Optic Technologies Enabling Fusion Ignition

Tayyab I. Suratwala, PhD, is the Program Director for Optics and Materials Science & Technology (OMST) in the NIF & Photon Science Directorate at Lawrence Livermore National Laboratory (LLNL). He has 28 years of experience in optical fabrication and materials processing. C. Wren Carr, PhD, is a Group Leader for Science & Technology for OMST at LLNL. He has 25 years of experience in the field of laser-induced damage in optical materials. Christopher J. Stolz is the former Group Leader for Optics Supply for OMST at LLNL. He has 36 years of experience in high fluence multilayer optical coatings and optical fabrication.

• List of Figures xvList of Contributors liiiPreface lvAcknowledgments lixGlossary of Symbols and Abbreviations lxi1 Introduction – Path to Ignition Enabled by Optics 1Tayyab I. Suratwala1.1 Ignition 11.2 National Ignition Facility 51.3 NIF Large Optics 71.3.1 Optic Technologies Development 81.3.2 Laser Damage Reduction 131.3.3 Optics Recycle Loop Strategy 151.3.4 Loop Management and Performance 181.3.5 Ingredients for Success 201.4 Book Organization 22References 24Part I Optic Manufacturing Technologies 292 NIF Optics 31Christopher J. Stolz, Kathleen I. Schaffers, Lana L. Wong, and Hoang T. Nguyen2.1 NIF Optics Functionality 312.2 Front-End and Diagnostic Optics 352.3 Amplifier Optics 372.3.1 Laser Glass 372.3.2 Cladding 392.3.3 Blast Shields 392.4 Vacuum Barriers and Focusing Optics 402.4.1 Spatial Filter Lenses (SF1-4) 402.4.2 Vacuum Windows (SW, TCVW, and GDS) 422.4.3 Off-Axis Wedged Focus Lens (WFL) 432.5 Beam-Steering Optics 442.5.1 Cavity Mirrors (LM1-2) 452.5.2 Transport Mirrors (LM4-8) 462.6 Polarizing Optics and Frequency Conversion 492.6.1 Polarizing Optics (PL, SC, and PR) 492.6.2 Frequency Conversion Crystals (SHG and THG) 512.7 Beam-Formatting Optics (Continuous Phase Plates) 522.8 Debris-Shield Optics 542.8.1 Disposable Debris Shield (DDS) 542.8.2 Fused-Silica Debris Shield (FSDS) 552.8.3 Grating Debris Shield (GDS) 562.9 Short Pulse Optics for Advanced Radiographic Capability (ARC) 582.10 Summary 65References 653 Optics Industry, Facilitization, and Sustainability 73ChristopherJ.Stolz3.1 Vendor Partnership Strategy 733.1.1 Technology Development 743.1.2 Facilitization 753.1.3 Pilot Production 793.1.4 Production 803.2 Manufacturing Rate Improvement 823.2.1 Continuous Melting of Laser Phosphate Glass 823.2.2 Fabrication of Crystal Optics 823.2.3 Grinding Technology of Glass Optics (ELID) 853.2.4 Computer Controlled Polishing of Fused-Silica Optics 863.3 Strategies for Robust Optics Supply 883.3.1 Competitive Versus Sole Source 883.3.2 Minimizing Optics Supply Risk 903.4 Institutional Partnerships 923.5 Sustainability for Multi-decade Operations 933.6 Summary 94Acknowledgments 94References 944 Nd-Doped Laser Phosphate Glass 99Tayyab I. Suratwala and Paul Ehrmann4.1 Introduction 994.2 Glass Composition and Properties 1004.3 Continuous Melting 1024.4 OH Content 1054.5 Fracture 1094.5.1 Slow Crack Growth 1094.5.2 Surface Tension via OH Diffusion 1124.6 Corrosion Resistance 1154.6.1 Weathering 1154.6.2 Haze: Ceria Reactivity with Surface 1194.7 Pt Inclusions 1224.8 Impurities 1244.9 Glass Quality, Selection Rules, and Performance 126Acknowledgments 130References 1305 KDP and DKDP Crystals 135Kathleen I. Schaffers and Tayyab I. Suratwala5.1 Introduction 1355.2 Crystal Composition and Properties 1365.3 KDP and DKDP Growth Technologies 1385.4 Technical Challenges 1425.4.1 Crystal Growth to Large Size 1425.4.2 D/H Exchange (E-Cracking) 1455.4.3 Reaction with Humidity (Etch Pits) 1485.4.4 