Laser Effects on IFE Final Optics N. M. Ghoniem University of California, Los Angels (UCLA) Laser IFE Program Workshop Naval Research Laboratory February 6 & 7, 2001 Tuesday, February 6, 2001 9/17/2018

Scope of Fusion Materials Research at UCLA Project Objectives (1) Modeling microscopic laser damage; (2) Computer-Aided-Design of IFE optics; (3) Optimization of experiments at UCSD/GA for laser damage resistant materials. Laser Effects On IFE Final Optics 1 (1) Flow localization & fracture; (2) Radiation hardening; (3) He effects on grain boundary fracture; (4) Segregation effects on fracture; (5) Ductile-to-brittle-transition (DBTT). Plastic & Fracture Instabilities 2 (1) Multiscale modeling of structure evolution; (2) Non-equilibrium phase stability; (3) Temperature & flux transient effects; (4) Computational design of fusion alloys. Design of Materials by Computer Simulations 3 9/17/2018

Research Motivation Successful Development of Laser Optics for Long-term Operation is Vital to Laser IFE Systems. The magnitude of Laser-Induced Damage Threshold (LIDT) Determines Reactor Economics. LIDT is a Strong Function of Number of Shots, and Degrades by a factor of 10, After only 10000 Shots. For Cu, Single Shot Values ~ 10 J/cm2. 9/17/2018

Summary of Experimental Observations on Laser Damage >120 60 120 Periodic void >1.2 Spot Melting 1.2 Star relief 0.6 0.9 Irregular relief <60 110-3 <0.6 Ti Hole-like 0.48 Periodic Cell 0.76 ? Sparse dots 0.16 210-8 <10 GaP 0.36 Grating 0.013 ~0.64 1~5 Ge 0.3 0.2 110-13 0.050.1Wm GaAs Star-like <10-4 510-11 2 VO2 Reflectivity Deformation Type E(J/cm2) LIDT p(s) P(MW/cm2) Material 9/17/2018

Laser-Induced Damage Threshold (LIDT) Laser-Induced Damage Threshold (LIDT) is a strong function of material & # of shots 9/17/2018

SURFACE DEFORMATION MECHANISMS Single Shot Effects on LIDT: Laser Heating Generates Point Defects Coupling Between Diffusion and Elastic Fields Lead to Permanent Deformation Progressive Damage in Multiple Shots Thermoelastic Stress Cycles Shear Atomic Planes Relative to one Another (Slip by Dislocations) Extrusions & Intrusions are Formed when Dislocations Emerge to the Surface 9/17/2018

DEFORMATION INSTABILITY MECHANISMS IN SINGLE SHOT Physical Mechanism of Feedback in Point Defect GDDI: Laser Intensity Distribution Related Equations 9/17/2018

SINGLE-SHOT EXPERIMENTS & MODELING Focused Laser-induced Surface Deformation Uniform Laser-induced Surface Deformation Computer Simulation Experiment Computer Simulation (Walgraef, Ghoniem & Lauzeral, Phys. Rev. B, 56, 23, (1997) 1536) Focused laser-induced surface deformation (Lauzeral, Walgraef & Ghoniem, Phys. Rev. Lett. 79, 14 (1997) 2706) 9/17/2018

EXPERIMENTAL OBSERVATIONS OF SURFACE DEFORMATION PATTERNS UNIFORM FOCUSED 9/17/2018

SURFACE STEP FORMATION BY DISLOCATIONS Edge Experiment Screw 9/17/2018

Importance of Dislocation-Surface Interactions Surface roughness due to PSB/surface interaction in a copper crystal fatigue tested. Strain amplitude of 2 x10-3, 120000 cycles [12, p.328]. Ma and Laird, 1989 Fatigue cracking is initiated at extrusions/inclusions which are formed by Persistent Slip Bands (PBS's) 9/17/2018

Motivation Behind Mesoscale Simulations Single-crystal plasticity Rules for dislocation motion and interaction (1mm- 100mm) Macroscale Poly-crystal plasticity Macroscopic constitutive relations Atomic scale (Å) Success depends on developing accurate 3-D dislocation dynamics models 9/17/2018

Dislocations Interact with Surfaces Before Forming Steps Internal Force field Black=Applied forces, Red= Image forces, Blue= Self forces Slip system: (101) [-111], 11 = 50 MPa 9/17/2018

Computer Simulations of Dislocation-Surface Interactions 9/17/2018

Dislocation-Surface Interaction Leads to Roughness Table of Contents 1. Thermophysical Properties 1. 1 Specific Volume of Sn 1. 2 Density of Sn 1. 3 Volumetric expansion coefficient () of liquid Sn: 1. 4 Compressibility 1. 5 Viscosity: 1. 6 Surface Tension: 1. 7 Vaporization 1. 8 Boiling Point 1. 9 Heat of Sublimation (Ls) and Vaporization (Lv): 1. 10 Critical Pressure (pc), Temperature (Tc), and Volume (Vc) 1. 11 Heat Capacity 1. 12 Electrical Resistivity () of liquid Sn 2. Thermodynamic Properties of Sn 2. 1 Enthalpy, Specific Heat, and Entropy of Sn-Vapor 2. 2 Heat of Dissociation, Reaction Enthalpy, and Ionization Potentials of Various Tin-Compounds 2. 2. 1 Heat of Dissociation 2. 2. 2 Reaction Enthalpies 2. 2. 3 Ionization Potentials 2. 3 Thermodynamic data of Sn-silicates 2. 3. 1 Specific heat (cp) of Sn-silicates as a function of temperature 2. 4 The Sn-H System 2. 4. 1 Hydrogen Solubility 2. 4. 2 Absorption of Hydrogen 2. 4. 3 H2-Adsorption 2. 4. 4 H2-Diffusion Coefficient 2. 4. 5 Reduction of Sn by atomic hydrogen 2. 4. 6 The SnH and SnD Molecule 2. 4. 7 Solubility of the gas composition H2-CO-CO2 2. 5 The Sn-Li System 2. 5. 1 Formation of Li2SnO3* Stability of Li2SnO3* 2. 6 The Sn-C System 2. 6. 1 Solubility 2. 6. 2 The Sn-C Molecule 2. 6. 3 The SnCO3 Molecule 2. 7 The Sn-Si System 2. 7. 1 Diffusion of Sn in solid Si 2. 7. 2 The Sn-Si Molecule 2. 8 Sn and Oxygen 2. 8. 1 Low Pressure Oxidation 2. 8. 2 Oxidation Mechanism: 2. 8. 3 Solubility of O in Sn 2. 9 The SnO-SiO2 System 2. 10 General Literature on Corrosion of Sn with Metals: High Density Low Density 9/17/2018