FY06 Engineering Research and Technology Report Introduction

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This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. ENG-06-0061-AD FY06Engineering Research and Technology Report

April 2007 Lawrence Livermore National Laboratory A Message from Steven R. Patterson Associate Director for Engineering

his report summarizes the core research, develop- Engineering Modeling and Simulation efforts Tment, and technology accomplishments in Law- focus on the research, development, and deployment of rence Livermore National Laboratory’s Engineering computational technologies that provide the foundation- Directorate for FY2006. These efforts exemplify al capabilities to address most facets of Engineering’s Engineering’s more than 50-year history of develop- mission. Current activities range from fundamental ing and applying the technologies needed to sup- advances to enable accurate modeling of full-scale DOE port the Laboratory’s national security missions. A and DoD systems performing at their limits, to advances partner in every major program and project at the for treating photonic and microfl uidic systems. Laboratory throughout its existence, Engineering FY2006 LDRD projects encompassed coupling has prepared for this role with a skilled workforce standard fi nite element analysis methods with “mesh- and technical resources developed through both in- less” methods to address systems at and beyond failure; ternal and external venues. These accomplishments integration of electromagnetic forces with structural embody Engineering’s mission: “Enable program mechanics solutions; and nonlinear materials treatments success today and ensure the Laboratory’s vitality for photonic systems. Tech Base projects included en- tomorrow.” hancements, verifi cation, and validation of engineering Engineering’s investment in technologies is car- simulation tools and capabilities; progress in visualiza- ried out primarily through two internal programs: tion and data management tools; and extensions of our the Laboratory Directed Research and Development competence in structural damage analysis. (LDRD) program and the technology base, or “Tech Measurement Technologies comprise activities Base,” program. LDRD is the vehicle for creating in nondestructive characterization, metrology, sen- technologies and competencies that are cutting-edge, sors systems, and ultrafast technologies for advanced or require discovery-class research to be fully under- diagnostics. The advances in this area are essential for stood. Tech Base is used to prepare those technolo- the future experimental needs in Inertial Confi nement gies to be more broadly applicable to a variety of Fusion, High-Energy-Density Physics, Weapons and Laboratory needs. The term commonly used for Tech Department of Homeland Security programs. Base projects is “reduction to practice.” Thus, LDRD FY2006 LDRD research featured transient record- reports have a strong research emphasis, while Tech ing extensions for streak cameras; investigations into Base reports document discipline-oriented, core terahertz systems for explosives detection; acoustic char- competency activities. acterization of mesoscale objects; and research on the This report combines the LDRD and Tech Base structure and properties of nanoporous materials. Tech summaries into one volume, organized into six Base projects included new capabilities for the fabrica- thematic technical areas: Engineering Modeling tion of photonic integrated circuits; the implementation and Simulation; Measurement Technologies; Micro/ of a new transient sampling data recorder; ultra-wide- Nano-Devices and Structures; Precision Engineering; band technology testbeds; computed tomography (CT) Engineering Systems for Knowledge and Inference; reconstruction tools; and tools to aid identifi cation of and Energy Manipulation. defects in large CT data sets.

ii FY06 Engineering Research and Technology Report Introduction

Micro/Nano-Devices and Structures encom- Engineering Systems for Knowledge and passes technology efforts that fuel the commercial Inference, an emerging focus area for Engineering as growth of microelectronics and sensors, while simul- well as for the country at large, encompasses a wide taneously customizing these technologies for unique, variety of technologies. The goal is to generate new un- noncommercial applications that are mission-specifi c derstanding or knowledge of situations, thereby allowing to LLNL and DOE. LLNL’s R&D talent and unique anticipation or prediction of possible outcomes. With this fabrication facilities have enabled highly innovative knowledge, a more comprehensive solution may be pos- and custom solutions to technology needs in Stock- sible for problems as complex as the prediction of disease pile Monitoring and Stewardship, Homeland Security, outbreaks or advance warning of terrorist threats. and Intelligence. FY2006 LDRD research included projects to FY2006 LDRD projects included novel capa- determine the location and contents of atmospheric re- bilities to perform automated front-end processing leases based on sensors in the fi eld, and new research of complex biological samples. Tech Base projects into decomposing extremely large semantic graphs. included the colocation of actuation MEMs with Tech Base efforts included a testbed to evaluate hier- electronic packages; implementation of self-assembly archical clustering, and analysis tools and application structures through block copolymer nanolithography; of a previously developed image content engine to and instantiation of new equipment capabilities for new inspection capabilities in optics. micro- and nano-fabrication. Energy Manipulation, a long time focus that is re- Precision Engineering core technologies are ceiving increased emphasis due to newly emerging ap- the building blocks for the machines, systems, and plications, encompasses the fundamental understanding processes that will be required for future Laboratory and technology deployment for many modern pulsed- and DOE programs. These technologies help ad- power applications. This area has broad applications for vance the Laboratory’s high-precision capabilities in magnetic fl ux compression generators and components manufacturing, dimensional metrology, and assembly. for modern accelerators. Precision engineering is a multidisciplinary systems FY2006 LDRD research included research into the approach to achieve an order of magnitude greater ac- fundamental mechanisms responsible for fl ashover of curacy than currently achievable. insulators subject to microsecond pulses. Tech Base FY2006 Tech Base projects included error budget- efforts involved capabilities to improve the switching and certifi cation of dimensional metrology tools, and ing performance of power MOSFETs, and solid-state uncertainty analysis for inspection shop measurements. replacements for ignitrons.

Lawrence Livermore National Laboratory iii Contents Introduction A Message from Steven R. Patterson ...... ii

Engineering Modeling and Simulation A New “Natural Neighbor” Meshless Method for Modeling Extreme Deformation and Failure Michael A. Puso ...... 2

Statistical Distribution of Material Properties and Improvements in DYNA3D Jerry Lin ...... 4

Finite Element Analysis Visualization and Data Management Elsie Pierce ...... 6

NIKE3D Support and Enhancement Michael A. Puso ...... 8

Broadband Radiation and Scattering Robert M. Sharpe ...... 10

Electro-Thermal-Mechanical Simulation Capability Daniel White ...... 12

Computational Electromagnetics Implementation Benjamin J. Fasenfest ...... 14

Three-Dimensional Vectorial Time-Domain Computational Photonics Jeff rey S. Kallman...... 16

Usability Enhancements for 3-D Photonic Design Tools Joseph Koning ...... 18

Laser Glass Damage: Computational Analysis of Mitigation Process James S. Stölken...... 20

Simulation Capability for Nanoscale Manufacturing Using Block Copolymers David Clague ...... 22

Sputtering Chamber and Capsule Thermal Modeling Aaron Wemhoff ...... 24

Experimental Validation of Finite Element Codes for Nonlinear Seismic Simulations Steven W. Alves ...... 26

Structure and Properties of Nanoporous Materials Anthony Van Buuren ...... 28

iv FY06 Engineering Research and Technology Report Contents

Enhanced Composite Modeling Tools Andrew T. Anderson ...... 30

Modeling Forming Processes Moon Rhee ...... 32

Multiscale Characterization of bcc Crystals Deformed to Large Extents of Strain Jeff rey N. Florando ...... 34

Temperature Capability for In-Situ TEM Nanostage Mary LeBlanc ...... 36

EMP Simulation and Measurement Data Analysis in Support of Laser Experiments Charles G. Brown, Jr...... 38

Measurement Technologies Standoff Explosives Detection Using THz Spectral Imaging Robert J. Deri ...... 42

Ultra-Wideband Technology Testbed Carlos E. Romero ...... 44

Urban Tracking and Positioning System Peter Haugen ...... 46

Ultrasonic Techniques for Laser Optics Inspection Michael J. Quarry ...... 48

Surface Acoustic Wave Microscopy of Optics Michael J. Quarry ...... 50

Ultrafast Transient Recording Enhancements for Optical-Streak Cameras Corey V. Bennett ...... 52

Evaluation of Ultrafast Recording Technologies for Reduction to Practice John E. Heebner ...... 54

Acoustic Characterization of Mesoscale Objects Diane Chinn ...... 56

Application of Laser GHz Ultrasound to Mesoscale Materials Robert Huber ...... 58

VisIt for NDE: Real-Time Visualization for Large NDE Data Sets John D. Sain ...... 60

X-Ray System Characterization William D. Brown...... 62

Lawrence Livermore National Laboratory v Contents

Computed Tomography Reconstruction Codes John D. Sain ...... 64

Super-Resolution Algorithms for Ultrasonic NDE Imaging Grace Clark ...... 66

Defect Detection in Large CT Image Sets Douglas N. Poland ...... 68

Nanobarometers: In-Situ Diagnostics for High-Pressure Experiments James S. Stölken...... 70

Micro/Nano-Devices and Structures Rapid Defense Against the Next-Generation Biothreat Raymond P. Mariella, Jr...... 74

Thermal-Fluidic System for Manipulation of Biomolecules and Viruses Kevin D. Ness ...... 76

Precision Sample Control and Extraction Component Klint A. Rose ...... 78

Single-Molecule Assay of DNA Integrity George Dougherty ...... 80

Colocation of MEMS and Electronics Satinderpall Pannu...... 82

Optoelectronic Device Fabrication Rebecca J. Nikolić ...... 84

Block Copolymer Nanolithography James Courtney Davidson ...... 86

Characterization of Deep Reactive Ion Etching of Dielectric Materials Satinderpall Pannu...... 88

Gray-Scale Lithography for Sloped-Surface 3-D MEMS Structures Christopher M. Spadaccini ...... 90

Absolute Conditioner for Fabry-Perot Microsensors Michael D. Pocha ...... 92

Implementing Nano-imprint Capability Robin Miles ...... 94

vi FY06 Engineering Research and Technology Report Contents

Silicon Nitride Furnace Installation Robin Miles ...... 96

High-Density Plasma Source Steven L. Hunter ...... 98

Precision Engineering Error Budgeting and Certifi cation of Dimensional Metrology Tools Jeremy J. Kroll ...... 102

Uncertainty Analysis for Inspection Shop Measurements Walter W. Nederbragt ...... 104

Engineering Systems for Knowledge and Inference Image Relational Search Engine David Paglieroni ...... 108

Dynamic Data-Driven Event Reconstruction for Atmospheric Releases Branko Kosovic ...... 110

Decomposition of Large-Scale Semantic Graphs Yiming Yao ...... 112

Semantic Graph Hierarchical Clustering and Analysis Testbed Tracy Hickling ...... 114

Image Content Engine for Finding Rings of Defects on Optics Laura M. Kegelmeyer ...... 116

Energy Manipulation Improving the Vacuum Surface Flashover Performance of Insulators for Microsecond Pulses Jay Javedani...... 120

Improving Switching Performance of Power MOSFETs Edward G. Cook ...... 122

Solid-State Switch Replacements for Ignitrons Edward S. Fulkerson, Jr...... 124

Author Index ...... 127

Lawrence Livermore National Laboratory vii

Engineering Modeling and Simulation FY 06 Engineering Research and Technology Report Report and Technology FY 06 Engineering Research LDRD

A New “Natural Neighbor” Michael A. Puso (925) 422-8198 Meshless Method for Modeling [email protected] Extreme Deformation and Failure

he objective of this work is to develop smooth particle hydrodynamics (SPH) Ta fully Lagrangian analysis approach and element-free Galerkin (EFG) have based on “natural neighbor” discretiza- been used for modeling such large defor- tion techniques to model extreme de- mations but have a variety of numerical formation and failure for analyses such problems that the new natural neighbor as earth penetration and dam failure. In approach can potentially solve. To suc- these problems, our standard Lagrang- cessfully use the new approach, issues ian ﬁ nite element approach fails due to such as numerical integration, time-step mesh tangling, whereas our Eulerian calculation, and adaptive point insertion codes do not allow us to track particles are treated. and free surfaces to the degree necessary. Meshless particle methods such as Project Goals The goal of this work is to develop a better meshless particle approach by (a) (b) overcoming the numerous problems 5 5 inherent in these methods. In short, 3 3 the new method should be more stable 4 4 and accurate than the current meshless approaches. The new approach will pro- 1 2 1 2 vide an improved method for modeling 6 6 extreme events such as earth penetration and dam failure. Furthermore, because 7 7 it is meshless the approach can be used for applications where nondestructive Figure 1. (a) Voronoi diagram formed about the cloud of points, used to compute evaluations are required, such as as-built natural neighbor shape functions and numerical integration. For example, nodal weapons analysis and biomechanics. strains and stresses at 1 were computed using Gauss points (red) on the Voronoi cell. (b) Approximation of Voronoi cell using an ellipse. This requires only approxi- Overall, a much larger class of problems mate calculation of the near neighbors. can then be solved.

(a) (b) (c) 2.0

1.6

1.2

Elliptical 0.8

Frequency Circular Finite element 0.4

0 10 20 30 40 50 Mode number

Figure 2. (a) Frequency vs. mode number for a 1-x-1 lattice of points with mesh spacing hx = 1 and hy = 0.5. The results using the natural neighbor based elliptical supports compare well with the fi nite element results. (b) First mode displacements using elliptical supports. (c) First mode displacement using circular supports.

2 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

Relevance to LLNL Mission kernels were also applied to other classi- Integrated Tetrahedral,” International Journal High-rate penetration dynamics has cal approaches in FY2006. for Numerical Methods in Engineering, 67, 6, been identifi ed as a challenge area in The natural neighbors are very im- pp. 841-867, 2006. engineering and the new particle meth- portant in providing locality (i.e., tight 3. Puso, M. A., and J. S. Chen, “A New ods developed here directly apply to this supports) for the sake of effi ciency and Stabilized Nodal Integration Approach,” Pro- area. Along with earth and armor pen- accuracy. We found that diagonalization ceedings International Workshop Meshfree etration problems, vulnerability evalu- of the mass matrix was valid only when Methods, 2005, in press. ation of infrastructure (e.g., dams) can the shape functions had tight support, 4. Chen, J. S., and M. A. Puso, “Strain be analyzed. Furthermore, as-built x-ray as demonstrated in Fig. 2. Because the Smoothing for Stabilization and Regulariza- tomography of NIF targets and in-vivo integration cells are no longer conform- tion of Galerkin Meshfree Methods,” Pro- MRI imaging for biomechanics create ing, results are not as accurate as those ceedings International Workshop Meshfree “point clouds” and are good examples using Voronoi cells when discretized Methods, 2005, in press. of where a meshless method could be points are not structured. To recover 5. Chen, J. S., W. Hu, and M.A. Puso, “Or- exploited for expediting stress analyses. accuracy, a method for computing a bital HP-Clouds and Higher Order SCNI for correction term was developed (Fig. 3). Solving Schrodinger Equation in Quantum FY2006 Accomplishments and Results Stabilization of the nodal integration Mechanics,” International Journal for Nu- Our FY2005 implementation re- is applied using the new cell approach. merical Methods in Engineering, in press. quired the creation of a Voronoi diagram These new meshless methods were as shown in Fig. 1a. This was used to then applied to simulation of an earth compute the natural neighbor shape penetrator (Fig. 4). Finally, new higher- FY2007 Proposed Work functions and conforming cells for nu- order meshless integration approaches Our major FY2007 goal is to validate the merical integration. In FY2006 we sim- were developed for treating problems in new methods and compare to more classi- plifi ed this approach such that nearest electronic structure. cal methods, e.g., MLSPH, MLPG. Our main neighbors would have to be computed validation concern is earth penetration but only approximately, as in Fig. 1b. In this Related References we will be looking at other experimental approach, the smooth kernels would be 1. Puso, M. A., “A New Stabilized Nodal results. If time permits, we will also use elliptical and approximately fi t Voronoi Integration Approach,” McMat Conference error indicators to do point insertion and cells. Linear exactness of the resulting Proceedings, 2005. conversion of fi nite elements into particles. shape functions is provided by using a 2. Puso, M. A., and J. Solberg, “A Formula- kernel correction. In fact, the elliptical tion and Analysis of a Stabilized Nodally

(a) (b)

Figure 3. Simulation of mode one crack on a set of randomly discretized nodes. The stresses Figure 4. Simulation of earth penetrator. Mesh- oscillate in (a) without correction but are very accurate with correction in (b). less particles are located near the penetrator and fi nite elements at outer locations. The red denotes tensile failure.

Lawrence Livermore National Laboratory 3 TechBase

Statistical Distribution of Jerry Lin (925) 423-0907 Material Properties and [email protected] Improvements in DYNA3D

YNA3D is one of the main explicit addition of new result display capabili- Dﬁ nite element analysis tools at LLNL ties, and continued compliance work on for fast transient response of structures. SQA and the Fortran90® standards. This project funds DYNA3D enhancements through implementation of user- Relevance to LLNL Mission requested features, general technical Many programs at LLNL require support, document update and Software new DYNA3D functionalities and/or Quality Assurance (SQA) compliance technical support to complete their for DYNA3D. missions. Some of these projects in- This project also supports Collabora- volve LLNL’s collaboration with other tor Program activities. The Collabora- institutions and federal agencies, such tor Program grants access to selected as the Las Alamos National Laboratory, licensed users to LLNL’s computational Homeland Security, Bureau of Reclama- mechanics/thermal codes in exchange tion, U.S. Army Corps of Engineers, and for the collaborators’ information and re- the Naval Surface Warfare Center. sults. These collaborative parties include our sister laboratories, U.S. government FY2006 Accomplishments and Results agencies, and other institutions. Statistical distribution of material yield/failure strength was introduced to Project Goals some of the material models. The inclu- For FY2006, the planned tasks in- sion of a distribution enables DYNA3D cluded the implementation of function- to simulate a manufactured product alities for various analytical needs, the more realistically.

Figure 1. Strain pattern (solid color, except for small amount Figure 2. Strain pattern of a biaxially loaded plate with the of data at upper right) of a biaxially loaded plate with no Weibull statistical distribution on the material failure strain. statistical distribution on the material failure strain.

4 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

A biaxially loaded plate provides A standard impacting bars problem an example. The plate is made of an is used to examine the algorithm’s ef- FY2007 Proposed Work isotropic-elastic-plastic material with a fectiveness. The simulation consists of We will continue our general technical user-assigned failure strain. A homoge- two identical isotropic elastic bars, one support for DYNA3D users, and the ongo- neous plate is assumed in the ﬁ rst run, at rest and the other with a unit initial ing modernization toward Fortran90®- which results in a uniform strain pattern velocity, undergoing an end-to-end compatible and SQA-compliance. We also (solid color), as depicted in Fig.1. A impact. The velocity histories at the plan to start or continue the following Weibull distribution is applied to the impact point of each individual bar are enhancements: failure strain in a subsequent run. The recorded for comparison. In Fig. 3, only 1. the integration of the surface class added distribution produces a clear frag- the traditional bulk viscosity is applied, entities such as boundary conditions in mentation pattern, more representative whereas in Fig. 4 the complementary output databases; for manufactured parts (Fig. 2). viscosity is added. A smoother velocity 2. the computation and display of the Over the years, velocity overshoot record without overshoot and continuous kinematics of parts of an analysis and excessive “ringing” has been an ringing is evident in the latter case. model, such as the rotational issue in many computational analyses, Other new features and improve- velocities/accelerations of a part or a especially in shockwave-related simula- ments of note in DYNA3D include collection of parts; and tions. A self-adjusting viscosity model added failure mechanisms for selected 3. the implementation of a unifi ed and was implemented into DYNA3D to material models, time-dependent gravity consistent stiff ness-proportional counter this difﬁ culty. This new algo- effect, streamlined restart and visual- damping for all element types. rithm, in addition to the existing bulk ization capabilities for the quasi-static viscosities, adds a complementary analysis phase, and additional result viscosity component at material points output for visualization. sustaining power dissipation.

1.1 1.1 Node 405 Node 405 1.0 1.0 Node1 Node1 0.9 0.9

0.8 0.8

0.7 0.7

0.6 0.6

0.5 0.5

0.4 0.4

0.3 0.3 Node velocity (x velocity) Node velocity Node velocity (x velocity) Node velocity

0.2 0.2

0.1 0.1

0 0

–0.1 –0.1 0 0.04 0.08 0.12 0.16 0.2 0 0.04 0.08 0.12 0.16 0.2 Time Time

Figure 3. Velocity histories of impacting bars without the self-adjusting Figure 4. Velocity histories of impacting bars with the self-adjusting bulk bulk viscosity. viscosity.

Lawrence Livermore National Laboratory 5 TechBase

Finite Element Analysis Elsie Pierce (925) 422-4063 Visualization and [email protected] Data Management

key component of our project activi- generated by our large computing plat- A ties is its support for post-processing forms. Mili provides the primary data and visualization tools, which include path between analysis codes and Griz. the Griz fi nite element post-processor, a parallel fi le combiner tool called Project Goals XmiliCS, and the Mili I/O Library. The primary goal of this effort These tools are heavily used by analysts is to provide on-going support for and engineers across LLNL and exter- LLNL’s post-processing tools. This in- nally to post-process data from a variety cludes efforts to add new capabilities of analysis codes, such as DYNA3D, to these tools for broad programmatic ParaDyn, NIKE3D and Diablo. requirements. Griz is our primary tool for visualizing fi nite element analysis results on Relevance to LLNL Mission 3-D unstructured grids. Griz calculates Post-processing tools such as Griz, and displays derived variables for a XmiliCS, and Mili provide impor- variety of codes. Griz provides modern tant user interfaces for our simulation 3-D visualization techniques such as capabilities and are critical elements in isocontours and isosurfaces, cutting LLNL’s simulation tool suite. planes, vector fi eld display, and particle traces. Griz also incorporates the abil- FY2006 Accomplishments and Results ity to animate all representations over We currently have many active users time. XmiliCS is a utility for combining for Griz and Mili coming from programs results from multiple processors that are at LLNL and also at LANL.

Global maximum: 5.87 x 10–3, Particle 141 Global minimum: –6.63 x 10–3, Particle 1117 Displacement scale: 1.0/1.0/1.0 Stress (X stress) 5.87 x 10–3 4.00 x 10–3 2.00 x 10–3 0 –2.00 x 10–3 –4.00 x 10–3

–6.63 x 10–3

Y Nem 31 X t = 74.3468 (state = 78/78) Z

Figure 1. Original particle confi guration at time=0. Figure 2. X Stress plot at time = 74.34 μs.

6 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

We made signifi cant progress in treated in Griz in much the same way We continued to support the integra- adding the capability for Griz and Mili that we treat problems with free-nodes, tion of Mili with the VisIt post-proces- to manage and display surface objects. so much of the same work completed for sor. This year we created a detailed list This is an essential step for facilitat- hypervelocity impact applications was of features used in Griz to close the gap ing the writing of boundary conditions leveraged. All of the options available between VisIt and Griz capabilities. We and data onto surfaces from the analy- for free-nodes can also be applied to par- worked with the VisIt team to enhance sis programs. To date the entire GUI ticles. Figures 1 and 2 are pictures taken VisIt so that it can be used with Mili implementation and database work has from Griz that show stress plots for a fi les generated from the heat-transfer been completed, and released. We are in rod that is represented with a fi eld of code Topaz3D, meeting a new program- the process of getting the surface class particles. Figure 3 is a still from a movie matic visualization requirement. capability used by our analysis codes. that was produced to show the interac- This year we successfully ported tion of standard elements with particles. Griz to new 64-bit Linux platforms. We added a signifi cant new capabil- FY2007 Proposed Work Griz performance seems quite good on ity to the Mili I/O Library that allows We will continue to provide support these platforms, and there have been no writing “non-state” at any point in the for our user base, currently numbering problems with the multi-monitor dis- simulation. This was created as a general approximately three dozen active users plays. Such hardware confi gurations are capability, but the fi rst application is to at LLNL, LANL, and several other sites. We becoming common for our analysts. support writing nodal mapping data in will continue our strategy of providing new We added a new feature in Griz to ParaDyn for multi-processor results. features in Griz and Mili to meet specifi c provide a “rubber-band” (RB) zoom, as We have completed the draft specifi - programmatic requirements while building requested by several users. Using the cation and project plan for an enhanced more long-term capabilities. For FY2007, RB zoom is much faster than the mouse Mili I/O Library. The plan calls for a the items that will have the most impact zoom, since the latter requires a refresh phased implementation with the fi rst will be putting the new Qt-based GUI into (a wire frame redraw) at each cursor deliverable being a library that is based production; providing a more robust I/O location change. This can amount to on more standardized I/O technology Library; and completing the enhancements hundreds of updates to the display for a than currently in use. This enhancement to the VisIt Mili plug-in. Our long-term goal single zoom. should reduce future maintenance costs is to make a complete migration to VisIt for We continued to add new features in for Mili and provide an easier path for model visualization. Griz to support advanced simulations of adding some complex features that have fragmentation and debris from hyperve- been requested by our users. locity impacts. This year we added the following new capabilities to support this study: 1) a capability to write out detailed tabular data for free-nodes; 2) the ability to plot time-history data for accumulated free-node velocity by material; and 3) a result for momentum. Griz is now using an advanced regression testing system based on an LLNL tool called Tapestry, and weekly automated builds and tests are performed for all of our major platforms. This year we made additional enhancements to the Griz confi guration and build system. We also implemented and released a new build system for the Mili Library. In support of an investigation into future meshing techniques, we added a new capability in Griz to plot results for meshless or particle-based algorithms. These problems have no mesh, but an unstructured collection of nodes that carry result quantities. These problems are Figure 3. Rendering in Griz of standard elements and particles.

Lawrence Livermore National Laboratory 7 TechBase

NIKE3D Support Michael A. Puso (925) 422-8198 and Enhancement [email protected]

he objective of this work is to Relevance to LLNL Mission Tenhance, maintain, and support the Structural analysis is one of the most implicit structural mechanics finite important functions of engineering and element code NIKE3D. New features LLNL in-house maintenance for its suite are added to accommodate engineer- of codes. NIKE3D, in particular, is a ing analysis needs across multiple premier code for handling diffi cult non- programs. Maintenance includes bug linear static structural analysis problems. fixes and code porting to the new platforms available to engineering FY2006 Accomplishments and Results analysts. User support includes assist- The fi rst production version of ing analysts in model debugging and mortar contact in NIKE3D was made general analysis recommendations. available at the end of FY2005. The fi rst production work using the feature truly Project Goals began in FY2006 and led to a number of Code enhancement generates new related refi nements. features to meet our engineering com- 1. Many contact problems have unin- munity’s user demands. Our goals to en- tended initial interpenetration due to hance NIKE3D included the following: discrepancies in meshing non-match- 1. add new features to, and correct ing curved surfaces. To treat these, a defects in, our mortar contact algo- fast nonlinear algorithm to compute rithms to enhance their production node relocations at problem initial- capabilities (details below); ization was implemented. 2. add several additional features to 2. New diagnostics to display mortar material models and update the contact activity (such as gap open- code’s Users Manual; and ings and slip) were added to help 3. implement an 8-byte integer version analysts diagnose models and solve of the WSMP direct linear equation problems. solver to handle very large stiffness 3. We worked closely with analysts on matrices; and interface NIKE3D to large weapons problems to evaluate Intel’s MKL library sparse direct solution strategies. We compared solver for LINUX platform. different quasi-Newton nonlinear solution strategies, fi nding Broyden’s Figure 1. Shape functions used to ap- (a) method was often better than the proximate pressure on the boundary N1 N2 N3 N4 edge of a 2-D domain. (a) Standard default Broyden-Fletcher-Goldfarb- mortar shape functions, NA; (b) dual Shanno (BFGS) method. mortar shape functions, NÂ. 4. We constructed 15 new QA problems specifi cally to test mortar contact. (b) 5. We implemented the dual mortar ap- N1 N2 N3 N4 proach into the production code for both mesh tying and contact. So far, we have seen that the mortar segment-to-segment approach is able to solve defense-related problems more reliably and accurately and often faster (due to fewer iterations) than the classical node-on-surface approach. On the

8 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation other hand, we found that standard mor- mortar contact (10-node tets, 20- and tar contact increases the “bandwidth” 27-node bricks) bringing it closer to FY2007 Proposed Work of the global stiffness matrix. To rectify production status (Fig. 2). 1. Our current mortar contact implemen- this, the dual mortar method originally tation uses an N2 search algorithm, created for mesh tying was implemented Related References the cost of which grows rapidly with into the production code. Whereas the 1. Puso, M. A., and T. A. Laursen, “A Mortar surface size. Better and faster search standard mortar contact method inter- Segment-To-Segment Frictional Contact algorithms will be implemented, e.g., polates the contact pressures using the Method for Large Deformations,” Computer a bucket sort. ﬁ nite element “hat” functions, NA, (Fig. Methods in Applied Mechanics and Engi- 2. The BFGS algorithm does not ef- 1a), the dual contact method uses dis- neering, 193, pp. 4891-4913, 2004. fectively handle the evolving active continuous shape functions, NˆA, for the 2. Puso, M. A., and T. A. Laursen, “A Mortar contact constraints during nonlin- pressure (Fig. 1b) that diagonalize the Segment-to-Segment Contact Method for ear iterations within a time-step. slave side constraint equations, i.e.: Large Deformation Solid Mechanics,” Com- Furthermore, the full Newton version = ˆ Γ =δ Γ puter Methods in Applied Mechanics and of the mortar contact involves unsym- GAB ∫ N A N B d AB ∫ N A d Engineering, 193, pp. 601-629, 2004. metrical stiff ness matrices even for 3. Puso, M. A., “A 3D Mortar Method for frictionless contact when the contact This reduced problem size and Solid Mechanics,” International Journal for surfaces are not fl at. Algorithms matrix factorization times from 25% to Numerical Methods in Engineering, 59, pp. that perform secant updates such as 40% on many benchmark and produc- 315-336, 2004. BFGS, but better account for active tion applications. Problem size is now 4. Flemsch, B., M. A., Puso, and B. I. constraints, will be investigated. often comparable to node-on-segment Wohlmuth,, “A New Dual Mortar Method for contact but still far more robust, as Curved Interfaces: 2D Elasticity,” Interna- demonstrated in Fig. 2. Additional work tional Journal for Numerical Methods in was also performed on the higher-order Engineering, 63, pp. 813-832, 2005.

(a)

(b)

(c) 0 Figure 2. Concentric thick spheres separated by contact surface and fl attened by –0.04 plates. (a) Sequence of deformations applied to 8-node brick elements. (b) Vertical –0.08 stress state on coarser mesh of 20-node brick elements. (c) Vertical force vs. plate displacement for standard, dual, and quadratic element type mortar methods. –0.12 Results using standard node-on-segment are also shown, but simulation failed –0.16 Standard mortar earlier in analysis. Dual mortar Applied force –0.20 Quadratic mortar –0.24 Node-on-segment –0.28 051015 20 Displacement

Lawrence Livermore National Laboratory 9 LDRD

Broadband Radiation Robert M. Sharpe (925) 422-0581 and Scattering [email protected]

lectromagnetic phenomena are a central domain, boundary-integral techniques Ethread through much of modern that are compatible with high-accuracy, engineering. There are two fundamen- fi nite element methods and capable of tal classes of applications: open region arbitrary accuracy. These approaches problems (where the energy propagates have been compared to the traditional in unbounded space) and closed region fi rst-order absorbing boundary condi- problems (where the energy is guided by tion for a variety of radiation and scat- a waveguide structure or cavity). tering problems. This effort strives to enhance our computational electromagnetics (CEM) Project Goals capability in broadband radiation and The ultimate deliverable is an en- scattering in open regions. Broadband hanced CEM capability that can provide fi elds consist of energy with a robust accurate and effi cient computational spectrum, and include applications such solutions to broadband radiation and as electromagnetic interference and scattering problems. The algorithms for electromagnetic compatibility noise improved RBCs will be incorporated analysis, broadband radar, and accelera- into LLNL’s existing EMSolve code. tor wakefi eld calculations. LLNL analysis codes are limited by the accuracy of radiation boundary conditions (RBCs), which truncate space. We have developed improved RBCs by extending the perfectly matched layer (PML) approach to non-Cartesian meshes, and by developing discrete-time-

Figure 1. Scattered far-fi eld generated by a broadside pulse hit- Figure 2. The electric fi eld magnitude on the ting a rocket. The hybrid RBC was used to avoid the necessity of a rocket surface and the equivalent vector currents huge air mesh. produced by the hybrid RBC.

