SEWG Meeting HIGH-Z, Ljubljana, October 2009 I. Tungsten distribution on limiters after WF 6 injection in TEXTOR II. SEM and EDX of Melted Tungsten Rods

SEWG Meeting HIGH-Z, Ljubljana, October 2009 I. 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, G. Sergienko, 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 Further studies

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

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 WF 6 mol/shot = 2 x 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.

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

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.

Analysis of tiles ALT-II 5/19ALT-II 1/19 Deposition zone Erosion zone Deposition zone Erosion zone Approximate area per plate [cm 2 ] Average areal content [at/cm 2 ] 1.23· · · ·10 15 Total content per plate [at] 3.68· · · · · ·10 16 Total content for all the plates* [at] 1.55·10 19 W balance Injected 2 x % Local deposition: Injection plate 0.02 x % Local deposition: Back plate (integrated) x % ALT-II (integrated) 0.16 x % Fluorine on ALT-II not found (below the detection limit).

Microscopy and EDX of ALT-II Can we detect 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

Microscopy and EDX of ALT-II Deposition zone

Summary Only ~1% of injected tungsten detected around the injection point on the test limiter retracted from TEXTOR after the experiment. ~15 % 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 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 ???

SEWG Meeting HIGH-Z, Ljubljana, October 2009 II. SEM and EDX of Melted Tungsten Rods M. Rubel 1, E. Fortuna 2, D. Ivanova 1, V. Philipps 3, G. Sergienko 3, E. Wessel 3 1 Alfv é n Laboratory, Association EURATOM – VR, Stockholm, Sweden 2 Faculty of Materials Science and Engineering, Warsaw University of Technology, Association EURATOM – IPPLM, Warsaw, Poland 3 Institute of Energy Research (Plasma Physics), Association EURATOM – FZJ, Jülich, Germany Background Tungsten rods were used for a Langmuir probe at TEXTOR for ICWC The probe was not removed and after ICWC and then exposed to regular pulses.

Surface topography Rod with melted tip A droplet of molten W was deposited on the adjacent rod Rod with a droplet

Surface topography and composition Re-solidified tungsten Inclusions of alumina from the rod isolation C – 3.8 wt.%, 6.1 at.% O – 51.9 wt.%, 62.4 at.% Al – 44.3 wt.%, 31.5 at.%

Summary Pronouced effects of melting are observed on the rods. No signs of blister formation in areas distant to the plasma (2-5 cm). The lack of blisters / bubbles on the rods agrees with all other observations of solid tungsten (plates and test limiters) exposed in TEXTOR (activity started in 1993). One may consider an experiment with exposure of tungsten rods in the SOL using a transfer system of the collector probe.

Surface topography