M. S. Tillack, J. E. Pulsifer, K. Sequoia Final Optic Research – Progress and Plans HAPL Project Meeting, Georgia Tech 5–6 February 2004

Overview 1.Expanded database on electoplated Al 2.Mechanical and optical improvements 3.Near-term plans –Scale-up –Distribution of samples –Efforts to improve mirror quality –Gasdynamic modeling –Integration

5-yr plan and progress to date startKrFtoday initial promising results at 532 nm attempts at thin film optics Phase I evaluation lower limits at 248 nm, chemistry control electroplate success

Percent Completion Phase I – February 2004 A. Quantify the threats (LIDT, x-ray, ion, neutron/gamma) B. Develop mitigation techniques C. Fabrication and integration (tasks extracted from Dec. 11, yr final optic plan)

Testing of electroplated Al continues

Ideally, fluence limits would be purely thermomechanical in nature Metals under primary stress usually follow a power law fatigue behavior

Our data doesn’t fit a power law very well 2 J/cm 2

R 2 = if we use a simple log fit

Damage morphology: moderate fluence At 18.3 J/cm 2 laser fluence:  Grain boundaries appear to be separating  Damage is still “gradual” at 18.3 J/cm 2

Damage morphology: high fluence At 33 J/cm 2 laser fluence:  Rapid onset (2 shots)  Severe damage (melting)  probably starts with grains

Do we shoot for years, buy a kHz laser, or perform accelerated testing? Palmgren-Miner rule: damage accumulated at different stresses is additive n i = number of cycles at stress level i N i = fatigue limit at stress level i

Precipitation hardening could extend the damage threshold 20 J/cm 2

Key questions for nano-precipitate hardened alloys Will scattering and absorption be acceptable with a small percentage of nano-scale 2nd phase material?  optical modeling of absoprtion and scattering Will the yield strength be improved under the constraints of particle size and fraction?  mechanical modeling Will something else go wrong?  experimental demonstration is needed (misfit)

Beam quality with incipient damage If incipient damage does not exceed the 1% beam perturbation criterion, then mirror damage occurs first (y scan)

5-yr plan starttoday 1. scale-up & testing 4. system definition improvements (material & optical) 2. irradiation testing (LLNL) 3. mitigation studies Phase I evaluation

FY04 plans: (1) Scale up Intermediate step between present (1-2”) and final ( cm) optic sizes Fabricate mirrors for testing on HAPL lasers ( J, 5-10 Hz) Increased attention to surface figure as well as microstructure morphology Near-term plan: –fabricate larger versions of Al on Al-6061 –with Schafer, procure Al on SiC mirrors –test on Electra this summer –test on Mercury

FY04 plans: (2) Sample distribution Radiation damage tests should use the reference optic –Al on Al-6061 can be obtained in 2-4 weeks (discussions with Alumiplate and ii-vi are underway) –Al on SiC tests should wait for validation We need protocols for characterization and testing Whoever needs optics, let’s talk.

FY04 plans: (3) Gasdynamic Modeling Contamination transport from the chamber to the optic –use computed velocity fields to track the motion of an embedded particle Chamber response to gas puffing –include a small blob of high-pressure chamber gas at the optic immediately preceding target yield

FY04 plans: (4) Integration Define the optical system in enough detail to deter- mine whether there are issues requiring R&D, e.g., –Develop the target/driver interface further (w/ GA) –Specify the beam steering and wavefront control methods ( e.g., where will these be achieved?) –Cooling and other mechanical design issues Define the design requirements and reference parameters in greater detail –Design lifetime: 10 8 shots –Operating temperature: 30˚C –Reflected beam smoothness: 1% (could tolerate more?) Need to organize the “final optic working group”

Final Optic Working Group

FY 2001|FY 2002|FY 2003 |FY 2004|FY2005 FY 2001|FY 2002|FY 2003 |FY 2004|FY2005 Original Final Optics Program Plan Scoping Tests: Irradiation & PIE (incl. annealing) Extended testing of prime candidates CONTAMINATION THREATS ModelingTest simulated contaminants ION SPUTTERING Calculate sputtering, gas attenuation X-RAY ABLATION Scoping tests (laser-based x-ray source) Damage modeling LIDT scoping tests for GIMM, materials development Mitigation Laser damage modeling, 3  data from NIF Modeling Mitigation RADIATION DAMAGE (neutron and gamma effects ) System Integration LASER-INDUCED DAMAGE