10 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

The result will be a 10- to 1000-fold 100 10–1 improvement in the accuracy of simulations. Improved algorithms and our existing high-performance computer hardware will place LLNL’s CEM activ- 10 10–2 ity among the top capabilities in the

world. This research and the resulting per time-stepTime capability will be documented in appro- error Maximum relative 1 10–3 priate peer-reviewed publications. 1 10 100 1 10 100 Hybrid subcycle frequency Subcycle frequency Relevance to LLNL Mission Figure 4. Pulsed Dipole Problem: computational Figure 5. Pulsed Dipole Problem: maximum rela- Electromagnetics is a truly ubiq- cost per time-step for the hybrid method as the tive error behavior for the hybrid method as the uitous discipline that touches virtually sub-cycling frequency changes. sub-cycling frequency changes. every major LLNL program. Our work supports the national security mission by reducing the time and money spent in Several different formulations for RBCs of our computation costs and error when building and testing existing programs. are now available, including boundary sub-cycling of the hybrid boundary ele- It will enable computer simulations conditions based on the electric fi eld, ment calculation is applied. for new devices and systems, perfor- magnetic fi eld, or both at the boundary. mance analysis of systems critical to A formulation using both the elec- Related Reference nonproliferation efforts, and the design tric and magnetic fi elds was found to Fasenfest, B., D. White, M. Stowell, R. of micropower impulse radar and other eliminate late-time stability issues due Sharpe, N. Madsen, J. Rockway, N. J. Cham- microwave systems. to interior resonances. We have collabo- pagne, V. Jandhyala, and J. Pingenot, “A rated with a professor at the University Hybrid FEM-BEM Unifi ed Boundary Condi- FY2006 Accomplishments and Results of Washington who is an expert on time- tion with Sub-Cycling for Electromagnetic Figures 1 to 5 are samples of our domain integral equations. It was found Radiation,” IEEE Antennas and Propagation FY2006 CEM work. We have completed that the boundary element time-step Society International Symposium, Albuquer- the development of the parallel hybrid could be different than the fi nite element que, New Mexico, July 9-14, 2006. fi nite element boundary element code. time-step. By sub-cycling the boundary element computations at some multiple of the fi nite element time-step, large 10 improvements in speed were observed, 1 especially for very large meshes. This 10–1 sub-cycling allows for a trade-off be- 10–2 tween speed and accuracy. 10–3 For a z-oriented pulsed dipole prob- 10–4 lem (with a known solution), we have Hybrid error achieved almost a 1000-fold increase in 10–5 ABC error Maximum relative error Maximum relative accuracy using our hybrid code (Fig. 3). 10–6 1 21 41 61 81 101 The conventional Absorbing Boundary Time step/80 Condition (ABC) method fails to con- verge when applied on a spherical grid Figure 3. Pulsed Dipole Problem: the maximum relative error for the hybrid solution and the with a maximum radius of 1. In contrast, conventional ABC boundary condition solution the hybrid solution shows good accu- as a function of time. racy. Figures 4 and 5 show the behavior

Lawrence Livermore National Laboratory 11 LDRD

Electro-Thermal-Mechanical Daniel White (925) 422-9870 Simulation Capability [email protected]

he purpose of this project is to metals, and MEMS. A robust ETM Tresearch and develop numerical simulation capability will enable LLNL algorithms for 3-D electro-thermal-me- physicists and engineers to better sup- chanical (ETM) simulations. LLNL has port current DOE programs, and will long been a world leader in the area of prepare LLNL for some very exciting computational solid mechanics, and long-term DoD opportunities. recently several solid mechanics codes have become “multiphysics” codes Project Goals with the addition of fl uid dynamics, Our goal is to develop a novel simu- heat transfer, and chemistry. How- lation capability that is not available ever, these multiphysics codes do not commercially or from the other national incorporate the electromagnetics that laboratories. We defi ne a coupled ETM is required for a coupled ETM simula- simulation as a simulation that solves, in tion. There are numerous applications a self-consistent manner, the equations for an ETM simulation capability, such of electromagnetics (primarily statics as explosively-driven magnetic fl ux and diffusion), heat transfer (primarily compressors, electromagnetic launch- conduction), and nonlinear mechan- ers, inductive heating and mixing of ics (elastic-plastic deformation, and

Figure 1. Simulation of Alfven waves (magnetic shear waves) using ALE3D. The simulation is of a small perturbation in the middle of the region; both Alfven waves and sound waves emanate from the perturbation. This is a snapshot of a time-dependent simulation, with the Shear waves arrows depicting the direction of the Compression magnetic fi eld. waves

12 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation contact with friction). Our approach is FY2006 Accomplishments and Results magnetic fi elds in the air. This method to add electromagnetics to two existing Electromagnetics was incorporated does not require a computational mesh mechanics codes, ALE3D and Diablo. into both the ALE3D and Diablo codes. of air regions, hence it signifi cantly sim- ALE3D is a heavily used Arbitrary- For ALE3D the key issue was plifi es problem set-up (i.e., meshing) for Lagrangian-Eulerian hydrodynamics advection of the electromagnetic fl ux complicated problems. The challenge is code; Diablo is an implicit Lagrangian density. We developed and imple- that the Green’s function method results thermal-mechanics code currently under mented a novel divergence-preserving in a dense matrix. We investigated low- development. Both codes are supported monotonic advection algorithm that rank QR compression of this matrix, by Advanced Simulation and Computing works on unstructured meshes. This resulting in an O(n log n) algorithm. (ASC). A fi nite element discretization algorithm was verifi ed by comparing will be used for the electromagnetics. computed results to canonical mag- In ALE3D the coupling of the electro- netohydrodynamic problems, to 2-D FY2007 Proposed Work magnetic equations, thermal equations, CALE simulations, and to previously In FY2007 the emphasis will be on code and mechanics equations will be done published experimental results. In verifi cation and validation, and we will in an operator-split manner; in Diablo Fig. 1 we show a simulation of linear revisit the previously developed numeri- these equations will be solved in a self- magnetohydrodynamic waves. This is a cal algorithms to improve accuracy and consistent implicit Newton iteration. good test of the magnetic fi eld advec- effi ciency as needed. We will simulate tion algorithm. The computed wave recent Offi ce of Naval Research railgun Relevance to LLNL Mission velocity was compared to the analyti- experiments, which will allow us to validate With this new capability, LLNL will cal velocity, with O(h2) convergence. the sliding electrical contact algorithms in have an unprecedented ability to simu- For the Diablo task, the key issue Diablo. We have begun collaborating with late, design, and optimize ETM systems. was continuity of fi elds and currents several experimental pulse-power projects, This project is aligned with LLNL’s core across a sliding contact. A prototype and we will research methods to incorpo- competency in Simulation Science and penalty method for electromagnetic rate dielectric materials into the electric Engineering. It contributes to LLNL’s sliding contact has been developed and fi eld update in order to address electric fi eld mission to enhance/extend its simulation implemented, and the performance is breakdown issues that are relevant. Our ini- capabilities, and specifi cally addresses being evaluated. We are also investigat- tial approach is to solve an auxiliary partial the need for simulation capability in ing an augmented Lagrange method for diff erential equation involving the singular the area of Energy Manipulation. This the electromagnetic sliding contact. A curl-curl operator. A recently developed project complements on-going ASC preliminary simulation result is shown multigrid algorithm will be used to solve work and will use ASC computers and in Fig. 2. the resulting system of equations. software such as linear solver packages In addition, a novel Green’s function and visualization tools. method was developed for dealing with

20 20 20

10 10 10 10 5 0 10 –5 5 10 0 –10 X-axis 0 5 10 –15 –5 X-axis 0 5 0 –10 –5 10 –15 0 –10 X-axis 5 10 –15 5

Figure 2. Sequence of snapshots of a preliminary sliding electrical contact simulation performed using the electromagnetics-enhanced Diablo code. The pseudocolor represents electric current density.

Lawrence Livermore National Laboratory 13 TechBase

Computational Electromagnetics Benjamin J. Fasenfest (925) 423-6056 Implementation [email protected]

hile improvements in commercial for broadband radiation and scattering Wcomputational electromagnetic problems. LLNL’s hybrid fi nite element (CEM) tools are increasing every year, boundary-element radiating boundary they lag academic advances by ten to condition offers improved accuracy, as twenty years. In addition, the major well as reduced sizes for the required commercial CEM tools are not gen- fi nite element mesh. This technology has eral enough to solve the unusual EM numerous applications, such as electro- problems encountered in LLNL applica- magnetic interference, broadband radar, tions, nor are they ported to the latest and accelerator wakefi eld calculations. massively parallel computers in use at Error estimators provide a good approxi- LLNL. For these reasons and others, we mation of the error in the solution of a have created in-house CEM tools such fi nite element problem without requiring as EMSolve. that the exact solution be known. By Recent projects in CEM have gener- visualizing the error estimate through- ated signifi cant algorithms and prototype out the problem, the mesh density or software in the areas of error estimators basis function order can be increased in and improved radiating boundary condi- areas with the largest error. This allows tions. Radiating boundary conditions convergence to an accurate solution with provide a numerical termination of space many fewer mesh refi nement iterations,

Figure 1. The inner surface of an accelerator induction cell. The round hole Figure 2. Cutaway image of an induction cell showing the fi rst vector eigenmode in the center is the beam tube. The four oblong holes connect this cell with of the cavity. The red lobes are areas identifi ed by the residual error estimator as its neighbor. The section of black mesh lines indicates the cutaway portion needing refi nement. The two lobes near the top are located near a sharp edge shown in Fig. 2. in the surface of the mesh and the elements there are relatively coarse, so one would expect that refi nement would be necessary. The third lobe was unexpected and on closer inspection it was found to contain poorly formed elements.

14 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation and the ability to produce more accurate electromagnetic diffusion, and full-wave solvers, eigenvalue solvers, and mag- solutions with less computing power. time- and frequency-domain EM. A netic diffusion solvers. Figures 1 and 2 This project focuses on fully inte- full-wave time-domain radiating bound- show sample results generated by the grating existing results into EMSolve to ary condition will be implemented and error estimators. The speed of the error be used to solve real problems of inter- tested for massively parallel simulations estimators was improved by about 60%, est. The algorithms and software need on LLNL’s supercomputers. Supporting and their convergence for multi-material to be fully combined into the EMSolve infrastructure, such as far-fi eld pat- and higher-order problems was tested framework and physics drivers, tested terns, radar cross-section, and plane- and verifi ed. and verifi ed in the new codes, and docu- wave scattering formulations will be A far-fi eld output was added so mented, so that they can be used easily. implemented. In addition, technical that the broadband frequency-domain In addition, supporting features need to and user documentation will be created far-fi eld and radar cross-section could be added to the code to take advantage to assist in applying the new features. be computed (Fig. 3). The hybrid of the new improvements. The implementation and documenta- radiating boundary condition was fully tion of these features will allow im- implemented within the EMSolve time- Project Goals proved accuracy with fewer simulation domain full-wave solver (Fig. 4). Its By the end of this project, signifi cant iterations for LLNL’s CEM work. parallel effi ciency and accuracy was upgrades to EMSolve functionality will tested and improved to allow scaling be complete. Error estimators will be Relevance to LLNL Mission to very large numbers of processors. A integrated within the EMSolve drivers for Electromagnetics is a discipline scattered-fi eld formulation was imple- that touches almost every major LLNL mented to solve plane-wave scattering program. EMSolve is currently being problems from composite structures. used to support national security mis- In addition, the amount of code doc- sions, the National Ignition Facility, and umentation was increased tremendously, the Stockpile Stewardship program. The both for the boundary-element and fi nite addition of new features to the EMSolve element portions of EMSolve. Several code, and their documentation, will al- other improvements to EMSolve were low for more accurate, faster results to made, including FORTRAN®-wrapping be produced for these critical projects. of the core computational library, consisting of hundreds of routines, improve- FY2006 Accomplishments and Results ments to the effi ciency of integration The error estimators were integrated rules, accurate memory usage computa- into the EMSolve codes, including time- tions, and the ability to defi ne fi elds on a domain and frequency-domain full-wave subset of the overall mesh.

4 RCS (dBsm) 3

0 100 150 200 250 300 350 400 450 500 550 600 Frequency (MHz)

Figure 3. Far-fi eld scattering produced by a Figure 4. Broadband radar cross-section for a rocket. The radar cross-section determines how visible an four-wavelength dielectric sphere with a relative object is to radar systems. The monostatic radar cross-section for a broadside pulse polarized along the permittivity of 3. rocket axis using the hybrid radiating boundary condition is displayed.

Lawrence Livermore National Laboratory 15 LDRD

Three-Dimensional Jeff rey S. Kallman (925) 423-2447 Vectorial Time-Domain [email protected] Computational Photonics

ustomers with requirements for secure (a) Cdata transmission, computer network- –60 –80 80 60 40 20 0 –20 –40 ing, and high-bandwidth instrumentation are accentuating the need for photonic integrated circuit (PIC) technology. PICs will be the high-speed processing chips of the future and will impact both commercial and LLNL program- 250 matic needs. Compact (LSI to VLSI), low-latency (sub-ps), wide-bandwidth (THz), ultrafast (100 Gb/s) miniaturized digital-logic, transmission, and sensor systems are potentially feasible. The de- 200 sign of novel integrated structures poses a considerable challenge, requiring models incorporating both microscopic and macroscopic physics. Despite the strong photonic mod- 150 eling capability at LLNL, new numerical methods are necessary as more complex photonic devices, materials, and confi gurations are devised. Three- dimensional time-domain (TD) design 100 tools are fundamental to enabling and accelerating technologies for the real- Figure 1. Field propagated ization of all-optical logic systems for from a Gaussian-triggered Auston-Switch THz source. data generation, transmission, manipu- The antenna and fi eld 50 lation, and detection. We have been emitted from it are shown doing the research necessary to create in (a). The time history these new numerical methods. of the fi eld at an on- axis Z receiver is shown in (b). The temporal spectrum of Project Goals X the fi eld is shown in (c). Y 0 We are fi lling the gap between existing modeling tools and those needed for LLNL missions by extending the (b) (c) x10–12 state of the art in simulation for the 1 –15 design of 3-D PICs. We have defi ned challenges that must be addressed in 0.5 our codes, such as models for optical 0 gain and nonlinearities, as well as mi- –20 croscopic, nonuniform, inhomogeneous Power Voltage –0.5 structures. Our tools leverage LLNL’s expertise in computational electromag- –1 netics (CEM) and photonics. We have developed models and algorithms for –1.5 –25 0 0.5 1 1.5 2 2.5 3 0 2 4 6 8 10 incorporation into a new generation Time (s) x10–12 Frequency (Hz) x1012 of 3-D simulation tools. These tools

16 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation are general enough to be adapted to surveillance applications; high-density no preferred direction for propagation. problems in many areas, and ﬂ exible optical interconnects for high- In support of both of these codes we enough to embrace the design of future performance computing (core of the have also been working on a program to mixed-signal systems as well as stand- ASCI mission); and detection devices generate accurate gain and absorption alone systems in disparate regions of the for homeland security. curves for semiconductor quantum wells EM spectrum. as a function of quantum well structure, FY2006 Accomplishments and Results wavelength, and carrier density. Relevance to LLNL Mission Most of our work has been concen- In the past year we spent time The ability to model complex 3-D trated in extending our two research researching algorithms for incor- photonic devices in the time domain codes: Quench3D and EMSolve. porating a vector finite element is essential to LLNL for a broad range Quench3D is a narrow-bandwidth scalar beam-propagation solver and a finite of applications. These include high- beam-propagation-method code built element carrier-diffusion model into bandwidth instrumentation for NIF for modeling large devices in which the Quench3D suite. The incorpora- diagnostics; microsensors for weapon light propagates in a preferred direction. tion of vector finite elements into the miniaturization within the DNT pro- EMSolve is a vector time-domain code BPM solver will allow us to model the grams; encryption devices and circuits used for modeling small devices with dependence of gain on polarization in for secure communications for NHI either complicated geometries and/or amplifier and laser structures. In addition we spent some time determining how the code should be parallelized. 200 100 We researched the algorithms neces- –100 0 sary for incorporation of carrier diffu- 0 –100 –200 sion and polarization models for 2- and 100 4-level absorption/gain in the EMSolve 200 suite. We also performed research on submesh modeling of carrier effects in 150 EMSolve. These codes can be used to efﬁ ciently examine power scaling in Auston-Switch-based THz sources and 100 model Vertical Cavity Surface Emitting Lasers (VCSELs). Using the results of 50 this research we were able to simulate the power scaling effects of Auston- 0 Switch-based THz sources. Figures 1 to 3 illustrate the results of this work. Z The quantum well modeling code –50 work primarily involved researching ex- Y tensions and corrections to the ground- X –100 work that had been laid in the summer of FY2005. Figure 2. Field propagated from a trio of Gaussian-triggered Auston-Switch THz sources. Related References (a) (b) x10–10 1. Bond, T. C., and J. S. Kallman, “Time- 100 1 Domain Tools for the Investigation of Gain-Quenched Laser Logic,” International 50 0.5 Semiconductor Device Research Symposium, Washington, DC, December 10-12, 2003. 0 0 2. Koning, J. M., D. A. White, R. N. Rieben, and M. L. Stowell, “EMSolve: A Three Polarization field Polarization Electric field V/m Electric field –50 –0.5 Dimensional Time Domain Electromagnetic Solver,” 5th Biennial Tri-Lab Engineering Conference, Albuquerque, New Mexico, –100 –1 0 1 2 3 4 5 6 0 1 2 3 4 5 6 October 21-23, 2003. –14 –14 Time (s) x10 Time (s) x10 3. Koning, J. M., “Terahertz Photo- Conductive Antenna Array Power Scaling Figure 3. Electric fi eld (a) and polarization (b) for a 2-level material illuminated by a beam of EM radiation. The polarization is computed using an auxiliary diff erential equation and is important in determin- Simulations,” Proceedings IEEE APS, ing the gain and/or absorption in VCSEL simulations. pp. 2631-2634, 2006.

Lawrence Livermore National Laboratory 17 TechBase

Usability Enhancements for Joseph Koning (925) 422-3713 3-D Photonic Design Tools [email protected]

number of algorithms have been team has written will be made widely A created to model novel and LLNL- available throughout LLNL on different specifi c devices. These algorithms computer architectures. were implemented in a suite of tools to model full 3-D, time-domain, nonlin- Relevance to LLNL Mission ear, photonics devices. This project Simulation is a core competency of was initiated to transition the suite of LLNL, and this work enhances the abili- research codes to production codes, ty of its engineers to model a broad class usable by a wider audience. The en- of devices. Potential users include the hancements to the research codes will photonic designers in NIF (high speed provide a set of packaged design tools diagnostics), DNT (weapons safe optical that can be run on a variety of serial sensors), DHS (radiation sensing), NSA and parallel computers. (gain quenched laser logic), NAI (fi ber amplifi ers), and PAT (components for Project Goals the linac coherent light source). The capability for engineers to model novel 3-D photonic devices in FY2006 Accomplishments and Results the time domain requires usable and The existing algorithms have three effi cient simulation codes. The specifi c main areas: enhancement of the full tasks of this project include the imple- vectorial, 3-D time-domain code EM- mentation of the existing algorithms, Solve; enhancement of the 3-D beam improving user interfaces, porting the propagation quench suite of codes; and codes to more common platforms, and the creation of a code to model semicon- running examples. The software that this ductor physics.

Figure 1. Confi guration system. The EMSolve code uses an XML-based Figure 2. vec_laser GUI showing initial conditions for simulation confi guration system, which enables fast simulation confi guration and easy in- of an optical amplifi er. The mesh is shown in color and the input tegration of new code features. The GUI uses java for cross-platform portability. waveform is shown in grayscale.

18 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

The EMSolve code includes a beam propagation method (BPM) code effects, and the integration limits have number of enhancements to simulate with coupled carrier diffusion called all been updated. Figure 3 shows the photonic devices. A coupled carrier dif- vec_laser. The GUI produced for this potential in a diffused quantum well fusion integrator/electrodynamics solver code is shown in Fig. 2. The vec_laser for different diffusion lengths. Figure 4 has been implemented for photonic code has been parallelized and ported to shows the trend of absorption for a TE integrated circuit simulations. In order to run on Intel-based parallel machines. polarization in an AlGaAs/GaAs quan- make this coupled system more effi cient, In the Intermixed Quantum Well tum well; with increasing carrier density a sub-mesh object was implemented to Physics modeling code the accomplish- saturation of the light-hole excitonic separate the carrier dynamics simulation ments for this year include implemen- peak occurs. grid from the full structure. In addition, tation of Version 2 for calculation of effi cient vector operations and fi nite ele- complex permittivities in quantum Related References ment library optimizations were imple- wells using a quantum mechanics 1. Koning, J. M., “Terahertz Photo- mented, providing a 12x speed improve- approach. Carrier induced effects are Conductive Antenna Array Power Scaling ment. Figure 1 shows the confi guration included: bandgap shrinkage is implicit Simulations,” Proceedings IEEE APS, system. Adding a new component adds in the calculation of electron wave- pp. 2631-2634, 2006. a tab to the confi guration window. This functions using an iterative approach 2. Koning, J. M., D. A. White, R. N. Rieben, advanced model was used to study THz to solve Schroedinger-like and Poisson and M. L. Stowell, “EMSolve: A Three photoconductive antennas. equations including many-body carrier Dimensional Time Domain Electromagnetic In a separate integrator a polariza- effects, bandgap fi lling, and free-carrier Solver,” 5th Biennial Tri-Lab Engineering tion model was implemented using both absorption effects. Excitonic effects are Conference, Albuquerque, New Mexico, 2- and 4-level absorption/gain models. also included. The potential distribution October 21-23, 2003. These polarization models will be used in the diffused well at quiescent state, 3. Bond, T. C., and J. S. Kallman, “Time- to simulate 3-D vertical cavity, surface- the carrier density distribution formula- Domain Tools for the Investigation of emitting lasers (VCSELs). tion, the iterative formulation of quasi- Gain-Quenched Laser Logic,” International The quench suite of codes has been Fermi levels, the interband absorption Semiconductor Device Research Symposium, augmented with a narrow bandwidth integrated with exciton saturation Washington, DC, December 10, 2003.

Diffused QW 105 0.20 14 0.1 x 1017 12 1 x 1017 0.15 Ld=0nm 2 x 1017 ) 10 17 Ld=1nm –1 3 x 10 Ld=2nm 5 x 1017 0.10 (cm Ld=3nm 8 17 A 7 x 10

6 0.05 Potential Uc(z) Potential 4 Absorption 0 2

–0.05 0 –60–40 –20 0 20 40 60 355 360 365 370 375 380 Location in z (nm) Frequency f (THz)

Figure 3. Potential distribution for the conduction band in a diff used Figure 4. TE absorption in a 7-nm AlGaAs/GaAs well. quantum well for diff erent diff usion lengths, Ld. The longer Ld, the smoother the transition from well to barrier and the wider the gap.

Lawrence Livermore National Laboratory 19 TechBase

Laser Glass Damage: James S. Stölken (925) 423-2234 Computational Analysis of stö[email protected] Mitigation Process

nderstanding and controlling the physi- studies and mitigation process develop- simulations of laser energy deposition Ucal processes that cause laser-induced ment could benefi t from a high-fi delity and subsequent material hydrodynamic damage to optical components is crucial predictive simulation capability that response that includes the dependence of to the success of many high-energy- incorporates the essential ingredients the energy deposition processes on local density experimental facilities, includ- of the laser-material interaction and the variations in state-dependent material ing LLNL’s National Ignition Facility resulting coupled material response in properties. energy deposition (thermal (NIF). Experimental and theoretical experimentally relevant confi gurations. transport) and hydrodynamic response investigations of laser-damage in silica We are addressing the technical chal- (momentum transport). A secondary goal glass and KDP crystals are legion and lenges associated with energy deposi- of the project is to determine how tightly- are actively being pursued within the NIF tion, dynamic material response, and coupled the EM and hydro simulation Program. The insight garnered from ex- the nature of the coupling between these schemes are for the deposition and the perimental data is limited by the extreme- two processes. Our approach is to adapt response. To accomplish these goals, spe- ly short time-scale (~1 ns) of the damage the current EM simulations capability cifi c objectives to enhance the hydro and events and the complex interplay between within EMSolve to simulate the time, EM simulation capabilities have been set. energy deposition and hydrodynamic space, and material state dependence The final objective is to couple the response. A further complication is the of the laser energy deposition process. hydro and EM simulations to facilitate stochastic nature of damage initiation, ne- The material’s dynamic response is then exploring how strongly this interac- cessitating a post priori approach where simulated using advanced multi-phase tion must be implemented. The degree the damage process must be deduced via equations of state (EOS) and failure of coupling required to adequately forensic reconstruction. models within the ALE3D multi-physics simulate a given phenomenon is Understanding laser-damage code. This also provides some facility to problem-dependent and greatly affects initiation and growth is just half of the model damage initiation in silica, which the computational costs and effi cacy of problem. Creating an effective strategy would provide a self-consistent facility the overall simulation methodology. to detect and mitigate laser damage is to establish initial conditions for mitiga- Our technical approach has been as the essential second part. One promising tion studies. follows. process is to use long wavelength (CO2) 1. Implement spatial and material state- laser energy to excise/anneal the damage Project Goals dependent EM properties, such as the site. Key parameters to be optimized The primary goal is to implement complex dielectric constant. Using include the laser wavelength, intensity, a capability to perform coupled EM a Lorenz-Lorentz formulism, we pulse duration, and scan pattern in explicitly modeled the dependence of relation to the size and type of dam- the material conductivity and permit- age site. Both damage initiation/growth tivity upon density (Fig. 1). This same approach explicitly accounts for the laser energy frequency dependence, Total field air Scattered field glass 150 thereby facilitating the investigation 100 of this important parameter in candi- 50 date mitigation processes. To improve 300 0 the quality of the boundary conditions μm 200 –50 100 of the EM simulations and enhance –100 0 their dynamic range, we adopted a –150 X –100 scattered electric-fi eld methodology –300 –200 –100 0 100 200 300 Z –200 Total (Fig. 2). Scattered Total field Y –300 field air densified glass field glass 2. Adapt existing models of material deformation, phase transformations, Figure 2. Three-dimensional rendering of laser and damage to simulate such process- Figure 1. Simulated Joule heating in glass around heat deposition similar to that shown in Fig. 1. an artifi cial defect with 20% greater permittivity Energy deposition varies by a factor of one hun- es under conditions relevant to laser and conductivity than the bulk glass. dred from blue to red. damage in silica glass. We adopted a

20 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

unifi ed-creep model for the deforma- density. The material density plays simulations (ALE3D) to the laser tion of silica at high temperatures a central role in both the hydro- energy deposition simulations (EM- using material parameters consistent dynamic response and the energy Solve) via a file passing mechanism with a linear viscous solid and a deposition. Furthermore, under (Fig. 4). This approach leverages temperature-dependent shear modu- high-pressure loading, such as existing capabilities within ALE3D to lus. The two-phase EOS is based on laser-induced shocks, the reference specify spatially and temporally vary- combining two analytic forms for the density of silica is modifi ed, providing heat sources using an external file. low and high-pressure phases with an ing material “memory” of previous irreversible kinetic relation (Fig. 3). history such as glass damage. Relevance to LLNL Mission 3. As a fi rst step, consider only a single A loosely coupled scheme is pro- Leveraging current computational material state variable: the material posed to connect the hydrodynamic capabilities will place LLNL’s Engi- neering Directorate in a key technical Pressure Relative volume role for both process and facilities 0 0 development. –2 –2 FY2006 Accomplishments and Results –4 –4 A two-phase EOS model has been adapted to account for the permanent –6 –6 densifi cation of silica glass that occurs –8 –8 under high-pressure loading. Model With densification (mm) With parameters have been fi t to the refer- –10 –10 ence density, bulk modulus, and thermal –6 –4 –2 0 2 4 6 –6 –4 –2 0 2 4 6 expansion coeffi cients associated with 0 0 both the high- and low-pressure phases. A simple model of brittle damage has –2 –2 been adapted to account for cracking –4 –4 under tensile loading, and has been successfully tested in conjunction with the –6 –6 above densifi cation EOS model. A scattered electric fi eld formulation has been –8 –8 implemented to improve the effi ciency Without densification (mm) Without of the EM simulations. The capability –10 –10 –6 –4 –2 0 2 4 6 –6 –4 –2 0 246 to account for spatially varying permit- mm mm tivity and conductivity has been imple- Figure 3. Residual pressure and relative volume following indentation of glass with a smooth circular mented. The dependence of the real and punch. Cross-section views of a 3-D simulation showing the interplay of the damage model with EOS imaginary parts of the refractive index that (do)/(do not) capture the pressure-induced densifi cation of silica glass. on material density and radiation wavelength has been accounted for in the framework of a Lorenz-Lorentz model ALE3D and implemented in the EMSolve code. hydrodynamic simulation Material density

Density FY2007 Proposed Work 2 –qe RN 1 We plan to couple the hydro and EM m 2 2 e A W – W0 + 2iDW Lorenz-Lorentz simulations via a fi le-sharing scheme by E(W) = 1 + 4π Heat 4π –q2 RN 1 model extending existing capabilities within the 1 – e 2 2 3 me A W – W + 2iDW ALE3D software and adapting the EMSolve 0 Permittivity software to import and export the requisite Laser frequency conductivity fi les. We will also continue testing the new capabilities created in FY2006 and assess EMSolve the effi cacy of the coupling scheme on electrodynamic benchmark problems. simulation

Figure 4. Loosely coupled scheme that includes the eff ects of laser frequency and material density.

Lawrence Livermore National Laboratory 21 TechBase

Simulation Capability for David Clague (925) 424-9770 Nanoscale Manufacturing [email protected] Using Block Copolymers

his project focused on simulation ca- Relevance to LLNL Mission Tpability for nanoscale manufacturing Repeatable control of nanoscale using block copolymers. The capabilities features such as lithographic masks and published in the literature enable predic- 3-D structures is a critical capability gap tion of the polymer combination and the at LLNL. This project will provide cus- ratio of polymers involved to achieve tom nanofabrication technology that will desired nanoscale features during melt enable the transition and deployment of solidiﬁ cation. Additionally, the length of many nanoscale devices and technolo- the polymer blocks qualitatively inﬂ u- gies into the programs. This enabling ences the temperature and time neces- capability will impact nanoscience and sary for the annealing process. technology at LLNL, and aligns with competency goals in predictive simula- Project Goals tion and micro-, meso- and nanoscale The goal of this project was to engineering, computational engineering, reduce to practice published, predic- and mesoscale fabrication. tive block copolymers simulation capabilities to augment and guide ex- FY2006 Accomplishments and Results perimental efforts to controllably form We reduced to practice 2-D and nanoscale features. 3-D Cahn-Hilliard-Cook (CHC) type

140 Spheres Lamellae Spheres bcc bcc 120 Hexagonal Hexagonal 100 cylinders cylinders

N – degree of incompatibility N – degree Gyroid C Spheres Spheres 20 close packed close packed Disordered 0 0 0.2 0.4 0.6 0.8 1 Volume fraction of ‘A’ block, f

Figure 1. Phase diagram for polystyrene and PMMA, predicted using self-consistent mean fi eld theory: χ is the Flory-Huggins parameter, which is a measure of block-block solubility; N is the degree of po- lymerization; and f is the number fraction of the reference polymer in the diblock.

22 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation models to predict nanophase formation were within 5% of the realized results. Related References in diblock copolymer systems. The mod- In Fig. 2, we show lamellae and cylin- 1. Kielhorn, L., and M. Muthukumar, els from the literature were reduced to drical phase separations. “Spinodal Decomposition of Symmetric both MatLab® scripts and Fortran90® In addition to reduction to practice Diblock Copolymer/Homopolymer Blends simulation capabilities. The potential of the 2-D CHC model, a 3-D version at the Lifshitz Point,” J. Chem. Phys., 110, nanophases that can be predicted with of the capability was reduced to prac- 8, 1999. the model include lamellae, cylinders, tice to enable prediction of 3-D effects 2. Chakrabarti, A., and R. Toral, “Late gyroids, and spheres (Fig. 1). and surface boundary conditions on Stages of Spinodal Decomposition in Three- Two-dimensional results from this nanoscale feature formation. Figure 3 Dimensional Model System,” Phys. Rev. B, effort enabled elucidation of conditions shows the 3-D results for lamellae and 39, 7, 1989. that produced lamellae and cylindrical spherical nanofeatures. 3. Matsen, M. W., and F. S. Bates, “Unify- features. Additionally, through the litera- Using these newly available capa- ing Weak- and Strong-Segregation Block ture, we were able to relate ﬁ nal features bilities, simulation results have been Copolymer Theories,” Macromolecules, 29, to real dimensions. When comparing collected to help guide block copolymer 4, 1996. predicted feature sizes with experiment, selection from commercial sources to it was found that the simulation results achieve desired feature sizes.

~ 20 nm ~ 28 nm

10 10

Figure 2. Predicted lamellae and cylindrical 20 20 nanofeatures using 2-D CHC-like model for a polystyrene/PMMA diblock copolymer 30 30 system. The volume fractions of the reference block were consistent with the phase 40 40 diagram shown in Fig. 1. Results were in very good agreement with experiments.

50 50

60 60

2-D lamellae 2-D lamellae

~ 20 nm

~ 21 nm Figure 3. Predicted 3-D lamellae and spherical nanofeatures for a polystyrene/ PMMA system. The average feature size is given on the images.

3-D lamellae 3-D cylinders

Lawrence Livermore National Laboratory 23 TechBase

Sputtering Chamber and Aaron Wemhoff (925) 423-9839 Capsule Thermal Modeling wemhoff [email protected]

he morphology of a thin fi lm grown Project Goals Tin a sputtering process has been This project focuses on the full shown to be heavily dependent upon the integration of all modes of heat transfer substrate temperature and the chamber from the capsule to the surrounding conditions, as illustrated in the Thorn- chamber environment: gas adsorption, ton structure zone diagram in Fig. 1. enclosure radiation, and wall-capsule Currently, measurements of the sub- contact. These modes of heat transfer strate temperature of spherical capsules are calculated using a standard fi nite el- in a sputtering process are extremely ement formulation, where the infl uence diffi cult due to the required motion of of each mode is designated via user- the capsule. Previous analyses for this defi ned input variables. Furthermore, process have involved a large number the infl uence of capsule motion on the of approximations and simplifi cations, aforementioned modes of heat trans- resulting in an uncertainty of +/- 70 ºC. fer is automatically calculated at each In this project, a predictive tool for capsule position. the capsule temperature is investigated and applied as part of the Diablo multi- Relevance to LLNL Mission mechanics fi nite element code, nearly The structure of thin fi lms is of eliminating this uncertainty since the vital importance to LLNL programs underlying mechanics of the system are and areas of interest. Equally valuable captured by the code. are the addition of new features to the

Columnar grains Transition structure consisting of densely packed fibrous grains Porous structure Recrystallized consisting of grain structure tapered crystallites Zone III separated by voids Zone II

1.0 Zone I Zone T 0.9 0.8 30 0.7 0.6 20 0.5 0.4 Substrate temperature (T/T ) Argon pressure 10 0.3 M (m TORR) 0.2 1 0.1

Figure 1. Thornton structure zone diagram.

24 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

Diablo code. The work performed in this project is part of a joint effort to improve the quality of sputtered ﬁ lms for NIF target preparation.

FY2006 Accomplishments and Results A specialized Neumann boundary Projected surface condition was added to Diablo. This module features a combination of thermal mechanics seen in the bulk node, Capsule contact, and convection algorithms. At each time-step the user-defi ned capsule position function allows for the auto- matic determination of the existence of contact, the location of contact along Facet the chamber wall (if applicable), and the updated enclosure radiation view factor set. View factors are effi ciently calculated by projecting each facet of the chamber wall using spherical trigonometry, as seen in Fig. 2. The capsule temperature is calculated at each time-step using a standard lumped capacitance approach. The numerical approach and implementation was Figure 2. Projected surface used in determination of capsule-facet view factor. verifi ed by comparing six test problems to known analytical solutions. In all cases the simulated capsule temperature agreed with the analytical solution within 0.3%. A further test problem featured the change in capsule temperature history when the capsule was removed from the sputtering pan surface at specifi c 460 times. Figure 3 shows that the change Time of removal in heat loss is greatly reduced after this 440 from surface contact is removed, which is consis- 0 s 420 tent with the reduction in heat transfer 5 s modes after the removal. 400 10 s 15 s 20 s Related Reference 380 Thornton, J. A., “Infl uence of Apparatus Geometry and Deposition Conditions on the 360 Structure and Topography of Thick Sput- tered Coatings,” J. Vac. Sci. Technol., 11, (K) temperature Capsule 340 pp. 66-67, 1974. 320

300 0 5 10 15 20 Time (s)

Figure 3. Temperature history of capsule for various durations of contact with the chamber wall surface.

Lawrence Livermore National Laboratory 25 TechBase

Experimental Validation of Steven W. Alves (925) 423-2391 Finite Element Codes for [email protected] Nonlinear Seismic Simulations

o further reﬁ ne LLNL’s abilities to slice of a reinforced concrete building Tsimulate reinforced concrete struc- using the NEES Large High- tures subjected to seismic events, our Performance Outdoor Shake Table computational codes and modeling ap- (LHPOST) at the University of proaches must be rigorously validated. California, San Diego (UCSD) (see Seismic excitations are long dura- Fig. 1a). Results from the shake table tion (~30 s), and large structures can experiment were provided so that the require very large numbers of elements, response of a finite element model of so seismic simulations of reinforced the structure could be compared to the concrete structures are computation- experimental response. ally intensive. Using the homogenized rebar model implemented in DYNA3D/ Project Goals ParaDyn to approximate the reinforcing The goal is to assess our capabil- is attractive because of its efﬁ ciency in ity to accurately model a full-scale computation and mesh generation com- reinforced concrete structure using a pared to explicitly modeling the rebar. homogenized rebar/concrete model as A series of shake table tests were implemented in the DYNA3D/ performed on a full-scale seven-story ParaDyn codes.

(a) (b)

Figure 1. (a) Experimental structure; (b) half-symmetry fi nite element model.

26 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

Relevance to LLNL Mission 2.17 Hz and 2.65 Hz, respectively (see measured roof displacement from the Simulation of the seismic response Fig. 2). experiment by about a factor of 2; and of reinforced concrete structures is of A more refi ned version of the mod- the simulated displacement oscillates importance to LLNL’s Nuclear Fuel el with enough discretization to capture at a much higher frequency, indicating Cycle and Reactor Program, the Global the characteristics of the rebar was cre- the model is too stiff (see Fig. 3). By Nuclear Energy Partnership (GNEP), ated for running dynamic analyses in comparing a test case of a wall modeled and the National Ignition Facility (NIF). ParaDyn. An instability was discovered with homogenized rebar to a wall with In general, validating this capability in the homogenized rebar/concrete ma- explicitly modeled rebar, we verifi ed allows LLNL to attract new projects in terial model that prevented completion that the homogenized rebar is not the the area of seismic analysis. This project of the analysis of the four, successively cause of the high stiffness. also promotes collaboration with UCSD. stronger consecutive earthquakes. The It is believed that the properties used instability arises out of a singularity in the model specify concrete that is too FY2006 Accomplishments and Results in the formulation of the underlying strong, that there may be mass that is not A version of the fi nite element concrete model, but the analysis up to accounted for in the model, and that damp- model was fi rst created for linear, static the point where the instability occurs is ing may be overestimated in the model. analysis in NIKE3D. From this analysis, uncontaminated. Perhaps most importantly, the concrete in natural frequencies and mode shapes of The nonlinear analysis was com- the actual structure was probably already the structure were determined. The fi rst pleted for the entire fi rst earthquake, damaged to a signifi cant degree from mode of the structure is torsional, and which is the smallest ground motion, settling and low-amplitude white noise the second mode is a fi rst-order canti- prior to the occurrence of the instabil- tests performed before the fi rst earthquake lever mode. The natural frequencies for ity. The simulated roof displacement motion was applied. This factor is not the torsional and cantilever modes are for this earthquake underestimates the captured in the current model.

