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Analysis of Deuterium Retention in Carbon-Seeded Tungsten Exposed to Plasma

This study investigates the retention of deuterium in tungsten exposed to carbon-seeded deuterium plasma. It explores the effects of substrate temperature and carbon deposition on deuterium retention. Results indicate that carbon contamination significantly increases deuterium retention in tungsten, primarily residing in carbon films formed during the deposition process. Additionally, the characteristics of the tungsten surface, such as the formation of blisters and pits, are influenced by temperature variations. These findings have implications for material migration and erosion in nuclear fusion environments.

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Analysis of Deuterium Retention in Carbon-Seeded Tungsten Exposed to Plasma

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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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