1. Tungsten distribution on limiters after WF 6 injection in TEXTOR M. Rubel, D. Ivanova Alfv é n Laboratory, Royal Institute of Technology, Association EURATOM – VR, Stockholm, Sweden V. Philipps, F. Nachtrod, C. Schulz, E. Wessel Institute of Energy Research (Plasma Physics), Forschungszentrum Jülich, Association EURATOM – FZJ, Jülich, Germany O U T L I N E Tile Analysis Estimation of tungsten balance Summary and Plans

2. WF 6 injection experiment: Motivation Local and global W transport Possibility of W layer deposition during plasma operation Impact of fluorine on plasma contamination and operation Fluorine long-term retention in plasma-facing components Toroidal Limiter Location of the test limiter

3. WF 6 injection conditions Toroidal direction Injection channel Polished graphite plate Injection during 7 NBI heated shots through hole in roof-shaped test limiter Shots without injection in between shots with WF 6 injection Limiter tip 1.5 cm in SOL 3 x 10 19 WF 6 mol/shot = 2 x 10 20 total 15 shots in total, 100 s plasma Hydrogen flux at injection (D +, r = 47.5) 4.x 18 /cm²s Experiment close to shut-down; 250 s of plasma after the experiment.

4. Analysis Methods SEM, EDX, EPMA SIMS NRA RBS poloidal 7 cm toroidal 11 cm Local transport 19 Tile number 19 from 3 ALT-II blades: Blade 5 near the injection point Blade 1 located ~180 o Blade 7 located ~90 o Long range transport

5. Analysis of tiles (RBS) Toroidal limiter tile Deposition zone Erosion zone W distribution along the tiles Messages: Similar deposition profiles on tiles from different locations. Somewhat greater content on the tile in the vicinity of the injection point.

6. Analysis of tiles ALT-II 5/19ALT-II 1/19 Deposition zone Erosion zone Deposition zone Erosion zone Approximate area per plate [cm 2 ] 3012030120 Average areal content [at/cm 2 ] 1.23·10 15 0.34·10 15 1.17·10 15 0.21·10 15 Total content per plate [at] 3.68·10 16 4.10·10 16 3.52·10 16 2.53·10 16 7.78·10 16 6.05·10 16 Total content for all the plates* [at] 1.55·10 19 W balance Injected 2 x 10 20 100 % Local deposition0.02 x 10 20 1 % ALT-II0.16 x 10 20 8 % Fluorine on ALT-II not found (below the detection limit).

7. Fuel content in flakes from ALT-II: Thermal desorption spectrometry Concentration ratio D/C ~ 0.08

8. Microscopy and EDX of ALT-II Can we detected tungsten deposition? If yes, what is the distribution, especially in the erosion zone? 20 m Accumulation of heavy impurities in pits in the erosion zone. M. Rubel et al. Fusion Eng. Des. 81 Ni C C, Cr, Ni, Fe, Mo, Si but no W detected Surface after WF 6 puffing experiment Erosion zone

9. Microscopy and EDX of ALT-II Deposition zone

10. Summary Only ~1% of injected tungsten detected around the injection point on the test limiter retracted from TEXTOR after the experiment. ~8% of injected tungsten found on the ALT-II limiter plates: tungsten detected mainly in the deposition zone; fairly uniform toroidal distribution No fluorine detected on the ALT-II (concentration below 10 16 cm 2 ) Plan for Future Studies Further tracing of F in deposits on ALT with nuclear techniques (very difficult). Chemical analysis of flakes from the deposition zone. Chemical form of Tungsten around the injection point: XRD method.