JET PFC Analysis, TFFT and the ILW

JET

J P CoadEURATOM/UKAEA Culham Division, Abingdon, UK

Introduction to TFFT and interaction with JETSummary of programme of analysis of JET samples removed in 2004Plans for JET samples removed in 2007Update on progress on the JET ITER-like wall

JET FT

Tritium in Tokamak

Tritium processes & Waste management

Test Beds

Neutronic& safety

Plasma Facing ComponentsEngineering

AGHS

Activation models

T spreading

Shutdown dose rate calculation

Collection ofOperating experience

Dust conversion factor of dust

Fatigue testing W coatings

Glow improvements

Active IRthermography

JET Flakes

CharacterisationJET Tiles

Improvement of gas balance

JET WDSsystem

T removalFrom tiles

Micro gaschromatography

Materialtransport

Retention incastellation

Microanalysisof cross section

detritiation

Erosiondeposition

LIBS

Heating of tilesIn JET NB test bed

AES/XPS T & Be JET

tiles

Fibres &neutrons

JET FT2008

Tritium in Tokamak

Tritium processes & Waste management

Test Beds

Neutronic& safety

Plasma Facing ComponentsEngineering

Benchmarking of CAD to MCNP interface

Shutdown dose rate prediction:

In situ opticalDust

measurements

Advanced study for detritiation

of non-plasma facing metals

Be Tiles detritiation

Material transport

+ erosion

tungsten erosion in the JET divertor

Microanalysis of plasma deposited

layers

tritium profile in carbon-based plasma-

facing componentsLIBS

Installation and commissioning

of the plasmatron

collection of data(VV & BeHF)

characterisation of mirrors

Laser lock in

Inspection ofbolometer

Tasks on Fusion Technology 2006-2007 and 2008

Plasma Facing Components (10)

Test Beds

Tritium in Tokamak (2)

Tritium process and waste management (4)

Engineering (4)Neutronics and Safety (2)

22 new tasks have been launched during WP 2006-07

15 tasks on going from previous years and 22 tasks launched during the year 2006

12

Presently FT has 37 running tasks

For the FT WP-2007-08 16 new tasks have been approved

for a total budget of ~2.4 m€

More and more papers published and/or presented at conferences

Active IR Thermography in metal environment

Goal: get rid of reflected flux and measure real surface T

Heat pulse = perturbation of T0

2 measurements and ratio surface T°

(Material Emissivity constant!)

(CEA, Semerok, Gauthier)

LIBS to characterise divertor PFC

test of laser detritiation on JET tiles

Goal : test in BeHF + assessment of efficiency

(CEA, Semerok and UKAEA, Widdowson and Coad)

300 microns

Laser treated zone

CFC substrate

Cleaning JET tiles by Laser Ablation

• total removal of film• some damage of the substrate• sharp boundary at edge of treated zone

Detritiation : inside gap generator

Goal : clean & detritiate castellations

D=60 mm

d= 0.8 mm

Power: 130W, Pressure: 69mbar

However, pattern not explained

Retention in castellations

Goal: characterise the retention in Be limiter castellations

(VR, Rubel)

• Cold self-sustained volumetric plasmaVolume: 18 litres Target diameter: ~25cm Ion energies: 20 - 500 eVMagnetic field: 0.2T Pulse duration: steady stateFlux density target: ~ 1020-1021 ions/m2.s

• Designed for PWI studies • Installation for operation in glove box• A gas mixture with a certain D/T ratio can be created in a volume

by measuring the pressure and the mass flow of D/T coming from volumes containing D and T. Both loops have a separate control system.

