1 DEUTERIUM RETENTION IN TUNGSTEN EXPOSED TO CARBON-SEEDED DEUTERIUM PLASMA * Igor I. Arkhipov,...

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DEUTERIUM RETENTION IN TUNGSTEN EXPOSED TO CARBON-SEEDED DEUTERIUM PLASMA *

Igor I. Arkhipov, Vladimir Kh. Alimov, Dmitrii A. KomarovRion A. Causey*, Robert D. Kolasinski*

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, RAS, Moscow, Russia

*Sandia National Laboratories, Livermore, USA

Outline

1. Introduction

2. Experimental

3. Results & Discussion

4. Conclusions

*This work was supported by the United States Department of Energy under Contract 512244 with Sandia National Laboratories

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Irradiation conditions

Pdiv, Pa Flux, D/m2s Ei, eV* C, at.% Tsur, K

ITER divertor [1] 4 ~1×1023-24 ≤100 ? 520 & 850

JET [2] ≤20 4 380-520

PISCES-B [3] ~1×1022 100 0.5; 1; 1.4 350-1200

Ion source [4] ~4×10-5 ~6×1019 500 1 300, 500

Magnetron [5] 1 ~1×1021 400 ≤1 390-1000

Introduction

[1] G.Federici et al., J. Nucl. Mater. 313-316 (2003) 11-22[2] J.P. Coad, et.al., J. Nucl. Mater. 313-316 (2003) 419-423[3] F.C. Sze et.al., J. Nucl. Mater. 266-269 (1999) 1212-1218[4] M.Poon, et al., J. Nucl. Mater. 337-339 (2005) 629-633[5] This work

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ITER divertor [1] 4 ~1×1023-24 ≤100 ? 520 & 850

JET [2] ≤20 4 380-520

PISCES-B [3] ~1×1022 100 0.5; 1; 1.4 350-1200

Ion source [4] ~4×10-5 ~6×1019 500 1 300, 500

Magnetron [5] 1 ~1×1021 400 ≤1 390-1000

Introduction

[1] G.Federici et al., J. Nucl. Mater. 313-316 (2003) 11-22[2] J.P. Coad, et.al., J. Nucl. Mater. 313-316 (2003) 419-423[3] F.C. Sze et.al., J. Nucl. Mater. 266-269 (1999) 1212-1218[4] M. Poon, et al., J. Nucl. Mater. 337-339 (2005) 629-633[5] This work

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Distribution of erosion/deposition areas in the JET divertor (1999-2001)*

*P.Coad, et al., J. Nucl. Mater. 313-316 (2003) 419

Introduction Material migration in divertor tokamaks

5

Sputtering yields curves for fusion relevant materials for irradiation by deuterium*(Physical sputtering yields for some ion mass are plotted in the case of W)

*G.F. Matthews, J. Nucl. Mater. 337-339 (2005) 1-9

Introduction

100

Erosion of carbon by deuterium

6

Scheme of erosion/re-deposition processes within the divertor*


IntroductionMaterial migration in divertor tokamaks

7

Ion impact energy at the outer divertor target for a completely detached N2 seeded shorts in JET. The effect of ELMs of different sizes is shown*

Introduction


Erosion of tungsten by tritium

8

D retention in C seeded D-plasma exposed W Experimental results

Dominant factors: 1. substrate temperature 2. whether carbon is deposited on the W surface

There is a carbon-impurity concentration of beginning of C-deposition:• 0.75% at 850 K• 1% at 750 K

Uncontaminated surface: 1. Blisters, bubbles and/or pits are formed 2. D retention decreases with temperature increase

C-contaminated surface: 1. a-C:D film or/and W2C layer are formed

2. D retention in C-contaminated W larger than in uncontaminated one• The most of deuterium are residing in the carbon films• Thin a-C:D film or W2C layer can significantly decrease D-retention in W

Introduction

9







Introduction

10







Introduction

11







Introduction

12



Introduction

100

Erosion of tungsten by carbon

13

W erosion as function of Te and C impurity concentration*

*K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310

Introduction Erosion of tungsten by carbon

14

In this work:

