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Outline Introduction Experimental Results & Discussion Conclusions

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Outline Introduction Experimental Results & Discussion Conclusions

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  1. DEUTERIUM RETENTION IN TUNGSTENEXPOSED 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 • Introduction • Experimental • Results & Discussion • Conclusions *This work was supported by the United States Department of Energy under Contract 512244 with Sandia National Laboratories

  2. Introduction Irradiation conditions [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

  3. Introduction Irradiation conditions [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

  4. Introduction Material migration in divertor tokamaks Distribution of erosion/deposition areas in the JET divertor (1999-2001)* *P.Coad, et al., J. Nucl. Mater. 313-316 (2003) 419

  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) Introduction Erosion of carbon by deuterium 100 *G.F. Matthews, J. Nucl. Mater. 337-339 (2005) 1-9

  6. Introduction Material migration in divertor tokamaks Scheme of erosion/re-deposition processes within the divertor* *G.F. Matthews, J. Nucl. Mater. 337-339 (2005) 1-9

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

  8. 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. 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. 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. 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. 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) Introduction Erosion of tungsten by carbon 100 *G.F. Matthews, J. Nucl. Mater. 337-339 (2005) 1-9

  13. W erosion as function of Te and C impurity concentration* Introduction Erosion of tungsten by carbon *K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310

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

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

  16. Experimental Irradiation conditions [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

  17. Experimental Irradiation conditions *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. 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

  18. Experimental Irradiation conditions [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

  19. W erosion as function of Te and C impurity concentration* Introduction Erosion of tungsten by carbon *K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310

  20. Experimental Experimental conditions * T=770 K **T=1030 K [1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388 [2] K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310

  21. Experimental Erosion of tungsten 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. 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) Experimental Erosion of tungsten by carbon *G.F. Matthews, J. Nucl. Mater. 337-339 (2005) 1-9

  23. Experimental Experimental conditions * 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. 313-316 (2003) 302-310

  24. Experimental The threshold energies of sputtering

  25. Experimental DEUTERIUM RETENTION IN TUNGSTENAT HIGH LEVEL OF SURFACE EROSION

  26. Experimental Experimental conditions * T= 773 K **T=1030 K [1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388 [2] K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310

  27. Diffusion coefficient for C in a wide concentration range for C in W* Introduction *K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310

  28. Experimental Experimental conditions * T= 773 K **T=1030 K [1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388 [2] K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310

  29. Experimental Experimental conditions * T= 773 K **T=1030 K [1] R. Fraunfelder, J. Vac. Sci.Technol. 6 (1969) 388 [2] K. Schmid, J. Roth, J. Nucl. Mater. 313-316 (2003) 302-310

  30. Experimental H diffusivity vs temperature for W 773 K E. Serra, G. Benamati, O.V. Ogorodnikova, J. Nucl. Mater. 255 (1998) 105-115

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

  32. 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 Experimental conditions * T= 773 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. 313-316 (2003) 302-310

  34. 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): • 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

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

  40. Results & Discussion TDS data

  41. Results & Discussion TDS data T1=650-710 K T2=900-1000 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): 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

  44. Fitting of TDS data are in progress

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

  46. 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 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

  48. Conclusions 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

  49. Conclusions 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

  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)

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