1. *This work was supported by the United States Department of Energy
DEUTERIUM RETENTION IN TUNGSTEN EXPOSED TO CARBON-SEEDED DEUTERIUM PLASMA * Igor I. Arkhipov, Vladimir Kh. Alimov, Dmitrii A. Komarov Rion A. Causey*, Robert D. Kolasinski* A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, RAS, Moscow, Russia *Sandia National Laboratories, Livermore, USA
Outline
Introduction
Experimental
Results & Discussion
Conclusions
*This work was supported by the United States Department of Energy
under Contract with Sandia National Laboratories

2. Irradiation conditions
Introduction
Irradiation conditions
Pdiv, Pa
Flux, D/m2s
Ei, eV*
C, at.%
Tsur, K
ITER divertor [1] 4
~1×
≤100 ?
520 & 850
JET [2]
≤20
PISCES-B [3]
~1×1022
100
0.5; 1; 1.4
Ion source [4]
~4×10-5
~6×1019
500 1
300, 500
Magnetron [5]
~1×1021
400 ≤1
[1] G.Federici et al., J. Nucl. Mater (2003) 11-22
[2] J.P. Coad, et.al., J. Nucl. Mater (2003)
[3] F.C. Sze et.al., J. Nucl. Mater (1999)
[4] M.Poon, et al., J. Nucl. Mater (2005)
[5] This work

3. Irradiation conditions
Introduction
Irradiation conditions
Pdiv, Pa
Flux, D/m2s
Ei, eV*
C, at.%
Tsur, K
ITER divertor [1] 4
~1×
≤100 ?
520 & 850
JET [2]
≤20
PISCES-B [3]
~1×1022
100
0.5; 1; 1.4
Ion source [4]
~4×10-5
~6×1019
500 1
300, 500
Magnetron [5]
~1×1021
400 ≤1
[1] G.Federici et al., J. Nucl. Mater (2003) 11-22
[2] J.P. Coad, et.al., J. Nucl. Mater (2003)
[3] F.C. Sze et.al., J. Nucl. Mater (1999)
[4] M. Poon, et al., J. Nucl. Mater (2005)
[5] This work

4. Material migration in divertor tokamaks
Introduction
Material migration in divertor tokamaks
Distribution of erosion/deposition areas in the JET divertor ( )*
*P.Coad, et al., J. Nucl. Mater (2003) 419

5. Erosion of carbon by deuterium
Introduction
Erosion of carbon by deuterium
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)
100
*G.F. Matthews, J. Nucl. Mater (2005) 1-9

6. Scheme of erosion/re-deposition processes within the divertor*
Introduction
Material migration in divertor tokamaks
Scheme of erosion/re-deposition processes within the divertor*
*G.F. Matthews, J. Nucl. Mater (2005) 1-9

7. Erosion of tungsten by tritium
Introduction
Erosion of tungsten by tritium
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*
*G.F. Matthews, J. Nucl. Mater (2005) 1-9

8. D retention in C seeded D-plasma exposed W Experimental results
Introduction
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

9. D retention in C seeded D-plasma exposed W Experimental results
Introduction
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

10. D retention in C seeded D-plasma exposed W Experimental results
Introduction
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

11. D retention in C seeded D-plasma exposed W Experimental results
Introduction
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

12. Erosion of tungsten by carbon
Introduction
Erosion of tungsten by carbon
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)
100
*G.F. Matthews, J. Nucl. Mater (2005) 1-9

13. W erosion as function of Te and C impurity concentration*
Introduction
Erosion of tungsten by carbon
W erosion as function of Te and C impurity concentration*
*K. Schmid, J. Roth, J. Nucl. Mater (2003)

14. Partially contaminated surface in C-seeded D-plasma
Introduction
In this work:
Partially contaminated surface in C-seeded D-plasma

15. Top view of magnetron cathode surface
Experimental
Top view of magnetron cathode surface
(6×8×0.5 mm3)
Ta mask

16. Irradiation conditions
Experimental
Irradiation conditions
Pdiv, Pa
Flux, D/m2s
Ei, eV*
C, at.%
Tsur, K
ITER divertor [1] 4
~1×
≤100 ?
520 & 850
JET [2]
≤20
PISCES-B [3]
~1×1022
100
0.5; 1; 1.4
Ion source [4]
~4×10-5
~6×1019
500 1
300, 500
Magnetron [5]
~1×1021
400 ≤4
[1] G.Federici et al., J. Nucl. Mater (2003) 11-22
[2] J.P. Coad, et.al., J. Nucl. Mater (2003)
[3] F.C. Sze et.al., J. Nucl. Mater (1999)
[4] M.Poon, et al., J. Nucl. Mater (2005)
[5] This work