Laser-Induced Surface Roughening in a Vacuum 1515.4.5 Fracture 1525.4.6 Liquid Inclusions 1555.4.7 Bulk Laser Damage and Laser Conditioning 1565.5 Summary 159Acknowledgments 159References 1596 3ω Finishing 163Tayyab I. Suratwala6.1 Sub-surface Mechanical Damage 1646.1.1 Grinding SSD Management 1646.1.2 Polishing SSD Management 1676.1.3 Scratch Forensics 1706.2 Role of Chemical Etching 1726.2.1 Strip Etch 1736.2.2 Bulk Etching 1746.2.3 Chemical Impurity Removal 1786.3 Strategy for 3ω Finishing and Production Impact 178References 180Part II Optic Laser-Induced Damage Reduction Technologies 1837 Laser-Induced Damage Mechanisms 185C. Wren Carr7.1 Laser-Induced Damage Process and Location Implications 1857.2 Initial Absorption 1877.3 Types of Laser-Induced Damage 1887.3.1 Gray Haze 1887.3.2 Exit Surface Damage on SiO 2 Glass 1897.3.3 Bulk Damage in KDP and DKDP 1917.3.4 Damage in MLD Coatings 1937.4 Initial Absorption Mechanisms 1947.4.1 Initial Absorption by Intrinsic Mechanisms 1947.4.2 Initial Absorption by Extrinsic Mechanisms 1967.5 Secondary Absorption 2017.6 Material Response 2057.6.1 Material Response After Damage 2057.6.2 Material Response Without Damage 210References 2108 Laser-Damage Measurement and Analysis Methods 215David A. Cross and C. Wren Carr8.1 Introduction 2158.1.1 Why Are Laser-Damage Measurements Needed? 2158.1.2 Misconceptions Concerning Laser Damage 2168.2 Measurement 2198.2.1 Material Laser Exposure 2198.2.2 Material Response 2218.3 Analysis 2238.3.1 Multimodal Registration 2238.3.2 Damage-Initiation Measurements 2278.3.3 Damage-Growth Measurements 232References 2379 Parameters Affecting Laser-Induced Damage Initiation and Growth 241Raluca A. Negres and C. Wren Carr9.1 Introduction 2419.2 Initiation 2439.2.1 Fluence, Wavelength, and Optic Quality 2449.2.2 Pulse Length and Shape 2459.2.2.1 Nanosecond Pulse-Width Regime 2459.2.2.2 Picosecond Pulse-Width Regime 2479.3 Growth 2489.3.1 Multi-shot Growth Behaviors 2499.3.1.1 Fluence, Wavelength, and Location 2499.3.1.2 Multi-wavelength Irradiation 2509.3.2 Single-Shot Growth Behaviors 2519.3.2.1 Probability of Growth 2539.3.2.2 Growth Rate 2579.4 Summary 261References 26210 Advanced Mitigation Process (AMP) 267Diana VanBlarcom10.1 Introduction 26710.2 Development of the AMP Process 26810.2.1 Etching to Mitigate Scratches 26910.2.2 Etching to Mitigate Chemical Impurities 27310.3 Production Implementation 27710.3.1 AMP Station 27710.3.2 AMP Recipes 27810.3.3 Post-AMP Surface Degradations 27910.3.4 AMP Production Rates 28110.3.5 Quality Assurance and Safety 28210.4 Conclusions and the Future of AMP 283References 28311 Debris-Induced Damage Reduction on 3ω-Fused-Silica Optics 285Rajesh N. Raman, Christopher F. Miller, and C. Wren Carr11.1 Evidence of a New Damage Source 28511.1.1 High Online Damage Initiation Rates After AMP 28511.1.2 Damage Spatial Distribution 28611.1.3 Debris on Optic and Damage Morphology 28811.1.4 Debris Morphology and Composition 29011.2 Sources of Debris 29211.3 Physics of Debris-Induced Laser Damage 29311.3.1 Deposition Mechanism 29311.3.2 Material Type 29611.3.3 Fluence and Particle Size 30211.4 Mitigation of Debris-Induced Damage and Impact 30311.4.1 Antireflection Coating on Grating Surface of GDS 30411.4.2 Fused-Silica Debris Shield (FSDS) to Protect GDS 30511.4.3 Metal Barriers to Block Debris Transit 30711.4.4 Laser Cleaning 308References 30912 Silica Sol–Gel Antireflective Coatings 311StephenH.Mezyk12.1 Introduction 31112.2 Single Layer Antireflective Optical Coatings 31312.3 Stöber Silica Sol–Gel 31512.4 Chemically Processing Stöber Silica for Enhanced Mechanical