Roof displacement – EQ1 FY2007 Proposed Work 2.0 Simulated We will work to better understand the Measured 1.0 singularity in the concrete model and determine how to deal with it. We will meet 0 with UCSD faculty to identify discrepancies between the computational model and –1.0 the test structure. We will then compare Displacement (in.) Displacement the simulated response from the updated –2.0 model to the experimental results. 0 5 10 15 20 25 30 Time (s)

Figure 3. Comparison of simulated roof displacement to measured roof displacement.

Figure 2. Left: torsional mode at 2.17 Hz; right: cantilever mode at 2.65 Hz.

Lawrence Livermore National Laboratory 27 LDRD

Structure and Properties Anthony Van Buuren (925) 423-5639 of Nanoporous Materials [email protected]

ur goal is to quantify the microstruc- of the pore structure in metal-oxide Oture of highly porous materials, and aerogels and metal foams to quan- to determine how processing of the po- tify density, pore size, pore distribu- rous material relates to the structure, and tion, and the aspect ratios of the cell ultimately to the mechanical behavior. backbone as a function of prepara- We quantify structural changes with a tion conditions; combination of small-angle x-ray scat- 2) extremely high-resolution diffraction tering (SAXS) and high-resolution x-ray imaging to determine the structure tomography. We use fi nite element mod- of the lattice of select, low-density eling, using the structures determined metal-oxide foam to provide a basis above, to study the effects of mechanical for interpreting the SAXS data; loading on the cell structures, and to 3) fi nite element modeling, using the map out relationships among process- structures determined in the fi rst ing, density, and strength. Synthesis and goal, to study the effects of mechan- processing variables affect kinetics of ical loading on the cell structures, nucleation, particle growth and the orga- and to map out relationships among nization of the aerogel networks. processing conditions, density, and strength; and Project Goals 4) determination of the extent of any Our goals are to perform the following: anisotropy in lattice architecture 1) high-spatial-resolution SAXS and and improve spatial resolution to synchrotron radiation computed examine and characterize graded- tomography (SRCT) measurements density structure.

106

105 ) –1 104

103

102

Scattered intensity (cm Scattered 101

100

10–1 0.001 0.01 0.1 Q (A–1)

Figure 1. Plot of scattering intensity as a function of the wave vector over three orders of magnitude in Q: 3 3 3 USAXS from 250 mg/cm (red line), 100 mg/cm (blue line), and 40 mg/cm (green line) Ta2O5 aerogel.

28 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

Relevance to LLNL Mission decrease in correlation length consis- This program develops critical extent with a shrinkage in the network FY2007 Proposed Work perimental technologies for many LLNL structure. Evidence for wetting was In FY2007 we plan to make USAXS applications. A key deliverable will be also observed. measurements to understand the eff ect of the ability to predict the mechanical In the Ta2O5 we did not observe a synthesis conditions on the change in struc- properties of nanoporous materials and large fraction of unconnected dangling ture; in particular, how synthesis conditions characterize gradient-density foam mi- mass fragments, which is inconsistent may aff ect the amount of mass at the nodal crostructures for future laser targets. with the percolation model. However, points in the aerogel. we did establish that, for the 100-mg/ In situ USAXS measurements will be 3 FY2006 Accomplishments and Results cm Ta2O5 foam (Fig. 2), approximately conducted on aerogels at temperatures The ultra-small-angle x-ray scatter- 85 % of the mass was confi ned to the where nitrogen gas will condense in the ing (USAXS) data shows that there are nodes, consistent with the formation of aerogel matrix. How the aerogel wets signifi cant changes to the cell structure fractal clusters. The exponents of the in a cryogenic fl uid is unknown, but it is of metal-oxide foams as a function of modulus vs fraction power laws are required knowledge if these foams are to be preparation conditions and density. In 3.74. Correcting the scaling laws for used in laser targets. Fig. 1 we show the scattering intensity the reduced apparent mass lowered the The small angle results will provide the as a function of wave vector, Q, for theoretical estimate to 1.7, consistent correlation length and beam thickness as a three different densities of Ta2O5 aero- with bending. Our results provide the function of density and processing param- gel. We fi nd that the smallest particles fi rst experimental support for a diffu- eters. From these measurements, stochastic that defi ne the strut width in the aerogel sion limited cluster aggregation model lattices will be generated for fi nite element do not increase with density and are 3 for aerogel growth. simulations. Simulations will then provide to 4 nm for all densities. However, the the elastic constants of the material. In ad- correlation length decreases suggest- Related Reference dition to providing the elastic constants of ing that strut length also decreases with Kucheyev, S. O., M. Toth, T. F. Baumann, the foam, fi nite element simulation will be increased density. In the USAXS, we A. V. Hamza, J. Ilavsky, W. R. Knowles, used to study thermo-elastic deformation. see evidence for large (> 500 nm) voids B. L. Thiel, V. Tileli, A. van Buuren, Y. M. in the aerogels with the lowest density. Wang, and T. M. Willey, “Structure of Low- We have also done in-situ measure- Density Nanoporous Dielectrics Revealed ments of structural changes in the Ta2O5 By Low-Vacuum Electron Microscopy and aerogel as a function of thermal cycling Small-Angle X-Ray Scattering,” accepted to down to 100 K. At 100 K we fi nd a Langmuir 2006.

20 nm

3 Figure 2. TEM image of a 100-mg/cm Ta2O5 aerogel.

Lawrence Livermore National Laboratory 29 TechBase

Enhanced Composite Andrew T. Anderson (925) 423-9634 Modeling Tools [email protected]

omposite materials are used in many evaluated. In the next phase, the predic- Cadvanced weapons systems and tions of these models were compared structures at LLNL. We have previously with experimental data, either in their enhanced our ability to simulate struc- native code or in our initial implemen- tural response and progressive failure tation. Finally, we implemented an of composite systems in ALE3D by experimentally validated fi ber compos- porting an existing composite constitutive ite material model into ALE3D. model from DYNA3D (Model 22, the Fiber Composite with Damage Model) Relevance to LLNL Mission into ALE3D. This year, a more advanced The improved fi ber composite mate- model (DYNA3D Model 62, the Uni- rial models can be used in simulations Directional Elasto-Plastic Composite (to failure) in the many LLNL programs, Model) has been implemented. The such as those for composite munitions, Uni-Directional Elasto-Plastic Compos- armor penetration, pressure vessels, and ite Model has already been successfully rocket motors. This effort also supports used to analyze the response of a fi ber LLNL work-for-others programs. This wound composite pressure vessel. Veri- project has been benefi cial in supporting fi cation and validation of the model’s the composite modeling efforts within implementation in ALE3D has also the DoD Joint Munition Program and been accomplished. the Focused Lethality Munition Pro- gram. This study supports LLNL’s en- Project Goals gineering core competency in high-rate A variety of composite models have mechanical deformation simulations of been described in the literature and large complex structures by providing an implemented in other codes. Our initial enhanced capability to model composite goal was to select the models to be structures with ALE3D.

Figure 1. Finite element model of the three-point bending tests.

30 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

FY2006 Accomplishments and Results response of three-point bending in After we completed a literature composite beams. The elastic response FY2007 Proposed Work survey of available fi ber composite mod- of the models was found to be accept- The DYNA3D Uni-Directional Elasto- els, we implemented two solid-element able, but the damage parameters needed Plastic Composite Model will be ported to models into ALE3D that are already additional refi nement. ALE3D. The failure algorithm from DYNA3D’s available in DYNA3D. The Fiber The Fiber Composite with Damage Fiber Composite with Damage model will Composite with Damage Model, which Model was implemented into ALE3D. be added to the ported material model. requires a laminate material descrip- An important part of this task was The progressive failure algorithm could be tion for each element, and the Uni- creating an algorithm to initialize and altered during the validation phase. A list of Directional Elasto-Plastic Composite update material directions at the ele- the projected milestones follows: Model, which uses a ply-level de- ment level. The model was validated 1. implement existing DYNA3D solid- scription of the fi ber composite, were against the same three-point bending element composite mode into ALE3D; determined to replicate all or most of experiments that were modeled with 2. streamline ability to output the necessary material responses. the DYNA3D simulations, and the orthotropic data information with The validation process was initi- results were found to closely match the prescribed local volume elements ated with DYNA3D using experimental DYNA3D predictions. (this data will enable the construct data. The two solid-element compos- Our results are illustrated in Figs. 1 of a global/local composite modeling ite models were used to predict the to 4. strategy that will facilitate higher fi delity); Uni lay-up three-point bending Quasi lay-up three-point bending 3. incorporate a failure algorithm that 350 400 includes matrix delamination, fi ber Delamination bottom 300 350 surface, compressive tensile and fi ber compressive failure; Compressive failure 300 failure top surface 4. use the model to predict dynamic 250 top surface 250 impact and three-point bending 200 200 responses; 150 150 5. perform relevant tests based on Force (lb) Force Force (lb) Force 100 100 expected responses; and Data 50 Data 6. compare tests to simulations and make 50 Calculation 0 Calculation modifi cations to models as necessary. 0 –50 0 0.1 0.2 0.3 0.4 0 0.20.4 0.6 0.8 1 Displacement (in.) Displacement (in.)

Figure 2. Verifi cation of the laminate model us- Figure 3. Verifi cation of the laminate model using ing three-point bending data for uni-directional three-point bending data for quasi-isotropic lay-up. lay-up.

Figure 4. Modeling of composite-cased penetrator.

Lawrence Livermore National Laboratory 31 TechBase

Modeling Forming Processes Moon Rhee (925) 424-4990 [email protected]

he ability to model and optimize Project Goals Tmaterial manufacturing processes and The goal of this project is to dem- predict resulting material properties is onstrate advanced material modeling important where product performance, capability for forming process simula- costs and/or waste reduction are con- tion and to work with production labora- cerns. DOE programs such as Reliable tories toward validating the models. The Replacement Warhead (RRW), Trans- capability will be valuable in the design formational Materials Initiative (TMI), and optimization of forming processes to and Responsive Infrastructure (RI) will achieve desired microstructures, proper- rely on rapid prototyping of complex ties, and performance characteristics. components. The goal of process modeling is to provide a simulation-based, Relevance to LLNL Mission rapid-design capability for effi cient This effort will contribute to LLNL’s production of high quality parts with role and core competency in numerical better control over the desired proper- modeling and material response. The ties. Application of process tools will capability demonstrated in this project reduce trial and production costs and is supportive of other forming processes shorten the time from product concep- where geometric fi delity and control of tion to production. Detailed under- material properties are critical. standing of material response and product performance predictions can FY2006 Accomplishments and Results be achieved by combining robust fi nite A material model for static recrys- element simulation tools from DOE’s tallization has been implemented into ASC program with advanced models of ALE3D for use in forming process material properties.

1.2

1.0

0.8 A B 0.6 C

0.4 Fraction recrystallized Fraction 0.2

–0.2 0.001 0.01 0.1 1 10 Time (s)

Figure 1. Recrystallized fraction plotted against time for aluminum. For A: ε = 10–7 s–1, ε = 0.3; for B: ε = 0.1 s–1, ε = 0.3; and for C: ε = 10–7 s–1, ε = 0.3.

32 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation simulations. The model is based on microstructure parameters such as grain size; prior deformation that creates a forest dislocation structure; and the Zener-Hollomon parameter, which is a function of temperature and strain rate. The model accounts for the material strength reduction resulting from dissolution of the forest dislocation structure as the grains recrystallize. Figure 1 shows a typical range of fraction recrystallized as a function of time following deformation under various strain and strain rate conditions. A rolling simulation of an aluminum slab was performed for validation, and a contour plot of recrystallized fraction at the end of the fi rst pass is given in Fig. 2. The fi gure shows that the most recrystallized portion of the rolled slab is the Figure 2. Hot rolling simulation of aluminum at 700 K. Red colors at the second element from the top and bottom surfaces indicate highest portion of recrystallization. offset from the top and bottom surfaces since the strain is higher at these locations. The variation in strength levels across the slab thickness results from a combination of increased strength due to strain hardening and strength reduction from recrystallization. Also, demonstrations of shock processing simulations of porous materials were performed. A constrained-random void confi guration model was constructed as shown in Fig. 3, where, under shock conditions, these voids collapse. The collapsing voids can signifi cantly alter local stress fi elds, and at the same time the temperature can increase dra- matically. The shock-processed material is subsequently deformed, so the effect Figure 3. Constrained-random void distribution, 10 % void fraction. of this prior processing on the material performance is of great importance. A 14 series of simulations using different Loading pressure 40 GPa 12 shock conditions, ranging from 30 GPa 10 GPa to 40 GPa, were carried out to 20 GPa demonstrate capability for constructing 10 10 GPa equation-of-state models for a porous 8 material (Fig. 4). The fi gure reveals that different values of bulk modulus 6

were observed, depending on the level (MPa) Pressure of initial pressure conditions. 4

Related Reference 2 Bontcheva, N., and G. Petzov, “Micro- 0 structure Evolution During Metal Forming 0.90 0.95 1 Process,” Computational Materials Science, Relative volume 28, pp. 563-573, 2003. Figure 4. Elasticity pressure vs. relative volume for void confi guration given in Fig. 3.

Lawrence Livermore National Laboratory 33 LDRD

Multiscale Characterization Jeff rey N. Florando (925) 422-0698 of bcc Crystals Deformed to fl [email protected] Large Extents of Strain

xperimental data are crucial in the Relevance to LLNL Mission Eprocess of constructing and validating Understanding and simulating the the multiscale crystal plasticity mod- plastic, or non-reversible, deformation els used in computer code simulations of body-centered cubic (bcc) metals, is of materials deformed under extreme a major component of LLNL’s stockpile conditions, such as high strain rate, high stewardship mission, and is applicable to pressure, and large extents of strain. The future NIF experiments. “6 Degrees of Freedom” (6DOF) experiment was designed specifi cally for this FY2006 Accomplishments and Results task and has provided data on the behav- Slip System Analysis. Previous ior of bcc crystals that may revolutionize years’ accomplishments included incor- the fi eld. porating a full-fi eld 3-D image correla- Until now, the experimental data tion strain measurement system into the and simulation efforts have focused 6DOF experiment. Sequential photos are on relatively small extents of plastic compared to determine the local move- deformation (0.5%). Both experiments ment of spots. Unlike traditional testing and modeling must now be extended to techniques, the 6DOF experiment allows large strain deformations on the order of essentially unconstrained deformation tens of percent. At these larger extents of the crystal. This unique set-up, shown of strain, the use of multiscale character- in Fig. 1, allows for an unprecedented ization tools can be improved to better examination of the deformation of understand the fundamental behavior. single crystals, including the complete displacement gradient matrix. Using Project Goals this technique, we have performed an The goal of this project is to de- analysis that calculates the activity of velop large strain experiments that will individual slip systems in a single crys- provide the essential data to enhance the tal from the image correlation data. The multiscale modeling capability through results for zinc single crystals are that the validation of dislocation dynam- for a pristine sample only the primary ics simulations and the development of system is active, as expected. However, continuum strength models. This work for a cold-worked and annealed sample, will increase LLNL’s ability to develop the analysis shows the unexpected result predictive strength models for use in that there is appreciable activity on the computer code simulations. primary as well as other slip systems.

Load

Half sphere

Sample z Reference flags

Translation platen

y Cameras x

Figure 1. 6DOF set-up with the image correlations cameras.

34 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

Copper single crystals experiments. Characterization of the de- overall orthogonal structure seen in the Experiments have been performed on formed material. Characterization of image correlation strain maps. copper single crystals that have also the deformed material, which is more shown surprising results. The image deﬁ nitive at larger strains, is essential Related References correlation strain map (Fig. 2) shows to understanding the underlying defor- 1. Lassila, D. H., M. M. LeBlanc, and G. J. slip along the primary (expected) and mation mechanisms in single crystal Kay, “Uniaxial Stress Deformation Ex- orthogonal to the primary slip sys- metals. One method of characterizing periments for Validation of 3-D Dislocation tem (unexpected). Using the image the deformed material is using the Dynamics Simulations,” J. Eng. Mat. Tech., correlation data, analyses have been x-ray microdiffraction beamline at the 124, p. 290, 2002. conducted that show that the slip is Advanced Light Source (ALS) at LBL. 2. LeBlanc, M. M., J. N. Florando, D. H. orthogonal and in some cases nearly The high-energy synchrotron light Lassila, T. Schmidt, and J. Tyson, II, “Image equal in magnitude to the primary source allows subsurface dislocation Correlation Applied to Single Crystal Plastic- system. Additional experiments ad- structure to be analyzed. This technique ity Experiments and Comparison to Strain dressing the effect of fabrication and can detect features over a larger area Gage Data,” Experimental Techniques, 30, 4, boundary conditions on the deforma- than is possible with Transmission p. 33, 2006. tion behavior also show appreciable Electron Microscopy (TEM). Copper deformation orthogonal to the primary single crystals, which show the orthog- system. This behavior cannot be onal slip, have been characterized at FY2007 Proposed Work explained using traditional theories. ALS using x-ray microdiffraction. Fig- Further experiments and characteriza- In addition, orthogonal slip has been ure 3, which is a map of the local rotations are needed to solidify the observation observed in hcp and bcc crystals, and tions in the sample, shows band struc- of orthogonal slip. Also, new theories and therefore may be a general mechanism tures in the material that are 90º from models, such as a dislocation dynamics that can be applied to a large number each other. This result suggests that the simulation that takes into account local of materials. local lattice rotations are related to the lattice rotations, need to be developed to account for this behavior.

% (tech.) 0

–2.0 Misorientation Loading direction angle (º) 0 Orthogonal to primary –4.0 0.075 0.150 Trace of –6.0 primary plane 0.225 –8.0 0.300 100 μm

–10.0 Figure 3. ALS results showing bands that are 90º from each other.

–12.0

–14.5

Figure 2. Axial strain map of copper single crystal overlaid onto the sample, showing deformation on the primary slip system and orthogonal to the primary system.

Lawrence Livermore National Laboratory 35 TechBase

Temperature Capability for Mary LeBlanc (925) 422-8954 In-Situ TEM Nanostage [email protected]

anomaterials are roughly deﬁ ned as Perhaps the most compelling ap- Nsolids with characteristic dimensions plication for the Transmission Electron that are 200 nm or less. The physi- Microscope (TEM) nanostage is to cal properties of nanomaterials are directly measure dislocation velocities, frequently very different from typical which are important material charac- bulk properties. For example, some teristics used in multiscale modeling. newly invented composite materials The nanostage also permits the direct that incorporate nanomaterials in their observation of dislocation reactions and structure have very high yield strength the resulting dislocation substructures, and excellent fracture toughness. In which can be used to validate disloca- essence, it is the very small dimen- tion dynamics simulations. sions and concurrent high surface- area-to-volume ratio of the nanomate- Project Goals rials that give rise to these properties. The goal of this project is to estab- It is important to be able to character- lish a new capability to experimentally ize the mechanical behavior of these measure the mechanical response of materials under different temperature nanomaterials and structures in the regimes, especially as nanomateri- TEM, over a range of temperature als and structures are used in various from 100 to 500 K. To accomplish programmatic applications including this goal, a loading stage must be built laser targets, materials for weapons, that is compatible with the TEM, and and sensing elements. a loading cartridge, which holds the nano-sized sample, must be fabricated to ﬁ t into the tip of the stage and transfer a continuously measured load onto the sample (see Fig. 1). The scope of the project is to establish and test the new capability, and provide documentation on the utility for future studies.

Silicon cartridge

250 μm

Optical fiber

Sample Fabry-Perot interferometer

Figure 1. Photographs of the loading cartridge. Counterclockwise: the cartridge in relation to a penny; the complete cartridge; blow-up near the sample region. The sample has not yet been thinned to transparency.

36 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation

Relevance to LLNL Mission This project will add to the increasing number of capabilities LLNL will need to characterize and use nanomaterials and structures. Nanoma- terials have the potential to play a key role in the development of sensors for programmatic applications. The ﬁ rst use of this capability will be to quantify the dislocation velocity as a function of applied stress in single crystals. These dislocation mobility 10 μm values have never been accurately measured, and are essential input for LLNL’s multiscale modeling program.

FY2006 Accomplishments and Results Sample Fabrication. Damage to Figure 2. SEM photograph of the sample thinned to electron transparency. The cross-section is the test sample during handling of diamond shaped with the minimum thickness (1.6 μm) near the sample center. the cartridge was an unexpected and signifi cant obstacle during FY2006. In response, fi xturing to hold the loading cartridge during Focused Ion Beam thinning of the sample was fabricated. The titanium frame for the cartridge was stiffened to reduce in-plane and out-of-plane bending, and an aluminum reinforcing plate was bonded to 3 mm the cartridge to prevent damage during Figure 3. Close-up of the stage tip with a loading cartridge installed. The cartridge is in unloaded installation into the straining stage. condition (loading wires slack) with the silicon side down. Successful thinning of the test sample to electron transparency has since been demonstrated by our collaborator at LBL (Fig. 2). Loading stage. The in-situ TEM Pole-piece straining stage has been fabricated, as- chiller from TEM sembled, and tested (Fig. 3). It is sized to fi t in LLNL’s Philips 300 TEM. The tip of the stage is cooled by a cold Cold finger fi nger that resides inside the microscope and is attached after the stage is inserted. Temperature measurements made in a vacuum chamber to simulate the microscope environment (Fig. 4) show that the loading cartridge temperature matches that of the tip. Mock tip with Data acquisition. A PC-based data cartridge acquisition system has been assembled, and software written to capture the TEM image (either from the microscope camera or an external camera), Figure 4. Photograph of the temperature conduction experiment. A mock tip was cooled using and up to eight channels of other data, conduction from the LN-cooled pole-piece chiller through copper braid to the cold fi nger that at- including load and temperature. taches to the stage tip. The cartridge and tip were within 1 °C; the cold fi nger was 5° cooler.

Lawrence Livermore National Laboratory 37 TechBase

EMP Simulation and Charles G. Brown, Jr. (925) 423-4435 Measurement Data Analysis in [email protected] Support of Laser Experiments

lectromagnetic pulse (EMP) is gener- Relevance to LLNL Mission Eated at short-pulse laser facilities such An understanding of the EMP in as LLNL’s Titan and Vulcan in England Titan, through simulation and analysis during target experiments. NIF also may in this project, could be extrapolated to produce EMP on target experiments. NIF to better mitigate EMP effects in This project focused on learning how to NIF and other laser systems. perform simulations of electromagnetic (EM) fi elds due to electrons from laser/ FY2006 Accomplishments and Results target interactions. During FY2006, we gained experience in performing simulations using the Project Goals EMSolve processing chain, which con- The overarching goal of this project sists of Cubit, EMSolve, and VisIt. Cubit is to simulate EMP due to electrons from is a meshing tool from Sandia National laser/target interactions in the Titan short- Laboratories that is used to construct pulse laser and to compare measurement models for EMSolve. VisIt is an LLNL results with the simulations. To accomplish code for visualizing simulation data. the simulation task, we use EMSolve, One of the most diffi cult tasks we an LLNL code that has been augmented faced was creating CAD models appro- with electron beam sources. Unlike most priate for EM simulation from the origi- available codes, EMSolve’s architecture nal mechanical CAD fi les. The original allows seamless integration of user-created Titan CAD model was far too detailed sources and boundary conditions. for direct transfer to EM simulation. In a

(a) (b)

Figure 1. Simplifi ed Titan model (a) with portholes, and (b) without portholes.

38 FY06 Engineering Research and Technology Report Engineering Modeling and Simulation related effort, an experienced mechani- on these examples. Figure 2 depicts the cal drafter removed features less than conical current source’s current density FY2007 Proposed Work 1 in., such as bolt holes. We then further and the resulting magnetic fi elds for one Our FY2007 work will include improving simplifi ed the models using Cubit and snapshot in time. The electric fi elds (not our CAD models to perform more realistic Microwave Studio, a commercial EM shown) have errors due to some aspects simulations; continuing to learn to use solver. We started simply and added com- of the source that we are currently work- EMSolve and working to improve its electron plexity. For example, we added simple ing to resolve. beam sources; assisting laser experiment versions of portholes (Fig. 1). teams in the measurement process to better Further, we used a simple cylindri- Related Reference understand the measurement systems; and cal geometry to learn how to use the Mead, M. J., et al., “Electromagnetic Pulse working with signal processing experts to EMSolve processing chain and to test Generation within a Petawatt Laser Target calibrate and analyze the data. the electron beam sources. We hope to Chamber,” Review of Scientifi c Instruments, write a simple EMSolve tutorial based 75, 10, pp. 4225-4227, October 2004.

(a) (b)

Figure 2. (a) Magnitude of current density of conical electron beam source. (b) Magnitude of resulting magnetic fi eld.

Lawrence Livermore National Laboratory 39

Measurement Technologies FY 06 Engineering Research and Technology Report Report and Technology FY 06 Engineering Research LDRD

Standoff Explosives Detection Robert J. Deri (925) 424-5343 Using THz Spectral Imaging [email protected]

tandoff detection of high-explosive (Fig. 1) that distinguishes them from S(HE) material RDX (1,3,5-trinitro- common background materials. Since 1,3,5-triazacyclohexane) is a difﬁ cult THz radiation can penetrate com- technical problem due to its low vapor mon fabric concealants, and provides pressure (10 ppt). On the other hand, reasonable resolution for imaging RDX is the one of the most widely applications, spectral imaging near available active ingredients in plastic 800 GHz may provide a solution to explosives such as C-4 and Semtex-H, the RDX detection problem. This and is commonly used for improvised project aims to evaluate the suitability explosive devices (IEDs). of near-THz multispectral imaging for RDX-based HE exhibit a distinc- reliable RDX screening of people at a tive sub-THz signature near 800 GHz safe ~30- to 50-m standoff distance.

Imaginary part of dielectric constant, scaled 1.2

Scaled to match peak amplitude at 800 GHz 1.0 PETN

0.8 M

0.6

0.4 Imaginary dielectric e” constant 0.2 M M 0 300 800 1300 1800 2300 Frequency (GHz)

e” Yamamoto e” Semtex teraview e” PSI “M” = RDX intramolecular mode

Figure 1. Spectra of several RDX-based high explosives (Green: C-4, Blue: RDX; Red: Semtex-H). RDX exhibits a peak at 800 GHz, which is common to all formulations. Additional resonances at higher frequencies are associated with the compound PETN.

42 FY06 Engineering Research and Technology Report Measurement Technologies

Project Goals THz spectral imaging. In particular, we innocuous materials such as skin and The two major project goals are: developed an approach for deconvolv- lactose. This work was presented at a 1. to assess the utility of THz spectral ing the spectral modiﬁ cations induced by-invitation-only NATO Workshop on imaging for the detection of RDX- by atmospheric propagation. We simu- explosives detection. based explosives, by developing a lated the performance of this system systems concept, supporting multi- using atmospheric absorption data Related References spectral detection algorithms, and from HITRAN (a standard database 1. National Academy of Sciences, Existing simulating system behavior in the of atmospheric absorption properties), and Potential Standoff Explosives Detection presence of atmospheric absorption, and material parameters obtained from Techniques, National Academies Press, 2004. obscurant losses, and noise; and our own limited set of experiments and 2. Woolard, D. L., E. R. Brown, M. Pepper, 2. to experimentally validate the over- from data reported in the literature. and M. Kemp, “Terahertz Frequency Sensing all system concept. Our simulation results suggest that and Imaging: A Time of Reckoning Future Our ﬁ nal goal is to demonstrate the proposed system can achieve stand- Applications?” Proc. IEEE, 93, pp. 1722- detection of RDX-based explosives at off detection of bulk HE at safe stand- 1743, 2005. 30 to 50 m through a concealant, using off distances (~30 to 50 m), even when 3. Yamamoto, K., et al., “Noninvasive multispectral imaging. the explosive is concealed by a few lay- Inspection of C-4 Explosive in Mails by ers of fabric. The results are obtained as Terahertz Time-Domain Spectroscopy,” Jap. Relevance to LLNL Mission sets of “receiver operation characteris- J. Appl. Phys., 43, L414, 2004. Explosives detection that enables the tic” curves, which show the probability 4. Bjarnason, J. E., et al., “Millimeter-Wave, interdiction of terrorists is an important that the system detects an explosive as Terahertz, and Mid-Infrared Transmission capability for LLNL’s missions in both a function of a system threshold setting. Through Common Clothing,” Appl. Phys. national security and homeland security. Ideally, the probability of detection Lett., 85, p. 519, 2004. should be high for explosives, and low FY2006 Accomplishments and Results for innocuous materials. In FY2006, we developed a systems Representative results are shown in concept and supporting algorithms for Fig. 2, for discrimination of C-4 against FY2007 Proposed Work For FY2007 and FY2008 we propose to verify experimentally our recently 0.6 developed algorithms for spectral detection of RDX in the presence of atmospheric 0.5 losses and concealants. We will fi rst explore Probability near-THz (800 to 900 GHz) imaging at the (detection) 0.4 necessary standoff distances. If results are favorable, we will extend the measure- 0.3 ments to two lower frequency bands to

Probability obtain the required multispectral coverage. 0.2 Probability (false alarm) 0.1

0 –1.0 –0.8 –0.6 –0.4 –0.2 0 0.20.4 0.6 0.8 1.0 Decision threshold

Figure 2. Receiver operating characteristic for 50-m standoff through a US Standard Atmosphere. The red curves show the probability of detection for diff erent explosives (C-4, Semtex, RDX); the blue curves show the detection probability for innocuous materials (diff erent scenarios and material types for skin and lactose). At threshold setting of 0.6, the curves indicate a high probability of explosives detection and low probability of false alarms for innocuous materials.

Lawrence Livermore National Laboratory 43 TechBase

Ultra-Wideband Carlos E. Romero (925) 423-2830 Technology Testbed [email protected]

ltra-wideband (UWB) systems emit UWB RF components could be carried Uextremely short electromagnetic out in support of LLNL efforts. pulses, where the pulse duration can range from tens of ps to 1 ns, corre- Relevance to LLNL Mission sponding to a spatial pulse width of LLNL has been a pioneer in UWB 3 mm to 30 cm. Since the energy of technologies, ranging from Micropower the pulse is distributed across sev- Impulse Radar (MIR) to Transmit- eral GHz, the power spectral density Reference Communication (TRC) sys- is much lower in magnitude than a tems. Many of our programs have a need narrowband system. To a narrowband to characterize RF propagation. system, UWB signals appear below the noise ﬂ oor, and are therefore very FY2006 Accomplishments and Results difﬁ cult to detect (Fig. 1). These char- In FY2006, UWB systems were used acteristics, including their propagation for many LLNL projects and programs: through harsh multipath environments, to trigger active armor defense systems, enable the technology to be used in a measure extreme particle velocities, wide range of applications from sens- begin investigation into interior building ing to imaging to communications. visualization, track intrusions for cargo container security, and communicate in Project Goals harsh urban and nautical environments. Our goal was to establish a uniform All these activities have one thing UWB testbed so that an accurate, repeat- in common, the need to characterize the able, streamlined characterization of RF propagation of existing and future

Narrowband system Ultra-wideband system

Time Time

Bandwidth Bandwidth = ~ 30 kHz several GHz

Frequency Frequency

Figure 1. Narrowband vs. UWB in time and frequency domains.

44 FY06 Engineering Research and Technology Report Measurement Technologies systems. Of particular interest were antenna characterization (beam pattern, gain); transmitter characterization (pulse shape, bandwidth, noise fl oor); receiver characterization (bandwidth, noise fl oor); channel capacity; low probability of intercept and detection (LPI/D); resistance to jamming; performance in multipath channels; material penetration characteristics; and propagation physics. As a result of this effort, a UWB test bed now exists at LLNL that can meet these needs. Our UWB testbed room has been retrofi tted so that radar absorbent material now lines the walls to produce a partial anechoic effect (Fig.2). A highly accurate, 3-axis gantry system permits reliable and repeatable experiments along the length and width of the room. This system is coupled with custom software to permit easy specifi cation of Figure 2. UWB testbed built to produce a partial anechoic eff ect. trajectory paths, both by scripts and a drawing board (Fig.3). Test equipment such as oscilloscopes, spectrum analyzers, network analyzers, digitizers, and interval counters, has been consolidated into one location, along with LabView code to create a repository for data acquisition and storing. A database has been established and populated with the RF characterization of several standard UWB confi gured systems. A series of radar cross-section (RCS) targets have been acquired and manufactured to provide baseline performance information. Protocols are in place for ongoing and future characterization efforts. This facility is available for use in RF characterization where a full anechoic chamber is not necessary. It is currently supporting a variety of projects.

Figure 3. Three-axis gantry software graphical user interface.

Lawrence Livermore National Laboratory 45 TechBase

Urban Tracking and Peter Haugen (925) 422-0749 Positioning System [email protected]

he Urban Tracking and Positioning and tag units operating in the same TSystem is a high-resolution urban environment, offering true 3-D location tracking demonstration system similar capabilities to multiple receivers. to GPS but suitable for indoor use in locales such as buildings and caves. Project Goals Indoor localization of radio devices is The goals of this project were to a daunting task due to the presence of combine LLNL UWB radio hardware severe multipath and low probability capable of collecting range measure- of a line-of-sight (LOS) signal between ments with LLNL software algorithms the transmitter and receiver. This harsh to perform the signal processing needed propagation environment for radio sig- to recover the RF signatures in high- nals is due to the shadowing and reﬂ ec- scattering environments. When com- tions from walls and objects. bined, these technologies create a com- In FY2005 we built a set of high- plete system capable of high-resolution accuracy ranging devices using ul- geo-location in poor RF environments, tra-wideband (UWB) RF signals and such as urban areas or inside buildings, algorithms for position estimation. where traditional geo-location technolo- UWB signals are particularly suited for gies such as GPS, are not available or ranging because of their short duration, do not yield sufﬁ cient accuracy. high-bandwidth pulses. Our ranging and positioning algorithms improve accu- Relevance to LLNL Mission racy by addressing some of the known Several LLNL programs have an challenges in UWB localization. In interest in the high strategic potential of FY2006 we expanded the capabilities of urban tracking. Applications for high- these units to support multiple masters accuracy systems for use in complex

Radio remote unit Radio tracking unit Transmit antenna 18 V impulse Receive transmitter Vref antenna ADG Start of Swept range sweep timing unit Embedded radar trigger control processor Transmit Video Sampling antenna output receiver 18 V impulse Receive transmitter antenna Embedded radar control processor

Figure 1. Block diagram of the round-trip TOF ranging pair, consisting of two units. The radio tracking unit sends a pulse to the remote unit, which replies with its own pulse. The main unit records the total round-trip TOF to extract the distance measurement.