17. Irradiation conditions
Experimental
Irradiation conditions
Pdiv, Pa
Flux, D/m2s
Ei*, eV
At.% C
Tsurface, K
ITER [1] 4
~1×
≤100 ?
520 & 850
JET [2]
≤20
PISCES-B [3]
~2×1022
100
0.5; 1; 1.4
Ion source [4]
~4×10-5
~6×1019
500 1
300, 500
Magnetron [5]
~1×1021
400 ≤4
*Ei≈ZUsheath + 2Ti ≈ Te(3Z+1),
Usheath≈3Te/e0
Ti≈Te/2
Ei- ion impact energy
Z- charge state of the impacting ion
Usheath- sheath potential
Te& Ti – temperatures of electrons and ions
[1] G.Federici et al., J. Nucl. Mater (2003) 11-22
[2] J.P. Coad, et.al., J. Nucl. Mater (2003)
[3] F.C. Sze et.al., J. Nucl. Mater (1999)
[4] M.Poon, et al., J. Nucl. Mater (2005)
[5] This work

18. Irradiation conditions
Experimental
Irradiation conditions
Pdiv, Pa
Flux, D/m2s
Ei, eV
At.% C
Tsurface, K
ITER [1] 4
~1×
≤100 ?
520 & 850
JET [2]
≤20
PISCES-B [3]
~1×1022
100
0.5; 1; 1.4
Ion source [4]
~4×10-5
~6×1019
500 1
300, 500
Magnetron [5]
~1×1021
400 ≤4
[1] G.Federici et al., J. Nucl. Mater (2003) 11-22
[2] J.P. Coad, et.al., J. Nucl. Mater (2003)
[3] F.C. Sze et.al., J. Nucl. Mater (1999)
[4] M.Poon, et al., J. Nucl. Mater (2005)
[5] This work

19. W erosion as function of Te and C impurity concentration*
Introduction
Erosion of tungsten by carbon
W erosion as function of Te and C impurity concentration*
*K. Schmid, J. Roth, J. Nucl. Mater (2003)

20. Experimental conditions
D ion energy, eV
Time, sec
Flux,
(m-2s-1)
Fluence,
Erosion,
nm/sec
200
1800
1× 1019
2× 1024
≤1 nm/sec
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
0.1
1× **
Thin C-W mixed layer
* T=770 K
**T=1030 K
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388
[2] K. Schmid, J. Roth, J. Nucl. Mater (2003)

21. Erosion of tungsten Experimental
Estimation: V erosion=1.5-2 μm/30 min ~1 nm/s ~6×1019 at.W/m2s
Initial surface
Closed area
Eroded surface
Plasma-impact area
Interference fringes
(Linnik micro-interferometer)

22. Erosion of tungsten by carbon
Experimental
Erosion of tungsten by carbon
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 (2005) 1-9

23. Experimental conditions
D ion energy, eV
Time, sec
Flux,
(m-2s-1)
Fluence,
Erosion,
W at./m2s
200
1800
1× 1019
2× 1024
≤6×1019
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
0.1
1× **
Thin C-W mixed layer
* T=770 K
**T=1030 K
1%C in plasma: 1018 C/m2s→ 1017 W/m2s
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388
[2] K. Schmid, J. Roth, J. Nucl. Mater (2003)

24. The threshold energies of sputtering
Experimental
The threshold energies of sputtering
Irradiation
T, K
Eth, eV
Kerosion at Ei= 400 eV
C+, N+, O+ →W
293
~35
~ 0.1
Ta+ →W ~2
D2+→W
≤0.0001
D2+→WO 65
D2+→WC
150 ≤

25. DEUTERIUM RETENTION IN TUNGSTEN AT HIGH LEVEL OF SURFACE EROSION
Experimental
DEUTERIUM RETENTION IN TUNGSTEN AT HIGH LEVEL OF SURFACE EROSION

26. Experimental conditions
D ion energy, eV
Time, sec
Flux,
(m-2s-1)
Fluence,
Erosion,
W at./m2sec
Temperature, K
200
1800
1× 1019
2× 1024
~6×1019
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
0.1
~ 1× **
Thin C-W mixed layer
* T= K
**T=1030 K
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388
[2] K. Schmid, J. Roth, J. Nucl. Mater (2003)

27. Diffusion coefficient for C in a wide concentration range for C in W*
Introduction
Diffusion coefficient for C in a wide concentration range for C in W*
*K. Schmid, J. Roth, J. Nucl. Mater (2003)

