P. Coad, J. Likonen, H. Bergsåker, M. Rubel, I. Uytdenhouwen, A. Widdowson JET mixed Be/C/O layers SEWG meeting on mixed materials, 9.-10.7.2007, JET.

P. Coad, J. Likonen , H. Bergsåker, M. Rubel, I. Uytdenhouwen, A. Widdowson

JET mixed Be/C/O layers

SEWG meeting on mixed materials, 9.-10.7.2007, JET

VTT TECHNICAL RESEARCH CENTRE OF FINLAND

VTT

2

Dump plate, saddle coil protection tiles: Main erosion source?

OPL:erosion

divertor:deposition (inboard)erosion (outboard)

IWGL:erosion deposition

Erosion/deposition at JETErosion/deposition at JET


VTT

3

Inner divertor: heavy deposition

Outer divertor: erosion

SIMS depth profiles from centre of lower inner divertor wall tile:

•High vessel temperature•Be/C > 1 •Deposit: thickness ~8 m

3/3

Erosion/deposition at JET (MkIIA)Erosion/deposition at JET (MkIIA)

Depth (m)

0 2 4 6 8 10 12 14

Inte

nsi

ty (

s-1)

100

101

102

103

104

105 1H2D9Be10B12C58Ni


VTT

4

Micrometer and SIMS results

Inner wall:• thickness increase towards the bottom at inner divertor wall (points 1-8), reaching a maximum of about 90 m• SIMS gives somewhat smaller values

Floor:• thick powdery deposits at points 10 and 16

Outer wall:• small amounts of erosion/deposition

Point

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Dep

ositi

on (

m)

-50

0

50

100

150

200

250

300Micrometer SIMS

Erosion/deposition at divertor (MkIIGB)Erosion/deposition at divertor (MkIIGB)

1

6/1 6/7

1

1

4

713 14

24

19


VTT

5


SIMS depth profiles from bottom of upper inner divertor wall tile:

•Deposit: 2 layers (thickness ~11 m). •Surface layer: mostly D, C and Be •Film underneath the surface layer: rich in Be •Vessel temperature decreased in Dec. 2000

Deposition at inner divertor (MkIIGB)Deposition at inner divertor (MkIIGB)

Depth (m)

0 5 10 15 20 25

Inte

nsit

y (s

-1)

100

101

102

103

104

105DBeCRe

bulk CFCBe-richC-

1/1

Re


VTT

6

Channel

0 200 400 600 800 1000

Cou

nts

500

1000

1500

2000

2500

3000

Energy (keV)

0 500 1000 1500 2000 2500

RBSSIMNRA

D

Be

12C

13C

OCr,Re

layer D (at%)

Be (at%)

12C

(at%)

13C (at%)

O (at%)

1 12 4 31 28 25

2 30 5 52 10

3 5 20 41 21

layer D (at%)

Be (at%)

12C

(at%)

13C (at%)

O (at%)

1 26 6 50 13 25

2 28 8 55 10

3 12 11 64 10

Composition of deposits (MkIIGB)Composition of deposits (MkIIGB)

RBS spectrum and SIMNRA simulation from the bottom of tile 1


VTT

7

MkIIGB1999-2001

16h

Spectroscopy:

20g Be (4x10-4 g/s)

450-480g C (9x10-3 g/s)

SIMS,RBS:

22g Be (4x10-4 g/s)

400g C (8x10-3 g/s)

MkIIA:

1kg C (15x10-3 g/s)

Surface analysis (SIMS, RBS, TOF-ERDA), inner divertor: Be 22 g

Assume that Be/C ratio (7%) arriving in the divertor is the same as the Be/C ratio in the main chamber (Be/C ratio on IWGL tiles is ~8%).

C: 420 g

Amount of deposited C:Tiles 1, 3 and 4: 310 g (SIMS, RBS)Louvres: 20 - 60 g (QMB and deposition monitor sample)

Septum: 10 g (RBS)Total: 340 - 380 g

Good agreement between surface analyses and optical spectroscopy

Be accumulation and C deposition (MkIIGB)

Be accumulation and C deposition (MkIIGB)


VTT

8

JG

03

.67

6-1

c

Depth (m)

0 5 10 15 20 25 30

Inte

nsi

ty (

s-1)

100

101

102

103

104

105HDBeB12CNiW


SIMS depth profiles from bottom of upper inner divertor wall tile:

•Low vessel temperature•Deposit: Be/C high

•Duplex structure of deposits on MkIIGB tiles due to He-phase at the end of C4 campaign

1/2

Deposition at inner divertor (MkIISRP)Deposition at inner divertor (MkIISRP)

bulk CFC

deposit W marker


VTT

9

layer D (at%)