46 FY06 Engineering Research and Technology Report Measurement Technologies urban environments is growing, and 2. Young, D., et al., “Ultra-Wideband 4. Lee, J., and A. Scholtz, “Ranging in a LLNL’s established technology in MIR (UWB) Transmitter Location Using Time Dense Multipath Environment Using an UWB radios and signal processing al- Difference of Arrival (TDOA) Techniques,” UWB Radio Link,” IEEE Journal on Se- lows us to be at the cutting edge. Conference Record of the Thirty-Seventh lected Areas in Communications, 20, 9, pp. Asilomar Conference on Signals, Systems 1677 - 1683, 2002. FY2006 Accomplishments and Results and Computers, 2003. 5. Smith, J., and J. Abel, “Closed-Form In FY2006, we added the capability 3. Jourdan, D., et al., “Monte Carlo Localiza- Least-Squares Source Location Estimation to support ranging and communication tion in Dense Multipath Environments Using from Range-Difference Measurements,” between multiple tracking and remote UWB Ranging,” Proceedings of the IEEE Con- IEEE Transactions of Acoustics, Speech, and radio units, permitting the 3-D loca- ference on UWB, Zurich, Switzerland, 2005. Signal Processing, ASSP-35, 12, 1987. tion of multiple units simultaneously. To accomplish this task we fi rst added Request Reply data-encoding capabilities into the UWB sent received ranging transaction that the radios previously used. Then we uniquely identifi ed the radar tracking and remote units so Tracking unit they can be addressed individually. Fi- Request Reply nally we implemented and embedded a received sent Time Division Multiple Access (TDMA) protocol scheme so multiple units could co-exist in the same environment, with- Remote unit out interfering with each other’s ranging and communications transactions. Figure 1 shows the updated hardware component diagrams; Fig. 2 shows Ttravel Tprocessing Ttravel their ranging transaction. For that trans- Time history action, the radio tracking unit sends an T0 Tround-trip TOF encoded pulse stream to the target radio remote unit. The remote unit receives Figure 2. The round-trip TOF, consisting of travel time to and from the remote unit (approximately equal) and time spent in processing at the remote location (a known value we can subtract). the request and responds with its own uniquely encoded reply. The tracking unit receives and time-stamps the reply to fi nd elapsed round-trip travel time, and thus distance. Distance measurements from multiple tracking radios can then be combined to compute a 3-D position estimation. A set of the complete remote and tracking hardware units can be seen in Fig. 3. Using this completed system we have tested and documented the ranging performance in several harsh environments, supporting other LLNL projects, including the United States Coast Guard ships and subterranean caves.

Related References 1. Gezici, S., et al., “Localization Via Ultra- Wideband Radios: A Look at Positioning Aspects for Future Sensor Networks,” IEEE Signal Processing Magazine, 22, 4, pp. 70 Figure 3. Completed UWB remote geo-location unit (top) and tracking radio (bottom). - 84, 2005.

Lawrence Livermore National Laboratory 47 TechBase

Ultrasonic Techniques for Michael J. Quarry (925) 422-2427 Laser Optics Inspection [email protected]

his project applied two ultrasonic techniques we used fused silica samples Tmethods that could be subsequently with programmed hemispherical ma- deployed to inspect NIF optics either chined pits with diameters ranging from on- or off-line. One method used ul- 0.5 to 5 mm. trasonic shear-wave, the other longitu- In FY2005, shear-wave experi- dinal-wave tomography. This project ments were performed on an optic has constructed ultrasonic hardware with hemispherical defects machined that generated images of damage to the into the surface. The shear wave surface of optics using a set of multiple technique is able to accurately image sensors that are applied to the outside and size all the defects. In FY2006, edge of the optic. The system was the tomographic experiments were built and demonstrated on glass with performed with a 32-element, 1-MHz programmed defects and actual laser linear array with point-like elements, damage to assess detection capabilities generating a broad beam. The data was and sizing abilities. The system is also reconstructed with a time-reversed portable, enabling fi eld-testing of optics MUSIC (Multiple Signal Classifi cation) or other structures. detection algorithm. A sample detection map shows 3- Project Goals and 5-mm hemispherical fl aws (Fig. 1). The goal is to detect and size laser The tomographic approach was able to damage on an optic with defects ranging detect only defects greater than or equal in size from 0.1 to 10 mm or larger by to 3 mm diameter. The 1-MHz linear ar- generating acoustic images of a laser- ray was not able to produce waveforms damaged optic that are easily interpreted with suffi cient signal-to-noise to detect by those less familiar with acoustics. the smaller fl aws. Based on these results,

Relevance to LLNL Mission NIF will beneﬁ t from nondestructive 0 1 MHz array methods that can assess damage to allow 50 for timely replacement of critically dam- 100 0.5 mm 1 mm 3 mm 5 mm aged optics or surface reﬁ nishing of re- useable optics. The electronic switching 150 technology and data acquisition inter- 200

face is also being used on an Advanced Z (mm) 250 Reconstructed area Development and Production Technol- 300 ogy (ADAPT) project for monitoring a 350 weapon production process. Fused silica optic 400 FY2006 Accomplishments and Results 0 100 200 300 400 We investigated the application X (mm) of two ultrasonic techniques, 1-MHz longitudinal waves with tomographic re- Figure 1. Tomographic detection map obtained construction and 10-MHz horizontally- from the 1-MHz array data overlaid on a schematic image of the defects, revealing the 3- and polarized shear waves, to image surface 5-mm hemispherical pits. The 0.5- and 1-mm pits damage in NIF optics. To evaluate the were not detected.

48 FY06 Engineering Research and Technology Report Measurement Technologies the shear-wave technique was chosen for reﬂ ected amplitude to the fourth power, depth, as shown in Fig. 3. Previous efforts demonstration, test, and evaluation on a which results in an acoustic image of with 5-MHz longitudinal data showed NIF fused-silica optic with laser damage the surface of the optic. a non-monotonic relationship. A higher created without vacuum loading condi- Shear-wave data were collected on the signal-to-noise ratio with virtually no tions (Fig. 2a). fused-silica optic shown in Fig. 2a. The effects of mode conversion or multiple The shear-wave technique uses shear-wave technique was able to accu- echoes from the bottom surface was narrow, highly-directed beams. The rately detect, locate, and size laser damage observed, compared to previous 5-MHz outer edge of an optic can be covered from 0.5 to 8 mm in diameter. Figure 2b longitudinal acoustic data. with shear-wave transducers on all four shows the 25.4-mm images of the sur- sides. Each transducer transmits a pulse face of 0.5-, 1.5-, 7- and 8-mm damage Related Reference into the optic and any damage reﬂ ects sites. These are size ranges in which NIF Martin, P., D. Chambers, and G. Thomas, the pulse back to the transmitter. The has interest. Surface damage size can be “Experimental and Simulated Ultrasonic transducers are multiplexed, and the directly measured on the image. Maximum Characterization of Complex Damage collected time waveforms are envel- depth correlates to maximum amplitude of in Fused Silica,” IEEE Transactions on oped and replicated across the width of the detecting waveform. The shear-wave Ultrasonics, Ferroelectrics, and Frequency the element. Multiplying the data sets data results in a monotonically increas- Control, 49, 2, pp. 255-265, 2002. from all four sides produces a map of ing amplitude as a function of maximum

(a) (b) 8 x 108 5 x 108

1.5 mm 0.5 mm 7 mm 8-mm site (mV)4 7-mm site (mV)4

8 mm

0 0

Figure 2. (a) A 430-mm-x-430-mm-x-43-mm NIF 2 x 105 5 x 106 optic with laser damage of various sizes. (b) Shear wave images (25.4 mm x 25.4 mm) of the surface around 8-, 7-, 0.5-, and 1.5-mm damage sites.

4 4 0.5-mm site(mV) 1.5-mm site (mV)

0 0

(a) (b) 10-MHz shear 5-MHz longitudinal 0.30 4.5 4.0 0.25 3.5 0.20 3.0 2.5 0.15 2.0

Amplitude (V) 0.10 Amplitude (V) 1.5 1.0 0.05 0.5 0 0 0 2 4 6 8 10 0 2 4 6 8 Maximum depth (mm) Maximum depth (mm)

Figure 3. (a) Depiction of 10-MHz shear wave yielding a monotonic relationship with maximum laser damage depth, while (b) the 5-MHz longitudinal-wave data has a non-monotonic relationship. Data is from sample shown in Fig. 2(a).

Lawrence Livermore National Laboratory 49 TechBase

Surface Acoustic Wave Michael J. Quarry (925) 422-2427 Microscopy of Optics [email protected]

e investigated the feasibility of Relevance to LLNL Mission Wsurface acoustic wave microscopy Surface acoustic wave microscopy to detect fi ne cracking in NIF optics. will enable the acoustic characterization Cracks occur in the surface of NIF of NIF optics without etching. Charac- optics from the grinding of the surface, terization of laser damage for mitigation and subsequent polishing still leaves purposes may also now be investigated. fi ne cracks. An Olympus UH-3 acoustic Mapping density gradients in JASPER microscope was refurbished to enable projectiles is another possible LLNL surface acoustic wave microscopy from application. Other applications include 200 MHz to 1 GHz on fused silica. The thin fi lms, grain structure visualiza- system uses high-frequency bulk and tion, and observation of biological cells surface acoustic waves to characterize without staining. surfaces, near surfaces, and thin fi lms. Feasibility studies were performed on FY2006 Accomplishments and Results polished fused silica. An Olympus UH-3 surface acoustic wave microscope was refurbished for Project Goals operation. Two-hundred-MHz and 400- The goal of the project is to show MHz acoustic lenses were found to be detection of fi ne cracking (1 to 15 μm) operational, while the 1-GHz lens was in the surface of a polished sample of damaged. However, we have access to fused silica over a 2-mm-x-2-mm area. a 1-GHz lens through our relationship

Sample

Figure 1. Olympus UH-3 acoustic microscope system.

50 FY06 Engineering Research and Technology Report Measurement Technologies

shown, in Fig. 4b. The crack lengths RF signal (in) RF signal (out) Transmitter Receiver along the surface are about 10 μm using the scale on the image to measure across the crack. A similar image could be obtained without etching. Plane acoustic Piezoelectric In the future, we will look at other wave transducer applications for surface acoustic wave Reflected microscopy. One important problem is wave looking at gradient density structures including JASPER projectiles. We can also improve the technology with new Sapphire lens lens and transducer designs. PZT is a Spherical much more efﬁ cient transduction mate- wave Water rial than the current ZnO. Frequency Y Specimen could be optimized with a tunable tone- burst generator. X Stage

Scanning direction Imaged area Figure 2. Diagram of the ZnO transducer and sapphire lens. with Pennsylvania State University. At lens at or near the surface of the sample. 1 GHz the lateral resolution of the system A Rayleigh surface wave and the bulk is 1 μm. The acoustic lens is designed waves interfere with each other. A with an F-number of 0.7 to optimize peak detector captures the peak of the surface and near surface resolution. reﬂ ected energy. The scanning process Figure 1 shows a picture of the takes about 10 s to form an image. system. A sample is placed on the stage, A fused silica Corning 7980 sample and an acoustic lens is raster-scanned (Fig. 3) with grinding and polish- over the sample to obtain an image. A ing fractures was examined with the diagram of the transducer and lens is Olympus system. An area of 1 mm2 was shown in Fig. 2. The transducer is driven scanned in the position indicated in Fig. 3. by tens of cycles of a tone-burst genera- The resultant image (Fig. 4a) shows Figure 3. Polished fused silica sample. The area tor. The burst travels down a sapphire many fine cracks. A zoomed-in im- investigated with surface acoustic wave micros- buffer rod and is focused through the age with an area of 0.25 mm2 is also copy is indicated by the arrow.

(a) (b)

1 mm 0.25 mm

Figure 4. (a) Image of the surface of polished fused silica, showing surface fractures with a crack length of about 10 μm as measured using the scale on the image. (b) Enlargement of the same approximate area shown in Fig. 3.

Lawrence Livermore National Laboratory 51 LDRD

Ultrafast Transient Corey V. Bennett (925) 422-9394 Recording Enhancements [email protected] for Optical-Streak Cameras

everal experiments at LLNL will a “time lens” through sum-frequency Srequire hard x-ray and neutron generation (SFG) of a broadband- diagnostics with temporal resolution chirped optical pump with the input of ~1 ps and a high dynamic range, signal in a nonlinear crystal because of particularly those experiments involv- the improved resolution it produces. ing ignition. The Linac Coherent Light The system was designed using all Source (LCLS) at the Stanford Linear guided wave technologies for compact- Accelerator Center (SLAC) will need to ness and robustness. Its fi ber optic input measure timing and pulse shapes of its accepts an ultrafast signal at a 1534-nm 100-fs FWHM x-ray pulse. These mea- wavelength. Available component limi- surement requirements are far beyond tations required re-scoping the project existing capabilities. to demonstrating temporal imaging with This is the fi nal year of a three-year 33x temporal magnifi cation (instead of project that has developed a “time- 100x) and 100-ps record length (instead microscope” front end for optical of 600 ps), although the original goals streak cameras, magnifying (temporally should still be possible after rebuilding (a) Diffraction Diffraction stretching) signals having ultrafast detail certain component technology capabili- so that they can be recorded with slower ties that industry no longer supports. %C- speed instruments with a much higher Additional goals include a resolution

%C ﬁ delity. The system is compatible with a < 300 fs and a dynamic range > 100:1. new class of ultrafast radiation detectors being developed, which produce a Relevance to LLNL Mission d1 d2 modulated optical carrier in response to The success of NIF is critical to Lens e ionizing radiation. LLNL’s stockpile stewardship mission. (b) !T !T- Our project is focused on delivering Project Goals the diagnostics needed for the critical Our goal is to ensure delivery of experiments to carry out that mission. Time Lens the next-generation ultrafast diagnos- J" J"1 e J"2 tics for experiments at LLNL’s NIF and FY2006 Accomplishments and Results Dispersion Dispersion other facilities such as LCLS. We’ve designed and implemented (c) Temporal imaging is based on a the temporal imaging system in space-time duality between how a Fig. 2 using specially designed ﬁ ber- Dispersed W input, ! T Time lens beam of light spreads due to diffrac- optic dispersive delay lines in the input ! T output, tion as it propagates in space and and time-lens pump generation arms of

WW WR how pulses of light disperse as they the systems. These arms also include Nonlinear propagate through dispersive media, optical fi lters and amplifi er stages to WR crystal Chirped pump such as grating systems or optical fi ber improve the fi nal signal to noise. The !RT (T 2T (Fig. 1.) There is also a one-to-one time lens uses sum-frequency mixing in a analogy between the quadratic spatial chirped-period periodically poled lithium phase modulation produced by a lens niobate (chirped-PPLN) waveguide Figure 1. Comparison of (a) spatial and (b) and imparting of a quadratic temporal because of the high-effi ciency broadband temporal imaging systems. (c) A time lens is produced by mixing the input signal with a chirped phase (equivalent to a linear frequency mixing that can be obtained. The fi nal out- optical pump pulse. chirp). We have chosen to implement put dispersion is in a specially designed

52 FY06 Engineering Research and Technology Report Measurement Technologies chirped fiber Bragg grating because 4. Yang, S.-D., A. M. Weiner, K. R. of the extremely large dispersion with Parameswaran, and M. M. Fejer, “400- FY2007 Proposed Work low loss that can be obtained. Photon-Per-Pulse Ultrashort Pulse Auto- With outside funding, we are continu- An input “ring down/up” test pat- correlation Measurement with Aperiodi- ing this project. We are developing an tern was generated by passing a train cally Poled Lithium Niobate Waveguides optical frequency chirp diagnostic that is of 2-ps FWHM pulses through a 2-x-2 at 1.55 mm,”Opt. Lett., 29, pp. 2070-2072, capable of recording the frequency chirp 50%:50% splitter and looping one out- 2004. of each 100-ps pulse in a high-repetition put of the splitter back to an input with 5. Durkin, M., M. Ibsen, M. J. Cole, and R. rate (620 MHz) sequence of optical pulses. a delay nearly, but not exactly, equal I. Laming, “l-m Long Continuously-Written Signals will have over 300 GHz (to 1 THz) to the repetition rate of the laser. This Fibre Bragg Gratings for Combined 2nd and of bandwidth and can be positively or path delay difference could be set to 3rd Order Dispersion Compensation,” Elec- negatively chirped. place successively weaker pulses before tronics Letters, 33, 22, pp. 1891-1893, 1997. or after a larger pulse passing directly through the splitter without looping back. Time delay could be set with 2.2-fs/step resolution of the controller. The time magnifi cation was calibrated by making precise changes to the input and observing the magnifi ed output change. Figure 3 shows the time magnifi ed output waveform recorded on a streak camera with the input delay between pulses set at 11.3 ps. The top scale is the actual time recorded on the streak camera and the bottom scale is the equivalent input time determined by dividing the output time by the observed –30.1x time magnifi cation. A signal decay rate of 21.4%/pulse can be observed, which Figure 2. Photograph of the temporal imaging system. is consistent with losses in the test pattern set up. The dynamic range in Output time on streak camera (ns) this single shot measurement is nearly 0.60.3 0 –0.3–0.6 –0.9 –1.2 –1.5 500 1000:1, with an input temporal resolution of 1.8 ps. Better temporal resolu- Output time on streak camera (ns) 0.6 0.3 0 –0.3 –0.6 –0.9 –1.2 –1.5 tion should be possible with additional 400 adjustment of the system. 105 ) 3

4 Related References 300 10 1. Bennett, C. V., and B. H. Kolner, “Up- conversion Time Microscope Demonstrating 103 Signal (counts) Signal 103x Magniﬁ cation of Femtosecond Wave- 200 forms,” Optics Letters, 24, 11, pp. 783-785, 102 Signal (counts) (x10 (counts) Signal –20 –10 0 10 20 30 40 50 June 1, 1999. Equivalent input time (ps) 2. Bennett, C. V., and B. H. Kolner, “Prin- 100 ciples of Parametric Temporal Imaging-Part I: System Conﬁ gurations,” IEEE J. Quantum Electronics, 36, 4, pp. 430-437, April 2000. 0 3. Bennett, C. V., and B. H. Kolner, “Prin- –20 –10 0 10 20 30 40 50 Equivalent input time (ps) ciples of Parametric Temporal Imaging-Part II: System Performance,” IEEE J. Quantum Figure 3. Many single-shot time magnifi ed “ring down” patterns recorded on an optical streak camera. Inset Electronics, 36, 6, pp. 649-655, June 2000. log scale plot: the weak pulses are diffi cult to see on a linear scale but clearly show on the log scale plot.

Lawrence Livermore National Laboratory 53 TechBase

Evaluation of Ultrafast John E. Heebner (925) 422-5474 Recording Technologies for [email protected] Reduction to Practice

his project addresses limitations progress in nonlinear optics, driven Tof technologies presently used for by the new fast all-optical switching single-shot, transient recording of ul- technologies for telecommunications trafast signals. Current instrumentation applications, has achieved a critical relies on high-bandwidth oscilloscopes, maturity. However, the lack of obvi- streak cameras, and Frequency Resolved ous commercial applications for high- Optical Gating (FROG) methods. The fidelity single-shot transient recording performance associated with these solu- technologies has limited progress in tions is fundamentally limited and will this approach thus far. fail to support upcoming programmatic requirements. The best candidate for Project Goals achieving these requirements is a hybrid We aim to conduct an initial scop- technology implementing 1) an all- ing and exploration of a technology optical sampler that routes serial sig- area that has high strategic potential nals into parallel channels at timescales for LLNL missions. Speciﬁ cally, we approaching 1 ps, followed by 2) detec- seek to compare selected classes of tion with an array of high-dynamic- integrated microphotonic devices that range integrating detectors. can be tailored to implement ultrafast This strategy circumvents the limita- nonlinear optical switching phenom- tions (Fig. 1) of current methods in an ena. We plan to construct a framework analogous manner to hybrid communica- and supplementary modeling tools re- tion strategies involving both serial opti- quired to uncover the nonlinear optical cal time division multiplexing (OTDM) materials, fabrication processes, and and parallel wavelength division multi- photonic architectures optimally suited plexing (WDM) for the high-bandwidth to handle next-generation instrumenta- transmission of information. Recent tion requirements.

105

Emerging requirements 104

Streak cams Figure 1. Parameter space (dynamic range vs. Oscilloscopes Hamamatsu speed) of existing recording technologies and C7700 emerging LLNL HEDS/NIF requirements. 103

Spectral Dynamic range Tektronix Frequency resolved optical gating 102 SCD5000 Tektronix TDS6804

101 10 ns1 ns 0.1 ns 10 ps 1 ps 0.1 ps 10 fs Temporal resolution

54 FY06 Engineering Research and Technology Report Measurement Technologies

Relevance to LLNL Mission light signal in proportion to the intensity merit and compatibility with integration The work directly addresses instru- of a secondary (control) light source can technologies for which LLNL carries mentation performance gaps identifi ed be engineered from these phenomena strong expertise. We furthermore sought by LLNL. Specifi cally, future HEDS through a variety of mechanisms. In an all-optical sampling mechanism that (high-energy-density science) ex- practice however, due to the relatively displays a strong, ultrafast response, and periments on NIF will demand transient weak nature of nonlinear optical interac- is robust to the fabrication errors, pulse recording technology possessing high tions, nonlinear optical engineering lags instabilities, and beam nonuniformities temporal resolution (< 10 ps), high dy- nonlinear electrical engineering (i.e., expected to be encountered in reason- namic range (> 1000:1), and scalability electronics) by some 50 years. Thus, ably toleranced systems. to multichannel geometries. No exist- applications of this promising technology We down-selected from among ing recording technology satisfi es these with relevance to optical sampling are multiple architectures to a defl ection demanding requirements simultaneously. posed with the following challenges: encoded geometry that implements The implementation of all-optical 1. The subset of materials that display bandfi lling and plasma effects in III-V sampling mechanisms for ultra-high- substantial nonlinear optical re- semiconductors. In direct analogy to fi delity transient recording represents sponse and maintain compatibility electron-based oscilloscopes and streak a radical but promising departure from with state-of-the-art integration cameras, the down-selected architecture conventional recording technologies. technologies is limited primarily to defl ects an optical beam onto a high- The characterization of ultrashort laser III-V semiconductors. dynamic-range detector array or camera pulses would benefi t directly from this 2. The effective speed of the signal for subsequent recording. technology. Furthermore, when coupled sampling will depend on the material with LLNL-pioneered radiation-to- response times (rise and recovery), Related References optical encoding technology, a poten- inter-gate propagation delays, and 1. Walden, R. H., “Analog-to-Digital Con- tial replacement for aging radiation– structured resonance bandwidths. verter Survey and Analysis,” IEEE J. Sel. sensitive transient recording instrumen- 3. The attainable dynamic range of the Area Comm., 17, pp. 539-550, 1999. tation is feasible. instrument will be further corrupted 2. Heebner, J. E., N. N. Lepeshkin, A. in practice by optical leakage and Schweinsberg, G. W. Wicks, R. W. Boyd, R. FY2006 Accomplishments and Results cross-talk at each of the sampling Grover, and P.-T. Ho, “Enhanced Linear and Nonlinear optical phenomena that gates due to fabrication imperfec- Nonlinear Optical Phase Response of Al- result in the optically-induced modifi cations, control pulse instabilities, and GaAs Microring Resonators,” Optics Letters, tion of the refractive index of a solid-state control beam nonuniformities. 29, pp. 769 -771, 2004. material include (Fig. 2) the optical Kerr To address these challenges, a major 3. Lowry, M. E. et al., “X-Ray Detection and Stark effects, the plasma effect, exci- component of our study consisted of by Direct Modulation of an Optical Probe ton screening, the bandfi lling (Burstein- the detailed investigation and identifi - Beam-Radsensor: Progress on Develop- Moss) effect, and the bandgap shrinkage cation of architectures that implement ment for Imaging Applications,” Rev. Sci. effect. All-optical switches that route a materials with high nonlinear fi gures of Instrum., 75, pp. 3995-3997, 2004.

Too slow 103

Multiple quantum well μJ exciton-based

/GW 1 Plasma refraction &

2 10 bandfilling in III-Vs

, cm Saturated atomic 2 absorption sodium 10–1 mJ Figure 2. Parameter space (sensitivity vs. speed) of existing nonlinear optical sam- Conjugated polymers, pling mechanisms in solid-state materials fullerenes capable of modifying optical properties on

10–3 weak Too a fast timescale. Kerr effect III-Vs

Electrostriction chalcogenides J threshold Energy Molecular 10–5 orientation CS2 Kerr effect SiO Nonlinear optical sensitivity, n Nonlinear optical sensitivity, 2

10–7 kJ 10 ns1 ns 0.1 ns 10 ps 1 ps 0.1 ps 10 fs Temporal response

Lawrence Livermore National Laboratory 55 LDRD

Acoustic Characterization Diane Chinn (925) 423-5134 of Mesoscale Objects [email protected]

esoscience is an emerging area of sufﬁ cient distances into materials of Mscience and engineering that focuses interest. For LLNL applications, meso- on the study of materials with dimen- scale structures are on the order of 25 sions, features, and structures that range to 200 μm thick. from a few millimeters down to a few micrometers. Mesoscale objects typical- Relevance to LLNL Mission ly have embedded features that require This work directly addresses metrol- characterization with resolution on the ogy and characterization gaps of interest order of a few micrometers. Mesoscale in LLNL’s engineering focus areas, nondestructive characterization technol- such as measurement technologies and ogies are required that can 1) penetrate nondestructive characterization. Of the into or through a few millimeters of different mesoscale characterization diverse materials; and 2) provide spatial challenges at LLNL, the targets prepared resolutions of about a micrometer. An acoustic technique is attrac- Picosecond Interferometer tive because it offers high sensitivity to pulsed laser receiver features such as thickness and interface source quality that are important to mesoscale objects. In addition to the resolution requirements, many mesoscale objects require a non-contact technique to avoid damaging fragile surfaces. R S Project Goals P This research will achieve micrometer resolution characterization by extending the range of laser-acoustic P testing to GHz frequencies. Materi- Surface (R), Shear (S), and longitudinal (P) als and the geometry of components waves generated used in most LLNL mesoscale objects necessitate the use of a non-contacting Figure 1. Schematic of laser ultrasound technology. Laser UT uses a pulsed laser as a source to technique at frequencies from 100 MHz generate acoustic waves and a laser interferom- to 10 GHz. This frequency range is eter to detect acoustic waves. The source and re- required to acoustically characterize fea- ceiver can be on the same side (as shown) or on tures from 5 to 0.5 μm in size. In order opposite sides of the object. The acoustic wave travels through the object before it is detected. to be applicable to mesoscale objects, Use of a pulsed laser gives temporal resolution to the GHz acoustic waves must propagate the detected signal.

56 FY06 Engineering Research and Technology Report Measurement Technologies for OMEGA and NIF are the most rel- includes laser and material parameters, 2. Hebert, H., F. Vidal, F. Martin, J.-C. evant. This proposal impacts the DNT, shows good agreement with measured Kieffer, A. Nadeau, and T. W. Johnston, NIF, Engineering, and Chemistry and data. Figure 3 shows the frequency “Ultrasound Generated by a Femtosecond Materials Science Directorates through dependence of the acoustic-wave at- and a Picosecond Laser Pulse Near the target fabrication and characterization. tenuation in the gold foil. The quadratic Ablation Threshold,” J. Appl. Physics, 98, relation to attenuation is characteristic of p. 033104, 2005. FY2006 Accomplishments and Results stochastic grain scattering where wave- 3. Huber, R. H., D. J. Chinn, O. O. Balogun, The primary research goal in the fi - length, λ, is proportional to the grain and T. W. Murray, “High Frequency Laser- nal year of this project is to understand size. At 0.8 GHz in gold, λ = 4 μm. From Based Ultrasound,” Review of Progress in GHz acoustic wave propagation and its micrographs of the gold, the grain size Quantitative Nondestructive Evaluation, potential for material characterization. was confi rmed to be approximately 4 μm. pp. 218-224, August 2005. Two major accomplishments in support This fi nding demonstrates that GHz laser 4. Martz, H., and G. Albrecht, “Nondestruc- of this goal are validation of laser- ultrasound can be a valuable tool in mate- tive Characterization Technologies For acoustic models with experimental rial characterization. Metrology of Micro/Mesoscale Assemblies,” data, and identifi cation and validation Proceedings of: Machines and Processes for of material attenuation modes in rela- Related References Micro-scale and Meso-scale Fabrication, tion to material microstructure. 1. Chambers, D., D. Chinn, and R. Huber, Metrology, and Assembly, ASPE Winter Theoretical and experimental wave- “Optical Mapping of the Acoustic Output of Topical Meeting, pp. 131-141, 2003. forms for a 25-μm-thick gold foil taken a Focused Transducer,” Proceedings of the 5. Scruby, C., Laser Ultrasonics: Techniques with the confi guration in Fig. 1 are shown 147th Acoustical Society of America Meet- and Applications, Adam Hilger, New York, in Fig. 2. The analytical model, which ing, p. 2526, 2004. 1990.

0.05 45 Theory Experiment 0.04 Experiment 40 Linear fit Quadratic fit 0.03 35

0.02

/f 30 A 0.01

Relative amplitude Relative 25 0 P18 P12 P14 P16 P8 P10 20 –0.01 P4 P6 Filtered waveforms Frequency range: 669 MHz – 900 MHz P2 bandwidth (0.2–1.5 GHz) Wavelength @ 800 MHz = 4 μm –0.02 15 20 40 60 80 100 120 140 160 180 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 Time (ns) f

Figure 2. Using the confi guration in Fig. 1, temporal signals from modeled Figure 3. Frequency dependence of the acoustic-wave attenuation in the (black) and measured (red) signals for a 25-μm-thick gold foil, show good 25-μm gold foil. Acoustic attenuation of the wave propagation increases correlation. Each peak in the signal represents an arrival of an acoustic wave with the square of the frequency. This dependence is characteristic of at the epicentral location. The analytical model includes laser energy, spot stochastic grain scattering. size, and pulse width as well as optical, thermal, and mechanical properties of the material.

Lawrence Livermore National Laboratory 57 TechBase

Application of Laser GHz Robert Huber (925) 424-2002 Ultrasound to [email protected] Mesoscale Materials

aser-based ultrasound offers non-contact Relevance to LLNL Mission Lnondestructive characterization for The National Ignition Facility is, materials and structures. A state-of- and will continue to be, a major program the-art laser-based ultrasound system at LLNL. This facility offers a unique has been installed at LLNL and demon- capability for conducting fusion and strated on numerous mesoscale samples. other HEDP experiments. The targets Mesoscale (μm scale features and up to required for these experiments will be mm extent) materials and their charac- some of the most complex ever devised, terization are of increasing importance and characterizing these targets prior to at LLNL in many ﬁ elds, including high- testing them is critical to determining energy-density physics (HEDP) and the success of the experiments. These other National Ignition Facility (NIF) targets are mesoscale structures and, as targets, and medical applications for such, require new nondestructive charac- determination of tissue health. terization tools.

Project Goals FY2006 Accomplishments and Results The goal of this work was to set up A new laser-based ultrasound a laboratory housing the state-of-the-art laboratory was set up to house the GHz laser-based ultrasound system and GHz laser-based ultrasound equipment demonstrate its ability to characterize (Fig.1). Numerous samples, including mesoscale materials. metal foils and samples with two layers

Sample

Detection laser Generation laser

Figure 1. GHz laser-based ultrasound system.

58 FY06 Engineering Research and Technology Report Measurement Technologies were tested. Raw and fi ltered waveforms scans were performed, and work is pro- Based Ultrasound,” Review of Progress in for a 25-μm-thick gold foil are shown in ceeding to allow automated 2-D scans. Quantitative Nondestructive Evaluation, Fig. 2. Raw and fi ltered waveforms for a Modifi cations were made to the system D. O. Thompson and D. E. Chimenti, Eds., two-layer (Al-Cu) sample are provided during the course of the year. These American Institute of Physics, Melville, New in Fig. 3. The Al and Cu thicknesses modifi cations are aimed at making the York, pp. 218-224, 2005. were 63 μm and 35 μm, respectively. system more robust and user-friendly. 2. Martz, H. E., and G. F. Albrecht, “Nonde- These tests demonstrated the system’s It is anticipated that more modifi cations structive Characterization Technologies for high spatial resolution for thickness will be suggested as operators get more Metrology of Micro/Mesoscale Assemblies,” measurement as well as its ability to experience and think of ways to improve Proceedings of: Machines and Processes characterize bonds. the system further. for Micro-scale and Meso-scale Fabrica- Ultrasound techniques are valuable tion, Metrology, and Assembly, ASPE Winter for characterizing bonds. Translation Related References Topical Meeting, Gainesville, Florida, Janu- stages were incorporated into the system 1. Huber, H., D. J. Chinn, O. O. Balogun, ary 22-23, pp.131-141, 2003. to allow scanning of objects. Linear and T. W. Murray, “High-Frequency Laser-

(a) (b) 0.02 0.5 Measured waveform Filtered waveform Bandwidth 0.2–1.5 GHz 0.4 0.01

0.3

0 0.2 P16 P18 P12 P14

Relative amplitude Relative amplitude Relative P10 0.1 P8 P6 –0.01 P4 0 P2

–0.1 –0.02 0 50 100 150 200 250 300 20 4060 80 100 120 140 160 180 Time (ns) Time (ns)

Figure 2. (a) Raw and (b) fi ltered waveforms on 25-mm-thick Au foil.

(a) (b) 5 x 10–3 1.0 Measured waveform

0.8

0 0.6

0.4 P6 P8 0.2 –5 x 10–3 Relative amplitude Relative Relative amplitude Relative P2 0 P4

–0.2 –1 x 10–2 0 10 20 30 40 50 60 70 80 90 20 3040 50 60 70 80 Time (ns) Time (ns)

Figure 3. (a) Raw and (b) fi ltered waveforms on Al-Cu bonded sample.

Lawrence Livermore National Laboratory 59 TechBase

VisIt for NDE: Real-Time John D. Sain (925) 422-3409 Visualization for Large [email protected] NDE Data Sets

LNL’s Center for Nondestructive Char- visualization are available in VisIt Lacterization (CNDC) needs a tool to by operating on small computed provide fast, real-time, 3-D visualization tomography (CT) data sets; of feature metrology within very large 2. test for limitations of visualization data sets. Considerable resources have of large data sets; been spent increasing the spatial resolu- 3. write a graphical user interface or tion and, therefore, the size of NDE data scripts incorporating visualization sets. Current data sets typically range features relevant to NDE data; and in size from 4 GB (1 voxel) to 108 GB 4. demonstrate VisIt to NDE users (27 voxels), and future data sets will to stimulate interest and obtain be 2 TB (512 voxels). Visualization feedback about desired features. of such data is currently performed off-line and can take days or weeks Relevance to LLNL Mission to complete. VisIt is a real-time, 3-D The project addresses LLNL’s need visualization and quantitative analysis for non-contact dimensional metrol- software tool that can use parallel pro- ogy of millimeter-sized 3-D structures cessing machines on multiple platforms (HEDS and ICF target requirements), to visualize large data sets in seconds or and highly improved imaging, process- minutes. We explored the capabilities of ing, and analyzing methods that are VisIt with the intent to facilitate its ap- applicable to large-size data sets ranging plication to very large NDE data sets. from terabytes to petabytes. The project also supports LLNL’s engineering core Project Goals competencies in nondestructive charac- The project goals were to: terization and signal/image processing 1. verify that features for NDE and control.

Ablator hemi outer diameter = 550 μm Inner capsule outer diameter = 216 μm

Ablator hemi outer diameter = 550 μm

SiO2 aerogel hemi outer diameter = 444 μm SiO2 aerogel hemi outer diameter = 444 μm

Figure 1. Schematic of the components that make up a double-shell target. The target consists of an inner shell (or capsule), a two-piece spherical aerogel intermediary shell, and a two-piece spherical outer shell. The three elements are concentric, with the aerogel shell acting as a spacer between the inner shell and outer shell. There are zero to a minimum number of air gaps in the fi nal assembly.