28. Experimental conditions
D ion energy, eV
Time, sec
Flux,
(m-2s-1)
Fluence,
Erosion,
W at./m2sec
Temperature, K
200
1800
1× 1019
2× 1024
~6×1019
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
0.1
~ 1× **
Thin C-W mixed layer
* T= K
**T=1030 K
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388
[2] K. Schmid, J. Roth, J. Nucl. Mater (2003)

29. Experimental conditions
D ion energy, eV
Time, sec
Flux,
(m-2s-1)
Fluence,
Erosion,
W at./m2sec
Temperature, K
200
1800
1× 1019
2× 1024
~6×1019
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
0.1
~ 1× **
Thin C-W mixed layer
* T= K
**T=1030 K
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388
[2] K. Schmid, J. Roth, J. Nucl. Mater (2003)

30. H diffusivity vs temperature for W
Experimental
H diffusivity vs temperature for W
773 K
E. Serra, G. Benamati, O.V. Ogorodnikova, J. Nucl. Mater. 255 (1998)

31. H diffusivity vs temperature for W
Experimental
H diffusivity vs temperature for W
773 K
R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388

32. H diffusivity vs temperature for W
Experimental
H diffusivity vs temperature for W
773 K
A.P. Zakharov, V.M. Sharapov, E.I. Evko, Soviet Mater. Sci. 9 (1973) 149

33. Experimental conditions
D ion energy, eV
Time, sec
Flux,
(m-2s-1)
Fluence,
Erosion,
W at./m2sec
Temperature, K
200
1800
1× 1019
2× 1024
~6×1019
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
0.1
~ 1× **
Thin C-W mixed layer
* T= K
**T=1030 K
Kdiffusion ~ 1× 10-9 m2s-1 →h=(Dt)1/2~ 1mm
[1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388
[2] K. Schmid, J. Roth, J. Nucl. Mater (2003)

34. Methods of the analysis
Experimental
Methods of the analysis
C/D-plasma irradiation: planar DC magnetron
Eions (D2+; C+; N+, O+, Ta+)= 400 eV
Flux=1×1019 D/m2s, 30 min
Mechanically & electrochemically polished
Hot-rolled tungsten foil (99.0 at.%)
Size = 6×8×0.5 mm3
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
Deuterium profiles:
Nuclear Reaction Analysis (NRA):
μm: D(3He,α)H reaction
μm: D(3He,p)4He reaction
Deuterium retention:
Thermal Desorption Spectroscopy (TDS)
D2 & HD molecules were detected by QMS
Temperature range: K
Heating rate = 3.2 K/s

35. Results & Discussion
NRA & TDS data m 6

36. Results & Discussion
NRA data 3

37. Results & Discussion
XPS data
(3 keV Ar at fluence=1×1019 Ar/m2 )

38. Results & Discussion
NRA data 3

39. Blistering in the temperature range 363-653 K
Results & Discussion
Blistering in the temperature range K
Pre-TDS; T=563 K at fluence=2× 1024 D/m2

40. Results & Discussion
TDS data

41. Results & Discussion
TDS data
T1= K
T2= K

42. Results & Discussion
TDS modeling: contributions from 1.4 eV traps and blisters (TMAP7) at 563 K

43. Three types of traps can explain our TDS data
Near-surface layer (≤ 0.5 m): 1.4 eV traps=
one D in vacancy
2. Sub-surface layer (≤ 7 m): eV=
D chemisorption on blister/bubble wall + D2 molecules inside
3. Bulk (up to 1 mm): eV traps=
D chemisorption on inner walls of small cavity and voids

44. Fitting of TDS data are in progress

45. Results & Discussion
NRA & TDS data m
Bulk trapping !

46. General experimental results
Results & Discussion
General experimental results
Strong W sputtering
Blistering
Enhanced D retention
NRA ≈ TDS from 363 to 563 K
NRA<<TDS from 563 to 773 K

47. Conclusions
General conclusions
Blistering & enhanced D retention even at strong W surface sputtering are revealed
Irradiation temperature of 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

48. Conclusions
General conclusions
Blistering & enhanced D retention even at strong W surface sputtering are revealed
Irradiation temperature of 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

49. Conclusions
General conclusions
Blistering & enhanced D retention even at strong W surface sputtering are revealed
Irradiation temperature of 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

50. Scheme of plasma-surface interaction
No erosion
D-C plasma
D  stop diffusion & retention
4 nm W
a-C:H film
Carbon-modified layer (W2C, WC)

51. Scheme of plasma-surface interaction
Erosion rate  1 nm/s
D-C plasma
 no limits for diffusion
 high retention level in bulk D
2 m
1 nm W
a-C:H film
Carbon-modified layer (W2C, WC)

52. To be or not to be for D retention in W strongly depends on irradiation parameters and surface conditions

53. Thank you for attention