Partially contaminated surface in C-seeded D-plasma

Introduction

15

Top view of magnetron cathode surfaceExperimental

Ta mask

(6×8×0.5 mm3)

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ITER divertor [1] 4 ~1×1023-24 ≤100 ? 520 & 850

JET [2] ≤20 4 380-520

PISCES-B [3] ~1×1022 100 0.5; 1; 1.4 350-1200

Ion source [4] ~4×10-5 ~6×1019 500 1 300, 500

Magnetron [5] 1 ~1×1021 400 ≤4 363-773


Experimental

17


Pdiv, Pa Flux, D/m2s Ei*, eV At.% C Tsurface, K

ITER [1] 4 ~1×1023-24 ≤100 ? 520 & 850

JET [2] ≤20 4 380-520

PISCES-B [3] ~2×1022 100 0.5; 1; 1.4 350-1200

Ion source [4] ~4×10-5 ~6×1019 500 1 300, 500

Magnetron [5] 1 ~1×1021 400 ≤4 363-773

Experimental


*Ei≈ZUsheath + 2Ti ≈ Te(3Z+1), Usheath≈3Te/e0

Ti≈Te/2

Ei- ion impact energyZ- charge state of the impacting ionUsheath- sheath potentialTe& Ti – temperatures of electrons and ions

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Pdiv, Pa Flux, D/m2s Ei, eV At.% C Tsurface, K

ITER [1] 4 ~1×1023-24 ≤100 ? 520 & 850

JET [2] ≤20 4 380-520

PISCES-B [3] ~1×1022 100 0.5; 1; 1.4 350-1200

Ion source [4] ~4×10-5 ~6×1019 500 1 300, 500

Magnetron [5] 1 ~1×1021 400 ≤4 363-773

Experimental


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W erosion as function of Te and C impurity concentration*


Introduction Erosion of tungsten by carbon

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Experimental conditions

Ei=400 eV Rp, nm

(SRIM 2003)

Kerosion Kdiffusion

(m2s-1)

Conclusion R

D2+→W 2 - 1× 10-9 * No limits for diffusion 1

C+→W 1 0.1 1× 10-19 ** Thin C-W mixed layer 2

Experimental

D ion energy, eV Time, sec Flux,

(m-2s-1)

Fluence,

(m-2s-1)

Erosion,

nm/sec

200 1800 1× 1019 2× 1024 ≤1 nm/sec

[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388[2] K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310

* T=770 K

**T=1030 K

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Erosion of tungsten

Experimental

Estimation: V erosion=1.5-2 μm/30 min ~1 nm/s ~6×1019 at.W/m2s

Closed area

Plasma-impact area

Interference fringes(Linnik micro-interferometer)

Initial surface

Eroded surface

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Experimental Erosion of tungsten by carbon

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Ei=400 eV Rp, nm

(SRIM 2003)

Kerosion Kdiffusion

(m2s-1)

Conclusion R

D2+→W 2 - 1× 10-9 * No limits for diffusion 1

C+→W 1 0.1 1× 10-19 ** Thin C-W mixed layer 2

Experimental

D ion energy, eV Time, sec Flux,

(m-2s-1)

Fluence,

(m-2s-1)

Erosion,

W at./m2s

200 1800 1× 1019 2× 1024 ≤6×1019


* T=770 K

**T=1030 K

1%C in plasma: 1018 C/m2s→ 1017 W/m2s

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Irradiation T, K Eth, eV Kerosion at Ei= 400 eV

C+, N+, O+ →W 293 ~35 ~ 0.1

Ta+ →W 293 ~2

D2+→W 293 160-200 ≤0.0001

D2+→WO 293 65

D2+→WC 293 150 ≤ 0.0001

The threshold energies of sputtering

Experimental

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DEUTERIUM RETENTION IN TUNGSTENAT HIGH LEVEL OF SURFACE EROSION

Experimental

26


Ei=400 eV Rp, nm

(SRIM 2003)

Kerosion Kdiffusion

(m2s-1)