Brief plasmatron facility description

Tominetti S. et al., Vuoto 26 (1997)

Plasma chamber

Gas, plasma, secondary ions and neutrals analyser

Gas inlet

CW

CW

CW

CW cooling water

TC

TC temperature control

I

I

I insulation

PM

PM

PM permanent magnets

T

T target

C CA

C cathode

A anode

UHV 1

UHV1 main pumping

UHV 3

UHV3 differential pumping

Sedano L. et al., Phys. Stat. Sol. 188 (2001)

1/81/5

1/2

1/11

3/13/23/43/4

3/8

4/24/44/94/10 6/1 6/4 6/9

7/17/37/57/77/88/18/48/78/88/108/11

6/3

1/81/5

1/2

1/11

3/13/23/43/4

3/8

4/24/44/94/10 6/1 6/4 6/9

7/17/37/57/77/88/18/48/78/88/108/11

6/3

1/81/5

1/2

1/11

3/13/23/43/4

3/8

4/24/44/94/10 6/1 6/4 6/9

7/17/37/57/77/88/18/48/78/88/108/11

6/3

Task Force E JET

JET MkII-SRP Divertor used 2001-2004

Key: 1/11 means tile 1, sample 11

Septum Replacement Plate (SRP)

Campaign included:• 4 weeks reversed field• trace tritium experiment• 13C-methane puffing on last day• operation with JET wall

temperature at 200°C

Inner Divertor Analysis

Depth (m)

0 10 20 30 40 50 60 70 80

Inte

nsit

y (s

-1)

100

101

102

103

104

105Be12C13CNi

SIMS profiles sample 3/8 exposed 1998-2004

Inner part (to right of line):•similar to film deposited 1998-2002•Outer part: (to left of line)• High Be + other metals (e.g. Ni) except close to surface• Little 13C at surface

JG

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Tile 1

Tile 3

Tile 4

Task Force E JET

• Film deposited 2001-2004 also has high Be/C ratio, although operations were at 200°C• He-fuelled campaign must be responsible for outer layer from 1999-2001• Film structure may be different allowing trapping of large amount of D

Tile 3: Deposition layer fills up the holes of the W layer

G3B

top

bottom

Micro-analysis cross sectionGoal: Composition of layers of 100µm thick via micro beam analysis of polished

cross sections. (% level of main constituents: C, D, O, Be and SS, spatial resolution of a few μm)

D2 mapping

(Tekes, Likonen and Emmoth, VR)

Tile 1-5, sputter cleaned

130 120 110 100

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

104 C

ount

s/s

Binding Energy (eV)

Be1s

310 300 290 280 270

0.0

0.1

0.2

0.3

0.4

0.5

104 C

ount

s/s

Binding Energy (eV)

C1s

550 540 530 520

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

104 C

ount

s/s

Binding Energy (eV)

O1s

890 880 870 860 850 840

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

104 C

ount

s/s

Binding Energy (eV)

Ni2p

Tile 1-5 before and after sputter cleaning

Before

After

Picture from previous divertor campaigns in JET as follows:• Erosion at outer divertor wall (tiles 7 and 8) [contrast to inner]• ~200 μm deposition on sloping part of tile 6 [same as inner]• No significant deposition in shadowed corner [contrast to inner]

New data from MkII-SRP campaign from• 13C puffing• IR measurements• Analysis of tiles• Deposition monitors, louvre clips from shadowed area

Erosion/deposition at the outer divertor

Task Force E

JET

JG

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Tile 8

Tile 7

Tile 6 Shadowed region

Deposition at outer divertor

Task Force E JET

JG

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Tile 8

Tile 7

Tile 6 Shadowed region

•4 weeks reversed field operation gave deposition at outer divertor (clear from the film effect in the infra-red camera)•During methane puffing local re-deposition observed

Deposition in outer shadow region [c.f. inner]:•Film on Deposition monitor slits ~20 μm [c.f. 90 μm]•Deposit inside monitor box 18 μm [c.f.35 μm], or 8.3 1019 atoms cm-2 [c.f. 25 1019 atoms cm-2]•Film on tile (SIMS) 8 μm [c.f. 80 μm]•Film on tile (section) 40 μm [c.f. 120 μm]•Louvre clips off-gas 0.49 MBq/day [c.f. 0.63 MBq/day]

G7B

12345678

0a1a

W Erosion

Outer divertor: SEM images

-1600 -1500 -14000.0

0.5

1.0

1.5

2.0

Initial RBS PIXE [a.u.]

