1. 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
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2. 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
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3. 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 Shots.
For Cu, Single Shot Values ~ 10 J/cm2.
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4. 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
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5. Laser-Induced Damage Threshold (LIDT)
Laser-Induced Damage Threshold (LIDT) is
a strong function of material & # of shots
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6. 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
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7. DEFORMATION INSTABILITY MECHANISMS IN SINGLE SHOT
Physical Mechanism of Feedback in Point Defect GDDI: Laser Intensity Distribution
Related Equations
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8. 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)
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9. EXPERIMENTAL OBSERVATIONS OF SURFACE DEFORMATION PATTERNS
UNIFORM
FOCUSED
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10. SURFACE STEP FORMATION
BY DISLOCATIONS
Edge
Experiment
Screw
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11. Importance of Dislocation-Surface Interactions
Surface roughness due to PSB/surface interaction in a copper crystal fatigue tested. Strain amplitude of 2 x10-3, cycles [12, p.328].
Ma and Laird, 1989
Fatigue cracking is initiated at extrusions/inclusions which are formed by Persistent Slip Bands (PBS's)
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12. 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
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13. 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
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14. Computer Simulations of Dislocation-Surface Interactions
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15. 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
Heat of Dissociation
Reaction Enthalpies
Ionization Potentials
2. 3 Thermodynamic data of Sn-silicates
Specific heat (cp) of Sn-silicates as a function of temperature
2. 4 The Sn-H System
Hydrogen Solubility
Absorption of Hydrogen
H2-Adsorption
H2-Diffusion Coefficient
Reduction of Sn by atomic hydrogen
The SnH and SnD Molecule
Solubility of the gas composition H2-CO-CO2
2. 5 The Sn-Li System
Formation of Li2SnO3*
Stability of Li2SnO3*
2. 6 The Sn-C System
Solubility
The Sn-C Molecule
The SnCO3 Molecule
2. 7 The Sn-Si System
Diffusion of Sn in solid Si
The Sn-Si Molecule
2. 8 Sn and Oxygen
Low Pressure Oxidation
Oxidation Mechanism:
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
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