sewg meeting high-z, ljubljana, october 2009 i. tungsten distribution on limiters after wf 6...
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SEWG Meeting HIGH-Z, Ljubljana, October 2009
I. Tungsten distribution on limiters after WF6 injection in TEXTOR
II. SEM and EDX of Melted Tungsten Rods
SEWG Meeting HIGH-Z, Ljubljana, October 2009
I. Tungsten distribution on limiters after WF6 injection in TEXTOR
M. Rubel, D. IvanovaAlfvén Laboratory, Royal Institute of Technology, Association EURATOM – VR,
Stockholm, Sweden
V. Philipps, F. Nachtrod, C. Schulz, G. Sergienko, E. WesselInstitute 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
WF6 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
WF6 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 WF6 injection
Limiter tip 1.5 cm in SOL
3 x 1019 WF6 mol/shot = 2 x 1020 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
poloidal7 cm
toro
idal
11 c
m
Local transport
19
Tile number 19 from 3 ALT-II blades:• Blade 5 near the injection point• Blade 1 located ~180o
• Blade 7 located ~90o
Long range transport
Analysis of tiles (RBS)
0,00
0,50
1,00
1,50
2,00
2,50
0 5 10 15
Poloidal direction [cm]
W c
on
ten
t [
E1
5/c
m2
] ALT-II 1/19
ALT-II 5/19
Toroidal limiter tile
Dep
ositi
on z
one
Ero
sion
zon
e
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 5/19 ALT-II 1/19
Deposition zone
Erosion zone
Deposition zone
Erosion zone
Approximate area per plate [cm2]
30 120 30 120
Average areal content [at/cm2]
1.23·1015 0.34·1015 1.17·1015 0.21·1015
Total content per plate [at]3.68·1016 4.10·1016 3.52·1016 2.53·1016
7.78·1016 6.05·1016
Total content for all the plates* [at] 1.55·1019
W balance
Injected 2 x 1020 100 %Local deposition:
Injection plate0.02 x 1020 1 %
Local deposition:
Back plate (integrated)0.134 x 1020 7 %
ALT-II (integrated) 0.16 x 1020 8 %
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
NiC
NiCr Fe
Fe
Ni Mo MoClMoNi
Mo Cl Ni
Fe
Cl
Ni
MoCr FeSi
CrOCr
C
1 2 3 4 5 6 7 8 9
keVFull Scale 681 cts Cursor: 0.093 (9 cts)
1
C, Cr, Ni, Fe, Mo, Sibut no W detected
Surface after WF6 puffing experiment
Erosion zone
Microscopy and EDX of ALT-II
Al
B
O
C
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5
keVFull Scale 555 cts Cursor: 0.091 (13 cts)
1
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 1016 cm2)
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. Rubel1, E. Fortuna2, D. Ivanova1, V. Philipps3, G. Sergienko3, E. Wessel3
1Alfvén Laboratory, Association EURATOM – VR, Stockholm, Sweden
2Faculty of Materials Science and Engineering, Warsaw University of Technology, Association EURATOM – IPPLM, Warsaw, Poland
3Institute 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
O
Al
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5
keVFull Scale 385 cts Cursor: 0.103 (0 cts)
1
WC W
W
W
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5
keVFull Scale 424 cts Cursor: 0.103 (8 cts)
3
Re-solidified tungstenInclusions 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