60 FY06 Engineering Research and Technology Report Measurement Technologies

FY2006 Accomplishments and Results 5. performing quantitative analyses. 2. visualization of multiple materials in A Windows-based PC platform for Visualization of data is constrained a single view using opacity control; VisIt was set up for NDE data. Several by the number of processors scheduled, 3. real-time analysis of metrology CT data sets (1283 to 1,2003 voxels in length of time required, and region information; and size) were placed locally on the PC and of interest desired. No limitations 4. comparative overlaying of CT data remotely on the Livermore Computing were encountered in this project. For with data generated by other means. (LC) OCF fi le system. Visualizations of example, visualization of the 1,2003- Some desired features for VisIt are: both local and remote data were per- voxel data set was done using 64 to 256 1. scripts for concentricity and wall formed. Figure 1 is a schematic of com- processors, and LC maintains several thickness of nested spherical shells; ponents of a double-sided shell target. machines with between 1-K and 4-K 2. “fl y-through” movies with opacity Figure 2 is a sample volume rendering processors and even one (“Blue Gene”) control; and of a 5123-voxel data set. The process- with 128-K processors. Large numbers 3. hierarchal data structures that permit ing time for larger data sets and/or more of processors can be scheduled for high-resolution “close-ups” of sub- complex operations decreased when LC visualization and/or analysis. sets of coarsely-sampled data sets. machines were used. VisIt contains many Some sample scripts were written useful features for NDE data applications to implement desired calculations. For Related References such as: example, one measures object spheric- 1. Childs, H., E. Brugger, K. Bonnell, 1. viewing 3-D objects from any angle; ity and another determines boundary J. Meredith, M. Miller, B. Whitlock, and 2. slicing data sets with planes oriented surfaces between materials of different N. Max, “A Contract Based System for Large in any direction; attenuation. Data Visualization,” Proceedings of IEEE 3. manipulating threshold and opacity Some attractive features of VisIt are: Visualization, 2005. levels to view object features within 1. the ability to perform remote desktop 2. Brown, W. D., and H. E. Martz, Jr., “X-ray the context of the whole data set; visualization of data stored on LC Digital Radiography and Computed Tomog- 4. extracting line-outs of data values; and OCF/SCF fi le systems; raphy of ICF and HEDP Materials, Subas- semblies and Targets,” Digital Imaginig IX, An ASNT® Topical Conference, Mashantuck- et, Connecticut, July 24-26, 2006.

Figure 2. VisIt volume rendering of a real double- shell target (as depicted in Fig. 1) while still mounted on its manufacturing pedestal. The rendering is of a 5123-voxel CT data set. The cutaway view provides a look inside both the inner and outer shells. The aerogel material has been removed from view via thresholding.

Lawrence Livermore National Laboratory 61 TechBase

X-Ray System William D. Brown (925) 422-7933 Characterization [email protected]

e are implementing a forward model Relevance to LLNL Mission Wfor x-ray system response that will A forward model for system re- enable us to predict the capability of our sponse will enable us to better perform systems and allow us to choose optimal experiments for DNT, NIF and NHI. system parameters. The system model will include four components of the FY2006 Accomplishments and Results x-ray systems: source, transport, x-ray Our approach included coding of scattering, and detector. The components spectral algorithms and comparison of will be used in conjunction with the the algorithms with known empirical LLNL HADES program to model the results. The ﬁ rst task was to validate x-ray system. a National Bureau of Standards x-ray source code called “Tubdet.” Tubdet Project Goals was originally implemented at LLNL The overall project goal is to model on a VAX and ported to the Macintosh the four components of the micro-XCT II in Absoft FORTRAN®. The latter Xradia system. For FY2006, we focused version was used to evaluate Tubdet’s on modeling the 150-kV Hamamatsu performance on selected spectra. Com- microfocus x-ray source. In FY2007, we paring Tubdet to experimental spectra will work on models for transport, scat- showed an overemphasis of the low-energy ter, and detection. continuum and characteristic lines in the

0.08

0.06

0.04

0.02 X-ray/chnl (arbitrary untis) X-ray/chnl

0 0204060 80 100 X-ray energy (keV)

Figure 1. A Tubdet model spectrum (red) compared to an experimental spectrum. The overemphasis of low-energy continuum and very strong characteristic lines are typical of the Tubdet performance.

62 FY06 Engineering Research and Technology Report Measurement Technologies

Tubdet-generated spectra. Figure 1 is a Next, we focused our efforts on 4. Finkelshtein, A. L., and T. O. Pavlova, comparison of a Tubdet model spec- modeling the continuum with the “Calculation of X-Ray Tube Spectral Distri- trum and an experimental spectrum characteristic lines of the spectra. Here butions,” X-Ray Spectrometry, 28, pp. 27–32, taken from a Toshiba x-ray tube head we implemented the Ebel and Finkelsh- 1999. with 1.2-mm Al inherent fi ltration. tein characteristic-line algorithms to 5. Fewell, T. R., R. E. Shuping, and K. R. Because of the poor match between generate the spectra. We compared the Hawkins, Handbook of Computed Tomogra- the Tubdet model and the experimental models with a selection of experimental phy X-ray Spectra, Bureau of Radiological data, Tubdet was determined not to be a data with differing characteristics lines Health, U.S. Dept. of Health and Human good choice for modeling tube spectra. (K and L), and anodes (Cu, Mo, W, and Services, Rockville, Maryland, April 1981. We then changed our focus to two Au). Neither of the models consistently other models, Ebel and Finkelshtein. matched absolute intensity measure- The names of the models refer to the ments. Model to experimental intensity fi rst authors of the papers. Both models ratios varied from 10% to 300% too FY2007 Proposed Work include separate descriptions of the high and the ratio of characteristics In FY2007, we will continue our work generation of Brehmsstrahlung and lines to the continuum varied by a fac- of modeling the source and begin work characteristic lines within the material tor of two. on a methodology to model the detector. and the attenuation of the x-radiation The detector consists of a CsI scintillator on transport to the surface. We imple- Related References mounted to a microscope objective. The mented the Brehmsstrahlung models of 1. Tao, G. Y., P. A. Pella, R. M. Rousseau, scintillator/objective is optically coupled to Ebel and Finkelshtein in Mathematica. “NBSGSC—A FORTRAN Program for a scientifi c grade charged-couple device. Figures 2 and 3 show a comparison Quantitative X-Ray Fluorescence Analysis,” Each component of the detector will need of the continuum models with the NBS Technical Note 1213, April 1985. to be modeled for an overall detector experimental data from a Machlett 2. Bhat, M., and J. Pattison, et al., “Diagnos- model. We will also include existing x-ray source. The model data has been tic X-Ray Spectra: A Comparison of Spectra transport codes and x-ray scatter models fi ltered to match the attenuation of the Generated by Different Computational Meth- to complete the model methodology for 2.7-mm Al fi ltration of the Machlett ods with a Measured Spectrum,” Med. Phys., the four components. We will use HADES to tube. Both models appear to provide 25, January 1998. generate an overall model of the system. excellent spectral shapes for the con- 3. Ebel, H., “X-Ray Tube Spectra,” X-Ray tinuum up to 120 kV. Spectrometry, 28, pp. 255–266, 1999.

x 109

5 2 x 1010

4 1.5 x 1010

3 1 x 1010 2 X-ray/chnl (AU) X-ray/chnl X-ray/chnl (AU) X-ray/chnl 5 x 109 1

0 0 0102030 40 0204060 80 100 120 X-ray energy (keV) X-ray energy (keV)

Figure 2. Measured spectra data (circles) compared to Ebel (red) and Fin- Figure 3. Measured spectra data (circles) compared to Ebel (red) and kelshtein (green) models at 40 kV. Measured data from Fewell handbook. Finkelshtein (green) models at 120 kV. Measured data from Fewell handbook.

Lawrence Livermore National Laboratory 63 TechBase

Computed Tomography John D. Sain (925) 422-3409 Reconstruction Codes [email protected]

he code, CCG-LCONE (for con- including the study of explosive samples Tstrained-conjugate gradient for large- for DoD and DOE, high-energy-density angle cone beam), has been used in physics for DNT, and surveillance of LLNL’s nondestructive evaluation work weapons components. Code documenta- for a number of years. Code documentation furthers this usefulness. tion has been needed to provide users and programmers with a guide to its FY2006 Accomplishments and Results theory and structure. This report, origi- We have completed the report, nally authored by LLNL retiree Jessie A. “CCG-LCONE, CT Reconstruction Jackson, presents a summary of the code Code, User and Programmer’s Guide,” and its documentation. which documents the theory behind parts of the code and the structure of the Project Goals code. It functions as both a user’s guide This project was to document the and a programmer’s guide. code CCG-LCONE, an x-ray reconstruc- CCG-LCONE is used to reconstruct tion tool. objects from images acquired on cone- beam radiographic systems. Relevance to LLNL Mission There are many CT techniques to An expanded x-ray computed create reconstructed objects. These tomography (CT) reconstruction tool methods consist of processing the pro- set will beneﬁ t several LLNL programs, jection data by ﬁ ltering, scaling and/or

Input parameter file

RECON

Input Input Cost data + data file i function y y (–) Δy yi

Initial Initial System Optimization object value model algorithm data file x0 x0 LCONE xi CCG (x)

Object Object x Output constraint Output constraints data file data files

Output Interim parameter output file data files

Figure 1. RECON-CCG-LCONE model.

64 FY06 Engineering Research and Technology Report Measurement Technologies

Original known as SCT fi les, and routines for slice Object Detector reading and writing data fi les in the VIEW fi le format. CCG-LCONE was Source Qcone angle created within this system. Figure 1 Slice 340 – Q= 0.3º shows the CCG_LCONE iterative opti- Reconstructed Slice 300 – Q= 1.4º Slice 60 – Q= 8.2º mization system within RECON. slices Slice 260 – Q= 2.6º CCG-LCONE has proved to be CBP effective for cone-beam CT problems. Figure 2 shows a comparison of simulated results for different algorithms. At Feldkamp four different cone angles the reconstruction results are shown for CBP, CCG Feldkamp and CCG-LCONE. CCG- LCONE obviously out performs CBP and Feldkamp. Figure 2. Large cone angle simulated cone-beam reconstruction comparison. CCG-LCONE is, however, slow and memory intensive, so it has been FFTs, and then essentially backprojecting based on a polar coordinated system generally used only in special cases. and summing the data. These methods has proved quite effective. One case where it has been effective is include Filtered Backprojection (FBP), A number of years ago LLNL’s in neutron imaging. Neutrons produce Convoluted Backprojection (CBP), and NDE staff developed a suite of re- noisy data, since they are heavy par- the Feldkamp Algorithm. FBP and CBP construction codes called RECON. ticles and cause a great deal of scatter- are designed to work on systems with Included in the system were routines ing. CCG-LCONE has been effective in parallel and fan beams, respectively. for reading and writing parameter fi les, processing this data, as shown in Fig. 3. These beams pass through only one slice of an object. Processing speeds for these CCG - slice 511 CBP - slice 511 methods are generally reasonable even for large detectors. Also the slices can be processed in parallel, further reducing the overall processing time. Cone-beam systems are more complicated. In a cone-beam system the beam can pass through a number of object slices. FBP and CBP are not designed to work for this case. The Feldkamp algorithm was developed for cone-beam geometries. However, for the sake of speed and memory it makes cer- Line out Line out tain simplifying assumptions, as a result Comparison of CCG and CBP slice 511 - line out it works reasonably well for small cone 0.05 angles but it is less effective for larger 0.04 cone angles. To provide a method that would 0.03 produce a more accurate reconstruc- 0.02 tion for large cone angles an iterative, optimization, cone-beam system was 0.01 created. The Constrained Conjugate 0 Gradient (CCG) method was selected as the optimization algorithm –0.01 in combination with a least-squares –0.02 cost function. A Linear Cone-Beam (1/mm) coefficient Linear attenuation (LCONE) ray-path system model was –0.03 1 101 201 301 401 501 601 701 801 901 1001 created. In fact, a number of different Cross-section voxels ray-path models have been created in an effort to improve the process- Figure 3. CCG-LCONE (red) and CBP (green) reconstruction comparison for ing speed. The latest ray-path model neutron imaging.

Lawrence Livermore National Laboratory 65 TechBase

Super-Resolution Algorithms Grace Clark (925) 423-9759 for Ultrasonic NDE Imaging [email protected]

enerally, one of the major desired constraints to regularize the ill-posed Gresults from a nondestructive evalu- problem. The algorithm consists of two ation (NDE) test of a mechanical part steps: 1) Optimal Least Squares System is a segmented image or image cube Identiﬁ cation (Wiener) to estimate the showing the locations and physical impulse response of the material under characteristics of cracks, inclusions, test, given the available transducer band- voids, delaminations, ablations, and width; and 2) Bandlimited Spectrum other ﬂ aws. A key NDE goal is to obtain Extrapolation (BSE) using constrained images having the best possible spatio- analytic continuation to expand the temporal resolution. Unfortunately, the available bandwidth and improve spatio- resolution of all ultrasonic measure- temporal resolution. ments is severely limited by the inherent fundamental band-limited spectral Project Goals transfer function of ultrasonic transduc- The goal of this project is to imple- ers, the uncertainty principle, and the ment BSE in combination with the diffraction limit. In the time domain, the Wiener algorithm in a user-accessible transducer causes severe ringing that can form to provide an important new limit resolution. ultrasonics super-resolution software Previous studies have shown that tool for NDE. We will 1) implement this ringing can be mitigated by solving the super-resolution algorithms for an ill-posed and ill-conditioned inverse processing signals (A-scans), images problem. The solution uses several (B-scans), and 3-D volumes (multiple

X Top view C-scan image B-scan image (horizontal slice, top view) (vertical slice, side view) .500

Y C1 F1 J1

.500 B1 F1 H1 2.953 A1 D1 G1

2.953 Side view Side view

1.020

Figure 1. Line drawings (top and side views) and images of an Al block insonifi ed with ultrasound in a water bath. The transducer was raster-scanned across the top surface in multi-monostatic mode. The drilled fl at-bottom holes are apparent in the top and side views. Tape was placed over the back of the holes to prevent water from entering. The B-scan represents a vertical slice through the volume. The C-scan represents a horizontal slice through the volume. The B-scan shows the front surface of the Al block at the top, the top surface of the holes in the middle, and the back surface of the block at the bottom. It can be seen from the B-scan that the spatio-temporal resolution (multi-colored lines) is compromised by the transducer ringing.

66 FY06 Engineering Research and Technology Report Measurement Technologies

B-scans); and 2) publish results of materials for sensor fusion studies the surface edges to appear broad and validation tests using simulated data and with ultrasound and x-ray computed unclear. The system identifi cation existing programmatic data. tomography; c) ultrasonic multi- (Wiener) results improve the resolution monostatic data set for the Stanford somewhat, but only within the limits of Relevance to LLNL Mission Geophysical Exploration Project; the transducer bandwidth. The Wiener Resolution enhancement will di- d) electromagnetic time-domain plus BSE results show that the surface rectly benefi t all LLNL programs that refl ectometry (TDR) signals for the edges have been delineated clearly as require ultrasonic imaging tests. Our stockpile stewardship project; sharp impulses. This is the desired reso- project also has been useful in improv- 4. a report describing the algorithms, lution enhancement. ing the results from time-domain refl ec- and user information for the soft- tometry for a weapons program. ware; and Related References 5. technical papers describing the 1. Clark, G. A., D. M. Tilly, and W. D. Cook, FY2006 Accomplishments and Results work. “Ultrasonic Signal/Image Restoration for This is the second year of a two- Even greater benefi t can be realized Quantitative NDE,” NDT International, 19, year project. All of the proposed deliv- in applications in which the raw refl ec- 3, June 1986. erables have been produced: tion wavelets are superimposed, as in 2. Papoulis, A., and C. Chamzas, “Improve- 1. a MATLAB implementation of the thickness measurements for very thin ment of Range Resolution by Spectral algorithms, complete with a Graphi- layers; i.e., adhesive thickness mea- Extrapolation,” Ultrasonic Imaging 1, pp. cal User Interface (GUI); surements. Here, the super-resolution 121-135, 1979. 2. algorithm validation tests with algorithms can separate the refl ections 3. Clark, G. A., and J. A. Jackson, simulated signals; in time/distance. “Super-Resolution Algorithms for Ultrasonic 3. algorithm validation tests with An aluminum block (Fig. 1) with Nondestructive Evaluation Imagery,” real programmatic data sets: a) an fl at bottom holes is used to show the 4th Joint Meeting of the Acoustical Society aluminum block containing known improvements obtained using the super- of America and Acoustical Society of Japan, fl at-bottom holes; b) a known resolution algorithms. With respect to Honolulu, Hawaii, November 28 – “phantom” object consisting of Fig. 2, the original data show low reso- December 2, 2006. concentric cylinders of various lution, as the transducer ringing causes

(a)3D volumes (b) B-scans (c) A-scans (center plane from 3D volume) (center slice from B-scan) Front surfaces of the holes Front Plane for Slice for Original B-scan A-scan Back

Back surface of the Al block

Front surfaces Front of the holes Plane for Slice for B-scan A-scan Wiener Back

Back surface of the Al block

Front surfaces of the holes

Slice for Plane A-scan for Front BSE B-scan Back Back surface of the Al block

Figure 2. Processing results for experiments with the Al block in Fig. 1. Ultrasonic 3-D volume data are used. (a) Original (raw) 3-D volume, the system identifi cation results (Wiener), and the Wiener plus BSE results. (b) Corresponding results for the B-scan (2-D vertical image (slice) depicted by the planes in (a). (c) Processing results for a single signal (A-scan) selected from the corresponding B-scans (b).

Lawrence Livermore National Laboratory 67 TechBase

Defect Detection in Douglas N. Poland (925) 422-4980 Large CT Image Sets [email protected]

his image analysis project is construct- platform with existing data management Ting a tool for performing computer- and visualization capabilities. Poten- assisted detection of small voids in tial platforms include VisIt, ImageRec computed tomography (CT) data sets. (currently used for reconstruction and The focus of year one is to identify analysis of programmatic CT data) and candidate algorithms and demonstrate Image Content Engine (ICE). satisfactory performance on a test object. The test object is a tungsten Project Goals ring with various holes on its inner The enhanced surveillance program circumference. The approaches being requires CT datasets that are up to sev- evaluated are mathematical morphology eral thousand voxels on a side (i.e., 8000 (MM) algorithms that operate on the x 8000 x 8000). The current method of CT datasets, model-based matching al- analysis requires a tomographer to view gorithms that operate on the sinograms sequences of several thousand images, (before reconstruction), and combina- where each image occupies several tions of these two. In year two the focus computer screens at full resolution. The will shift to implementing the proven goal of this project is to create a tool that algorithmic approach within a software will reduce these datasets to a ranked set

3 2 1 5 4 (a) 7 6 13 12 11

Hole Diameter Depth 10 index (μm) (μm) (b) (c) 1 1952 400 9 2 1020 930 3 1035 460 8 4 244 247 5 257 115 6 138 52 7 138 124 8 508 508 9 508 406 10 406 406 (d) 11 406 305 #1 #8 12 305 406 13 305 305

Figure 2. GDM/sinogram processing of tungsten ring. (a) Unpro- Figure 1. Tungsten ring test object with 13 holes drilled into its inner surface. This cessed sinogram (outlined segment is shown in (b) after process- cutaway sketch shows the hole locations, while the table lists their sizes. Note ing). (b) Portion of processed sinogram. (c) Match surface output that in the images used for this work, holes #4 through #7 are very diffi cult to from GDM algorithm. Brightness corresponds to degree of match impossible to detect manually; they are not found by our algorithms. to sinusoid of a given phase and amplitude. (d) Final GDM output, with peaks corresponding to holes #1 and #8 labeled. To the left of #8 are seen the peaks corresponding to holes #9 through #13 (the latter disappearing into the noise).

68 FY06 Engineering Research and Technology Report Measurement Technologies of candidate voids that can be quickly the fact that it does not require image tool for MM/CT, and that combining validated or rejected by the tomographer reconstruction. The results reveal that their results in this way could lead to and possibly even program personnel. this method was able to identify 8 holes, a more robust and sensitive algorithm. The enhanced surveillance program the smallest of these being #12 (305 μm This must be left for future work. has produced a tungsten ring with sur- x 406 μm). rogate defects drilled into it (Fig. 1) Once the CT image reconstruction Related References for use in studying the ability of their is performed, we looked for defects in 1. Paglieroni, D. W., W. G. Eppler and D. systems and analysts to detect this class either 2-D image slices or 3-D volumes. N. Poland, “Phase Sensitive Cueing for 3D of defects. Of the 13 holes in this ring, We searched for localized bright (inclu- Objects in Overhead Images,” SPIE Defense 9 (ranging from 305 to over 1000 μm) sions) or dark (voids) regions indica- and Security Symposium: Signal Process- are well resolved by the CT system and tive of defects in these data using MM ing, Sensor Fusion and Target Recognition are readily discernible in the processed fi lters and tophat reconstruction (Fig. 3). XIV, Proc. SPIE, 5809, pp. 431-442, Orlando CT data (the remaining 4 are less than Based on max/min operations in a local Florida, March 2005. 300 μm in diameter); one key suc- neighborhood, MM fi lters are nonlinear, 2. Brase, J. M., D. W. Paglieroni, D. N. cess metric is that our algorithm must and use a shape sensitive “structure ele- Poland, G. F. Weinert, C. W. Grant, A. S. place these 9 voids at the top of our ment.” They can solve many problems Lopez, and S. Nikolaev, “Image Content ranked list of candidate voids. not amenable to solution by classical lin- Engine (ICE): A System for Fast Image Da- ear fi ltering methods. The results reveal tabase Searches,” SPIE Defense and Security Relevance to LLNL Mission that this method was able to identify 9 Symposium: Optics and Photonics in Global This project will produce a tool that holes, the smallest of these being #13 Homeland Security, Proc. SPIE, 5781, pp. will increase the effi ciency of enhanced (305 μm x 305 μm). 150-154, Orlando, Florida, March 2005. surveillance program tomography Using both simulated and real data, 3. Serra, J., Image Analysis and Mathemati- analysts, allowing them to focus their at- we implemented and evaluated these ap- cal Morphology, Academic Press, New York, tention on resolving ambiguous suspect proaches. We found that the MM/CT ap- New York, 1982. voids (i.e., voids less than 300 μm). proach is more robust for these data sets This tool will provide a well character- due to the low sinogram SNR associated ized analytical package, ensuring uni- with small defects. The MM algorithm form analysis of each region of these on 3-D CT data successfully ranks all FY2007 Proposed Work large data sets. This tool will also make 9 target holes (≥ 300 μm in diameter) We are in the process of quantifying the these data sets more accessible to other in the tungsten ring dataset at the top performance of the MM algorithm using technical staff, who may not be tomog- of the candidate void list. This was ac- real weapon component CT data, and will raphy experts, by performing necessary complished with fewer false alarms than then implement automated parameter preprocessing and quickly guiding them the sinogram processing, thus the initial selection (e.g., automated thresholding to regions with suspect voids. fi nding is that MM processing alone is based on global and local statistics). The the most effective algorithm. There is fi nal steps will be algorithm integration FY2006 Accomplishments and Results still promise that GDM/sinogram analy- and a report on future work. CT scanning produces 2-D radiog- sis could be developed as a confi rmatory raphy projections and volumetric CT image data that can be viewed in many (a) (b) (c) different ways. Our initial approach was to emulate a common strategy for leveraging these different data types: identify candidate voids in the CT data and then refer to the sinograms for corroboration. Sinograms are created by extracting a given row (elevation) from each radiograph in the sequence and stacking them, creating an image in which voids form a distinct sinusoid pattern due to the rotation of the object during imaging. We looked for these sinusoid patterns using the Gradient Direction Matching (GDM) algorithm created through the ICE, a powerful model-based matching tool (Fig. 2). Figure 3. MM/CT processing of tungsten ring. (a) Individual reconstructed CT image slice containing holes #8 through #13 (ranging from 508 μm to 305 μm diameter). (b) Result of applying MM alternating This approach was attractive due to the sequential fi lter and complementing the image. (c) Result of highlighting the voids after 3-D MM white success of GDM in similar problems and tophat reconstruction and thresholding steps.

Lawrence Livermore National Laboratory 69 LDRD

Nanobarometers: In-Situ James S. Stölken (925) 423-2234 Diagnostics for High-Pressure stö[email protected] Experiments

he mechanistic understanding of resolution of the peak local pressure. Thigh-pressure phenomena requires Preliminary work indicates that the the capability to probe the local mate- fabrication, deployment, and read-out rial response at high spatial resolu- of the nanoscale pressure sensors are tion using experiments with complex possible. We are executing a com- loading history. Such experiments rely prehensive plan to explore the scale heavily on computational simulations dependence, concentration limits, and for the interpretation of local condi- pressure sensitivity of nanoscale pres- tions such as temperature and pressure sure sensors. The ﬁ nal product shall be history. The development of an in-situ an in-situ nanoscale pressure sensing nanoscaled pressure sensor provides capability that has been calibrated a means to assess the quality of these over a wide range of pressures (from simulations through the direct mea- 30 to 300 kbar) and a range of defor- surement of local peak pressure and mation conditions from quasi-static comparison with simulation. to weak shocks. The development of The diagnostic developed under an in-situ, nanoscale pressure sensor this project consists of nanoscale will provide both a valuable tool for sensors that are imbedded within, or many existing high-pressure applica- in contact with, the medium to be tions and an enabling technology for measured. They record the local peak new uses and novel experiments; thus pressure and may be read-out follow- complementing many existing Labora- ing the experiment using a variety tory programs in nanoscale modeling, of micro-spectroscopy techniques. material failure and fracture, and laser- The small size of the nanosensors, driven experiments. A natural exten- combined with low volume fractions, sion would be to design new materials limits the inﬂ uence of the sensors on to extend the useful pressure range of the high-pressure phenomena being the proposed sensors to both lower and studied while allowing for high spatial higher pressures.

20 Pressure (GPa) Pressure

0 11.25 μm 0 200 400 600 800 1000 Depth from drive surface (μm)

Figure 1. Micrograph of incipiently spalled and Figure 2. Computed peak pressure profi le due to recompressed copper sample. a laser-driven shock.

70 FY06 Engineering Research and Technology Report Measurement Technologies

Project Goals loading. The proposed nanosensors The project goal is to develop an in- complement many existing Laboratory situ diagnostic for high-pressure experi- programs in multi-scale modeling, mate- ments capable of providing local peak rial failure and fracture, and laser-driven pressure information at high resolution experiments. Potential application to (<1 μm) and over a broad range of pres- three classes of experiments is envi- sure (30 to 300 kbar). Key issues to be sioned: Quasi-Static Experiments in Bulk addressed shall include calibration and Materials, Unsteady Shocks in Bulk 1 μm sensitivity analysis of the nanosensors Materials, and High Explosives. From to quasi-static conditions. Major goals gas-gun and laser-driven experiments to Figure 4. Micrograph of sub-micron silica sensors of the proposed research are to quantify Site 300 and NTS U1a test shots, there is embedded in a copper matrix. the extent of pressure induced changes a need for an accurate, local measure of in the sensor material, determine their material peak pressure. dependence on sensor size, and establish Raman shift upon the particle size, a the sensitivity of pressure induced struc- FY2006 Accomplishments and Results key research question to be addressed tural changes to static loading. Figures 1-4 illustrate our results. A by this project. Results obtained this last key question regarding the existence year show, as suspected, a clear change Relevance to LLNL Mission and nature of the densifi cation mecha- in the size dependence for the smallest The study of high-pressure phenom- nism in silica nanoparticles has been particles (< 80 nm in Fig. 3). Note that ena is at the core of many DNT and NIF explored. The issue was whether or not each experimental point represents an related programs, with many impor- the densifi cation phenomena observed entire sequence of spectra taken upon tant applications in the range of a few in bulk silica occurred in nanoparticles. loading and unloading of each sample. hundred kilobars, such as fragmentation Since the success of the entire project As a consequence of the success of this and spall. Such experiments rely heavily is predicated upon this, it was crucial to year’s experiments a record of invention on computational simulations for the experimentally verify this assertion. The has been fi led and a preliminary patent interpretation of local conditions such results of a series of Raman spectros- is being pursued. as temperature and pressure history. The copy and diamond anvil experiments development of an in-situ nanoscaled on silica nanoparticles are quite intrigu- Related References pressure sensor provides a means to ing. The permanent shift in the Raman 1. Brazhkin, V. V., and A. G. Lyapin, “High- assess the quality of these simulations spectra is clearly visible, consistent with Pressure Phase Transformations in Liquids through the direct measurement of local the published results in bulk silica glass. and Amorphous Solids,” J. Phys. Condens. peak pressure and comparison with sim- To the best of our knowledge, this is Matter, 15, 36, pp. 6059–6084, September ulation. Such a capability is especially the fi rst such measurement in nanopar- 17, 2003. useful in laser-driven experiments with ticles as a function of particle size. Not 2. Cowley, J. M., “Applications of Electron complex wave profi les and non-steady unexpected is the dependence of the Nanodiffraction,” Micron, 35, 5, pp. 345- 360, 2004. 3. Garvie, L. A. J., and P. R. Buseck, Raman shift as a function Pressure dependence “Bonding in Silicates: Investigation of the of the maximum pressure of the Raman spectra Si L-2, L-3 Edge By Parallel Electron Energy- 530 Silica 1.2 μm, no Loss Spectroscopy,” Amer. Mineralogist, 84, pressure medium 0.1 GPa 5-6, pp. 946-964, May-June 1999. 4. Kubota, A., M. J. Caturla, J. S. Stölken, and 520 9 GPa Nanosilica* 15 nm 21 GPa M. D. Feit, “Densifi cation of Fused Silica Due 30 GPa to Shock Waves and Its Implications for 351 510 21 GPa nm Laser Induced Damage,” Optics Express, 11 GPa 8, 11, pp. 611-616, May 21, 2001. 500 5. Sugiura, H., R. Ikeda, K. Kondo, and T. Nanosilica 80 nm, 1 GPa Yamadaya, “Densifi ed Silica Glass After 490 no pressure medium Shock Compression,” J. Appl. Phys., 81, 4, Bulk, ambient pressure pp. 1651-1656, February 15, 1997. 0 5 10 15 20 25 30 200 400 600 800 1000 Pressure (GPa) Raman shift (cm–1)

Figure 3. Permanent shift in Raman spectra as function of peak pressure and particle size (15, 80, and 1200 nm). 15 nm particles show distinctly diff erent pressure dependence.

Lawrence Livermore National Laboratory 71

Nano-Devices Micro/ and Structures

FY 06 Engineering Research and Technology Report LDRD

Rapid Defense Against the Raymond P. Mariella, Jr. (925) 422-8905 Next-Generation Biothreat [email protected]

ioengineered and emerging pathogens We will also create less costly, but more Brepresent a signifi cant threat to hu- general multiplex assays for viruses, us- man health. The best defense against a ing multiplex, ligation-dependent probe rapidly expanding pandemic is to isolate amplifi cation (MLPA). the pathogen quickly from biological samples so that it may be identifi ed, Relevance to LLNL Mission characterized, and have treatments By making it possible to rapidly iso- developed against it. The one persis- late and detect engineered and naturally tent technology gap in the process of emerging biothreats, this project con- identifying and quantifying the pres- tributes to the nation’s defense against ence of pathogenic agents has been bioterrorism, which is central to LLNL’s sample handling and preparation that homeland security mission. In addition, must precede any assay. Also, we need this project supports LLNL’s mission in higher-performance, multiplex assays for bioscience to improve human health. families of rapidly-mutating RNA viruses. FY2006 Accomplishments and Results Project Goals In FY2006, we established a Bio- The objective of this project is to Safety Level 1 (BSL-1) lab in which replace burdensome, manual techniques we propagate the virus MS2 using the for sample handling and preparation host bacterium E. coli. We developed with new automated technologies. We harvesting and clean-up procedures of use microfl uidics with ultrasonics, the MS2, as well as fl uorescent staining electrophoretics, and dielectrophoret- techniques for this virus. Using micro- ics to separate and purify viruses from fl uidic systems, we determined that the biological and environmental samples. “gold standard” solution for handling

(a) 0 V (b) 2 V

Top of microchannel

Buffer input MS2, transported

MS2 input

Bottom of microchannel 0.7 mm

Figure 1. Monochrome photographs of a low-conductivity solution of fl uorescently-labeled virus MS2, fl owing in a microchannel with top and bottom electrodes (not seen). There are two solutions being introduced from the left of the channel: the upper solution is a clean buff er and the lower solution contains the labeled MS2. In the left-hand photograph, there is no voltage applied and the laminar fl ow and relatively low diff usivity of the MS2 confi ne the MS2 to the bottom half of the fl ow. In the right-hand photograph, with 2 V applied perpendicular to the fl ow, the MS2 has been almost entirely transported up into the buff er solution, as desired.

74 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures

FY2007 Proposed Work A 40-plex assay for detection of known viruses and viral families is now under development. Quantifi ed viral RNA and DNA have been purchased so the assay sensitivity can be accurately determined. A multiplex assay will be designed for detection of respiratory pathogens. This assay will include the pathogens previously Clarified sample tested so the diff erent assay formats can be compared for sensitivity, specifi city, and ease of development and automation. We will work with Dr. Aaron Brault a highly regarded UC Davis arbovirologist, to Yeast To waste design and test an MLPA assay for detection of arboviruses circulating in the Western U.S. This assay will be used to identify arboviruses present in mosquito pools and human clinical samples. As multiplex assays are developed, probes will be pooled within a single assay to determine the number of probes that Figure 2. Photograph of yeast fl owing in a 0.5-mm microchannel that has an ultrasonic standing wave, perpendicular to the image plane and running along the center of the fl ow channel. Ultrasonic trans- may be multiplexed using this technique ducer is outside of viewing area. and the speed of assay development. Prior to using human nasopharyngeal samples, we will use prepared mixtures of viruses, Viral Transport Medium, is detection of viruses was successfully viruses with bacteria and eukaryotic cells incompatible with electrophoretic ma- designed and tested using a combina- in our research on microfl uidic separa- nipulations of particles, due to its high tion of multiplex ligase-dependent tion techniques. Some examples of these electrical conductivity. We developed a PCR and suspension microarray (Lu- mixtures are the bacteriophage MS2 buffer exchange process that produced minex platform) detection of signal. with its host bacteria, E. coli, and BSL-1, MS2 in solutions with conductivities be- Eight probe sets were tested in MLPA Risk-Group-1 virus such as fowlpox virus low 0.1 mS. With this, we successfully multiplex reaction with DNA target. vaccine with its host cell, DF-1, derived transported MS2 in the manner desired Six of the eight probes were multi- from chickens. (Fig. 1). plexed with minimal effort. The assay We also investigated the manipula- was also able to detect target DNA de- tion of baker’s yeast (S. cerevisiae) as spite the presence of mismatches in the a model for human cells. In accordance probe sequences, indicating that the with theory, the use of acoustic radia- assay will tolerate the diversity char- tion pressure from an ultrasonic stand- acteristic of viral genomes. Conserved ing wave was easily able to transport regions for all vertebrate-infecting suspended yeast cells, fl owing in a viral families have been identifi ed microfl uidic channel, in a matter of and will be used for subgroup-specifi c seconds over a distances of 100’s of μm. MLPA probe design. The protocol and Using an ultrasonic standing wave in a probe design parameters are currently microchannel, we moved and confi ned being optimized to increase multiplex the fl owing yeast cells to the bottom depth and assay sensitivity. half of the channel, so that it could be We have also established col- directed to the waste reservoir and not to laborations with two of the world’s the collection reservoir (Fig. 2). leaders in virus discovery, Prof. Forest Since receiving funding for this Rohwer at SDSU and Prof. Joe Derisi project, an MLPA protocol for rapid at UCSF.