and Environmental Stability 31612.5 Wet-Film Deposition Processes 31912.6 Ellipsometry for Process Control 32012.7 Volume Production of Sol–Gel Thin Films 32312.8 Conclusion 325References 32613 Multilayer Dielectric Coatings 329Colin M. Harthcock13.1 Introduction 32913.2 MLD Design Fundamentals 32913.2.1 Complex Index and Reflectivity 33013.2.2 Admittance of Optical Thin Films 33113.2.3 MLD Coating-Design Examples 33413.2.4 Polarization and Angle of Incidence 33713.3 Laser-Damage Resistance 34013.3.1 Electrical-Field Intensification 34013.3.2 Optical Bandgap 34213.3.3 Absorbing Precursors and Their Mitigations 34513.3.3.1 Molecular and Atomic-Level Precursors 34513.3.3.2 Within Coating Particulate Precursors 34813.3.3.3 Foreign-Object Debris Precursors 35013.4 Coating Structure and Deposition Energetics 35613.5 Coating Deposition Process Variables and Methods 359References 36214 Optics Recycle Loop 367Pamela K. Whitman and Brian J. Welday14.1 Operation Strategy 36714.2 Enabling Technologies 37214.3 Optics Recycle Loop Process 37314.4 Models to Describe the Optics Recycle Loop 38014.4.1 Growth Rate of Fused-Silica Glass Damage 38114.4.2 Analytical Model of Optics Exchange Rate 38214.4.3 System Initiation Rate 38314.4.4 Multi-loop Model 38414.5 Historical Performance and Tailorability 38614.6 Summary 390Acknowledgments 390References 392Part III Optic Recycle Loop Technologies 39515 Custom Processing Equipment 397Vaughn E. Van Note and Henry A. Hui15.1 Introduction 39715.2 Systems Engineering Approach 39815.3 Integrated Product Review Board 40015.3.1 Failure Modes and Effects Analysis 40215.3.2 Concept of Operations 40415.3.3 Work Authorization Process 40515.4 Advanced Mitigation Process (AMP) Station 40615.5 Meniscus Coaters 40915.6 Diffractive Optic Full Aperture System Test (DOFAST) 41115.7 Assembly Stations 41315.8 GDS Imprinting System 41615.9 Sustaining Capabilities and the Future 418Acknowledgments 421References 42116 Optics Inspection and Data Management 423Laura M. Kegelmeyer16.1 Optics Inspection Camera Systems on NIF 42316.1.1 SIDE System for Imaging the Target Chamber Vacuum Window 42516.1.2 LOIS for Imaging Main Laser Optics and Switchyard Mirrors 42516.1.3 FODI for Imaging Final Optics and Some Switchyard Mirrors 42816.2 Finding, Identifying, and Tracking Damage on NIF Optics 43016.2.1 Image Analysis and Machine Learning 43116.2.2 Fiducials and Defect Tracking Through Time and Space 43616.3 Data Management and Applications 43816.3.1 Integrated Analyses, Databases, and Reporting 43816.3.2 Tools for Data Visualization 44016.4 Summary 442Acknowledgments 442References 44317 Online Programmable Shadow Blockers 445Rajesh N. Raman, Tayyab I. Suratwala, and Pamela K. Whitman17.1 Programmable Spatial Shaper Device Capability 44617.2 Blocker Deployment and Optic Exchange 44617.3 Blocker Constraints 44917.4 Blocker Distribution Optimization 45117.5 Production Metrics and Historical Behavior 454References 45518 Optic Metrology 457Mike C. Nostrand18.1 Full-Aperture Tools 45918.1.1 Defects in the Antireflective coating using FADLiB 45918.1.2 Surface Damage and Digs Using DMS 46018.1.3 Surface Phase Objects 46218.1.4 General Surface Features Using TID 46318.1.5 Diffraction-Grating Efficiency and Uniformity Using DOFAST 46418.2 Sub-aperture Tools 46818.2.1 Phase and Amplitude of Phase Objects Using PSDI 46818.2.2 Downstream Modulation Using MMS 47018.2.3 Removing Coating Defects from Crystals Using FLRT 47018.2.4 Crystal Phase-Matching Angles Using CATS 47218.2.5 Threat-Determination Software 47318.3 Commercial Tools 47418.3.1 Full-Aperture Tools 