Am

ou

nt

of

W

[10

19 a

t./c

m2]

Position [z-coordinate, mm] 50 µm

• Inhomogeneous erosion• Full erosion of W in some places

(IPP, Majer)

13C-methane puffing experiment in 2004

Task Force E JET

•31 similar pulses on last day of operation•ELMy H-mode discharges:- BT 1.2T, IP 1.2 MA, ~7.5 MW additional heating•Total of 4.3 1023

molecules 13C-methane puffed in outer divertor from 48 locations

Approximate line of W-stripe is shown as white dashes

JETTask Force E

Field line plot showing strike points and SOL region for the 13C-puffing experiment

•Occasional sweeps of strike-point position for Langmuir probe data•Collector probe on reciprocating probe in SOL at top of machine

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Task Force E JET

Tile 1

Tile 3

Tile 4

Tile 8

Tile 7

Tile6

Amounts of 13C measured on divertor tiles by SIMS and IBA

Note: Measurements on one poloidal line have been extrapolated, assuming toroidal symmetry

Tile Number 13C amount

1 2.7% 3 0.5% 4 3.8% SRP ? 6 2.5% 7 10.9%* 8 6.1% Total 26.5%

* based on average of two poloidal scans

SRP

Local deposition of 13C on G3B

19-23(max) x1018 atoms/cm2

13-18.9 x1018 atoms/cm2

10-12.9 x1018 atoms/cm2

7-9.9 x1018 atoms/cm2

1-6.9 x1018 atoms/cm2

Total number deposited 13C in this area is ~215 x1018 atoms

Tungsten stripe

13C injection

20mm

Cores cut for SIMS analysis

Modelling of the 13C puffing for the inner divertor

Method• EDGE2D follows injected 13C atom trajectories with NIMBUS• EDGE2D ELM model of Kallenbach used (modified for smaller ELMs)• effects of sputtered carbon and re-erosion not included• impurity transport coefficients in private flux region chosen 10x SOL value• SOL flows in main chamber created by external force, classical drifts important in private flux region

3 paths dominate the 13C migration • most of carbon re-deposited on the outer target • a few % migrates via the main chamber SOL to the inner target (as also seen on a reciprocating probe at the top of the machine), and accounts also for the deposition on the inner baffle• a few % migrates via the private flux region by action of ExB drift to vicinity of inner strike point

Task Force E JET

SIMS

IBA

poloidal distance around the divertor (mm)

0 500 1000 1500 2000

13C

dep

osite

d / c

m2 /

13C

inje

cted

10-8

10-7

10-6

10-5

10-4

10-3final fit

J Strachan modelling for 13C experiment

Conclusions from 2004 samples

• Deposition at the inner divertor is not sensitive to wall temperature• Significant erosion of W-markers has been observed at the outer divertor, of interest to the ITER-like Wall Project at JET. • Infra-red temperature measurements clearly show when thin films are forming at the outer divertor• Some deposition occurred in shadowed region at outer corner in 2001-4, but the balance between erosion and deposition in this region requires further exploration• 13C-methane was puffed at the outer divertor in 2004, and preliminary modelling shows reasonable agreement with deposition at inner divertor

Task Force E JET

10μm

7μm

72μm

44cm3

67cm3

99cm3

105cm3

233cm3 17cm3

464cm3

26μm

10μm

38μm

33μm

41μm

19cm3

24cm3

60g on louvre

18μm 300μm 32μm

Tile analysis programmefor tiles removed in the 2007 shutdown

Objectives:•Distribution of 13C injected in April 2007 at outer mid-plane•Erosion of W-coatings in critical areas for ILW•Erosion/deposition behaviour to compare with QMB data•Results of rotating collector experiment (inc. Be evaporation)•Mirror tests for ITER•C-redeposition at load-bearing tile

Cross-section of JET 2005-7

JET-HD divertor 2005-

Quartz Micro-balance at the inner divertor

tile 1

tile 3

tile 4

QMB-system

quartzcrystal

carrier rib tile 1

tile 3

tile 4

QMB-system

quartzcrystal

carrier rib

JET ITER-Like Wall

• Update on materials, timescales

• Development of W coatings on CFC

• Be coatings on inconel

• Be markers

View inside JET 2005-7

Beryllium Coatings on Cast Inconel (I)

• Evaporated 8 m Be coating on inner wall Inconel cladding• Estimated maximum load in JET: 0.5 MW/m2 in 20 s corresponding to 10 MJ/m2

Steps in the material qualification process:• Optimisation of the deposition process (Nucl. Fuel Plant, Romania).• Pre-characterisation of layers: purity, structure, uniformity.• High Heat Flux testing (Forschungszentrum Jülich).• Characterisation after testing.

