 2008 Tile 3, exposed Region of tile shadowed by adjacent tile

J.P. Coad 19 H Workshop, Salamanca 3 June 2008 JET septum Almost complete separation of inner and outer divertor, somewhat analogous to ITER

J.P. Coad 20 H Workshop, Salamanca 3 June 2008 Campaign averaged strikepoint position 0.8 mm 2.5 mm 15 mm Source Fit to sticking monitors: 99% with sticking 0.9 <1% with very low sticking Hydrocarbon migration in JET Migration to ITER pump ducts may not be large Long term analysis in collaboration with TF FT Recent analysis of septum shows low deposition ! Mayer, Rubel, Coad

J.P. Coad 21 H Workshop, Salamanca 3 June 2008 Conclusions Thick deposits of 13 C-H found in shadowed zone where puffed methane enters divertor Overall 13 C balance only marginally improved Pattern of deposition in JET may be influenced by particle flow Septum/PFR data in JET are encouraging for ITER dome, BUT this may be totally misleading