Lawrence Livermore National Laboratory 75 LDRD

Thermal-Fluidic System Kevin D. Ness (925) 423-1856 for Manipulation of [email protected] Biomolecules and Viruses

e are developing a reconfi gurable Project Goals Wfl uidic system that demonstrates the The project goal in the fi rst year ability to simultaneously perform separa- was to develop an automated TGF tions, concentrations, and purifi cations of instrument to improve the separation biomolecules and viruses using tempera- resolution and throughput when applied ture gradient focusing (TGF). Many proj- to front-end processing of biological ects throughout LLNL, particularly those samples. Goals for years two and three related to pathogen detection, mitigation are to identify two specifi c application and protection, require the manipulation areas to demonstrate the novel sample of biomolecules or viruses to accurately manipulation capabilities inherent to quantify the presence of a particular TGF: 1) the purifi cation and separation substance or to accurately synthesize and of different virus strains in complex investigate the function of a molecule. samples (Fig. 2); and 2) to perform TGF, a novel microfl uidic technol- protein concentration and separations for ogy, is an equilibrium gradient version in vitro transcription/translation (IVT) of capillary electrophoresis (CE) that protein expressions. allows for the stationary fractionation (a) Medium fractionation and concentration (up to 10,000 x) of target analytes on the dimension of bulk Flow E-field or free-solution electrophoretic mobility. In this technique, a delicate balance is achieved in a microchannel between a net fl uid fl ow and an opposing electro- (b) Concentrate and wash phoretic velocity gradient to capture charged analytes at a specifi c location Flow E-field (Fig. 1). TGF then separates the analyte Figure 1. Schematic of TGF. Bulk fl uid based on the physicochemical property motion (yellow arrow) is balanced by an of bulk or free-solution electrophoretic opposing electrophoretic velocity (red mobility, which is related to the analytes arrow) to capture analytes at a unique (c) Fine separation of viruses spatial location within a specifi c electro- surface charge (zeta potential) and hy- phoretic mobility range. drodynamic drag (shape and size). Flow E-field

Fluid TGF: The Technology Fluid well well 12 3 Fractionated sample Micro-channel Background Fluid motion Electrophoresis Viruses

Hot Applied temperature gradient Cold Figure 2. Schematic of TGF as applied to viral front-end sample preparation. (a) Viral samples are loaded and captured using TGF. Capture condi- μEx u tions are set to capture the viruses of interest (focusing), allowing some background contami- E Net velocity x μEx u nates to fl ow through to waste (purifi cation). (b) Potential second buff er is fl ushed through μEx u system to perform further sample clean-up (buffer exchange). (c) The TGF separation resolution Net velocity Capture point is adjusted in real-time to fractionate the sample into viral groupings (separation) to further simplify x downstream detection and identifi cation.

76 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures

To accomplish this, precise control major new DOE program, Genomics: 7. characterized labeled proteins using over temperature (<1 ˚C), voltage (<10 V) Genomes to Life for protein produc- processes such as SDS-PAGE, native or current (<1 μA) and fl ow rate (1 nL/ tion and characterization. gel, absorbance, and the limit of min) is required, and in-house equip- detection (Fig. 5); and ment and procedures must be devel- FY2006 Accomplishments and Results 8. established external collaborations oped to address these needs. In FY2006, we accomplished the with industry and academia. following: Relevance to LLNL Mission 1. purchased equipment for two TGF TGF specifically addresses LLNL’s test stations, secured laboratory need for the detection of biomol- space, submitted IWS and received FY2007 Proposed Work ecules, viruses or cells at low concen- approval; Future work is to modify the static trations through enhanced collection, 2. surveyed current state of microbial TGF instrument to operate in a dynamic separation, and purification strategies. electrophoresis; “sweeping” mode to adjust capture condi- This is facilitated by performing the 3. developed an in-house microfl uidics tions in real-time to increase the dynamic necessary front-end sample prepara- stable fl ow (nL/min) and pressure range of captured analytes. Work will also tion through concentration procedures, source (0.1 Pa) (Fig. 3); begin to transition from separations in and removing noisy background sig- 4. performed fl ow experiments leading “clean” buff ered samples to separations nals/contaminants. This project sup- to stable valve switching and steady in “complex” real-world environmental plies LLNL’s engineering programs fl ow at the nL/min range; samples and the purifi cation of specifi c with a novel capability to perform bio- 5. developed glass chip fabrication analytes from these “dirty” samples. molecular, viral, and cellular control protocols for microchannel fabrica- in a flexible format to address a wide tion and port holes; range of programmatic assay condi- 6. developed a fl uorescently labeled tions. In addition, this aligns LLNL protein electrophoretic mobility capabilities with the requirements of a marker set (Fig. 4);

730 Fluorescence limit of detection 10000 10 ms 710 100 ms 1 s 690 1000 10 s

670

Intensity (AU) 100 Flow rate (nL/min) rate Flow

650 Commercial pump LLNL system 10 630 –9 –7 –5 –3 –1 0 100 200 300 400 10 10 10 10 10 Time (s) Molarity (M)

Figure 3. Flow rate stability comparison of commercially available pump ver- Figure 5. Data showing the TMR probe detection limit using the TGF sus LLNL fl ow control system developed for precision sample manipulation. microscopy equipment with varying fl uorophore concentrations and exposure times.

*2.8 GoX *5.4 PhB UL *1.9 194.8 kDa UL 160 kDa Ov UL 45 kDa *.23 Lys *.12 UL Apr 14.4 kDa UL 6.5 kDa *Estimated dye molecules per protein molecule

Figure 4. Image of a denaturing PAGE protein separation experiment showing the molecular weight shift observed between fl uorescently labeled (L) and unlabeled (U) proteins.

Lawrence Livermore National Laboratory 77 TechBase

Precision Sample Control Klint A. Rose (925) 423-1926 and Extraction Component [email protected]

ncorporating microfl uidic-based technol- extraction of these sample volumes Iogies into bio-analytical instruments with minimal effect on the main micro- has many benefi ts, including reduced fl uidic module’s performance. sample consumption, faster response An illustration of this concept times, and improved sensitivity. To is shown in Fig. 1. These functions achieve these benefi ts, microfl uidic should be achieved in platforms with analysis often requires sample concen- fabrication protocols that are standard tration and separation techniques to in the LLNL cleanroom. isolate and detect an analyte of interest. Complex or scarce samples may also Relevance to LLNL Mission require an orthogonal separation and This project addresses needs identifi ed detection method or off-chip analysis for in LLNL’s Engineering roadmaps for the confi rmation of results. To perform these detection of biomolecules (DNA, RNA additional steps, the concentrated sample and proteins) and viruses at low concentra- plug must be extracted from the primary tions (10 to 1000 copies/ml). Specifi cally, microfl uidic channel with minimal loss this project addresses the necessary (and of sample and with minimal dilution. often neglected) front-end sample prepara- Extracting these samples requires pre- tion through precise control and high-yield cise metering and control of nanoliter sample extraction of targeted analytes volumes of fl uid. from upstream concentration, purifi cation Extraction of concentrated samples and/or separation-based microfl uidic de- has been demonstrated, requiring vices. This new functionality will enable constant control of complex electrode additional off-chip postprocessing pro- structures. This project reduces to prac- cedures such as DNA/RNA microarray tice sample extraction using droplet analysis, RT-PCR, and culture growth to and bubble generation techniques. validate chip performance. Many LLNL These methods are integrated with programs will benefi t from the improved the equipment and software necessary front-end preparation offered by the pre- to improve sample exchange among cision fl uidic control and sample extrac- LLNL microfl uidic technologies and tion capabilities created by this project. improve their functionality. This technology will enable LLNL to supply the next generation biothreat detection instrumentation by improving microfl uidic device performance. Processing channel

Project Goals Step 1: concentrate “Push” channel The overall goal of this project is sample to deliver a universal ability to manipulate and extract small volumes Step 2: cap sample for extraction of ﬂ uid (pico- to microliters) from Capping solution micron-scale channels. The desired channel system functions include precise and Figure 1. Flow-rate stability comparison of com- reproducible control of small volumes mercially available pump versus fl ow-control of ﬂ uid within a microchannel, and the system created for precision sample extraction.

78 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures

FY2006 Accomplishments and Results 3. Demonstrated the capping of sam- to be a more effective technique for We have accomplished our overall ples in a microfl uidic channel using partitioning samples. goal by delivering the protocols and air bubbles and fl uorinert droplets, microfl uidic architecture necessary as shown in Fig. 3. Capping with Related References for manipulating and extracting small incompressible fl uorinert droplets 1. Lin, R., D.T. Burke, and M. A. Burns, “Ad- volumes of fl uid from micron-scale provided the most reproducible dressable Electric Fields for Size-Fractioned channels. Specifi c results and accom- results compared to air. Sample Extraction in Microfl uidic Devices,” plishments include the following: 4. Verifi ed effectiveness of capping Analytical Chemistry, 77, pp. 4338-4347, 2005. 1. Used a system for precise sample samples to eliminate loss of solute. 2. Hung, L.-H., et al., “Alternating Droplet control, which includes a fl ow-rate Fluorinert-capped fl uorescent samples Generation and Controlled Dynamic Drop- sensor as feedback for a pressure were analyzed over thirty minutes let Fusion in Microfl uidic Device for CdS unit. This system reduced the stan- and demonstrated no diffusion or Nanoparticle Synthesis,” Lab on a Chip, 6, dard deviation in fl ow rate to 5% of detectable loss in concentration. pp. 174-178, 2006. that for a commercially available 5. Demonstrated through modeling and 3. Tan, Y.-C., V. Christini, and A. P. Lee, precision pump. experimental fl ow measurements that “Monodispersed Microfl uidic Droplet Genera- 2. Created protocols for fabricating proposed injection of samples into tion by Shear Focusing Microfl uidic Device,” microfl uidic chips for extraction. fl uorinert or air (inverse of capping Sensors and Actuators B, 114, 1, pp. 350-356, This protocol includes the hydro- technique) results in sample loss 2006. phobic coating necessary for cap- greater than 20% and dilution of origi- 4. Gartecki, P., et al., “Formation of Droplets ping aqueous samples. An example nal concentration by greater than 50% and Bubbles in a Microfl uidic T-Junction— is shown in Fig. 2. (Fig. 4). This result shows capping Scaling and Mechanism of Break-Up,” Lab on a Chip, 6, pp. 437-446, 2006.

100 0.4

50 0.2 Percent yield Percent Extracted/initial concentration

0 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Figure 2. Microfl uidic chip and mesoscale package for sample Time (s) extraction. The extraction protocol can be integrated into existing microfl uidic devices with the addition of a single input channel. Figure 4. Results from fi nite element models predicting the extraction yield (blue, left axis) and dilution (green, right axis) for a sample injected into the carrier solution as a function of time. The insets depict the concentration profi le of a concentrated plug at times t = 0 s (upper left) and t = 2 s (lower Fluorinert caps right) as the plug is injected from the primary channel into the side channel with pressure-driven fl ow. As expected, the percentage of sample extracted increases with time (blue plot) but the concentration (green plot) peaks at Fluorescent sample ~50% of the sample.

H2O AirH2OH Air 2O

Figure 3. Demonstration of sample capping technique in which air bubbles or fl uorinert droplets are injected around a sample. These techniques segregate the sample and enable extraction with minimal loss and dilution.

Lawrence Livermore National Laboratory 79 TechBase

Single-Molecule Assay George Dougherty (925) 423-3088 of DNA Integrity [email protected]

NA molecules are susceptible to size, and geometry. A single molecule Ddamage resulting from fl ow through assay to characterize damage is par- microchannels in microfl uidic devices ticularly useful for microfl uidic devices and systems. This damage, which can where the concentration of DNA is low, take the form of either single- or double- such as low copy number DNA analy- strand breaks, is dependent on the size sis. In these cases, bulk assays, such as of the channels, fl uid fl ow speeds, and electrophoresis, are not sensitive enough the size of the DNA molecules that fl ow to characterize the damage to the DNA. through the device. This damage can In this project we measured the make it diffi cult to analyze the DNA elasticity of single lambda-phage using processes such as DNA sequenc- DNA molecules (contour length ing, polymerase chain reaction (PCR), = 16.4 μm) before and after flow and labeling of specifi c sequences with through microfluidic devices. Optical fl uorescent probes to search for specifi c traps were used to stretch single DNA DNA molecules. molecules attached to 1-μm beads as An assay to characterize the degree shown in Fig. 1. The displacement of of damage is important because it allows the bead in each optical trap varied one to optimize microfl uidic device linearly with applied force, much like parameters such as fl ow speed, aperture a bead on a spring, and the image of the bead on a quadrant photodiode detector was used to accurately measure qpd F = –kx (Hooke’s Law) the elastic tension the DNA molecule To comp. AB experienced as the distance between

CD the traps increased. Figure 2 shows x the difference in elasticity between

Figure 1. Two optical traps 80 Overstretch (orange laser beams) are Inextensible transition used to hold, stretch, and 60 WLC measure the elasticity of a Exo single lambda-phage DNA 40 molecule via 1-μm beads dsDNA ssDNA attached to the ends. Force (pN) Force 20 Crossover Poly 1.064 μm point 0 010.5 1.5 2 Condenser Fractional extension

Figure 2. Diff erences in the elasticity of double- stranded DNA (dsDNA) and single-stranded DNA Lamp (ssDNA).

80 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures double-stranded DNA and single- what fragmentation of the original DNA Related References stranded DNA that forms the basis of would have looked like. 1. Bustamante, C., Z. Bryant, and S. B. Smith, this assay. It takes much greater force Next, we stretched individual lamb- “Ten Years of Tension: Single-Molecule DNA to stretch double-stranded DNA than da-phage DNA molecules that fl owed Mechanics,” Nature 421, pp. 423-427, 2003. it does single-stranded DNA, and through a multichannel cell at very low 2. Brewer, L. R., M. Corzett, and R. Balhorn, this fact can be used to detect DNA speeds (0.3 μL/s). Figure 4 shows the “Protamine-Induced Condensation and De- molecules that contain single-stranded characteristic “overstretching transition” condensation of the Same DNA Molecule,” portions, due to single-strand nicks, or and is very similar to the graph shown Science 286, pp. 120-123, 1999. where strands have been pulled apart in Fig. 2. However, at higher fl ow rates 3. Bianco, P. R., et al., “Processive Translo- due to shearing forces. damage to the DNA was evidenced by cation and DNA Unwinding by Individual a dip in the overstretching transition Recbcd Enzyme Molecules,” Nature 409, Project Goals shown in Fig. 5. The dip is indicative of pp. 374-378, 2001. The project goals were to 1) identify damage to the molecule and results from 4. Brewer, L., M. Corzett, E. Y. Lau, and a DNA biosensor for testing; 2) perform a portion of the molecule becoming R. Balhorn, “Dynamics of Protamine 1 control measurements on DNA at very single-stranded. This data is supported Binding to Single DNA Molecules,” J. Biol. low fl ow speeds; 3) test DNA integrity by Fig. 2, which indicates that there is Chem., 278, pp. 42403-42408, 2003. using both gel electrophoretic and DNA a large difference in the elasticity of single-molecule elasticity measure- single- and double-stranded DNA at ments to determine the degree of both forces close to 65 pN. double- and single-strand breaks; and This technique represents a sensi- 60 4) optimize the fl ow speed and ge- tive way to measure damage to single ometry of the microfl uidic device to DNA molecules that occurs when 40 minimize DNA damage. DNA fl ows through small channels at Force (pN) Force high fl ow rates. Further work will be 20 Relevance to LLNL Mission required to obtain more quantitative The expertise gained from this proj- information about the extent of the 0 ect will enable LLNL to develop micro- damage to the DNA. 10 12 14 16 18 20 22 24 26 28 30 fl uidic devices for DNA biosensors with DNA extension (μm) a higher effi ciency of detection. The Figure 4. Elasticity of a single lambda-phage increased effi ciency of DNA detection 1 Kb plus A B C D DNA molecule taken after an initial fl ow rate of ladder No flow 1 μl/s 5 μl/s 10 μl/s will be the direct result of assessing the 0.3 μL/s through a microchannel fl ow cell. damage to DNA samples after they pass through microfl uidic biosensors, and 80 then optimizing fl ow speed and biosensor geometry to minimize this damage. 60

40 FY2006 Accomplishments and Results First we performed control measure- 20 Force (pN) Force ments on lambda-phage DNA during fl ow through microfl uidic devices using 0 both bulk- and single-molecule tech- –20 niques. We fl owed lambda-phage DNA 12 14 16 18 20 22 24 26 28 30 DNA extension (μm) through a “packed bed reactor” at fl ow Figure 3. Gel electrophoresis of lambda-phage speeds between 0 and 10 μL/s. Gel DNA molecules that have been run through Figure 5. Elasticity of a single lambda-phage DNA electrophoresis of the resultant DNA re- a “packed bed reactor” (courtesy E. Wheeler) molecule taken after an initial fl ow rate greater vealed no double-strand breaks. This is at fl ow rates of A) 0 μL/s, B) 1 μL/s, C) 5 μL/s, than 1 μL/s through a microchannel fl ow cell, and D) 10 μL/s. No double-strand breaks were showing a strong dip in the middle of the over- shown in Fig. 3. A 1-kb sizing standard observed. The leftmost lane contains a 1-kb stretching transition. This dip shows that a portion run in the left-most lane gives an idea sizing ladder. of the molecule is single-stranded, possibly due to fl uid shear forces.

Lawrence Livermore National Laboratory 81 TechBase

Colocation of MEMS Satinderpall Pannu (925) 422-5095 and Electronics [email protected]

his project bridges the gap between microfabricated metal bumps will en- Tmicro-electro-mechanical systems able MEMS devices to be fabricated in (MEMS) sensors and the necessary conventional processes and then bonded integrated circuits to communicate with to an integrated circuit. and control/manipulate the MEMS. Since the advent of MEMS, electrical Project Goals interconnections have been made using This project established an enabling macroscopic wires to electrically bond technology to colocate MEMS devices the MEMS devices to integrated circuits with integrated circuits. SLMs were used for control and sensing. For a growing as the demonstration system since these number of applications, the associated systems beneﬁ t from both the scalability parasitic resistance and capacitance, and the increased sensitivity of colocated as well as the large number of wires integrated circuits. Arrays of micro- required, are not acceptable as an inter- mirrors (for the SLM), as well as the connect strategy. Several groups have corresponding high-voltage drivers were produced MEMS devices and integrated fabricated. The two dies were colocated circuits monolithically by fabricating by metal compression bonding. The re- the electronics next to the MEMS or sulting system was tested for mechanical using low temperature materials that and electrical functionality. An array of can be deposited without exceeding 25 micro-mirrors bonded to high-voltage the thermal budget of the integrated drivers was assembled and tested. circuits. However, these strategies severely limit the types of MEMS devices Relevance to LLNL Mission that can be fabricated monolithically This project has relevance to a with integrated circuits. Further, for variety of LLNL interest areas. The applications that require dense arrays ability to integrate MEMS devices and of MEMS devices such as spatial light integrated circuits is an enabling tech- modulators (SLMs), packaging den- nology within LLNL. This technology sity is a vital metric. The area increase enables a new generation of devices for incurred by placing MEMS devices next a wide variety of applications: chemi- to integrated circuits is not acceptable. cal and biological sensors; targeting The technology to bond MEMS and tracking and location; biomedical and integrated circuit dies together with devices; high-speed optical processing;

Figure 1. Schematic of MEMS and electronics overall process fl ow fabricated separately for the assembly of Gold MEMS and integrated bumps circuits. MEMS handle wafer removed Electronics Chips bonded together MEMS device MEMS Chips flipped over

Electronic

82 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures and NIF target fabrication. This project FY2006 Accomplishments and Results Further, the micro-mirrors and integrat- has resulted in technology needed for In FY2006, the array of micro- ed circuits were assembled and tested. the creation of meso- to microscale mirrors and the high-voltage integrat- Figures 1 to 3 illustrate our results. The devices with nanoscale precision. ed circuits were fabricated and tested. details for each subtask are given below. MEMS fabrication. The MEMS micro-mirrors were fabricated in the fi rst quarter of FY2006. A large fraction of the fabrication process was carried out in LLNL’s cleanroom. However, LPCVD deposition of polysilicon and silicon dioxide, which required well-characterized tools, was carried out at the UC Berkeley microfabrication facility. In the second quarter of FY2006, mechanical substi- tutes for the integrated circuit device were fabricated so the micro-mirror could be released and tested. The MEMS were released and tested in the third quarter of Layout of MEMS actuator FY2006. CMOS fabrication. We outsourced Released MEMS actuator two integrated circuit fabrication runs in FY2006 based on plans completed in Frequency response of amplifier FY2005. The fi rst two integrated circuit 25 runs were shown to perform as predicted and work as expected, and a third CMOS 20 run, which would have provided a backup 15 in case one of the fi rst two runs failed, was cancelled. Vout 10 Vout (V2(5,2)) Assembly. A fabrication process for w/ 11.2 pF w/ 34 pF forming gold bumps for metal compres- 5 w/ 70 pF sion bonding was created with an exter- 0 nal vendor. The MEMS micro-mirrors 10001 10 100 100000 10000000 were then assembled to the integrated Frequency circuits by compression bonding the ASIC design Demonstration of CMOS amplifier gold bumps against the corresponding metal pads on the integrated circuit die. Figure 2. The schematics on the left side depict the layout of the MEMS micro-mirror and the integrated The MEMS micro-mirrors were then circuit. the images on the right side depict the fabricated micro-mirror and the measured frequency separated from their substrate by break- response of the integrated circuit. ing small silicon tethers. Testing. The MEMS micro-mirrors were demonstrated to respond to electro- static actuation on mechanical models of the integrated circuit die. The testing of Figure 3. MEMs micro- mirrors colocated with the assembled device is ongoing. integrated circuits. Integrated MEMS Related References circuits micro-mirror 1. Stappaerts E., “Differentially-Driven MEMS Spatial Light Modulator,” U. S. Patent Number 6,791,735. 2. Singh, A., D. A. Horsley, M. B. Cohn, A. P. Pisano, and R. T. Howe, “Batch Trans- fer of Microstructures Using Flip-Chip Solder Bonding,” Journal of Microelectromechanical Systems, 8, 1, pp. 27-33, March 1999. 3. Humpston, G., and S. J. Baker, “Diffusion Bonding of Gold,” Gold Bulletin, 31, 4, 1998.

Lawrence Livermore National Laboratory 83 TechBase

Optoelectronic Device Rebecca J. Nikolić (925) 423-7389 Fabrication [email protected]

ptoelectronic devices are a core pillars with a fi ll factor of 50 %, (where Otechnology at LLNL. In order to the fi ll factor is the percent of semi- fabricate many of the desired opto- conductor used for pillars). Additional electronic devices, plasma etching is microfabrication tasks will be carried out frequently required to construct struc- in order to demonstrate a pillar-structured tures with 3-D shapes. Additionally, neutron detector. plasma etching is required to connect multiple devices within a semiconduc- Relevance to LLNL Mission tor wafer. The plasma etching that is This work is supporting both inter- needed requires vertical and smooth nally- and externally-funded projects sidewalls to allow for such integration that require advanced InP-, GaAs- and and also for device performance. Si-based process technology. There are In this project we have addressed many different devices having broad the device integration requirements applications that share the same fabrica- by determining methods to fabricate tion hurdles. Having this technology will turning mirrors. We also have a large allow deployable microfabricated systems effort in the area of pillar fabrication, for several applications that are at the core which is being considered for thermal of LLNL’s national security missions, neutron detectors. In this area we have such as: high-speed radiation diagnostic made advances in terms of fi ll factor devices for NIF, single-transient recording and aspect ratio, as well as the deter- technologies, devices for encryption ap- mination of process recipes to fabri- plications, and radiation detection. cate a demonstration device. This is a two-year project and the signal routing FY2006 Accomplishments and Results component was addressed in the fi rst The work focusing on data routing year of the project (FY2005), while the elements for inverters was carried out in second year of the project is primarily FY2005. The scope of work for FY2006 concerned with the pillar fabrication is focused on building a technology methods and the required techniques toolbox required to fabricate a pillar- to fabricate a demonstration device for structured neutron detector. Two major thermal neutron detection. areas were enhanced: 1) high-aspect- ratio etching, and 2) fabrication methods Project Goals for a demonstration detector (see fi gure). For data routing we will create turn- Within the high-aspect-ratio etching ing mirrors, splitters and combiners. work, we have increased our aspect ratio The fabrication processes studied satisfy to 10. This yields 2-μm-diameter pillar requirements of specifi c ongoing proj- geometry, with a 2-μm separation and ects as well as increase our technology 20-μm pillar etch depth. The fi ll factor toolbox. Pillar structures are demonstrat- for this pillar area is 50 % for our ed with a geometry of at least 100 x 100 1-cm-x-1-cm chip.

84 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures

Within the area of demonstration multi-layer stack, (400/400/2000 Å), Isolation of Pillarlike Structures by CMP detector fabrication, we implemented and for the n+ side, a titanium single and Etchback Processes,” Electrochemical processing recipes for our pillar-struc- layer (2000 Å). Both of these metalliza- and Solid-State Letters, 8, 5, pp. G125-7, tured neutron detector. This included tion schemes form a silicide upon an- May 2005. the speciﬁ cation and procurement of nealing, yielding a low-resistance metal 3. Cheung, C. L., R. J. Nikolic, C. E. -5 2 lithographic masks, the evaluation of contact of RC < 10 Ω-cm . Reinhardt, and T. F. Wang, “Fabrication of methods to deposit the boron materials, Nanopillars by Nanosphere Lithography,” which is the neutron-converting mate- Related References Nanotechnology, 17, pp. 1339-1343, rial for this particular device, as well as 1. Nikolic, R. J., C. L. Cheung, C. E. Reinhardt, March 2006. lapping, polishing and etching tech- and T. F. Wang, “Roadmap for High Efﬁ ciency 4. Shultis, J. K. and D. S. McGregor, niques of boron. Processes to fabricate Solid-State Neutron Detectors,” SPIE “Efficiencies of Coated and Perforated low-resistance contacts to silicon were - International Symposium on Integrated Semiconductor Neutron Detectors,” IEEE demonstrated. This included ohmic con- Optoelectronic Devices, Photonics West, Transactions on Nuclear Science, 53, 3, tact formation to both p+ and n+ silicon: Boston, Massachusetts, October 2005. pp. 1659-1665, June 2006. for p+ Si a platinum/titanium/gold 2. Suligoj, T., and K. L. Wang, “A Novel

(a) (b) Incoming Charged neutrons particles Boron

Silicon

10 μm

(a) Micrograph, showing the etched silicon pillars used in the Pillar Detector. Pillars are 20 μm in height and spaced about 2 μm apart. (b) Thermal neutron detector: incoming neutrons interact with the pillars within a semiconductor matrix.

Lawrence Livermore National Laboratory 85 TechBase

Block Copolymer James Courtney Davidson (925) 423-7168 Nanolithography [email protected]

lock copolymer technology has been membranes and nanotemplates for Bused increasingly for patterning na- ordered detector arrays. noscale features in polymers, silicon and metals. Highly-ordered nanoscale fea- Project Goals tures are produced in thin (nanometer- Our interest in block copolymers thick) self-assembled fi lms. In diblock has been to leverage existing efforts in copolymer systems these fi lms consist of order to establish a core nanolithogra- two covalently bonded polymer chains. phy capability. First year goals were These systems form distinct domain to form a collaboration to assist in the structures due to phase separation of the defi nition and stand-up of a diblock chemically dissimilar polymers during copolymer process within LLNL. This solidifi cation. Depending on the relative process was based on the polystyrene volume fraction, domains can form as (PS) and polymethylmethacrylate spheres, cylinders, or lamellae oriented (PMMA) diblock copolymer. A second either perpendicular to or parallel to the goal was the dimensional characteriza- surface with a period on the order of 10 tion of these nanostructures using ex- to 100 nm. isting analytical tools including SEM, Recently, advanced directed block AFM, and TEM. An additional goal of copolymer self-assembly is showing this effort was to incorporate fi ndings great promise for controlled nanolithog- from an associated modeling effort to raphy techniques for achieving advanced prescribe block copolymer specifi ca- SEMI lithography nodes and high-density tions for dimensional characterization periodic pore arrays and gratings. Still and parametric studies. Second year others have demonstrated the potential of goals include a continued use and re- nanofeature masks for fabricating com- fi nement of predictive modeling for the ponents for micro- and optoelectronics, 2-D process and extension toward 3-D magnetic storage devices, nanopore nanolithography.

Figure 1. SEM of self-assembled DiBCP thin fi lm with ~ 60 nm period. Figure 2. SEM of a 40-nm period thin fi lm produced by etching out the The hex pack PS (light gray) cylinders are vertically oriented and ~ 30 spherical PMMA domain, leaving a PS (light gray) mask. to 35 nm in diameter.

86 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures

Relevance to LLNL Mission shown in Figs. 1 and 2. These fi lms were Related References Reducing a block copolymer nano- characterized using SEM, and AFM to 1. Segalman, R. A., “Patterning with Block lithography process technology to prac- determine feature sizes as small as 25 nm Copolymer Thin Films,” Materials Science tice maps directly onto LLNL’s Micro/ (Fig. 3). and Engineering R 48, pp. 191-226, 2005. Nano-Devices and Structures roadmap An initial wet etch process was 2. Black, C.T., et. al., “Integration of Self- initiative. This is an enabling technology demonstrated to remove the PMMA Assembled Diblock Copolymers for Semi- that will initially provide a capability of component in the film. This proved conductor Capacitor Fabrication,” Applied nanoscale mask lithography with applica- to be prerequisite for increasing the Physics Letters, 79, pp. 409-411, 2001. tions to NIF targets and sensor systems topology and thus contrast in the SEM 3. Adamson, D.H., et. al., “Large Area Dense integration for NHI and DNT. Example observation. We worked with various Nanoscale Patterning of Arbitrary Surfaces,” applications include x-ray gratings, volume fractions of the PS/PMMA Applied Physics Letters, 79, 2, pp. 257-259, nanobridge wires, nano-dimension anten- system to demonstrate the different 2001. nas and resonators, high surface area for domain formations, including lamel- 4. Kim, S. O., H. H. Solak, M. P. Stoykovich, high-energy-density storage capacitors lae, although these were observed N. J. Ferrier, J. J. de Pablo, and P. F. Nealey, and batteries, novel radiation detectors, only in the parallel configuration. “Epitaxial Self-Assembly of Block Copoly- and graded density targets. These efforts were repeated on both mers on Lithographically Defi ned Nanopat- silicon and oxide substrates in keeping terned Substrates,” Nature, 424, pp. 411-414, FY2006 Accomplishments and Results with our intent to demonstrate the util- 2003. First year efforts resulted in the dem- ity of the process for increased surface 5. Weilun, C., C. Harteneck, J. A. Liddle, onstration of a 2-D self-assembled block area. These parametric studies also E. H. Anderson, and D. T. Atwood, “Soft copolymer process. We worked with served to validate predictive modeling X-Ray Microscopoy at a Spatial Resolution staff at LBNL and UCB to defi ne and es- efforts. These results are providing in- Better than 15 nm,” Nature, 435, pp. 1210- tablish a well-characterized PS/PMMA sight to polymer system selection for 1213, 2005. process at LLNL. Requisite polymers proposed predictive graded-density and solvents were specifi ed and materi- film fabrication next year. als were procured. An experimental plan We also began to defi ne and estab- FY2007 Proposed Work with process controls was put in place to lish a dry etch process for the removal Our next eff orts will focus on extension work with solvents at high temperature of the PMMA polymer. Process steps of existing processes to demonstrate 3-D to obtain monolayer fi lms. have been identifi ed to pursue para- nanolithography. First we plan to enhance Cylindrical and spherical block metric defi nition of a dry process in our block copolymer fabrication capability copolymer structures were fabricated as order to fabricate robust etch masks. by expanding the base process to allow for extended long range ordering. This will require control of interfaces and substrate Cursor Marker Spectrum zoom Center line Offset Clear etching for enhanced domain alignment. A Section analysis L 56.140 nm parallel computational modeling eff ort to 7.0 RMS 2.780 nm 1c DC predict best polymer systems for extended Ra (1c) 2.220 nm order is also planned. This builds on FY2006 0 Rmax 10.209 nm nm Rz 10.209 nm modeling eff orts. Rz Cnt 2 Radius 47.258 nm A primary FY2007 focus will be to eval- –7.0 Sigma 0.516 nm 0 100 200 uate triblock copolymers. Such fi lms are less nm Surface distance 25.021 nm surface-dependent and have been shown Horiz distance (L) 20.144 nm Spectrum Vert distance 11.498 nm to allow subsequent removal for building Angle 29.717º Surface distance 63.452 nm laminated structures. This, coupled with 100 Horiz distance 56.140 nm variation of block copolymer systems, will 200 x 100 nm/div Vert distance 0 nm lead to varied density of fi lms. Additionally z 15 nm/div Angle 0º 300 Surface distance our current process is to be expanded to 3Q1, 20 s dry etch Horiz distance Vert distance nmq1_20secetch.004 3Q1, 20 s dry etch DC Min permit lift-off of arbitrary thin fi lms, such 3q1_20secetch.007 Angle Spectral period DC as metals. This will enable fabrication of Spectral freq 0 /nm nanometer features for surface-enhanced Spectral RMS amp 3.773 nm Raman scattering and templated carbon Cursor: fixed Zoom: 2:1 Cen line: off Offset: off nanotube-based chemical sensors.

Figure 3. AFM scan of vertically-oriented cylindrical block copolymer. Cylinders are in close-pack hexagonal formation and are approximately 30 nm in diameter with a 63-nm period.

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Characterization of Deep Satinderpall Pannu (925) 422-5095 Reactive Ion Etching of [email protected] Dielectric Materials

igh-aspect-ratio microstructures in sili- etch rate of the mask), aspect ratio (ratio Hcon have been available for almost of width of feature being etched to the a decade due to the advent of the Bosch fi nal depth of etched feature), and side- process. Similar high-aspect-ratio micro- wall profi le angle as the fi gures of merit. structures in dielectric materials such as These basic recipes can then be tailored silicon dioxide have not been available to etch program-specifi c microdevices. until recently. This project established base recipes for the reactive ion etching Relevance to LLNL Mission of dielectrics using a new deep reactive This project has relevance to a variety ion etcher (DRIE). The dielectrics of of LLNL interest areas. The ability to etch interest are silicon dioxide and silicone dielectric materials with high-aspect ratios elastomers. There exists no commer- brings a unique fabrication technique to cially available high-aspect-ratio etching areas in meso-, micro-, and nanotechnol- of silicone. With this project, LLNL ogy. This fabrication capability enables now has a unique capability in advanced a new generation of devices for a wide dielectric defi nition and etching. This variety of applications: chemical and new fabrication capability enables the biological sensors; targeting, tracking, generation of advanced devices for a and location; biomedical devices; high- wide variety of applications. This project speed optical processing; and NIF target involved the optimization and character- fabrication. This project has resulted in ization of recipes for the deep reactive fabrication capabilities needed for the ion etching of dielectrics. development of meso- to microscale devices with nanoscale precision. Project Goals This project established a new LLNL FY2006 Accomplishments and Results capability to etch high aspect ratio Experiments were formulated to structures in silicon dioxide and silicone. characterize the etch performance of Basic recipes were tested to etch both silicon dioxide and silicone in a Surface materials using etch rate, mask selectiv- Technologies Systems Advanced Oxide ity (ratio of etch rate of substrate to the Etch platform. The fi gures of merit were

Table 1. Performance of optimized recipe for silicon dioxide (quartz). Feature size Aspect ratio Etch rate Selectivity Profile angle 50 μm 4:1 1.25 μm/min 4.5 89˚ 100 μm 2:1 1.3 μm/min 4.6 89˚ 200 μm 1:1 1.4 μm/min 5 89˚ 400 μm 1:2 1.5 μm/min 5.2 90˚

Figure 1. 100-μm holes and trenches etched 200 μm deep in a quartz (silicon dioxide) substrate using silicon shadow mask.