HHF testing in JUDITH to determine the layer durability limits:

1. Screening test by stepwise increase of power density: 0.4 – 3 MW/m2.

2. Cyclic test: 50 consecutive loads of 1.0MW/m2 for 10 s.

Message: No damage to layers exposed to the energy load of 19.8 MJ/m2.

200

700

5 m5 m

Original surface Tested: 1.8 MW/m2, 11 sTest: 1.8 MW/m2, 11 s

Beryllium Coatings on Cast Inconel (II)

SUMMARY OF RESULTS:• High uniformity and purity of coatings (oxygen only in a thin surface layer).• Layers survive power loads of 2.55 MW/m2 in 6.2 s (18.1 MJ/m2)• Melting of beryllium observed above 3 MW/m2.• No damage by 50 thermal cycles of 1 MW/m2 for 10 s each (10 MJ/m2 pulses).

0

200

400

600

800

1000

1200

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0

delta T, 3.3 ~ 3.6 mmdelta T, >4.0 mm

6.2 s, delta T

Energy density [MJ/m2]

extrapolation, ~11 s pulseon 3.5 mm Inconel case~ 11 s pulses,

thickness 3.3 ~ 3.6 mm

6.2 s pulse, thickness 4 mm

~ 11 s pulses, thickness > 4.0 mm

Surface Temperature versus Energy Density

Tem

per

atu

re

[oC

]

Conclusion: The layers meet operational requirements for JET-ILW.

PISCES

PC-Be data scaled () to Eckstein’s value

10-3

10-2

10-1

0 50 100 150

PC-Be (20060817)GA-Be (20060802)ROM-Be (20060802)

Eckstein (D+-->Be)

YB

e

Ei [eV]

20

06

08

02

&2

00

60

81

7

(10-3) = 7.7x102

Erosion of Beryllium Coatings on Cast Inconel:Exposure of Be to Deuterium Plasma in PISCES (UCSD)

D.Nishijima, J.Hanna, R.Doerner

GA & Romanian Be coatings show increased YBe’s at higher Eion compared to Poly Crystalline(PC)-Be.

Development of Beryllium Marker Tiles (I)AIM: The assessment of beryllium erosion from the main chamber wall (limiters)

Beryllium Tile (3 cm)

Nickel interlayer (2-3 m)

Be layer (7-9 m)

30 m

m

28 mm

Be coupon with marker coating.

For HHF testcoupons are with a

hole for a thermocouple.

Steps in the R & D process

• Production of optimised layers by Thermionic Vacuum Arc method

• High Heat Flux testing

• Broad characterisation of layers before and after testing.

Main Result of HHF test:

Layers withstand without damage 4.5 MW m-2 for 10 s.

Beryllium Marker Tiles (II)

Depth (m)

0 2 4 6 8 10 12 14

Inte

nsi

ty (

s-1)

100

101

102

103

104

105 BeCAlSiCaFeNi

Be test coupon with marker layers

Topography of Be coating

Depth (m)

0 2 4 6 8 10 12 14

Inte

nsi

ty (

s-1)

100

101

102

103

104

105 BeCAlSiCaFeNi

SIMS depth profiles

After HHF test

Fresh

Remaining Work: Produce and Install Tiles in JET

Inner Wall Structure with Location of Marker Tiles

Conclusions

• Analysis of tiles removed in 2004 shutdown almost complete

• Analysis has started on a new poloidal selection of tiles removed in 2007

• Preparations are in hand for the ILW installation in 2009-2010, including solid Be and W tiles, Be coatings on inconel, and marker tiles.