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Helium Behavior and Surface Roughening of Solid Tungsten Q. Hu, M. Andersen, S. Sharafat, and N. Ghoniem University of

Helium Behavior and Surface Roughening of Solid Tungsten Q. Hu, M. Andersen, S. Sharafat, and N. Ghoniem University of California Los Angeles High Average Power Laser Meeting Naval Research Laboratory Washington, DC March 3-4, 2005. Outline. Helium Retention and Release: IFE

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Helium Behavior and Surface Roughening of Solid Tungsten Q. Hu, M. Andersen, S. Sharafat, and N. Ghoniem University of

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  1. Helium Behavior andSurface Roughening of Solid Tungsten Q. Hu, M. Andersen, S. Sharafat, and N. Ghoniem University of California Los Angeles High Average Power Laser Meeting Naval Research Laboratory Washington, DC March 3-4, 2005

  2. Outline • Helium Retention and Release: • IFE • Experiments • Modeling Surface Roughening • Defect-diffusion-deformation (EWG) • Stress-induced (ATG) • thermo-mechanical Fatigue • Conclusions & Future Directions

  3. IFE:Local APA (He/ W-atom) per shot SRIM:

  4. Comparison of DPA (Displacement / W-atom):

  5. Comparison of APA (He/W-atom):

  6. HEROS: Temperature Profile Input UNC Temperature temporal Profile: (uniform through the thickness) Temperature C 2000 850 Snead, Oct.’04 48 60 Time sec IEC Temperature = 940C (constant & uniform)

  7. current goal HEROS: Temperature Profile Input IFE Temperature Temporal Profile: (uniform through the thickness) Temperature C 1800 1200 0.2 110-3 Sharafat, June’04 Time sec Efforts are under way to reach Tmax=2800oC

  8. 6x1017He/cm2 940 °C Helium 1 mm IEC:Bubble Concentration (cm-3) Evolution E = 30 keVT = 940oC7x1015 He/cm2-s

  9. IEC:Bubble Radius Evolution 100 nm 10 nm 1 nm E = 40 keVT = 940oC7x1015 He/cm2-s

  10. Helium Snead, Oct. ‘04 UNC (angled carbon foil):Bubble Concentration (cm-3) E = 800 kev - 1200 keV; T = 850oC – 2000 oC ; He = 3x1016 He/m2

  11. 100 nm 10 nm 1 nm UNC:Bubble Radius Evolution E = 800 kev - 1200 keV; T = 850oC – 2000 oC ; He = 3x1016 He/m2

  12. Helium current planned IFE:Bubble Concentration (cm-3) Evolution Energy & Impl. Profile: Debris + Burn; Tmax=1800oC

  13. 10 nm 1 nm IFE:Bubble Radius Evolution Energy & Impl. Profile: Debris + Burn; Tmax=1800oC

  14. Comparison of Bubble Density Range During a Pulse : 1016 1015 1012 1013 1014 108 Cb (1/cm3) IFE(Burn + Debris) ~ 3 um UNC(carbon film) ~ 1.7 um IEC(40 keV) ~ 0.3 um Peak Bubble Density

  15. Why do Surfaces become Rough? • Does roughness increase or decrease? • What Determines the Length Scale? • Will Roughness Saturate? • Will Cracks form from Rough Surfaces?

  16. X-rays, Laser, and Ions all Induce Roughness Latkowski et.al, JNM, submitted Kawakami & Ozawa, Applied Surface Science 218 (2003) Nd-Yag Laser 532 nm Renk, HAPL- Feb 04, Powder Met.

  17. Helium Implantation Induces Roughness!! Tokunaga, et al., JNM, 329-333 (2004)

  18. Mechanisms of Surface Roughening Emelyanov-Wa1graef -Ghoniem (EWG) Defect diffusion coupled with deformation Asaro-Tiller-Grinfeld (ATG) Balance between surface strain (destabilizing) and curvature (stabilizing) Phys.Rev.L, in pres D. Walgraef, N.M. Ghoniem, and J. Lauzeral, "Deformation Patterns in Thin Films Under Uniform Laser Irradiation", Phys. Rev. B, 56, No. 23: 15361-15377 (1997). PDF J. Lauzeral, D. Walgraef, and N.M. Ghoniem, "Rose Deformation Patterns in Thin films Irradiated By Focused Laser Beams", Phys. Rev. Lett.79, No. 14: 2706-2709 (1997).