Conclusion R

D2+→W 2 - ~ 1× 10-9 * No limits for diffusion 1

C+→W 1 0.1 ~ 1× 10-19 ** Thin C-W mixed layer 2

Experimental

D ion energy, eV

Time, sec

Flux,

(m-2s-1)

Fluence,

(m-2s-1)

Erosion,

W at./m2sec

Temperature,

K

200 1800 1× 1019 2× 1024 ~6×1019 363-773


* T= 773 K

**T=1030 K

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Diffusion coefficient for C in a wide concentration range for C in W*


Introduction

28


Ei=400 eV Rp, nm

(SRIM 2003)

Kerosion Kdiffusion

(m2s-1)

Conclusion R



Experimental

D ion energy, eV

Time, sec

Flux,

(m-2s-1)

Fluence,

(m-2s-1)

Erosion,

W at./m2sec

Temperature,

K

200 1800 1× 1019 2× 1024 ~6×1019 363-773


* T= 773 K

**T=1030 K

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Ei=400 eV Rp, nm

(SRIM 2003)

Kerosion Kdiffusion

(m2s-1)

Conclusion R



Experimental

D ion energy, eV

Time, sec

Flux,

(m-2s-1)

Fluence,

(m-2s-1)

Erosion,

W at./m2sec

Temperature,

K

200 1800 1× 1019 2× 1024 ~6×1019 363-773


* T= 773 K

**T=1030 K

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H diffusivity vs temperature for W773 K

E. Serra, G. Benamati, O.V. Ogorodnikova, J. Nucl. Mater. 255 (1998) 105-115

Experimental

31


R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388

Experimental

32


A.P. Zakharov, V.M. Sharapov, E.I. Evko, Soviet Mater. Sci. 9 (1973) 149

Experimental

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Ei=400 eV Rp, nm

(SRIM 2003)

Kerosion Kdiffusion

(m2s-1)

Conclusion R



Experimental

D ion energy, eV

Time, sec

Flux,

(m-2s-1)

Fluence,

(m-2s-1)

Erosion,

W at./m2sec

Temperature,

K

200 1800 1× 1019 2× 1024 ~6×1019 363-773


* T= 773 K

**T=1030 K

Kdiffusion ~ 1× 10-9 m2s-1 →h=(Dt)1/2~ 1mm

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Methods of the analysisExperimental

Mechanically & electrochemically polishedHot-rolled tungsten foil (99.0 at.%)

Size = 6×8×0.5 mm3

C/D-plasma irradiation: planar DC magnetron Eions (D2+; C+; N+, O+, Ta+)= 400 eV

Flux=1×1019 D/m2s, 30 min

Deuterium profiles:Nuclear Reaction Analysis (NRA):• 0 - 0.5 μm: D(3He,α)H reaction•0.5 - 7 μm: D(3He,p)4He reaction

Deuterium retention:Thermal Desorption Spectroscopy (TDS)•D2 & HD molecules were detected by QMS•Temperature range: 300-1100 K•Heating rate = 3.2 K/s

Profiles & chemical state of impurities:X-ray Photoelectron Spectroscopy (XPS)• Depth profiles of C, O, W • 3 kev Ar+, 2×2 mm2, 0.4 μm

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NRA & TDS data

300 400 500 600 700 800Irradiation tem perature, K

0

2

4

6

8

1

3

5

7D

eute

riu

m r

eten

tio

n,

×10

20

D/m

2 D+C- plasma, 200 eV D+, ~2×1024 D/m2

NRA data, 0-7 mTDS data

Results & Discussion

6

m

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NRA data

0 1 2 3 4 5 6 710 -4

10 -3

10 -2

10 -1

100 363 K 383 K 463 K 563 K 653 K 773 K

D c

on

ce

ntr

ati

on

[a

t.%

]

Depth [m]


3

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XPS data

2 9 0 2 8 8 2 8 6 2 8 4 2 8 2 2 8 0

4 0 0 c /s

C 1s

D + C p la s m aT

exp = 3 8 3 K

g ra p h ite

D p la s m aT

exp = 4 9 3 K

W2C

W C

d is o rd e re d CX

PS

in

ten

sit

y

B in d in g en erg y [eV ]