47418.3.2 Reflected and Transmitted Wave Front 47418.3.3 Sub-aperture Tools 47518.3.4 Optical-Surface Profiling 47518.3.5 Optical Microscopy 47518.3.6 Ellipsometry 47718.4 Summary 478References 47919 Repair of Flaws and Laser-Induced Damage 481Isaac L. Bass, Todd Noste, and Scott K. Trummer19.1 Laser-Damage Repair on Fused Silica 48119.1.1 Damage-Mitigation Requirements 48319.1.2 Stationary-Beam Mitigation 48419.1.3 Moving-Beam Mitigation 48519.1.4 Rapid Ablation Mitigation 48619.1.5 RAM Applied to Exit-Surface Damage 48919.1.6 On-Axis Downstream Intensification from Exit-Surface RAM Cones 49019.1.7 Damage Resistance of RAM Cones 49119.1.8 Managing Redeposit from RAM Cones 49319.1.9 Residual Stress from RAM Cones 49619.1.10 RAM Applied to Input Surface Damage 49719.1.11 RAM Applied to AR-Coated GDSs 50119.1.12 RAM Cones Contribution to Obscuration 50419.1.13 Reliability, Availability, and Maintainability of Mitigation Equipment 50419.1.14 Investigation of Mitigation at 4.6-μm Wavelength 50519.2 Laser-Damage Initiation-Site Repair on KDP Crystals 50519.2.1 Anatomy of a KDP Mitigation Site 50619.2.2 Ductile Machining of KDP 50819.2.3 Crystal Mitigation Station 50819.2.4 Commissioning the CMS and Mitigation Sites 51019.2.5 KDP Damage-Site Mitigation Challenges 51419.2.6 Future Efforts and Upgrades 515Acknowledgments 515References 51520 Laser-Induced Damage Repair Automation 521Scott K. Trummer20.1 Repair Process for 3ω Fused-Silica Optics 52120.1.1 Preprocessing 52220.1.2 Software Setup 52320.1.3 Optic Registration 52320.1.4 Pre-mitigation Inspection 52320.1.5 Mitigation and Post-mitigation Analysis 52420.1.6 Postprocessing and Data Export 52420.2 OMF Automation 52420.2.1 Data Handling and Expanded Software Capabilities 52520.2.2 Pre-mitigation Inspection and Protocol Assignment 52720.2.3 Mitigation and Post-mitigation Inspection 53420.2.4 Limitations of Automation 53720.3 Production Metrics 539References 54121 Laser-Induced Damage Identification Using AI 543Christopher F. Miller and David A. Cross21.1 Improving Lifetime of Recycled Optics 54421.2 The All Microscopy Hitlist (AMH) 54521.2.1 Requirements and Process Strategy 54621.2.2 Optic Verification and Large-Optic Scan 54721.2.3 Optic Montage Analysis 55021.2.3.1 Feature Finding 55121.2.3.2 Large-Feature Analysis 55221.2.4 Small-Site Inspection and Classification 55521.3 Maximizing the Utility of Optic Repairs 55621.3.1 Optic Triaging 55621.3.2 End-of-Life Optics 557References 55822 On-Optic Shadow Cone Blockers 561Eyal Feigenbaum, Allison E. Browar, Isaac L. Bass, and Rajesh N. Raman22.1 Inherent Advantages and Challenges 56122.1.1 On-Optics Shadowing Approach and Its Advantages 56122.1.2 The SCB-Resulting Expanding Wave and Subsequent Exit Surface Damage 56422.1.3 Size Limitations on the Diameter of Conic-Shaped SCB 56722.2 Approaches for Implementation of Larger SCBs 56922.2.1 Rounded Sidewalls SCB 57022.2.2 Larger Shadowed Area Using SCB Arrays 57622.3 Utilization and Application Considerations 57822.3.1 FODI “Bleeding” and Potential Solutions 57922.3.2 Implementation and Testing of SCB Online 580References 58623 Contamination Management from Nonoptical Materials 587Liang-Yu Chen and Tayyab I. Suratwala23.1 Particle Debris and Residue 58823.1.1 Surface-Particle Cleanliness Measurement 58823.1.2 Nonvolatile Residue (NVR) Measurement 58923.1.3 Gross and Precision Cleaning 59123.2 Airborne Molecular Contaminants (AMCs) 59423.2.1 Vacuum-Outgas Test 59423.2.2 High-Temperature Bakeout to Remove Volatile Organics 60123.2.3 Polymer Example: Silicone 60323.3 Summary 605Acknowledgments 606References 606Index 609