  19. Surface roughness due to PSB/surface interaction in a copper crystal fatigue tested. Strain amplitude of 2 x10-3, 120000 cycles [12, p.328]. Fatigue cracking is initiated at extrusions/inclusions which are formed by Persistent Slip Bands (PBS's) Ma and Laird, 1989

  20. Asaro-Tiller-Grinfeld (ATG) Instability y=a cos(wx)

  21. Asaro-Tiller-Grinfeld (ATG) Instability (cont.)

  22. Unstable Region Stable Region

  23. Unstable Region Stable Region

  24. Roughness Growth for HAPL Target

  25. Roughness Decay for Xapper

  26. Conclusions & Future Directions • Both UNC and IEC cover different regions of the APA and DPA phase space, however: • UNC Bubble concentration are lower than IFE (UNC~1015 /cm3 IFE 1016 /cm3 ) • IEC Bubbles densities are comparable with IFE, however they are very close to the surface • Based on Experiment plus IFE simulated HEROS results, high helium recycling coefficients may be achieved for IFE Tungsten Armor • Impact of large & simultaneous damage caused by D, T & n ? • Qualitative understanding of surface roughening • Role of defect-induced stresses on roughness? • Plan full-scale modeling for thermal+defect+surface evolution for IFE & Dragonfire, Xapper, and Rhepp experiments (Mike Andersen thesis topic). • Does roughness saturate, or does it lead to cracks? • Modeling fatigue failure & internal cracking with Dislocation Dynamics.

  27. Backup Files

  28. Temperature Distance Volume Diffusion Surface Diffusion T2 T1 Bubble T1 < T2 Bubble Kinetics of HEROS • The He-Bubble Release code (HEROS) now includes all major Bubble Kinetics phenomena. • Random Walk • Migration in Temp. Gradient • Bubble Volume Diffusion • Bubble Surface Diffusion • Bubble Coalescence (Brownian) • Bubble Coalescence (dT/dx) • Bubble Loss at Free Surfaces • Bubble Loss to Grain Boundaries HEROS Bubble Kinetics includes:

  29. Range in Solid Tungsten (mm) FOLLOWED by Debris:start ~1ms; end ~ 2ms ? FIRST the “Burns”:start ~ 0.1ms; end ~1ms 4He Debris and Burn Spectra

  30. Bubble Kinetics Reaction By Vol Diffusion: +Drift By Surf Diffusion: By Vol Diffusion: + Coalescence By Surf Diffusion: + Surface Loss In first 0.1m:

  31. Tungsten Helium 100 mm Precipitates Dislocation Lines Grain Boundaries HEROS: Spatial Model Includes

  32. Determine APA and DPA Profiles in W per Shot APA : He-atom / W-atom DPA : Displacement / W-atom (damage) • SRIM: Input - Ion Type, Ion Energy, Target MaterialOutput - DPA/ion, Ion Range, other damage statistics • Threat data is only known at specific ion energies. • Pick small bin-size to interpolate between known data points. • Add Damage and Ion Range of all energies and interpolate to get DPA and APA distributions in target material.

  33. IFE:Local DPA (Displacement / W-atom) SRIM:

  34. IEC:Local APA (He/ W-atom) SRIM:

  35. IEC:Local DPA (Displacement / W-atom) SRIM:

  36. Snead, Oct. ‘04 UNC(angled carbon film):Local APA (He/ W-atom) SRIM:

  37. UNC (angled carbon film):Local DPA (Displacement / W-atom) SRIM:

  38. Renk, Oct’04 Dummer, 1998: as received Tungsten Baklava Structure of RHEEP Exposed W-Samples

  39. Mostly along GB Diffusion much faster along GB Self Diffusion in Tungsten

  40. Parameters P. Bettler and F. Charbonnier, “Activation energy for the surface migration of tungsten atoms in the presence of a high-electric field,” Phys. Rev., Vol 119(1), p.85-93, 1960. Qs = 3.14 eV without field, and 2.44 eV with field.

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