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Institute of Energy Research – Plasma Physics | Association EURATOM – FZJA. Litnovsky et al., Progress report on the task WP10-PWI-01-02-02/FZJ/BS, EU TF PWI SEWG on fuel retention, Garching, July 19-20, 2010.

Investigations of fuel accumulation and material transport into gaps of ITER-like

castellated structures

A. Litnovsky, M. Freisinger, V. Philipps, P. Wienhold, H.-G. Esser,

S. Brezinsek, D. Rudakov, S. Allen, T. Dittmar, E. Tsitrone B. Pequourie,

TEXTOR, Tore Supra and DIII-D teamsProgress reports on the task: WP10-PWI-01-02-02/FZJ/BS

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A. Litnovsky et al., Progress report on the task WP10-PWI-01-02-02/FZJ/BS, EU TF PWI SEWG on fuel retention, Garching, July 19-20, 2010.

TDS measurements on Tore Supra tiles:

a part of DITS project

TORE SUPRA

Please see the talk of E. Tsitrone for an overview of entire DITS project

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TDS measurements on DITS samples TORE SUPRA

Samples from different areas of TPL:

Erosion zone;

Zone with thick deposits;

Zone with thin deposits.

Several samples with flakes;

13 samples measured, 6 samples are to be outgased.

In the frame of the DITS project, several graphite

samples from Tore Supra toroidal limiter (TPL)

delivered to FZJ for the TDS measurements

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TDS facility at FZJ: overview

Main parameters:

Sample dimensions: maximum 55 mm;

Maximum temperature: 1150oC (oven can go up to

1200oC);

Separate vacuum evacuation of sample

chamber;

Programmable temperature increase: unlimited time (can

be days);

Sample weight: samples up to 200 g are OK;

Temperature control: thermocouple in the oven (if necessary – may be installed

in the sample);

Calibration technique: calibration leaks.

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TDS facility at FZJ: main components

Sample mounting and transport system

Oven

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1.4E18

7.8E17

1E20

1.85E18

1.34E18

3.06E187.13E19

2.03E19

3.87E20

6.61E18

2.54E20

X

bulk

top flakes

to be done

Preliminary TDS results: cartography

Color legend:

6.3E181.39E18

bulktop

Thin deposits*

Thick deposits*

* B. Pequourie, PSI 18 Toledo, Spain, May 2008 + J. Nucl. Mater., 390–391 (2009) 550

Erosion zone*

TORE SUPRA

Approximate dimensions of samples: 25×25×3 mm

Standard samples were supplied by W. Jacob (IPP Garching)

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Preliminary first TDS results: trends

Erosion zone Thin deposits

Thick deposits Fuel accumulation in flakes

Fuel inventory (absolute): Dtops/Dbulk~70;

Dtops/C~ 0.04-0.6%

Almost no D.

High temperature

Fuel inventory (absolute): Dtops/Dbulk~3;

Dtops/C~ 0.01-0.04%

Almost no D

Measurements are in progress

Fuel inventory (absolute): Dflakes/Dbulk~0.1;

Dflakes/C~ 40-80%

Highest fuel inventory so far

Lowest temperature

No firm results yet

TORE SUPRA

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Exposure of ITER-like castellated structures in the DIII-D divertor

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Exposure on DiMES manipulator at the

level of divertor floor; Exposure in PFR; Non-heated sample;

Exposure 1 (2008):

8 identical NBI-heated discharges with

partially detached plasmas in the divertor;

Exposure 2 (2009):

3 days in piggyback mode;

Scheme of exposure

Castellated DiMES

Strong and optimized shaping

0.2 mm 1.0 mm

A B

Castellation blocks (W)

Exposure of castellation in DIII-D divertor

View of castellation after

exposure

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Exposure 2 Strong deposition both on toroidal and poloidal gaps:

deposits with thickness of up to 250 nm were

detected in the gaps according to SIMS and

colorimetry; Carbidization of tungsten at the interface between

deposit and substrate (SIMS); Small or negligible metal mixing in the deposit layers

both in poloidal and toroidal gaps: results from

EPMA and SIMS. Strong asymmetry in the deposition in toroidal gaps:

full similarity with TEXTOR results.

Exposure of castellation in DIII-D divertor: current results

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Fuel removal castellated structures: O-bake experiment in DIII-D

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O-bake experiment in DIII-D: general information

Demonstrate an oxygen bake on the DIII-D tokamak and recover high performance plasma operation (with only clean vents)

Demonstrate removal from several tiles with a second oxygen bake

Goals:

O-bake experiments 2010: 2 hours; 20% O + 80% He; 13 mbar; 350oC; 1st experiment: 13.04.2010, 2nd experiment: 27.04.2010 (with castellation)DiMES

(castellation at 350oC)

Tile shelf with samples(350oC->160oC)

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O-bake experiment in DIII-D: exposure of castellation

Tungsten ITER-like castellation was exposed in the DIII-D divertor during 2nd O-bake exposure Poloidal gaps were coated a-C:D film prior to O-bake; a:-C-D film was pre-characterized via identical witness sample

Details:Castellated DiMES sample

Pre-coated poloidal gaps

First impression: exposure did not change much

before after

Next steps-analyses in the gaps: EPMA, NRA, SIMS/DEKTAK

4.5*1017 C/cm2

(EPMA)~ 70 nm

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Castellated limiter IV for TEXTOR

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Castellated limiter IV:castellation at different angles to B field

Critical region: the edges must be at the same height and position

Features

3 angles: 3o, 10o, 20o

Rectangular and moderately

shaped geometries of cells

Activities 2010: Castellation manufacturing: done;

Holder manufacturing: in progress;

Thermal simulation of castellation: in progress.

Miranda van den Berg, Gregory De Temmerman (TEC, FOM)

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Finalizing TDS measurements;

Analyses of data and providing an input to DITS.

TDS measurements on DITS samplesPlans 2010:

Investigations of fuel accumulation and material transport into gaps of ITER-like

castellated structures WP10-PWI-01-02-02/FZJ/BS

Analyses are underway on the castellated samples exposed

in Tore Supra and DIII-D tokamaks.

The effectiveness of deposit and fuel removal from

castellated structures using O-bake technique in DIII-D is

being studied.

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Finalizing surface analyses of deposits;

Analyses of all the data from all gaps;

Recommendations on castellation shaping.

Comparison of TEXTOR and DIII-D results.

Plans 2010 (continued):

Finalizing the thermal loads simulation and holder

manufacturing;

Exposure in TEXTOR.

Castellated limiter IV (TEXTOR)

Analyses of deposits and fuel distribution in the gaps;

Assessment of the O-bake effectiveness in DIII-D.

O-bake experiment in DIII-D

Castellation exposures in DIII-D

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Thank you

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