88 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures etch rate, sidewall profi le, aspect ratio, selectivity decreases as the aspect ratio rate was used as the fi gure of merit. The and mask selectivity. A photolithography increases. Overall, the fi gures of merit results are summarized in Table 3. mask was produced which had holes and are all in desirable ranges for all the In summary, base recipes for high- stripes which varied in feature size from feature sizes and are similar to high-aspect- aspect-ratio etching of silicon dioxide 50 μm to 500 μm. Several masking ma- ratio silicon etch systems. Figure 2 shows and silicone were tested using a silicon terials were evaluated including silicon, an array of 200-μm holes etched 200 μm shadow mask. The fi gures of merit are chromium, and photoresist. The silicon deep in quartz. similar to the values obtained on high- shadow mask gave the highest selectiv- Similar experiments were con- aspect-ratio silicon etch systems. ity to both silicon dioxide and silicone. ducted on silicone. Recipes were tested Several recipes were tested to op- to optimize the fi gures of merit listed Related References timize the fi gures of merit listed above above using a silicon shadow mask. A 1. Garra, J., T. Long, J. Currie, T. Schneider, using a silicon shadow mask. A sum- summary of the results for holes etched R. White, and M. Paranjape , “Dry Etching mary of the results for holes etched in in the silicone on a silicon substrate is of Polydimethylsiloxane for Microfl uidic the silicon dioxide (quartz) substrate is given in Table 2. Systems,” Journal of Vacuum Science and given in Table 1. Figure 3 shows the etch of 100-μm Technology A: Vacuum, Surfaces, and Films, Figure 1 shows the etch of 100-μm holes to a depth of 200 μm in silicone 30, 3, pp. 975-982, May 2002. holes and trench to a depth of 200 μm on a silicon substrate. Again, as with the 2. Tserepi, A., G. Cordoyiannis, G. Patsis, in quartz (crystalline silicon dioxide). In quartz etch recipes, the etch rate and the V. Constantoudis, E. Gogolides, E. Valamontes, typical high-aspect-ratio etching, trench- selectivity decreases as the aspect ratio D. Eon, M. Peignon, G. Carty, C. Cardinaud, like features are not limited by diffusion- increases. Overall, the fi gures of merit and G. Turban, “Etching Behavior of based processes and hence these features are all in desirable ranges for all the fea- Si-Containing Polymers as Resist Materi- do not demonstrate the performance ture sizes and are similar to high-aspect- als for Bilayer Lithography: The Case of of the system. Hole-like features are ratio silicon etch systems. A wafer-to- Poly-Dimethyl Siloxane,” Journal of Vacuum diffusion-limited and provide a more wafer uniformity study was conducted Science and Technology B: Microelectronics diffi cult challenge for high-aspect-ratio on 15 silicone wafers to determine the and Nanometer Structures, 21, 1, pp. 174-182, etching. Hence the etch rate and the repeatability of the process. The etch January 2003.

Table 2. Performance of optimized recipe for silicone-on-silicon substrate. Feature size Aspect ratio Etch rate Selectivity Profile angle 50 μm 4:1 1.0 μm/min 2.5 89˚ 100 μm 2:1 1.15 μm/min 2.6 89˚ 200 μm 1:1 1.2 μm/min 2.9 89˚ 400 μm 1:2 1.25 μm/min 3.0 89˚

Table 3. Results of wafer-to-wafer uniformity study conducted on 15 silicone wafers. Figure of merit 50 μm 100 μm 200 μm 400 μm Mean etch 1.05 μm/min 1.12 μm/min 1.20 μm/min 1.32 μm/min rate Run to run 5.2% 3.8% 2.9% 2.2% uniformity

Figure 2. Array of 200-μm holes etched 200 μm deep in a quartz (silicon dioxide) substrate using silicon shadow mask.

Figure 3. 100-μm holes etched 200 μm deep in silicone on a silicon substrate using silicon shadow mask.

Lawrence Livermore National Laboratory 89 TechBase

Gray-Scale Lithography Christopher M. Spadaccini (925) 423-3185 for Sloped-Surface 3-D [email protected] MEMS Structures

icrofabrication techniques that in the standard photoresist exposure Moriginated from the IC community process. This results in locally varied typically yield 2-D extruded geometries photoresist exposure and correspond- or structures with limited angles due to ingly varied depth/thickness upon wet crystallographic orientation. Gray-scale chemical development. After DRIE, lithography in MEMS is capable of the 3-D depth profi le is transferred to generating a gradient height profi le in the silicon substrate and altered, based photoresist, and subsequently in silicon, on the etch selectivity to silicon ver- after deep reactive ion etching (DRIE) or sus photoresist. By varying the optical other dry etching techniques. Our work density and spacing of the gray levels on has sought to establish this 3-D micro- the photomask, an arbitrary angle in the fabrication capability at LLNL. Gray- silicon microstructure can be achieved. scale lithographic techniques previously This capability will enable a whole new reported in the literature were used to class of microstructures not previously baseline and calibrate arbitrary sloped- considered manufacturable at LLNL. surface, 3-D microstructures at LLNL. Typically, photolithographic pro- Project Goals cesses involve a photomask with only The result of this work will be the an opaque “dark fi eld” and a transparent capability to fabricate arbitrary angle, “clear fi eld,” resulting in 2-D features sloped-surface, 3-D microstructures. with relatively straight sidewalls in the Deliverables include: photoresist. The gray-scale technique 1. a well-defi ned process for fabricat- is performed by using a photomask ing 3-D MEMS structures (sloped with multiple, discreet “gray-levels” surfaces) of arbitrary angle based on or with pixilated features to locally a combination of parameters such as modulate the intensity of UV light used photomask optical density, spacing of

Figure 1. Calibration squares of varying optical density and micro-lens arrays on the HEBS glass gray-scale photomask.

90 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures

gray levels, photoresist thickness, and profiles were then characterized using Finally, DRIE of the photore- photoresist development time; and a SEM and an optical interferometer. sist profiles was performed and 3-D 2. documentation of the process and Figure 2 shows interferometer mea- features in the silicon substrates were parametric study for general use so surements of photoresist profiles for obtained. Figures 3 and 4 show SEMs that the LLNL microfabrication com- the micro-lens features. By care- of the micro-lens arrays and the munity at large can easily fabricate ful measurement of the remaining varying height calibration squares in a microstructure with an arbitrary photoresist height, a calibration curve silicon. The overall etch depths for sloped surface. of resist thickness versus photomask these features were ~120 μm and the optical density for a given set of pro- AZ4620 thick photoresist was used. Relevance to LLNL Mission cess conditions was generated. These As a result of this work LLNL now The ability to fabricate sloped curves can then be used by engineers has the capability to produce arbitrary, surfaces at an arbitrary angle in silicon to design gray-scale photomasks for 3-D, sloped-surface microstructures microsystems allows for a host of new custom applications. for a variety of applications. geometries not previously considered, and will shift the overarching microfabrication paradigm away from 2-D struc- +2085.45 tures. The availability of this technique +2085.45 will advance the core microfabrication competencies at LLNL, which provides nm vital support to both internal and exter- nm nal customers. –701.46 1.11

FY2006 Accomplishments and Results –701.46 High-energy beam-sensitive (HEBS) 3 glass from Canyon Materials, Inc. was se- mm 2 lected as the material for the photomask. HEBS glass is doped with a photoinhibi- 1 0 0 tor that changes opacity when exposed to Height (μm) 0 1.48 –1 mm an electron beam. The change in optical 00.2 0.4 0.6 0.8 density of the glass varies with the inten- Distance (mm) sity of the beam, thus controlling the gray levels. The theoretical minimum feature Figure 2. Optical interferometer measurement of micro-lens photoresist profi les. size for a gray level is the thickness of the beam, and ~1000 discreet gray levels of varying optical density are possible. The photomask used in this work contained a variety of features intended to calibrate the gray-scale process in LLNL’s cleanroom, and show some of the capabilities of the technique. Features included micro-lens arrays, grating structures, tapered structures of varying height, and calibration squares of varying height to correlate photoresist thickness to mask optical density. Figure 1 shows some of the features on the photomask. Two types of photoresist were calibrated with the gray-scale mask. These included AZ4620 thick resist and AZ1518 thin resist. A range of thicknesses (~1 to 10 μm) of each of these photoresist types were spun onto silicon wafers, exposed to UV Figure 3. SEM of varying height calibration Figure 4. SEM of micro-lens arrays after DRIE in light, and developed. The photoresist squares after DRIE in silicon. silicon.

Lawrence Livermore National Laboratory 91 TechBase

Absolute Conditioner for Michael D. Pocha (925) 422-8664 Fabry-Perot Microsensors [email protected]

igh-fi delity fl ight tests are required Project Goals Hby the weapons stockpile steward- This is the fi rst year of a two-year ship mission to assure weapon viability project to reduce to practice several without underground testing. Addition- concepts for miniature OGG and OFP ally, embedded sensors in future reli- sensors, as well as techniques for able replacement warheads (RRWs) implementing the necessary absolute will monitor state-of-health and ageing. measurement signal conditioners for These applications require miniature, these and similar sensors. The sensor minimally invasive sensors and readout fabrication was begun in this fi rst year systems. Sensors also need to be optically and will conclude with demonstration read out to reduce exposure of sensitive of working devices in the second year. components to electrical energy. Several Our goal for the absolute conditioner different sensors are available to measure was to demonstrate, in the laboratory, parameters such as acceleration, strain, our concept for the miniaturizable displacement, pressure, and temperature, conditioner, for the fi rst year, and to at various locations within test assemblies. explore miniaturization techniques in This effort is focusing on two important the second year. new sensors, an optical gap gauge (OGG) and an optical force probe (OFP). While a Relevance to LLNL Mission variety of miniature sensors (commercial High-fi delity fl ight tests to assure and custom made) are available, current weapon viability without underground signal conditioners (readout systems) are testing and implementation of future big and bulky (usually rack mounted), and RRWs are central to the LLNL weapons unacceptable for LLNL applications. stockpile stewardship mission.

Figure 1. Optical gap gauge spacers for enhanced sensitivity.

92 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures

FY2006 Accomplishments and Results be multiplexed with multiple devices on that a preliminary model, which can be Fabrication of the OFP, as part of a single fi ber, and is resistant to particu- implemented with commercial compo- this effort, requires several new methods late or other contamination. nents, reduces the conditioner volume of silicon processing, sensor assembly, The OGG fabrication has been to approximately 3 in3. We estimate that and packaging. Accomplishments were modifi ed to scale its sensitivity. Used as a further order of magnitude in volume made in all these areas. A commercial a Fabry-Perot (FP) sensor, the OGG re- reduction is possible when several readout system has also been specifi ed quires the separation between the fi ber’s custom MEMS components are fully and purchased to help the testing of the core and the sensor’s beam to increase to implemented. new OFPs. achieve greater displacement sensitivity. Figures 1 to 3 illustrate our results. A major concern is joining of the Processing to accomplish this has been optical fi ber to two silicon halves that demonstrated. form the transducer. Specifi cally, aniso- The absolute conditioner effort FY2007 Proposed Work tropic plasma etching of silicon has been included fringe visibility experiments; New OGGs of varying displacement sen- defi ned to form grooves to assist with fi ber preparation; a gap movement sitivities will be fabricated. The fabrication fi ber mounting. Brazing of the sensor linearity study; full conditioner model- and testing of the new OFP will continue. components has also been defi ned to im- ing for simulation of light sources and Implementing a fully miniaturized version prove joints used to date. Assembly jigs predictive understanding of practical of the absolute conditioner is an extensive and methods have been created to assist limitations imposed by several opti- task beyond the scope of this project. But, handling of silicon parts and sensor as- cal components; and fi nally, testing the we will explore miniaturization technology, sembly. Finally, packaging methods have effectiveness of various computational and attempt to fabricate the reduced-size been defi ned to encapsulate the OFP. The algorithms for extracting the sensor functional model that was created in new OFP will have a total thickness of gap (the key measurement parameter) FY2006. 140 μm, is thermally compensated, can from the raw fringe data. A key result is

~0.3”

~4”

~2”

Figure 3. Representation of repackaging of commercial components, which can lead to a readout system that fi ts within a 3- in.3 volume.

Figure 2. Fiber braze joint, bonding fi ber to capillary for use in FP-based microsensors. Brazed and bonded joints off er long-term sensor stability and hermetic sealing.

Lawrence Livermore National Laboratory 93 TechBase

Implementing Nano-Imprint Robin Miles (925) 422-8872 Capability [email protected]

hotolithography is a common technique potential future projects can benefi t from Pfor patterning features on planar sub- nano-imprinting methods. In particular, strates. Photosensitive polymer coated projects such as graded density targets on the substrate is illuminated through where low densities (on the order of a mask and upon development of the 1% of a 1.2 gm/cc material) are desired, polymer, the pattern of the mask is trans- structures for block-copolymers, nano- ferred to the substrate. These techniques electrodes for dielectrophoresis, and new are used at LLNL to make MEMS sen- optical devices such as ring-resonators sors, microfl uidic devices, and photonic for sensors will require nanostructures components. While micron-sized fea- that can be produced using this technique. tures are common, sub-micron, achieving nanoscale features, typically require Project Goals expensive equipment. The current EV aligner in the micro- Nano-imprinting is a new method fabrication facility is capable of per- of “lithography” wherein sub-micron forming nano-imprint lithography. The features are stamped into the polymer goal of this project was to characterize coating using a 3-D mask rather than il- this process so that this technique could luminating through the traditional planar be applied to future program needs. glass mask. The advantages of nano-imprinting are low cost and reduced capital Relevance to LLNL Mission equipment complexity for producing Several future projects may rely on nanoscale features. Many commercial the ability to produce devices with sub- semiconductor companies are consider- micron features. Among the potential ing using this technique in their fabrica- applications of this capability are the tion lines. graded density reservoirs for equation- Competing sub-micron lithographic of-state targets. Other program applica- techniques such as e-beam lithography tions include next-generation sensors for are expensive. Focused Ion Beam (FIB) weapons surveillance, radiation detec- fabrication is both expensive and practi- tion, and bio-security where nanoscale cal for use over only a limited area of devices and structures will lead to the material. A number of current and signifi cantly improved performance.

94 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures

FY2006 Accomplishments and Results master silicon or quartz mask are used to We received training on nano- deﬁ ne features across a 100-mm wafer. imprinting. The equipment uses UV We purchased a quartz master mask with curable resists as opposed to the major- sub-micron features. We have used this ity of nano-imprinting techniques, technique to produce patterns on both glass which use thermal processing methods. and silicon substrates. A sample test pattern Polydimethylsiloxane (PDMS) sec- is shown on a glass substrate in the ﬁ gure. ondary masks made from molds of a Line widths of 100-500 nm are possible.

Test pattern nano-imprinted on a glass substrate.

Lawrence Livermore National Laboratory 95 TechBase

Silicon Nitride Robin Miles (925) 422-8872 Furnace Installation [email protected]

ow-stress silicon nitride windows which adversely affected the quality Lare used as a component of targets of the silicon nitride fi lms. Further, the for many high-energy physics experi- former system was very variable in its ments. These are thin (50 to 500 nm output, exhibiting very non-uniform thick) substrates upon which materials fi lms across a wafer and from wafer to of interest are applied such as metal wafer. These attributes made produc- fi lms or occasionally biological materi- ing acceptable fi lms slow, tedious als. The windows have been used in work. The new silicon nitride system targets for OMEGA, Jasper, ALS at will greatly improve the quality of the LBNL and at the Center for Accel- fi lms processed in this facility. erator Mass Spectrometry (CAMS). A window fabricated for CAMS is Project Goals depicted in Fig. 1. The goal of this project was to These windows are fabricated in install a new low-stress silicon nitride LLNL’s cleanroom facilities. Often, furnace that would provide uniformly many hundreds of windows are fab- thick nitride films across a set of ricated for a particular target applica- 25 wafers. The furnace would be used tion. A new silicon nitride furnace for particular non-organic substrates was installed under this project and is to maintain cleanliness. a great improvement over the former system. The former system was a Relevance to LLNL Mission multi-user system in which a variety Several programs at LLNL use of materials were processed including targets in accelerator or laser systems carbon. Occasionally, the former sys- to measure material properties such as tem would become contaminated with opacity, to conduct warm dense matter particulates, possibly from organics, experiments, or to serve as a gas barrier

Silicon nitride pyramid Figure 1. Silicon nitride window fabricated for CAMS.

96 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures for the measurements of gas proper- FY2006 Accomplishments and Results lines, manifolds, and gas sensors with ties. Silicon nitride windows can be an Low-stress nitride is a non- special consideration given to the toxic important component of those targets. stoichiometric ﬁ lm produced in a reaction nature of the gas; 2) installing custom Silicon nitride windows are also used between ammonia and dichlorosilane at thermocouples, interlocks, and brackets; to produce photocathodes for streak about 800 ºC at 300 mTorr. We completed 3) installing a vacuum capability; and cameras for these experiments. the installation process, which involved 4) installing a controller. The completed tasks such as 1) installing and testing gas system is shown in Fig. 2.

Figure 2. Silicon nitride deposition furnace.

Lawrence Livermore National Laboratory 97 TechBase

High-Density Plasma Source Steven L. Hunter (925) 423-2219 [email protected]

e acquired and evaluated a new type The current to the orifi ce electromagnet Wof high-density plasma source for is kept constant, while the current to sputter deposition. The plasma “beam” the steering electromagnet is adjusted used for sputtering is generated remote- to steer the high-density plasma beam ly, and its path to the target is defi ned by onto the target. The target bias poten- the orthogonal locations of two electro- tial accelerates the argon atoms across magnets: one at the orifi ce of the plasma the dark-space sheath and sputters the tube and the other just beneath the target target material. plane. An example confi guration of a vacuum chamber with the plasma source Project Goals for sputter deposition is shown in Fig. 1. We performed a study to determine One advantage of this source is that the deposition rate dependency of the the high plasma density lends itself to high-density plasma source on deviations higher deposition rates, an important from the optimal geometric confi gura- parameter in the production of metal tion. The study was performed during oxides. Another, more subtle advantage the reactive deposition of niobium is the ability to independently control oxide. The effect on deposition rate was the deposition rate and the target bias determined by moving the plasma source voltage. This adds another means to away from the target in one direction, control oxide properties that are not and by moving the target assembly away available in typical magnetron sputter in an orthogonal direction. Deposition sources. The electromagnets enhance parameters were established to produce the electron mean free path in the space nonabsorbing niobium oxide fi lms of between the plasma orifi ce and the about 100-nm and 350-nm thicknesses. target. When the RF power is applied to The quality of the niobium oxide fi lms the coils around the plasma source, the was studied spectroscopically, ellipso- argon atoms in this region are ionized. metrically, and stoichiometrically.

Vacuum chamber Orifice electromagnet Substrate

PLS unit

Target Steering assembly electromagnet

Figure 1. High-density plasma source confi guration for sputter deposition.

98 FY06 Engineering Research and Technology Report Micro/Nano-Devices and Structures

Relevance to LLNL Mission Test Lab, and its performance was 40, 4, pp. 2443–2445, July 2004. Over the last several years, LLNL evaluated. Figure 2 is an image of the 2. Hockley, P. J., M. J. Thwaites, and has been working towards miniaturiza- source in operation. The deposition G. Dion, “High Density Plasma Deposition,” tion and survivability of ﬁ reset com- rate characteristics of the high-density Society of Vacuum Coaters 48th Annual ponents for integration onto a single plasma source were evaluated. Reactive Technical Conference Proceedings, 2005. substrate for weapons applications. sputtering with a high-density plasma 3. Moulder, J. F., W. F. Stickles, P. E. Sobol, Nanostructure multilayer technology source of niobium in the presence of an and K. D. Bomben, Handbook of X-Ray (NML) is a key factor in the component oxygen partial pressure produced stoi- Photoelectron Spectroscopy, J. Chastin and work. Improvements have been made chiometric niobium pentoxide, which R. C. King, Jr., Eds., Physical Electronics toward increasing the capacitance, is an important material for program- USA, Eden Prairie, Minnesota, p. 111, 1995. energy density, and dielectric strength of matic missions. 4. Venkataraj, S., R. Drese, O. Kappertz, our NML capacitors by testing different R. Jayavel, and M. Wuttig, “Characterization materials and sputtering processes. Related References of Niobium Oxide Films Prepared by 1. Vopsaroiu, M., M. J. Thwaites, S. Rand, Reactive DC Magnetron Sputtering,” FY2006 Accomplishments and Results P. J. Grundy, and K. O’Grady, “Novel Phys. Stat. Sol. A, 188, 3, pp. 1047–1058, The high-density plasma source Sputtering Technology for Grain-Size 2001. was acquired, installed in the Vacuum Control,” IEEE Transaction on Magnetics,

Figure 2. High-density plasma source in operation.

Lawrence Livermore National Laboratory 99

Precision Engineering FY 06 Engineering Research and Technology Report Report and Technology FY 06 Engineering Research TechBase

Error Budgeting and Jeremy J. Kroll (925) 422-6437 Certifi cation of Dimensional [email protected] Metrology Tools

he creation of radiographic and and measured among the various instru- Tultrasonic measurement tools has ments. The differences in the measure- progressed from providing qualitative ments are compared within the context information to providing quantitative of the formulated error budgets. information. There has not been a quan- By validating error budgets for non- titative error budget prepared for these traditional metrology tools, we are ap- tools, in the same manner that error bud- plying a known engineering technique to gets have traditionally been created for both scientiﬁ c and technical problems. coordinate measuring machines, e.g., the Atomic Thickness Measuring Machine Project Goals (ATMM). In this effort, we formulate an The goal is to produce validated error budget for nondestructive evalua- quantitative error budgets for the Xradia tion (NDE) tools such as the Xradia CT CT microscope and the Laser UT system, (computed tomography) microscope, which will enable a structured approach and the Laser UT (ultrasonic testing) for improving the capabilities of these system shown in Fig. 1 machines as well as provide insight into These conclusions are compared with the effect of individual error sources. error analyses from traditional Coordi- nate Measuring Machines (CMM) tools Relevance to LLNL Mission such as ATMM. In addition, one to three The advantage to LLNL is a broader characteristic artifact parts are fabricated view of dimensional metrology that

X-axis

Figure 1. Tabletop GHz laser-acoustic measurement system (Laser UT).

102 FY06 Engineering Research and Technology Report Precision Engineering extends beyond the traditional tools. and the results can be integrated into the Related References LLNL programs obtain improved error budgets. Each linear or rotational 1. Huber, R. H., D. J. Chinn, O. O. Balogun, quantifi cation of the uncertainties in the axis has six degrees of freedom. To char- and T. W. Murray, “High Frequency Laser- fabrication of targets or other compo- acterize an axis we measure each degree Based Ultrasound,” Review of Progress in nents and new synergy among various of freedom individually and then com- Quantitative Nondestructive Evaluation, projects. Initial testing will be per- bine the results to obtain an uncertainty August 2005. formed on workpieces that are relevant in the position of the object. 2. Martz, H. E., Jr., and G. F. Albrecht, “Non- to LLNL’s mesoscale investigations. The Laser UT system, which con- destructive Characterization Technologies for sists of three linear stacked axes, has Metrology of Micro/Mesoscale Assemblies,” FY2006 Accomplishments and Results been fully characterized. Initial data Proceedings of Machines and Processes for Initial parameterization of error analysis has begun. Figure 2 shows the Microscale and Mesoscale Fabrication, Me- sources within the Xradia CT micro- linear displacement accuracy (LDA) of trology, and Assembly, ASPE Winter Topical scope and the Laser UT system has been the x-axis slide. The LDA is the differ- Meeting, Gainesville, Florida, pp. 131-141, completed. Using these error sources, ence between a calibrated distance along January 22-23, 2003. an error budget framework, consisting a straight line and the distance indicated of three major components—source, ob- by the axis feedback. This linear posi- ject, and detector—was created for each tion data indicates that, excluding the system. Work has begun to describe fi rst point, the slide has an accuracy FY2007 Proposed Work how these errors propagate through the of 11 μm. The fi rst point disparity was For FY2007, we will fully characterize subsequent object retrieval algorithms to determined to be a preloading issue and the Xradia CT mechanical stages. The stage determine system sensitivity. had been observed by the Laser UT error data for both NDE machines will be To produce 3-D measurements, both operator, but had not been diagnosed. analyzed and used to populate the error NDE systems rely on mechanical stages The measurements completed include budgets. Characteristic artifact parts will be to move the object under investigation. six error measurements on each axis, as fabricated. These artifacts will be measured The object motion, as defi ned by the well as three measurements to character- on both CMM and NDE tools to validate the stages, is a signifi cant portion of the ize the orthogonality between axes. error budgets. Finally, validated quantita- error budget framework. Using accepted Fixturing for the metrology of the tive error budgets will be delivered for the stage characterization techniques, these rotary axis of the Xradia CT machine Xradia CT and Laser UT machines. stage motion errors can be measured has been completed.

X axis LDA (measured - commanded) 0.005

Run 1A 0 Run 1B Run 2A Run 2B –0.005

–0.010 LDA error (mm) error LDA –0.015 11 μm

–0.020

–0.025 0 2468 10 12 14 Slide position (mm)

Figure 2. Linear displacement accuracy of the x axis for the Laser UT.

Lawrence Livermore National Laboratory 103 TechBase

Uncertainty Analysis for Walter W. Nederbragt (925) 424-2807 Inspection Shop Measurements [email protected]

he LLNL inspection shop is chartered Project Goals Tto make dimensional measurements The goal of this project is to begin of components for critical program- providing measurement uncertainty matic experiments. These measurements statements with critical measurements ensure that components are within toler- performed in the inspection shop. To ac- ance, and provide geometric details that complish this task, we need comprehen- can be used to further refi ne simulations. sive and quantitative knowledge about For these measurements to be useful, the underlying sources of uncertainty for they must be signifi cantly more accu- measurement instruments. Moreover, rate than the tolerances that are being measurements of elemental uncertain- checked. For example, if a part has a ties for each physical source need to be specifi ed dimension of 100 mm and a combined in a meaningful way to obtain tolerance of 1 mm, then the precision an overall measurement uncertainty. and/or accuracy of the measurement should be less than 1 mm. Using the Relevance to LLNL Mission “10-to-1 gaugemaker’s rule of thumb,” The measurements made by the the desired precision of the measurement inspection shop are used to make should be less than 100 μm. Currently, decisions about accepting or rejecting the process for associating measurement critical parts. The inspection shop is uncertainty with data is not standard- widely used within LLNL’s engineering ized, nor is the uncertainty based on a programs, and the measurements are thorough analysis. This project aims to typically accepted as being “suffi cient- augment the efforts within the LLNL ly” accurate. This assumption should be inspection shop with a standardized and verifi ed by a measurement uncertainty commensurately rigorous approach to analysis, which is the accepted practice determining and reporting uncertainty. at all of the other NNSA sites. There is a

Uncertainty analysis flow chart

Certify instrument Instrument certification (requires taking extensive Fix or adjust instrument instructions document Figure 1. Analysis fl owchart for determin- instrument measurements) ing the measurement uncertainty of a particular measurement tool. The yellow boxes represent tasks that are already Determine uncertainty Use certification performed; the green boxes represent sources: measurements new tasks to be implemented in FY2007. – Master reference where applicable – Reproducibility – Thermal expansion – Elastic deformation Measure, calculate, Calculate measurement – Scale calibration estimate, and/or find uncertainty based on the – Instrument geometry the uncertainty geometry and use of the – Artifact effects values instrument being analyzed Based on uncertainty analysis, add additional measurement Uncertainty statement: Based on uncertainty requirements to write an uncertainty analysis analysis results, add certification document document for distribution system compensation where applicable to customers of that where applicable particular instrument

104 FY06 Engineering Research and Technology Report Precision Engineering signifi cant risk to programs if measure- of Standards and Technology (NIST) ment data is in error, which could lead and PSL were studied. FY2007 Proposed Work to the use of components that are outside 6. The uncertainty analysis of the There are over a dozen instruments on of specifi cations. Precision Inspection Shell Measur- the critical inspection equipment list that ing Machine (PrISMM) was initiated need to have their measurement uncertain- FY2006 Accomplishments and Results (Fig. 2). ties determined. These machines will be During the year, six tasks were Two reports were written to docu- divided into groups: Coordinate Measure- completed: ment this work. One report covers the ment Machines (CMMs, of which there are 1. The role of the inspection shop, as current operation of the inspection shop, six in the inspection shop); shell measure- defi ned in various DOE/NNSA doc- including descriptions of the critical ment instruments (PrISMM and the rotary uments, was reviewed and analyzed. measurement machines; the other report contour gauge); and other measurement 2. The critical equipment in the inspec- describes a plan for implementing uncer- instruments, such as Moore measurement tion shop was investigated to under- tainty analysis in the inspection shop machines and the Y/Z machine. In the fi rst stand uses and limitations. quarter, the rotary contour gauge and 3. The relationship between the Pri- Related References PrISMM will be analyzed to determine their mary Standards Lab (PSL) at Sandia 1. Doiron, T., and J. Stoup, “Uncertainty measurement uncertainties because there National Laboratories and the LLNL and Dimensional Calibrations,” Journal of is a higher level of programmatic interest in inspection shop was examined. Research of the National Institute of Stan- completing analysis of these machines. Us- 4. A plan was created to perform dards and Technology, 120, 6, pp. 647-676, ing this information, in the second quarter, uncertainty analysis on the criti- 1997. the CMMs will be analyzed. In the third and cal measurement equipment in the 2. Taylor B. N., and C. E. Kuyatt, “Guide- fourth quarter, the remaining machines will inspection shop. Figure 1 shows an lines for Evaluating and Expressing the be analyzed. At the end of the fourth quar- uncertainty analysis fl owchart. Uncertainty of NIST Measurement Results,” ter, preliminary measurement uncertainty 5. Uncertainty analysis methods and National Institute of Standards and Technol- data sheets for each instrument will be tools used by the National Institute ogy, Technical Note 1297, 1994 Edition. available to customers. Moreover, our understanding of the measurement machines will be greatly enhanced. This knowledge PrISMM measurement uncertainty analysis: error sources will be applied to improve the certifi cation Probe Probe Process and accuracy of the existing machines. path accuracy errors accuracy

LVDT Probe Rotary Thermal Setup probe tip table effects errors Mastering Gaging Data force Machine Laser acquisition geometry interferometers Figure 2. Hierarchical error source breakdown for PrISMM. The error sources at the top (blue) are general error categories. The errors at the bottom Y-slide Upper-slide Upper Z-slide (red) are specifi c error sources (only three are straightness straightness pitch shown). The low level errors need to be determined, by measurement, calculation, estimation, and/or specifi cation, to create an error budget. Precision inspection shell measuring machine (PrISMM)

Upper Z Rotary axis

Y axis

Lower Z

Lawrence Livermore National Laboratory 105

Engineering Systems for Knowledge and Inference

FY 06 Engineering Research and Technology Report LDRD

Image Relational David Paglieroni (925) 423-9295 Search Engine [email protected]

nformation science is concerned with ﬁ rst be transformed into formatted Iextracting knowledge from raw data tables or semantic graphs containing sources. In surveillance and site moni- items of interest extracted from the toring applications, data from in situ data. Patterns of interest must then be radiation, biological, chemical or motion extracted from these tables or graphs, or sensor networks can be used to construct naturally occurring patterns must be dis- dynamic measurement ﬁ elds from which covered. By creating statistical models anomalies can be detected. Passive for dynamic activities of interest, whose and active remote sensing systems are components are tied to such patterns, now capable of producing still image one can evaluate a set of observed pat- coverage over broad area landmasses, terns against the hypothesis that a par- and video for persistent surveillance of ticular activity of interest is occurring or designated sites. is about to occur. Alternatively, one can One overarching goal of informa- discover correlations between patterns tion science is to develop a multi-step in historical data so that anomalies can process for transforming raw data into be detected and predictions can be made knowledge. Unformatted raw data must from incoming data.

Image Gradients Edges Roads

Figure 1. Example of road extraction.

Image Gradients Gradient Corner direction matches Figure 2. Example of corner extraction.

108 FY06 Engineering Research and Technology Report Engineering Systems for Knowledge and Inference

The Image Relational Search Engine images. PRMs constructed by experts R (IRSE) Project focuses on specifi c as- specify spatial and temporal relation- n–1 pects of the overall problem described. It ships between these items precisely or addresses only one voluminous raw data with uncertainty. L source—imagery from remote sensors. n–1 R The focus of IRSE is limited to extract- Relevance to LLNL Mission L1 1 ing items of interest such as roads, IRSE addresses needs in knowledge T buildings, and vehicles from images, and extraction from overhead images related L then searching for patterns that contain to LLNL’s mission. IRSE is relevant to 0 combinations of items that relate to each national security problems involving R0 other in a prescribed way. broad area image search, and database/ graph evolution, query, and prediction. Project Goals Figure 4. Graphical depiction of Single Transmit- The goals of the IRSE project are: FY2006 Accomplishments and Results ter Model with one transmitter item, T, n links, L, and n receiver items, R. 1) develop algorithms that advance the Our linear consolidation algo- state of the art in extracting roads and rithm produces road extraction results buildings from images; and 2) develop from images (Fig.1) that go beyond of position, size and orientation, by a customized code layer on top of a the state of the art. Gradient Direc- finding groups of corners that satisfy commercial search engine code that tion Matching algorithms developed rectangular shape constraints (Fig.3). leverages novel algorithms for fi nding for matching 3-D objects to images An algorithm for matching Single matches to multi-component Probabi- have been modified to extract corners Transmitter Models (a type of PRM) to listic Relational Models (PRMs) in da- of buildings (Fig.2). We have devel- databases and graphs has also been de- tabases and graphs. The databases and oped algorithms that quickly extract veloped (Fig.4). Matching is posed as graphs contain items extracted from buildings from images, independent a minimum cost assignment problem in which candidate items are assigned to model links in an optimal way. Our method is unique in that it accounts for the following factors simultaneously: 1. the relative signifi cance (importance) of each concept in the pattern model; 2. the similarity between corresponding concepts in the pattern match and the pattern model; 3. the degree of relational consistency between the pattern match and the pattern model; 4. probabilistic uncertainty associated with the pattern model; and 5. links missing from the pattern match.

Related References 1. Chen, B., and D. Paglieroni, “Using Gra- dients, Alignment and Proximity to Extract Curves and Connect Roads in Overhead Images,” Proc. SPIE D&SS, pp. 17-21, April 2006. 2. Paglieroni, D., et al, “Phase Sensitive Cueing for 3D Objects in Overhead Images,” Proc. SPIE D&SS, 5809, pp. 28-30, March 2005. 3. Kuhn, H., “The Hungarian Method for the Assignment Problem,” Naval Research Logistics Quarterly, 2, pp. 83-97, 1955. Figure 3. Example of rectangle extraction (dimensions from 25 to 75 pixels).

Lawrence Livermore National Laboratory 109 LDRD

Dynamic Data-Driven Branko Kosovic (925) 424-4573 Event Reconstruction for [email protected] Atmospheric Releases

he release of aerosols and chemical Monte Carlo (SMC) methodologies. Our computational framework incor- Tspecies into the atmosphere creates a The inverse dispersion problem is ef- porates multiple stochastic algorithms, downstream plume. Our effort has been fectively addressed by reformulating it operates with a range and variety of to sample the plume and then estimate as an effi cient sampling of an ensemble atmospheric models, and runs on mul- the location of its source. We attempt to of predictive simulations, guided by tiple computer platforms, from laptops answer the critical questions: How much statistical comparisons with data. and workstations to large-scale comput- material was released? When? Where? ing resources. We developed a multi- What are the potential consequences? Project Goals resolution capability for both real-time Accurate estimation of the source Our goal was to develop a flexible operational response and high-fi delity term is essential to accurately predict and adaptable data-driven event- multi-scale applications. plume dispersion, effectively manage reconstruction capability for atmo- the emergency response, and mitigate spheric releases that provides: Relevance to LLNL Mission consequences in a case of a release of 1. quantitative probabilistic estimates This project directly aligns with hazardous material. We have developed of the principal source-term param- LLNL’s homeland and national security a capability that seamlessly integrates eters (e.g., the time-varying release missions by addressing a critical need observational data streams with predic- rate and location); for atmospheric release event recon- tive models to provide probabilistic 2. predictions of increasing fi delity as struction tools. Our efforts support the estimates of unknown source term an event progresses and additional rapidly growing number of operational parameters consistent with both data data become available; detection, warning, and incident char- and model predictions. Our approach 3. analysis tools for sensor network acterization systems being developed uses Bayesian inference with stochas- design and uncertainty studies; and and deployed by the Department of tic sampling based on Markov Chain 4. a model for quantifi cation of disper- Homeland Security and the Department Monte Carlo (MCMC) and Sequential sion model errors. of Energy. The event reconstruction

(a) (b) Probability distribution 0.25

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500 0.15 400

300 0.10

Downwind distance (y/H) distance Downwind 200

100 0.05

0 0 200 400 600 800 Crosswind distance (x/H) 0

Figure 1. Example of event reconstruction for a release in an urban environment using an operational puff -dispersion model and concentration measurements from the fi eld tracer experiment Joint Urban 2003 in Oklahoma City. (a) Color contours (blue) represent probability distribution of source location; the actual source is denoted with a triangle. (b) Color contours represent the plume from one of three likely locations (the probability distribution mode on the far South of (a)) that most closely corresponds to the actual release rate. Sensors are denoted with squares and color-coded according to measured concentrations.