Be (at%)

12C

(at%)

13C (at%)

O (at%)

1 16 5 61 5 11

2 19 10 50 18

3 11 20 39 28

layer D (at%)

Be (at%)

12C

(at%)

13C (at%)

O (at%)

1 12 22 43 3 20

2 6 14 54 20

3 11 5 62 13

Composition of deposits, RBS (MkIISRP)Composition of deposits, RBS (MkIISRP)

RBS spectrum and SIMNRA simulation from the bottom of tile 1

CrO

13C

12CBe

D

JG

03

.67

6-1

c


VTT

10

JG

03

.67

6-1

c

layer D (at%)

Be (at%)

12C

(at%)

13C (at%)

O (at%)

1 18 0.5 57 9 15

2 16 3 68 13

3 15 3 68 13

Depth (m)

0 5 10 15 20 25 30

Inte

nsi

ty (

s-1)

100

101

102

103

104

105HDBeB12CNiW

Composition of deposits, floor (MkIISRP)Composition of deposits, floor (MkIISRP)

12C

13C

O

Be

D

RBSSIMS


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11

Erosion/deposition at JETErosion/deposition at JET

Inner divertor Outer divertor

MkIIA Heavy deposition, Be/C ratio high Erosion (no markers)

MkIIGB Heavy deposition, films have duplex structure (C- and Be-rich layers), no Be on floor tile, deposited C quantified

Erosion (markers eroded completely)

MkIISRP Heavy deposition, Be/C ratio high, some Be on floor tile

Erosion/deposition (due to rev B campaign?)

see our review paper Coad et al.: Overview of material re-deposition and fuel retention studies at JET with the gas box divertor , Nucl. Fus. 46 (2006) 350.


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12

Nature of the films

All analysis is done ex-situ and this may introduce much of the observed oxygen and affects H/D/T levels

We have a good idea of the atomic Be/C composition, but no idea of the chemical composition. For example it is sometimes assumed that the Be/C is “beryllium carbide” – is this really true?

XPS/AES can demonstrate the chemical state, but only analyses a few monolayers at the surface, so needs to be combined with profiking in some way

Carbides may be detected by XRD, if present There are many other film properties that would be of interest, such as

density, electrical and thermal coefficients, thermal desorption etc


VTT

13

JG

03

.67

6-1

c

Erosion/deposition at JET divertorErosion/deposition at JET divertor

deposit

3µm W

CFC

W

W


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14

Micro beam analysis (MkIIGB)Micro beam analysis (MkIIGB)

2D image for D and Be on sample 3/1

Concentration profiles of Be and D on sample 3/1, taken from tile 3, exposed in JET 1999-2001.


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15

XPS analysis of tile sample 1-5 before and after sputter cleaning

Before

After

Sample 1-5, rough quantification

0

1000

2000

3000

4000

5000

6000

7000

280290300310320

Cou

nts

/ s

Binding Energy (eV)

-3000

-2000

-1000

0

Residuals

C1s

C1s

C1s A

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

530540550560570

Cou

nts

/ s

Binding Energy (eV)

-4000

-3000

-2000

-1000

0

Residuals

O1s

O1s

8000

9000

10000

11000

12000

13000

14000

15000

16000

17000

18000

850860870880890900

Co

unts

/ s

Binding Energy (eV)

-7000

-6000

-5000

-4000

-3000

-2000

-1000

0

1000

Re

sidu

als

Ni2p

Ni2p

100

200

300

400

500

600

700

800

900

110120130

Co

unts

/ s

Binding Energy (eV)

-220

-210

-200

-190

-180

-170

-160

-150

-140

-130

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

Re

siduals

Be1s

Be1s

Be1s A

Ni3s or Carbide ?

Name Peak BE FWHM (eV) Area At. % C1s 284.8 1.85 8663.2 38.81O1s 532.19 2.52 18437.93 28.02Be1s 113.85 1.77 917.81 21.28Ni2p 853.82 1.87 13125.55 0.99

C1s A 287.4 2.77 1668.99 7.48Be1s A 110.96 2.84 147.41 3.42

Conclusions

Most important deposition in JET occurs at the inner divertor

The deposits left on tiles 1 and 3 are mixtures of C & Be (+ other metals), most C migrates to inner divertor corner

Almost nothing is known about the chemical state or physical properties of the films

P. Coad, J. Likonen, H. Bergsåker, M. Rubel, I. Uytdenhouwen, A. Widdowson JET mixed Be/C/O layers SEWG meeting on mixed materials, 9.-10.7.2007, JET.

Documents

c deposition mkiigb

jet slide

erosion divertor

structure c

d slide

inner divertor corner

mixtures of c

jet divertor deposit