WP10-PWI-01-02-01(02)/TEKES/BS(PS)Characterization of retention mechanisms in AUGMonitoring meeting of the EFDA PWI SEWG on Gas Balance and Fuel Retention, 19-20 July, 2010

Antti Hakola

VTT Technical Research Centre of FinlandCollaborators:

S. Koivuranta, J. Likonen: VTT

T. Haikola, J. Kolehmainen, S. Tervakangas: DIARC-Technology Inc.

K. Krieger, M. Mayer, R. Neu, V. Rohde, K. Sugiyama: IPP-Garching

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What was proposed?

• analyze a set of marker tiles, exposed to AUG plasma during the 2009 experimental campaign, and study retention of deuterium in them

Secondary Ion Mass Spectrometry (SIMS) analyses at VTT in Finland Nuclear Reaction Analyses (NRA) at IPP-Garching

• produce new marker tiles for erosion, deposition, and retention studies in AUG

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Marker tiles for the 2009 AUG campaign

• inner and outer strike-point tiles (4, 4B, and 1)• two different 3B tiles; one of them magnetically connected

to an ICRH source• tiles had 15-mm wide uncoated stripes, tiles 1 and 3B

also 15-mm wide and 2-5 m thick Ni stripes, and 1-1.5 m thick W coating

2 × tile 3B

Tile 1Tile 4BTile 4

W1 m

W, 1 m

W1.5 m

W, 1 m

Ni5 m

Ni, 2 m

C

C

C

C

15 mm

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What was done: SIMS and NRA analyses

• NRA analyses performed in March 2010 at IPP Garching 2.5-MeV 3He+ ions used measurements done at 5-10 mm steps along each marker stripe

• SIMS analyses done in April-May 2010 at VTT, Finlandsamples drilled from each tile for analyses5-keV O2

+ ions used

measurement points at 20-30 mm steps along each marker striperesults converted to quantitative ones with the help of the NRA data

Photograph of tile 1 before and after drilling SIMS samples

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Results (1): SIMS depth profiles of D on W

0 1000 2000 3000 4000 5000 60001

10

100

1000

10000

100000

Tile 4, s = 494 mm

Inte

nsity

(1/

s)

Time (s)

H D

10B

12C

13C

52Cr

60Ni

184W

0 1000 2000 3000 4000 5000 60001

10

100

1000

10000

100000Tile 1, s = 1162 mm

Inte

nsity

(1/

s)

Time (s)

H D

10B

12C

13C

52Cr

60Ni

184W

Below inner strike point (deposition zone in the private flux region)

Above outer strike point (erosion zone)

Sputtering rate approximately 0.3-0.4 nm/s largest retention in < 500-nm thick layer

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Results (2): D on W

Tile 4

Tile 1 Tiles 3B

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Results (3): D on C

Tile 4

Tile 1 Tiles 3B

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Results (4): D on Ni

Tile 1

Tiles 3B

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Comparison between different substrates: tile 1

• deuterium peaks below the outer strike point in the private flux region and on a thin stripe in the middle of the tile (resulted from an injection experiment)

• clear differences between the different materials: retention largest in carbon (graphite)

• Ni stripe complicated: stripe heavily eroded between 1060 and 1160 mm (strike-point region)

NRA results in this region not reliable, SIMS results cannot be evaluated at all

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Comparison between different substrates: tile 4

• deuterium peaks below the inner strike point in the border region between tiles 4 and 4B (private flux region)

• again carbon is responsible for larger D inventories than tungsten; notice that the values are order of magnitude higher than in tile 1

• SIMS results do not show as prominent peaks as NRA, particularly in the case of C

lack of data points in the critical region but impossible to obtain samples for SIMS analyses in that region.

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• retention largest on graphite and lowest on Ni

• tile 3B-II (magnetically connected to an ICRH source) shows somewhat larger D inventories than tile 3B-I (no magnetic connection

Comparison between different substrates: tiles 3B

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Evolution of D inventory on W (2007-2009)

• tile 1: retention decreased by a factor of 2-10 from 2007 to 2009

BUT change from VPS tiles to other coatings

• tile 4/4B: thicker co-deposited layers below the inner strike point in 2009 than in 2007 or 2008

VPS tiles 2007 & 2008Marker tile2009

PVD tile2007Marker tiles2008 & 2009

PVD tile2007Marker tiles2008 & 2009

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New marker tiles for 2010 AUG campaign

Mo 2 m

Korund, Ra = 5.5 mGlas, Ra = 0.75 mOriginal, Ra = 0.38 m

Korund, Ra = 6.4 mGlas, Ra = 3.9 mOriginal, Ra = 2.7 m

W 2 m

W 3 m

Mo 3 mCr 3 m

Al 4 m

W + 5% Ta 3 m

W 3 m

Tile 1: poloidal regions with different surface roughness

Tile 1: poloidal stripes for erosion/deposition studies

Coating half of these tiles belongs to task WP10-PWI-01-02-02/TEKES/PS

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Conclusions

• marker tiles exposed to AUG plasma during the 2009 experimental campaign analyzed using SIMS and NRA

• retention of deuterium in the tiles has been determined: largest retention in graphite, lowest in nickel deuterium accumulated in deposition-dominated regions of the divertor together with carbon and boron tile 3B with magnetic connection to an ICRH antenna shows more D than

the tile 3B without such a connection

• new marker tiles for erosion, deposition, and retention studies in AUG have been produced