110 FY06 Engineering Research and Technology Report Engineering Systems for Knowledge and Inference capability developed by this project 5. continued developing and testing G. Sugiyama, “Event Reconstruction for is targeted for integration into the effi cient stochastic sampling and Atmospheric Releases at the Continental next-generation National Atmospheric convergence algorithms; Scale: A Case Study: Algeciras, Spain, May Release Advisory Center and a new 6. implemented components of a 1998,” Tenth Annual George Mason Univer- Interagency Modeling and Atmospheric multi-resolution capability for more sity Conference on Atmospheric Transport Analysis Center, based at LLNL. effi cient sampling for source charac- and Dispersion Modeling, Fairfax, Virginia, terization; August 1-3, 2006. FY2006 Accomplishments and Results 7. tested a computational framework 3. Kosovic, B., G. Sugiyama, S. Chan, F. In FY2006 we accomplished the including hybrid MCMC-SMC Chow, K. Dyer, R. Glaser, W. Hanley, G. following: algorithms on massively parallel Johannesson, S. Larsen, G. Loosmore, J. K. 1. implemented an operational Gauss- platforms; and Lundquist, A. Mirin, J. Nitao, R. Serban, ian puff dispersion model for the 8. continued performance enhancement and C. Tong, “Stochastic Source Inversion simulation of urban dispersion into of the computational framework on Methodology and Optimal Sensor Network the MCMC capability, and tested the range of platforms for effi cient Design,” Ninth Annual George Mason Uni- it using data from the Joint Urban event reconstruction of complex versity Conference on Atmospheric Transport 2003 experiment in Oklahoma City atmospheric releases. and Dispersion Modeling, Fairfax, Virginia, (Fig. 1); July 18-20, 2005. 2. extended the event reconstruction Related References 4. Johannesson, G., et al., “Sequential Monte- capability to handle complex conti- 1. Chow, T., B. Kosovic, and S. Chan Carlo Approach for Dynamic Data-Driven nental scale atmospheric releases; “Source Inversion for Contaminant Plume Event Reconstruction for Atmospheric Re- 3. successfully demonstrated the Dispersion in Urban Environments Using lease,” Proceedings of the Nonlinear Statisti- continental scale MCMC capabil- Building-Resolving Simulations,” Sixth Sym- cal Signal Processing Workshop, Cambridge, ity using a real world example of posium on Urban Environment at Eighty- UK, September 13-15, 2006. accidental release of radioactive Sixth Annual American Meteorological 5. Neuman, S., L. Glascoe, B. Kosovic, material at Algeciras, Spain, in Society Meeting, Atlanta, Georgia, January K. Dyer, W. Hanley, and J. Nitao, “Event 1998 (Fig. 2); 30 – February 2, 2006. Reconstruction with the Urban Dispersion 4. developed an error quantifi cation 2. Delle Monache, L., K. Dyer, W. Hanley, Model,” Sixth Symposium on Urban Envi- model for data, input parameters, G. Johannesson, B. Kosovic, S. Larsen, G. ronment at Eighty-Sixth Annual American and internal model output error; Loosmore, J. K. Lundquist, A. Mirin, and Meteorological Society Meeting, Atlanta, Georgia, January 30–February 2, 2006.

(a) (b) May 30-31 May 31 - June 1 48ºN 48ºN Spain 44ºN 44ºN 40ºN 40ºN 36ºN 36ºN 32ºN 32ºN 12ºW 12ºW Algeciras 6ºW 0º 6ºE 12ºE 18ºE 6ºW 0º 6ºE 12ºE 18ºE

June 1-2 June 2-3 48ºN 48ºN 44ºN 44ºN 20 km

40ºN 40ºN 1 m/s 36ºN 36ºN Morocco 32ºN 32ºN 12ºW 12ºW 6ºW 0º 6ºE 12ºE 18ºE 6ºW 0º 6ºE 12ºE 18ºE Location probability

0.02 0.04 0.06 0.08 0.10 0.12 0.14

Figure 2. Example of continental scale event reconstruction using operational 3-D Lagrangian particle dispersion model and data from accidental release of Cs-137 at Algeciras, Spain, in 1998. (a) Contours represent simulated plume dispersion from the actual source over a period of four days; circles represent sensor locations. The actual source is denoted with a square. (b) Contours represent probability distribution of source location superimposed on the wind fi eld obtained from a mesoscale model.

Lawrence Livermore National Laboratory 111 LDRD

Decomposition of Large-Scale Yiming Yao (925) 422-1922 Semantic Graphs [email protected]

raphs are frequently used to analyze Project Goals Gmany types of complex systems such Existing hierarchical algorithms as the World Wide Web and biological for community identifi cation, such as and social networks. “Communities,” or the high quality algorithm developed densely connected clusters, tend to form by Girvan and Newman, are capable of naturally in these graphs, where there processing only graphs with up to ap- are strong underlying relationships, proximately ten thousand nodes, due to such as protein modules in biological their prohibitively high computational networks or autonomous systems on complexity. We expect our two-stage the Internet. The identifi cation of these approach to eventually process graphs communities, particularly in very large with up to a billion nodes. During the graphs, can enable us to more effectively course of our research, we will make and effi ciently analyze their underlying signifi cant contributions to path count- structure. To this end, we are developing ing and graph transformation algorithms a new, two-stage hierarchical approach in the fi eld of graph theory. However, for identifying communities. from a practical standpoint, we expect The crux of our technique is its fi rst the outcome of this project to help stage, in which the graph is effi ciently resolve a variety of outstanding opera- transformed into a tree of bi-connected tional issues encountered by various components (BCCs) (Fig. 1). This LLNL programs that leverage semantic transformation facilitates the parallel graph technologies. identifi cation of communities within the BCCs during the second stage of the Relevance to LLNL Mission algorithm, greatly increasing computa- LLNL has been developing semantic tional effi ciency. graph technologies in recent years in an

a b g abcd fgh c d f h

e e p p i o lk (j) j no (j) q j q k n

l m lm (j)m

Figure 1. A graph and its tree of BCCs.

112 FY06 Engineering Research and Technology Report Engineering Systems for Knowledge and Inference effort to enable large-scale data mining modularity, which is a signifi cant 2. Newman, M. E. J., and M. Girvan, “Find- and information discovery through the improvement on White and Smyth’s ing and Evaluating Community Structure in fusion of knowledge from numerous integer quadratic programming (IQP) Networks,” Phys. Rev. E, 69, 026113, 2004. and disparate information sources into model. We have used our ILP model to 3. White, S. and P. Smyth, “A Spectral massive semantic graphs. We now face fi nd the optimal community structures Clustering Approach to Finding Communities a new and critical challenge, however, in several well-studied graphs found in in Graphs,” Proceedings of the 5th SIAM In- to decompose these massive graphs into the published literature (e.g., Fig. 2). ternational Conference on Data Mining, 2005. meaningful sub-graphs that analysts We intend to submit two journal papers 4. Zachary W., “An Information Flow Model can effi ciently interrogate, to discover based upon these accomplishments. for Confl ict and Fission in Small Groups,” behaviors and relationships of interest. During our research, we have also Journal of Anthropological Research, 33, Community decomposition techniques found an effi cient solution to a query pp. 452-473, 1977. divide semantic graphs into manageable, problem that had arisen from LLNL’s semantically homogeneous sub-graphs semantic graph technology efforts. The and thus provide the foundation for transformation of a semantic graph building information analysis environ- into a tree of BCCs has led to a simple FY2007 Proposed Work ments vital to various LLNL activities. solution for identifying all simple paths In the coming year, we intend to of up to a user-specifi ed path length be- focus our efforts on developing the FY2006 Accomplishments and Results tween two vertices of interest (Fig. 3). parallel implementation of the two- During FY2006, we have completed We presented these fi ndings at the Risk stage community partitioning approach, the algorithms that identify BCCs Analysis for Homeland Security and as well as on enhancing the individual within a semantic graph, and we have Defense conference in March, 2006. algorithms in both stages. We will designed and implemented the BCC- continue to seek new application areas based algorithms for applying Girvan Related References where the BCC transformation can lead and Newman’s community identifi ca- 1. Girvan M., and M. E. J. Newman, “Com- to significant enhancement of computation technique. We have also created munity Structure in Social and Biological tional performance. the fi rst integer linear programming Networks,” Proc. Natl. Acad. Sci. USA 99, (ILP) model for maximizing Newman’s pp. 7821-7826, 2002.

19 10 t 16 3 t 12 23 14 8 33 1 15 4 2 21 34 13 18 9 22 30 27 20 28 6 24 s s 32 11 26 17 5 Figure 3. All simple paths between nodes s and t (left) are trans- 7 formed into the sole path linking them in the BCC isomorphic 25 29 transformation (right).

Figure 2. Optimal community structure for Zachary’s “karate club.”

Lawrence Livermore National Laboratory 113 TechBase

Semantic Graph Hierarchical Tracy Hickling (925) 422-0219 Clustering and Analysis Testbed [email protected]

LNL has invested more than a decade techniques, performance evaluation Lon semantic graph-based information frequently requires signifi cantly subjec- representation in an effort to improve tive assessment and therefore, extensive the effi ciency of data storage and analy- analyst interaction. We will provide sis, and therefore facilitate knowledge tools to help guide analysts in evaluat- discovery. Effective use of graph data ing many aspects of algorithm perfor- frequently requires the modifi cation mance, such as estimating the strength and application of a variety of infer- of cluster relationships, or the optimality ence techniques. Knowledge discovery of a graph partition. In addition, we will systems based upon semantic graphs, enhance the interpretability of algo- however, are rarely optimal for en- rithm outcomes by providing use cases abling the construction and testing of for a selection of desirable algorithms these algorithms. together with a manual for advanced We are addressing this defi ciency by operation of the testbed. building a testbed to serve as a compan- ion to analysts and the information sys- Relevance to LLNL Mission tems they use. Its fundamental purpose Semantic graphs provide an will be to permit rapid prototyping of exciting glimpse into the future of graph-based algorithms in an environ- knowledge extraction and inference in ment equipped to evaluate and compare support of LLNL’s intelligence/security effi ciency and performance. Due to the mission and other science and technol- unique needs of LLNL in regard to mas- ogy applications. Large knowledge sive graphs, we chose an environment discovery systems have the potential that emphasizes hierarchical clustering methodologies as the foundation of the analysis process, together with other Semantic algorithms that may be applied within graph this framework.

Project Goals The testbed will provide a suite of modular algorithm components, catego- rized according to their typical function in graph analysis algorithms, which may be combined and sequenced to create distinct algorithms for evaluation and comparison. Algorithm evaluation will take place within a testing framework suitable for the evaluation of numerical algorithm results as well as for the visualization of non-numerical algorithm output, such as the dendrogram in Fig. 1. Particularly Figure 1. Example of a dendrogram representa- in the case of hierarchical clustering tion of a hierarchical graph clustering algorithm.

114 FY06 Engineering Research and Technology Report Engineering Systems for Knowledge and Inference to revolutionize our ability to perform Related References real-time inference activities, since 1. Bollobás, B., Random Graphs, Cambridge FY2007 Proposed Work massive graphs are capable of fusing University Press, 2001. We will complete a beta version of terabytes of multisource data that con- 2. Duch, J., and A. Arenas, “Community the testbed by the conclusion of the third ceal complex relationships. This testbed Detection in Complex Networks Using quarter in FY2007. The tasks remaining for will make further work on analysis Extremal Optimization,” Phys. Rev. E, 72, completion involve building the visualiza- techniques more effi cient and cost- 027104, 2005. tion plug-ins necessary for performing effective, leading to more productive use 3. Newman, M. E. J., and M. Girvan, “Find- benchmarking and non-numerical results of semantic graphs and the knowledge ing and Evaluating Community Structure in analysis, as well as implementing the discovery systems that exploit them. Networks,” Phys. Rev. E, 69, 026113, 2004. algorithm sequencer. We will implement 4. Gross, J. L., and J. Yellen, Handbook of a suite of commonly used metrics in FY2006 Accomplishments and Results Graph Theory, CRC Press, 2004. graph theory and will fi nalize the testbed Our testbed is being built as a plug- 5. Guimerà, R., and L. A. N. Amaral, with the implementation of a number of in to Everest, a relatively mature graph “Cartography of Complex Networks: use cases to verify and validate the fi nal visualization environment at LLNL, and Modules and Universal Roles,” J. Stat. software product. A manual for proper use has been modifi ed to run either inde- Mech., P02001, 2005. will be provided. pendently or within a larger system. We invested a signifi cant amount of time analyzing Everest’s current architecture, an immense, constantly evolving body of program code. The testbed environment has been reconciled with Everest to be compliant with its restrictions while taking maximal advantage of its many features, such as the graph-based maintenance of panel states, and the ability to group nodes interactively. We have completed an I/O plug-in that will allow the testbed to ingest semantic graphs of an XML-based default format together with a commensurate ontology, as shown in Fig. 2. The base architecture operates in Figure 2. Screenshot of the testbed with data of the such a way that each of the various com- default format, DyNetML, loaded. ponents of the testbed will reside in a visualization panel that can be operated and maintained independently. These Template Girvan & Newman panels, though not yet functional, have Calculate betweenness (Re) Calculate a metric on each edge been built, and we have made signifi cant Partition with highest progress on the underlying implementa- modularity is tion for the algorithm sequencer. Remove edge with considered optimal Graph operation We have successfully built an algo- highest score rithm template that approximates the general structure with regard to func- Binary decision New partition created? tionality of most hierarchical decomposition algorithms. The template is Calculate/store Yes: add partition to general enough to accurately describe a graph information dendrogram; calculate large number of algorithms, but detailed new modularity enough to suggest a modularized collec- Repeat until stopping No: repeat until tion of graph metrics and operations that criterion satisfied modularity decreases can be wrapped and interchangeably inserted into algorithm prototypes (Fig. 3). Figure 3. Example algorithm (Girvan and Newman) expressed in template form.

Lawrence Livermore National Laboratory 115 TechBase

Image Content Engine for Finding Laura M. Kegelmeyer (925) 422-0924 Rings of Defects on Optics [email protected]

n prior years, LLNL’s Image Content (which fi nds in-focus defects in images IEngine (ICE) project produced a fast, of the NIF optics) by fi nding indirect robust technique for fi nding patterns in evidence of defects for which we can- images, called GDM (Gradient Direction not physically focus the cameras. The Matching). This algorithm differs from indirect evidence we want to fi nd is the other template matching algorithms in diffraction ring pattern that is formed that it correlates a template with an im- downstream of the interaction between a age after both are fi rst transformed into plane wave of the illuminating laser light images containing only gradient direc- and the spherical wave of the obscuring tion information (Fig. 1). defect (Fig. 2). The resulting ring pattern will match Project Goals with the custom luminance disk template Our goal was to customize and apply when both are transformed into gradient the GDM technique from ICE to support space and correlated with the GDM tech- one of the optics inspection require- nique. Once diffraction rings are found, ments for the National Ignition Facility we can incorporate our knowledge of (NIF): fi nding rings of defects on optics the ring location with predictions about (FRODO). defects that are not in focus and we can Our objective was to augment the NIF also improve our confi dence metrics for Optics Inspection analysis capabilities defects that we can detect directly.

Figure 1. Luminance disk matching. Top: diff raction ring pattern (left) and corresponding direction fl ow fi eld (right). Bottom: luminance disk model image (left) and corresponding gradient direction fl ow fi eld (right). Arrows point in direction from dark to light.

116 FY06 Engineering Research and Technology Report Engineering Systems for Knowledge and Inference

Relevance to LLNL Mission The fringe contrast level ratio is The GDM technique has already R = (Imax– Imin)/(Imax+ Imin), been benefi cial to several areas within where Imax and Imin are the maximum the NIF directorate. One is to fi nd and minimum intensities, respectively. diffraction rings, as planned. Another, A ROC curve showing performance unexpected benefi t is that it also robustly with different parameter settings is and effectively fi nds halos in off-beam- shown in Fig. 4, demonstrating the fi nal line laboratory images needed to verify success of the FRODO project. An the quality of optic coatings. BioSci- additional effort is underway to incor- ences, NDE, and Chemistry are other porate these results into the NIF Optics areas where the FRODO results can be Inspection Analysis process. usefully applied to fi nd circular features in complex images. Related References 1. Paglieroni, D.W., W. G. Eppler, and FY2006 Accomplishments and Results D. N. Poland, “Phase Sensitive Cueing for This year saw successful completion 3D Objects in Overhead Images,” Defense of the project milestones, from the initial & Security Symposium, Proc. SPIE, 5809, concept to the fi nal characterization Orlando, Florida, March 2005. of FRODO for NIF Optics Inspection. 2. Chen, B. Y., L. M. Kegelmeyer, J. A. We produced tools to create a training Liebman, J. T. Salmon, J. Tzeng, and D. W. Figure 3. Image from a camera focused on a set and to generate Receiver Operating Paglieroni, “Detection of Laser Optic Defects main laser power amplifi er, with diff raction rings labeled with colored circles: blue circle indicates Characteristic (ROC) curves in order to Using Gradient Direction Matching,” SPIE a ring with fringe contrast level ratio irradiance evaluate algorithm performance. Then, Photonics West LASE Symposium: 8th Inter- above a value of 0.15; red circles have fringe we used an optimization program, AP- national Workshop on Laser Beam and Optics contrast level ratio irradiance below 0.15. PSPACK, to optimize parameters used Characterization, Proc. SPIE, 6101, January in the FRODO codes. Optimized param- 21-26, San Jose, California, 2006. eters were incorporated into FRODO 3. Kolda, T., and G. Gray, et al., 1 and used to analyze the training set. An Asynchronous Parallel Pattern Search, DR 15 0.8 DR 25 image showing detected rings is shown Sandia National Laboratories, http://soft- DR 5 in Fig. 3. ware.sandia.gov/appspack. 0.6

0.4 True positive True

0.2

0 0 0.2 0.4 0.6 0.8 1 False positive r Opaque scattering Plane wave (laser) source Figure 4. ROC curve for the results of FRODO analysis for an image of a main laser power am- Irradiance (r) plifi er. The three separate curves were obtained Distance to image using three diff erent radii for the luminance disk plane z radius (DR) in the GDM algorithm. A y-axis value of 1 indicates that all labeled rings in the image were identifi ed, whereas a value less than 1 indicates that FRODO did not fi nd all the labeled Upstream rings. The graphs show that FRODO fi nds large, laser optic clear rings easily, but has trouble with fainter Interference rings when using a larger disk radius size. intensity pattern

Downstream laser optic

Figure 2. Diff raction ring patterns arising from the interference between a plane wave and an opaque scattering source, e.g., a defect scattering site.

Lawrence Livermore National Laboratory 117

Energy Manipulation

FY 06 Engineering Research and Technology Report LDRD

Improving the Vacuum Surface Jay Javedani (925) 422-8569 Flashover Performance of [email protected] Insulators for Microsecond Pulses

ne of the main areas of pulsed-power experimental confi gurations to induce OR&D is high-voltage insulation fl ashover by introducing plasma or ge- and dielectric breakdown, which is ometry effects to the insulator. very often the limiting factor in attain- ing the highest possible performance Project Goals in pulsed-power devices. The surface The objective of this investigation of an insulator exposed to vacuum can has been to address outstanding issues fail electrically at an applied fi eld more and establish a sound understanding than an order of magnitude below the of the mechanisms that lead to surface bulk dielectric strength of the insulator. fl ashover, and evaluate the most promis- This mode of breakdown, called surface ing techniques to improve vacuum fl ashover, imposes serious limitations insulators that enable high-voltage op- on the power fl ow into a vacuum region. eration at stress levels near the intrinsic While many researchers have studied bulk-breakdown limits of the material. this problem over several decades, there The high-voltage vacuum insulators for is still no consensus of opinion about DARHT-II at LANL, for ZR at SNL, the underlying mechanisms that fully and for Phoenix at LLNL would directly explain this phenomenon. benefi t from this work. These results A detailed understanding of the will also be very useful to other elec- breakdown mechanism must be achieved trically stressful systems in the pulse so that improvements in the insulator power community. performance can be made. This understanding is achieved by staging key Relevance to LLNL Mission computational models and supporting For many systems the delivery of pulsed power into a vacuum region is the most critical factor impacting performance and reliability, and the past two HV feedthru 100 kV variable pulser (< 10 µs pulse) decades have seen a sustained growth in Vacuum chamber the diversity and complexity of device –7 (~10 Torr) applications where vacuum is required to support high voltages and high electric fi elds. The applicability of our investigation in fl ashover performance spans scientifi c apparatus such as high-current particle-beam accelerators, high-power radio frequency and microwave sources, high-power laser sources, pulsed neutron sources, nuclear weapons effects simulators, lightning and electromagnetic pulse effects simulators, x-ray and proton 100 nF, 200 kV radiography machines, inertial fusion capacitors drivers, directed energy weapons, and electromagnetic launchers. As such, the results have a signifi cant impact on the Figure 1. Operational testbed. LLNL national security mission.

120 FY06 Engineering Research and Technology Report Energy Manipulation

FY2006 Accomplishments and Results (a) 80 Computational and circuit model- 0.0 mm CTJ ing was used to design an experimental 60 2.5 mm CTJ testbed (Figs. 1 and 2) to study the 4.5 mm CTJ 6.5 mm CTJ insulator breakdown mechanism. The 40 No insulator testbed was fabricated and assembled and is operational at LLNL. 20 The testbed is comprised of a -7 (kV)Applied voltage vacuum chamber (70 l, 10 Torr) with 0 several access ports; a variable 100-kV pulser with 200-ns rise-time and up to –20 10-μs fl at-top pulses that is connected –0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 to the anode electrode disk by a HV Time (μs) cable through a vacuum feedthru; a (b) 600 spring-loaded cathode electrode disk 0.0 mm CTJ 500 2.5 mm CTJ that is set at 1.0-cm gap distance from 4.5 mm CTJ the anode; a liquid voltage resistive di- 400 6.5 mm CTJ vider (VRD) monitoring the output of No insulator the pulser; and a Pearson 110 current 300 transformer measuring current on the 200 cathode support stalk. (A) Current To investigate surface fl ashover in 100 the widely used 45˚ conical insulator 0 confi guration, we installed a 45˚ con- –100 ventional HD polyethylene insulator in –0.1 0.1 0.3 0.5 0.7 0.9 the gap (visible in Fig. 2). With applied Time (μs) +100-kV pulses of 5 μs duration, the Figure 3. (a) Voltage waveform, and (b) current waveform, for +80 kV-discharge for velvet at diff erent insulator held off the applied voltage, positions of CTJ. but experienced fl ashover if a source of plasma/electrons in the form of a small of 1.4 to 2.7 cm/μs are inferred from FY2007 Proposed Work piece of velvet (1.0-mm diameter) was these signals. The actual fl ashover oc- The detailed electron dynamics prior introduced in the vicinity of the insula- curs when the plasma that is launched to and including fl ashover are not yet fully tor on either of the electrode’s surfaces. from the cathode reaches either the understood and an investigation has been Figure 3 shows the voltage collapse insulator or the anode electrode, limited by the temporal and spatial resolu- and drawn current for the cases when whichever happens fi rst. The insulation of our experimental and analytical tools. the velvet is placed on the surface tor, however, provides a much quicker To overcome these limitations and enable of the cathode insulator at discrete conduit to the anode electrode at ns the investigation, we will: distances away from the cathode triple time scales that cannot be resolved by 1. emplace faster diagnostic probes (D-dots junction (CTJ) for an applied voltage present 20-MHz bandwidth-limited with 3-GHz bandwidth) to resolve the of +80 kV. Plasma expansion velocities voltage and current probes. details of the insulator fl ashover; 2. replace the solid-anode electrode with Related References a thin aluminum foil backed with BC422 1. Anderson, R. A., “Surface Flashover: scintillator to facilitate pictures of the Three Decades of Controversy,” Fourteenth expanding plasma from its initiation point Negative International Symposium on Discharges and with a fast intensifi ed camera; and electrode Electrical Insulation in Vacuum, Santa Fe, 3. introduce a secondary electron ava- 45º insulator New Mexico, September 1990. lanche physics capability into a 2-D/3-D 2. Stygar, W. A., et al., “Improved Design programmable intelligent computer of a High-Voltage Vacuum Interface,” Phys. (PIC) code and verify its accuracy for Current Rev. ST Accel. Beams, 8050401, 2005. our application. probe 3. Houck, T. H., et al., “Study of Vacuum During FY2007 we will complete these Insulator Flashover for Pulse Lengths of tasks and execute a detailed investigation Figure 2. Test chamber with a HD polyethylene Multi-Microseconds,” LINAC, Knoxville, of the phenomenology prior to completing insulator installed between electrodes. Tennessee, August 2006. a physics description and extracting the engineering guidelines that are critical to our support of programs.

Lawrence Livermore National Laboratory 121 TechBase

Improving Switching Edward G. Cook (925) 422-7871 Performance of [email protected] Power MOSFETs

s their switching and power handling Project Goals Acharacteristics improve, solid-state The primary goal of this project is devices are fi nding new applications in to improve the switching performance pulsed power. This is particularly true of power MOSFETs for use in high rep- of applications that require fast trains of rate, short-pulse, high-power applica- short-duration pulses. High-voltage (600 tions by improving the confi guration of to 1200 V) metal-oxide-semiconductor the gate-drive circuits and the circuit fi eld-effect transistors (MOSFETs) are layouts used in these systems. This especially well suited for use in these requires evaluation of new commer- systems, as they can switch at signifi cant cial gate-drive circuits and upgrading peak power levels and are easily gated LLNL-created circuits. In addition, these on and off very quickly. MOSFET op- circuits must be tested with the fastest eration at the shortest pulse durations is available high-voltage power MOSFETs. not constrained by the intrinsic capabilities of the MOSFET, but rather by the Relevance to LLNL Mission capabilities of the gate drive circuit and Solid-state pulsed-power circuits are the system physical layout. This project replacing older technology devices such sought to improve MOSFET operation as vacuum tubes and thyratrons, which in a pulsed power context by addressing have availability and reliability issues. these issues. This is especially true in a number of

VS+ VH 1 VS+ VH 8 1μF 2 OE Out 7 Vcc 3 Trigger2 IN VL 6 4 Gnd VS– 5 S2 3 EL7158 G2 5,6 4 RL D2 VS+ VH D1 1 VS+ VH G1 7,8 8 2 2 S1 1 OE 107 Out Si4532ADY 7 3 Trigger1 IN Vs– VL 6 4 Gnd VS– 5 EL7158

Level shifting circuits MOSFET totem pole circuit Power Energy storage MOSFET and load

Figure 1. MOSFET gate-drive test circuit.

122 FY06 Engineering Research and Technology Report Energy Manipulation

LLNL programs, such as the accelera- circuit composed of discrete compo- high-frequency or pulse applications. In tor and laser efforts, where MOSFET- nents, as shown in Fig. 1. This circuit this respect, the gate-drive circuit and the switched inductive adder circuits allow uses commercially available level shift- power MOSFET should be considered to detailed control of voltage waveforms ing components and discrete MOSFETs be an integrated system. that would be impossible with the previ- arranged in a totem-pole confi guration. The ultimate result of this project has ous technology. Fast solid-state pulsed To achieve the best control, multiple been that the gate-drive circuit and its power is therefore an enabling technol- independent trigger pulses are used to associated knowledge base have entered ogy that fi nds applications in both new overcome the limitations of turn-on and the arsenal of LLNL capabilities that are and existing programs at LLNL, which turn-off delays, shoot-through, and the available, as needed, to its programs. For frequently push the limits of switching MOSFET Miller capacitance. example, the circuit is presently being re- speeds and short-duration pulses. The best of the commercial gate- fi ned prior to fi nal implementation in the drive circuits are capable of generating Kicker Pulser of the International Linear FY2006 Accomplishments and Results pulses having a minimum pulse duration Collider so that it can provide 3- to 4-ns We have identifi ed several com- (measured at the base of the pulse) of pulses with rise and fall times of 1 ns mercial gate-drive devices that exhibit 12 to 16 ns. With the LLNL gate-drive over a wide operating range. excellent stability and are capable of circuit layout, we have been able to generating pulses with fast rise and fall reduce the minimum pulse width to 5 ns Related References times and at high burst frequencies. with rise and fall times (10 to 90%) of less 1. Hickman, B. C., and E. G. Cook, “Evalu- These devices are very useful for many than 2 ns. Results are shown in Fig. 2. The ation of MOSFETs and IGBTs for Pulsed pulsed-power applications. However, switching speeds of this circuit, as mea- Power Applications,” International Pulsed these commercial circuits are inherently sured by rise and fall times, are approxi- Power Conference, Hollywood, California, incapable of generating pulses of very mately twice as fast as those achieved with June 2001. short pulse duration. Their internal struc- the commercial circuits. Additionally, we 2 Cook, E. G., B. C. Hickman, B. S. Lee, ture limits the minimum pulse width to a have operated this circuit at burst frequen- S. A. Hawkins, E. J. Gower, and F. V. value that maintains stable operation and cies of 3 MHz for 50 pulse bursts with no Allen, “Solid-State Modulator R&D at prevents the production of oscillating degradation in the measured waveforms. LLNL,” International Workshop on Recent gate-drive pulses. This level of gate-drive circuit perfor- Progress in Induction Accelerators, In an effort to generate shorter dura- mance can only be realized when operated Tsukuba, Japan, October 2002. tion pulses, we have turned to an LLNL with MOSFETs that are optimized for

Tek Run: 5.00GS/s Sample Trig? T[ ] Δ: 334 V @: 330 V C4 fall 1.56 ns 4 unstable histogram

C4 rise 1.78 ns unstable histogram

M 5.00 ns Aux 320 mV 26 Jul 2006 Ch4 100 V 11:12:03

Figure 2. Pulse width results with gate-drive circuit layout.

Lawrence Livermore National Laboratory 123 TechBase

Solid-State Switch Edward S. Fulkerson, Jr. (925) 423-5978 Replacements for Ignitrons [email protected]

gnitron-type power-pulsed switches, Explosive Facility (BEEF); and 2) Ioften used for high-current handling, providing a basis for a 30-kV, 500-kA pose problems associated with mercury series/parallel solid-state switch for hazards, auxiliary cooling, shock limits, BEEF, NIF, and the Environmental and reliability in fi eld deployments. Measurements Laboratory (EML). Transitioning to solid-state technology offers advantages in many applica- Relevance to LLNL Mission tions, but demonstration of performance Among the many applications at is needed for acceptance. The goal LLNL for high current/energy capacitive of this project is to evaluate the new- discharge units (CDUs) are: magnetic est commercially available solid-state fl ux compression generators (DNT); switches beyond manufacturers’ ratings, fl ashlamp banks (Lasers/NIF); pulsed to determine limits of high current and high-fi eld magnets (Sustained Sphe- high dI/dt for short pulse durations, and romak Physics Experiment (SSPX)); to evaluate suitability for LLNL’s pulsed EM Launchers/Rail Guns (NAVY); and power applications. compact electric power conversion.

Project Goals FY2006 Accomplishments and Results The goals of this project included Six state-of-the-art commercial 1) the demonstration of a 10-kV, 20-kA thyristors (8 kV, 90 kA) were procured solid-state replacement for the ignitron for evaluation. A general purpose high- used at LLNL’s Big Experimental current (>100 kA) testbed has been

5.25

12.0 17.0

Inductor loop here 2x cables

Dielectric

10.439 RPX SIRE/assembly – draft TBD bank Tony Ferriero 6/6/06

Figure 1. Mechanical drawing of testbed.

124 FY06 Engineering Research and Technology Report Energy Manipulation constructed that is capable of testing Fundamentals of Power Electronics, a wide range of solid-state switch Kluwer, Academic Publishers, United King- FY2007 Proposed Work components. Initial high-voltage/ dom, 2001. We plan to conduct tests on a unit low-current “leakage” testing has been 3. Williams, B.W., Power Electronics: procured in FY2006 and create a reliable completed. Figures 1 to 3 illustrate our Devices, Drivers, Applications and Passive “operational envelope” for pulse power system and set-up. Components, McGraw-Hill, New York, applications by operating the units be- New York, 1992. yond the manufacturer’s specifi cations for Related References 4. Kassakian, J., M. Schlecht, and G. peak current and dI/dt. We will investigate 1. Arnold, P. A., “Solid-State Replacements Verghese, Principles of Power Electronics, both series and parallel operation of the for Hydrogen Thyratrons,” http://www-eng. Addison-Wesley, Reading, Massachusetts, devices to extend both peak voltage and llnl.gov/pdfs/lsr_sys_opt-3.pdf 1991. current capabilities. 2. Erickson, R. W., and D. Maksimovic,

Figure 2. Assembled 2-thyristor stack. Figure 3. Light-triggered thyristors.

Lawrence Livermore National Laboratory 125

Author Index

Author Index Alves, Steven W...... 26 LeBlanc, Mary ...... 36 Anderson, Andrew T...... 30 Lin, Jerry ...... 4 Bennett, Corey V...... 52 Mariella, Raymond P., Jr...... 74 Brown, Charles G., Jr...... 38 Miles, Robin ...... 94, 96 Brown, William D...... 62 Nederbragt, Walter W...... 104 Chinn, Diane ...... 56 Ness, Kevin D...... 76 Clague, David ...... 22 Nikolić, Rebecca J...... 84 Clark, Grace ...... 66 Paglieroni, David ...... 108 Cook, Edward G...... 122 Pannu, Satinderpall ...... 82, 88 Davidson, James Courtney ...... 86 Pierce, Elsie ...... 6 Deri, Robert J...... 42 Pocha, Michael D...... 92 Dougherty, George ...... 80 Poland, Douglas N...... 68 Fasenfest, Benjamin J...... 14 Puso, Michael A...... 2, 8 Florando, Jeff rey N...... 34 Quarry, Michael J...... 48, 50 Fulkerson, Edward S., Jr...... 124 Rhee, Moon ...... 32 Haugen, Peter ...... 46 Romero, Carlos E...... 44 Heebner, John E...... 54 Rose, Klint A...... 78 Hickling, Tracy ...... 114 Sain, John D...... 60, 64 Huber, Robert ...... 58 Sharpe, Robert M...... 10 Hunter, Steven L...... 98 Spadaccini, Christopher M...... 90 Javedani, Jay ...... 120 Stölken, James S...... 20, 70 Kallman, Jeff rey S...... 16 Van Buuren, Anthony ...... 28 Kegelmeyer, Laura M...... 116 Wemhoff , Aaron ...... 24 Koning, Joseph ...... 18 White, Daniel ...... 12 Kosovic, Branko ...... 110 Yao, Yiming ...... 112 Kroll, Jeremy J...... 102

Lawrence Livermore National Laboratory 127 Manuscript Date April 2007 Acknowledgments Distribution Category UC-42 This report has been reproduced directly from the Scientific Editor best copy available.

Lawrence Livermore National Laboratory Technical Information Department’s Digital Library http://www.llnl.gov/library/

This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. ENG-06-0061-AD