1. 1. Qualifying carbon as PFC Erosion (see report S. Brezinsek ) along plasma wetted areas, effect of substrate Local C migration to gaps Fuel retention O GDC Cleaning of redeposited C layers ICRH O-He conditioningplasmas Report of FZJ activities in EU PWI TF V.Philipps, S. Brezinsek (for P. Mertens) EU-PWI-Task Force T r i l a t e r a l E u r e g i o C l u s t e r TEC

2. T r i l a t e r a l E u r e g i o C l u s t e r TEC 2. Qualifying high Z plasma facing components (see SEWG presentation by R. Neu) main aims: Behaviour under high loads up to and beyond melting database for W spectroscopy (W-sources) 3. Development of in situ laser based thermal desorption spectroscopy to measure fuel retention Aim: measure in situ fuel retention on PFC shot by shot 4. Modelling of erosion deposition and ITER predictions

3. 1. Local C transport Local 13 C tracer injection through limiters in TEXTOR Similar experiments in JET, participation on AUG Textor summary: low local re-deposition fraction (~ 0.3-4%) and deposition pattern requires assumption of enhanced transport (modelled by higher re-erosion (compared with substrate) of redeposited carbon fragments) JET 13 C injection outer divertor: high redeposition fraction, however uniform 13 C distribution after outer divertor injection along strike point, despite localised injection points ( 52), needs similar assumptions AUG: high redeposition fraction, toroidal pattern under modelling EU-PWI-Task Force T r i l a t e r a l E u r e g i o C l u s t e r TEC

4. A.Kreter, ITPA Toronto

5. Roof like limiters often used EU-PWI-Task Force T r i l a t e r a l E u r e g i o C l u s t e r TEC C substrate D CxHyCxHy Physical sputtering Roth formula C Ero marks the redeposited species with a higher probability for re-erosion, only on plasma wetted areas

6. Picture: Harry Reimer torroidal direction erosion - zone deposition - zone Carbon Molybdenum Tungsten 37 mm 19 mm >1 mm C Mo W Erosion Deposition Ero Tridyn ongoing to model material mixing and deposition EU-PWI-Task Force T r i l a t e r a l E u r e g i o C l u s t e r TEC Compare deposition and mixing on C, W, Mo Test for new ERO Tridyn

7. Migration to gaps: (see also SEWG G. Counsell) A series of dedicated experiments under erosion and deposition dominated conditions Difference between toroidal and poloidal gaps Effect of shaping EU-PWI-Task Force T r i l a t e r a l E u r e g i o C l u s t e r TEC

8. Exposure of W castellated limiter in the SOL of TEXTOR: A. Litnovsky for EU TF PWI Meeting, Ljubljana, Nov. 13-14, 2006 20 o Toroidal direction Poloidal direction SOL Plasma Shaped cells 10x10x12(15)mm Rectangular cells 10x10x15 mm The shape of a castellation cells can be optimized to reduce impurity and fuel transport into gaps Motivation Experimental details Shaped and rectangular cells exposed under the same plasma conditions (controlled with spectroscopy); Series of repetitive discharges; Each cell mounted separately; Post-exposure analyses with SIMS, Dektak, NRA and EPMA (FZJ, IPP Garching and RWTH Aachen). Gaps 0.5 mm The influence of the shape of castellation on fuel accumulation and C deposition in gaps

9. Photograph after exposure NB31 DMS780 EK98 Deuterium retained in the samples 0 1·10 21 2·10 21 3·10 21 4·10 21 TDS1 (limiter tip) 2·10 25 D/m 2 TDS2 (22mm outside LCFS) 4·10 24 D/m 2 Deuterium retained [D/m 2 ] EK98 DMS780 NB31 EK98 DMS780 NB31 Thermal desorption measurements Limiter temperature: T bulk : 470 K (1st pulse) – 520 K (last pulse) T surface (close to limiter tip) increases by 100 K during pulse D/(H+D) 80% No significant difference of graphite types seen 32 reproducible discharges 177 s total duration

10. spectrometers

11. Temperature in Laser Spot measured (max+Laser) Aim: release all fuel without ablation of layer Parallel to LIBS

12. Suppression of eddy currents: 8 stacks assembled insulated bulk tungsten lamellae attached to a fishbone–like wedge, which is tied to a cross-like adapter Design of a W bulk tile for the JET ILW project Larger engineering effort

13. 6 mm 1.5 – 7 degree Shaping of all lamellas will be done Does not affect power handling due to heat diffusion across the lamella (3D Ansys calculations EU-PWI-Task Force T r i l a t e r a l E u r e g i o C l u s t e r TEC Within the ILW, the individual lamellas will be shaped to proetect of hot spots Not foreseen in ITER brush design Issue card for ITER

14. In total about 8000 W lamellas HHF cyclic tests: 7 MW/m 2, 10 s ~ 140 pulses No macroscopic damage, but Micro-cracks at the loaded surface No impact of micro-cracks on the HHF performance (up to the number of pulses investigated)