main chamber: limiters · marker layer. marek rubel iaea tm47136| daejeon, korea| december 15-19,...

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


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.



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.


D i v e r t o r

Be

W+

CF

C

Be

Be Be

Be

Be

Divertor cross-section


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


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


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)


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


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


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


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.


main chamber: limiters · marker layer. marek rubel iaea tm47136| daejeon, korea| december 15-19,...

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