(3 keV Ar at fluence=1×1019 Ar/m2 )

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NRA data

0 1 2 3 4 5 6 710 -4

10 -3

10 -2

10 -1

100 363 K 383 K 463 K 563 K 653 K 773 K

D c

on

ce

ntr

ati

on

[a

t.%

]

Depth [m]


3

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Blistering in the temperature range 363-653 K


Pre-TDS; T=563 K at fluence=2× 1024 D/m2

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TDS data

0 100 200Time, s

0

4

8

12

2

6

10

Des

orp

tio

n f

lux,

×10

18 D

/m2 s

400

600

800

1000

300

500

700

900

Tem

per

atu

re,

K

D+C plasm a W PC363 K383 K463 K563 K653 K773 KTemperature


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TDS dataResults & Discussion


0

2

4

6

1

3

5

7

Deu

teri

um

ret

enti

on

, ×

102

0 D

/m2 D+C- plasma, 200 eV D+, ~2×1024 D/m2

First peakSecond peak

T1=650-710 KT2=900-1000 K

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TDS modeling: contributions from 1.4 eV traps and blisters (TMAP7)

at 563 K


1.0

0.8

0.6

0.4

0.2

0.0

De

sorb

ed

Flu

x (n

orm

aliz

ed

)

1000800600400

Temperature (K)

TMAP7 Simulated TDS spectrum563 K exposure temperature

1.4 eV trap contribution blister (100 nm caps) bister (1 micron caps) blister (5 micron caps)

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Three types of traps can explain our TDS data

1. Near-surface layer (≤ 0.5 m): 1.4 eV traps=

one D in vacancy

2. Sub-surface layer (≤ 7 m): 1.8-2.1 eV=D chemisorption on blister/bubble wall + D2 molecules inside

3. Bulk (up to 1 mm): 1.8-2.1 eV traps=

D chemisorption on inner walls of small cavity and voids

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Fitting of TDS data are in progress

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NRA & TDS data


0

2

4

6

8

1

3

5

7D

eute

riu

m r

eten

tio

n,

×10

20

D/m

2 D+C- plasma, 200 eV D+, ~2×1024 D/m2

NRA data, 0-7 mTDS data


Bulk trapping !

m

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General experimental results

Strong W sputtering

Blistering

Enhanced D retention

NRA ≈ TDS from 363 to 563 K

NRA<<TDS from 563 to 773 K


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General conclusions

Blistering & enhanced D retention even at strong W surface sputtering are revealed Irradiation temperature of 550-600 K corresponds to

transition from a near/sub-surface to a bulk D trapping in polycrystalline W foils

Carbon influence: enhanced W erosion;

W2C barrier layer formation & increased D retention

Conclusions

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General conclusions

Blistering & enhanced D retention even at strong W surface sputtering are revealed Irradiation temperature of 550-600 K corresponds to

transition from a near-surface to a bulk D trapping in polycrystalline W

Carbon influence: enhanced W erosion;

W2C barrier layer formation & enhanced D retention

Conclusions

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General conclusions

Blistering & enhanced D retention even at strong W surface sputtering are revealed

Irradiation temperature of 550-600 K corresponds

to transition from a near-surface to a bulk D trapping in polycrystalline W

Carbon influence:

enhanced W erosion;W2C barrier layer formation & enhanced bulk D retention

Conclusions

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Scheme of plasma-surface interaction

W

Carbon-modified layer (W2C, WC)

D-C plasma

D stop diffusion & retention

No erosion

a-C:H film

4 nm

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Scheme of plasma-surface interaction

W

Carbon-modified layer (W2C, WC)

D-C plasma no limits for diffusion high retention level in bulk

Erosion rate 1 nm/s

D

1 nm

2 m

a-C:H film

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To be or not to be for D retention in Wstrongly depends on irradiation

parameters and surface conditions

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Thank you for attention

1 DEUTERIUM RETENTION IN TUNGSTEN EXPOSED TO CARBON-SEEDED DEUTERIUM PLASMA * Igor I. Arkhipov,...

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