Chamber Materials - overview and plans

1. OFES Supported Materials Research • Fatigue thermomechanics (Ghoniem presentation) • High temperature swelling of graphite fiber composite Critical issues from Chamber Materials Plan (HAPL) • Transmissive Optics Formation and annealing of absorption centers Modeling of cascade and surviving defects in silica • Reflective Optics Laser induced damage threshold Environmental effects (dust/debris) Modeling surface modification under repetitive pulsing • Structural Materials Metallic structure - fatigue and pulsed irradiation effects Composite System - CFC lifetime Refractory Armored Composites - basic fabrication and performance Modeling - Defect formation and migration in graphite • Safety Tritium retention in graphite Chamber Materials - overview and plans

2. Materials Working Group Effort Advisory Group, including: Jake Blanchard (UW) Nasr Ghoniem (UCLA) Gene Lucas (UCSB) Lance Snead (ORNL) Steve Zinkle (ORNL) • Transmissive Optics (Zinkle) • Reflective Optics (Zinkle, Blanchard, Ghoniem) • Structural Materials (Snead, Ghoniem, Blanchard, Lucas) • Safety (Snead)

3. Critical Path Issues - Graphite Composite Kiss of Death Tritium retention(for graphite) Co-deposition Swelling and Lifetime Crucial Fatigue Properties Thermal conductivity RES (for graphite) Procrastinate Design codes Manufacturing large structures Designing 100% elevated temperature structure Composite architectural design

4. OFES Swelling of CFC’s

5. Critical Path Issues Refractory Armored Materials Kiss of Death Material development Fatigue Properties Exfoliation due to ions Issues relating to structural material Crucial Thermal contact resistance and thermal conductivity Embrittlement (W grain growth, hydrogen effects, irradiation) In-situ or ex-situ repair Differential thermal and irradiation expansion Procrastinate Manufacturing large structures Tungsten mobility/safety issues ???

6. Refractory Armored Composites • Data mining completed - refractory armored graphite fiber composites appear hopeless for IFE - W - SiC system unstable ~ above 1200°C - Mo - SiC system unstable ~ above 1400°C • Development program underway (ORNL) - Refractory : Tungsten (W-Re), Moly (Mo-Re, Mo-Zr-B) - SiC : CVD beta-SiC, Hot Pressed alpha-SiC, SiC/SiC • Castellated surface modeling (Blanchard U.W.) Refractory powder Titanium Refractory SiC SiC SiC Refractory powder First substrate castellation: 200 mm deep x 200 mm wide SiC

7. Infrared Rapid Melt Processing and Thermal Shock 5 MW/m2 60 ms 10 ms, ? MW/m2 bursts SiC Specifications: Argon plasma (up to 1MW) Pulse length : 10 ms (no shuttering) Rep Rate : 5-10 Hz Maximum heat flux at maximum area : 5 MW/m2 at 2.5 x 35 cm Maximum heat flux attainable :12. 5 MW/m2 at 2.5 x 20 cm

8. Discovery of Unprecedented Strength Properties in Iron Base Alloy ODS ferritic • Time to failure is increased by several orders of magnitude • Potential for increasing the upper operating temperature of iron based alloys by ~200°C. Work being pursued by DOE OFES, DOE Fossil Energy, others • IFE will explore grading of new W containing ferritics to W armor

9. Input into Optics S.J. Zinkle, et al. HAPL IFE Program Workshop San Diego, April 4-5, 2002 NRL IFE 2/2001

10. Methodology for selecting candidate radiation-resistant transmissive optics • Initial list of ~100 optical materials was screened to select materials with high transparency between 200 and 500 nm • Numerous optical materials rejected due to too low of band gap energy (e.g., carbides and most nitrides) • Requirement of Eg>4 to 6 eV (UV cutoff <200-300 nm) eliminates many promising candidates, including SiC, ZnO, TiO2, LiNbO3 and SrO (DPSSL and KRF); and MgO, ZrO2, Y2O3 and zircon (for KrF) • Radiation effects literature reviewed for remaining candidates to select most promising candidates

11. Original List of Candidate Optical Materials (transparent at 200-500 nm)

12. Candidate Radiation-resistant Optical Materials (no radiation-induced absorption peaks near 248 or 351 nm) Alkali halides (NaBr, KCl, etc.) are less promising due sensitivity to radiolysis (displacement damage from ionizing radiation)

13. Dielectric Mirrors •Previous work on irradiation damage in dielectric mirrors showed poor performance - LANSCE irradiation, ~100°C, many dpa - Layered silica structures, glassy substrates More radiation stable materials are being assembled for irradiation - Sapphire substrate - TiO2 (CTE 6.86 E-6) high-Z layer - Al2O3 ( CTE 6.65E-6) low Z layer - MgAl2O4 (CTE 6.97E-6) low Z layer

14. IFE Optics Irradiation • Capsules to be irradiated to 0.001, 0.005, 0.01 and 0.05 dpa. Irradiation temperature tentatively 300°C • Reflective optics for LIDT measurement supplied by Tillack (Aluminum, SiC, Molybdenum) • Transmissive optics by Payne and Zinkle (KU-1 and Corning fused silica, oxides tbd based on white paper) • Dielectrics by Snead and Payne (Sapphire sub. TiO2/MgF2 bilayer, Sapphire and TiO2/MgAl2O4) • Samples to be shipped to LLNL following irradiation • Status : Design work complete, safety documentation under review Capsule parts on order, samples on their way

15. Subwavelength Mirrors • Subwavelength mirrors use periodic features of order l/3 to l/2 to form a surface waveguide which reflects light in a narrow waveband with very high reflectivity (as high as 99.9%). • Higher reflectivity allows the use of smaller mirrors. • Current research is for near-IR wavelengths. Near-UV wavelengths would simply require smaller feature size. • Anti-reflectivity coatings can be used to protect the mirror surface. • This technology is only in the development stage. Transparent Coating Reflective Substrate

16. Anti-reflective protective coatings • Transparent anti-reflective coatings can be used to protect the surface of IFE mirrors. • Mechanical damage to the anti-reflective coating from debris would not effect the reflective properties of the underlying mirror surface. • Roughening of the anti-reflective coating is not necessarily detrimental to its operation. • Radiation induced change to absorption in the coating would still be an issue, but the coating would be much thinner than a transmissive optic.