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RHEPP Tungsten Update

RHEPP Tungsten Update. Tim Renk Sandia National Laboratories Beam Applications & Initiatives Department HAPL Program Workshop Atlanta, GA February 6, 2004. Supported by NRL by the HAPL program by DOE NNSA DP.

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RHEPP Tungsten Update

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  1. RHEPP Tungsten Update Tim Renk Sandia National Laboratories Beam Applications & Initiatives Department HAPL Program Workshop Atlanta, GA February 6, 2004 Supported by NRL by the HAPL program by DOE NNSA DP Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,for the United States Department of Energy under contract DE-AC04-94AL85000.

  2. Pulsed Power Sciences, Sandia National Laboratories TJR 11/25/03 400 shot Map N shots on Tungsten (Room Temperature): Roughening only above threshold • Polished W exposed to 400 shots N beam: 1.0 < fluence < 3.7 J/cm2 • Room Temp (RT) exposure • Roughening occurs above 1.25 J/cm2, consistent with single-shot reflectometer roughening threshold • Powder Met Mo (one point at 2.5 J/cm2 ): roughness stays near unexposed value • Above threshold, roughening is a severe function of fluence. Maximum Ra exceeds 22 µm, with P-V height above 70 µm

  3. Pulsed Power Sciences, Sandia National Laboratories TJR 11/25/03 W (Powder Met) roughening: SEM images as function of shot number: 60 to 1000X (N 60X @ 6 J/cm2) (N 250X @ 2.5 J/cm2) He 450X @ 1-1.3 J/cm2) (N 600X @ 4.0 J/cm2) (N 1000X @ 2.5 J/cm2)

  4. Pulsed Power Sciences, Sandia National Laboratories TJR 11/25/03 60-shot exposure of PM W (500C) @ 6 J/cm2: Resolidification from 2-3 µm depth, consistent with SIM modeling, no cracking Hi-Mag image, showing uniform single-xtal (right) and disordered single-xtal (left) In depth grains (N 1000X @ 2.5 J/cm2) Simulation results: Melt Depth: 2.3 µm Melt Duration: 627 ns MaxTemp: 6648K I.e. above ablation threshold (for 65 ns) Ra = 0.4-0.6 µm Ablation step: 1-2 µm (165 - 330Å/pulse)

  5. Pulsed Power Sciences, Sandia National Laboratories TJR 11/25/03 XTEM of 60X-treated PM W (right) show no cracking in depth Bright-Field TEM image TEM image from 5 µm depth

  6. Pulsed Power Sciences, Sandia National Laboratories TJR 11/25/03 FIB-XTEM of 1000-pulse W at 2.25 J/cm2 (ave): Deep horizontal/vertical cracking without melt • Polished Powder Met W exposed to 100 shots N beam @ 2.25 J/cm2 ave /pulse, ~ melting temperature at surface. No melt layer observed. • 600°C exposure • Sample cracking horizontally/vertically down to 10 µm depth • Suspect fatigue-cracking Near-surface 5 - 10 µm depth

  7. Pulsed Power Sciences, Sandia National Laboratories TJR 11/25/03 FIB-STEM of 1000-pulse W at 2.25 J/cm2 (ave): No melting or recrystallization evident Near-surface 5 - 10 µm depth Simulation results: Melt Depth: 0.2 µm Melt Duration: 91 ns MaxTemp: 3752K (from 600C) Ra = 2.3 - 4.5 µm

  8. Pulsed Power Sciences, Sandia National Laboratories TJR 2/4/2004 We may have an alternative ‘Foam’ Supplier Source: Center for Collaborative Research/Research Center for Advanced Science and technology (CCR/RCAST) Prof. Tatsuhiko Aizawa • Type1: W-25Re alloy, cell-structured No carbon, only W-25Re alloy Column thickness: 50-100 µm Pore: < 50 µm • Type 2: W-25Re Alloy, honeycomb No carbon, only alloy column thickness: 100 µm • Prof. Aizawa to visit SNL March 22, 2004

  9. Pulsed Power Sciences, Sandia National Laboratories TJR 11/25/03 Summary • Tungsten: surface roughening excessive (PowderMet), with fatigue cracking below surface maybe even worse. Mitigating: CVD/SingXtal, alloying with Re, heating. Cracking looks like enough to compromise performance as armor coating. • Roughening occurs over hundreds of shots. Topology may stabilize for W by 1000 shots, looks to increase for other metals beyond this. • Below the roughening threshold (1.25 J/cm2), W may be topologically stable to repeated ion exposure. • No W recrystallization below melting temp appears to take place • Both 60X-6J/cm2 and 1000X-2.5J/cm2 sample response consistent with SIM modeling • Next: treatment of W on SiC, extended treatment of various samples to 2,000 shots

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