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Material Erosion and Migration in JET with Metal
Plasma-Facing Components: Impact on Fuel
Inventory and Modification of Test Mirrors
Marek Rubel
Deccenial IAEA Technical Meeting on Atomic, Molecular and
PWI Interaction Data for Fusion Science and Technology
Daejeon, Korea| December 15-19, 2014
Research Team
A.Widdowsonb, E. Alvesc, C.F. Ayresb, A. Baron-Wiechecb,
S. Brezinsekd, N. Catarinoc, J.P. Coadb, H.G. Esserd, A.
Garcia-Carrascoa, K. Heinolae, D. Ivanovaa, J. Likonenf,
G.F. Matthewsb , M. Mayerg, P. Peterssona and
EUROfusion Contributors
• aRoyal Institute of Technology (KTH), VR, 100 44 Stockholm, Sweden
• bCCFE, Culham Science Centre, Abingdon, OX14 3DB, UK
• cIST/ITN, Lisbon, Portugal
• dForschungszentrum Jülich, IEK-4, D-52425, Jülich, Germany
• eUniversity of Helsinki, PO Box 64, 00014 University of Helsinki, Finland
• fVTT, PO Box 1000, 02044 VTT, Espoo, Finland
• gMax Planck Institute for Plasma Physics, Garching, Germany
Marek RubelIAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 2
Be
Be
Beon
Inconel
W
Be
JET Tokamak with ITER-Like Wall:
Beryllium and Tungsten
Marek RubelIAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 3 Marek RubelIAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 4
Erosion-Deposition Diagnostics in JET-ILW:
Marker Tiles and Probes
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 5
Marker Tiles at JET with ITER-Like Wall
Beryllium Tile (4 cm)
Nickel interlayer (2-3 !m)
Be marker coating (7-9 !m)
Beryllium Marker Tiles
tile carrier
Poloidal Limiter segmented tile
Tungsten Marker Tiles
in the Divertor
W
Mo
W
3 !m W – 1!m Mo
on W-coated CFC
Main Chamber: LIMITERS
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 6
Beryllium Inner Wall Guard LimitersMessages:
• Modification of Be limiters by:– Erosion
– Arcing
– Deposition
Top
Mid-plane
Bottom
• The greatest erosion, 80 !m,
measured in the central part of
mid-plane limiters.
Erosion
Ro
ug
h d
ep
osit
No d
epo
sitio
n
0 µm
100 µm
-80 µm
6 h limiter plasma
Power Loads & Deuterium Distributionon Tile of Inner Wall Guard Limiters
Toroidal position (mm)
top IWGL
centre
of tile
low IWGL
mid-plane
0.0
1.5
1.5
0.0
3.0
1.5
0.0
-150 150
D c
on
ten
t (1
018
cm
-2)
Messages:
• Very low D content in areas of
greater power loads.
• Structure in deposition profiles
is related to tile shaping and
gaps between segments.
• The average D content is low,
< 1x1018 cm-2, much below
levels in JET-C.
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 8
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 9
Outer Poloidal Limiters
centre
of tile
mid-plane OPL
Toroidal position (mm)-150 150
0.0
6.0
3.0
D c
on
ten
t (1
018
cm
-2)
Messages:
• Very low D content in
in the cetral part.
• Strong erosion of the
marker layer.
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 10
D i v e r t o r
Be
W+
CF
C
Be
Be Be
Be
Be
Divertor cross-section
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 11
Inner Divertor:Region of Greatest Deposition
Messages:
• Top of Tile 1 is the only region in the divertor with thick deposits.
• Low D content even in thick deposits.
Tile
1
15 !m
8 !m
0.15 !m
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 12
Composition and Structure of Deposits
Be, O, D, N, C, W
20 !m
Messages:
• Co-deposits contain a mix of Be with D and small content of W, O, N, C
• Not uniform deposition is related to the substrate structure.
Operation in the divertor: 13.1 h
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 13
Comparison of Deposition:
JET-C versus JET-ILW
coloured fringes with thin deposits
JET-ILW 2011-2012JET-C 2007-2009
Divertor Tile 4 (2BNG4C)
thick deposit 60 !m
very thin deposit
Test mirrors: Inner divertor
> 20 !m 0.3 !m
JET-C JET-ILW
Reduced (~20 x) carbon content in
the divertor; S. Brezinsek et al, 2014
Message: Very thick deposits seen in JET-C are not formed in ILW (2011-2012)
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 14
Modification of Test Mirrors
All optical systems in ITER will rely on metallic first mirrors.
A comprehensive test in JET is done on the request of the ITER Design Team (2002).
Three stages of the program:
I 2005 – 2007
II 2008 – 2009
III 2011 – 2012
Test mirrors were retrieved during the major shutdowns.
JET-ILW
JET-C
Test mirrors Over 90 test mirrors :
Polycrystalline Mo
Rh-coated Mo
Location of mirror carriers:
Main chamber wall
Divertor: inner, outer, base
shutter
cassette
holder
rotating
collector
Wall bracket assembly
20 c
m
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 15
Mirrors in JET-ILW: Reflectivity Change
Inner Divertor
Initial Mo
3.0 cm 0.0 cm
Initial Rh
1.5 cm (Rh)
Message:
Reflectivity loss for all divertor
mirrors.
Main Chamber
Initial Mo Initial Mo
Initial Rh
Initial Mo
1.5 cm (Rh)
1.5 cm
4.5 cm 3.0 cm
0.0 cm
Messages:
• For Mo mirrors reflectivity retained in the
400 – 1600 nm range (but reduced in the
UV range 250 – 400 nm.
• Rh-coated mirrors lost 30% reflectivity.
Deposit
on the mirror
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 16
Inner Divertor (#69 Rh-coated)
The deposited layers are composed of Be, C, W, Inconel metals.
Be is a dominant element in deposits.
Concentration of C dropped since the restart phase of JET-ILW.
Wall Probes: Mirrors in Inner Divertor
Heavy Ion ERDA
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 17
Inner Divertor (#69 Rh-coated)
High retention of N is observed as a result of impurity seeding.
The deposited layers are composed of Be, C, W, Inconel metals.
Be is a dominant element in deposits.
Concentration of C dropped since the restart phase of JET-ILW.
Wall Probes: Mirrors in Inner Divertor
Heavy Ion ERDA
Unit 3E, 3 cm (#94) Unit 4B, 3 cm (#99)
Outer wall
Thickness of the modified layer is approximately 20 – 30 nm.
Mix of species in a thin surface layer.
Small quantities of Ni, Fe, W are detected by XPS.
Wall Probes: Main Chamber Wall
Heavy Ion ERDA
SUMMARY: ESSENTIAL
• Low deuterium inventory:
– Absolute: below 5x1018 cm-2
– Relative: Be/D > 10 in thick deposits
• Thick deposits on the upper part of inner divertor: Tiles 0 & 1.
• Deposition pattern agrees with modelling (K. Schmid, 2014)
• Thin deposits (< 0.3 !m) in the divertor in ILW in comparison tovery thick layers (100 !m) in JET-C.
• Low absolute amounts of carbon in deposits.
• Strongly reduced transport to shadowed areas:
– reduced/eliminated carbon source,
– but … W and Be detected on mirrors.
• Degradation of divertor mirrors – need for replacement in ITER.
• Retained total reflectivity of Mo mirrors in the main chamber –periodic refreshment by Mo evaporation.
Marek Rubel IAEA TM47136| Daejeon, Korea| December 15-19, 2014 | Page 19
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