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December 1997

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• Advances in Multilayers• Down-to-Earth Astrophysics• Breast Cancer Detection

NondestructiveEvaluation

Lawrence

Livermore

National

Laboratory

About the Review

A recent collaboration brought BIR Inc. ofLincolnshire, Illinois, to work with Livermoreresearchers in nondestructive evaluation (NDE).Here, BIR’s trailer was the site of an experimentusing active and passive computed tomographyto identify and quantify materials inside nuclearwaste drums. The feature article, beginning onp. 4, describes this technique as well as othermethods in the Laboratory’s NDE repertoire—optical, radiographic, thermal, x-ray, andgamma-ray imaging.

• •

About the Cover December 1997

Lawrence

Livermore

National

Laboratory

Also in this issue: • Multilayer X-Ray Optics• Breast Cancer Detection• Astrophysics

NondestructiveEvaluationNondestructiveEvaluation

Lawrence

Livermore

National

Laboratory

Lawrence Livermore National Laboratory is operated by the University of California for theDepartment of Energy. At Livermore, we focus science and technology on assuring our nation’s security.We also apply that expertise to solve other important national problems in energy, bioscience, and theenvironment. Science & Technology Review is published ten times a year to communicate, to a broadaudience, the Laboratory’s scientific and technological accomplishments in fulfilling its primary missions.The publication’s goal is to help readers understand these accomplishments and appreciate their value tothe individual citizen, the nation, and the world.

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Prepared by LLNL under contractNo. W-7405-Eng-48

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S&TR is a Director’s Office publication,produced by the Technical InformationDepartment, under the direction of the Office of Policy, Planning, and SpecialStudies.

2 The Laboratory in the News

3 Commentary by Spiros Dimolitsas

Features4 Advancing Technologies and Applications in Nondestructive

Evaluation Lawrence Livermore’s Nondestructive and Materials Evaluation Section has been developing breakthrough technologies that serve specialized scientific inspection needs and stretch the concept of nondestructive evaluation.

12 Atomic Engineering with MultilayersLivermore researchers have developed multilayers with more than 75 different elements to improve the performance of precision materials. So close to perfection, multilayers from Livermore are in great demand.

Research Highlights20 Marrying Astrophysics with the Earth23 Continuing Work in Breast Cancer Detection Technologies

26 Patents

27 1997 Index

Abstracts

S&TR Staff December 1997

LawrenceLivermoreNationalLaboratory

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Available fromNational Technical Information ServiceU.S. Department of Commerce5285 Port Royal RoadSpringfield, Virginia 22161

UCRL-52000-97-12Distribution Category UC-700December 1997

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HILE research and development budgets have recentlydeclined, the nation’s and the world’s economies

continue to grow, to a large extent fueled by scientific andtechnological innovations. The growing economic importanceof innovation creates opportunities upon which the Laboratorycan capitalize, especially as private long-term R&D investmentcontinues to decrease. The flexibility of people and the breadthand depth of core technologies in Livermore’s EngineeringDirectorate together enable Laboratory programs to make themost of these opportunities.

One example of the strength within Engineering isnondestructive evaluation (NDE), a capability like many inEngineering that contribute to most Laboratory program missionsand enable successful outcomes of Laboratory technology. Thefollowing article, “Advancing Technologies and Applicationsin Nondestructive Evaluation,” reports on the kinds of speciallytailored engineering approaches for which Livermore isparticularly known. And with collaborations outside theLaboratory, the NDE capability also broadens Livermore’sinfluence among the technical disciplines of measurement,monitoring, and controls.

In meeting the increasingly faster-paced cycles ofinnovation and change, Engineering’s role is to foster unique,science-based technologies that will substantially enhance theLaboratory’s ability to initiate and execute programs. Forexample, NDE’s unique facilities, a variety of energy sources(such as x-ray and gamma-ray instrumentation), and the abilityto digitally acquire, process, and image data place the Laboratoryat the forefront of inspection, characterization, and certificationtechniques. Other examples of Engineering’s contributions toapplied science programs include microtechnologies (seeS&TR,July/August 1997), regenerative fuel cells (S&TR, May 1997),and computational electromagnetics (S&TR, March 1997).

Engineering also works to enhance the Laboratory’sexternal visibility by supporting external collaborations. For

W

3

Science & Technology Review December 1997

Commentary by Spiros Dimolitsas2 The Laboratory in the News


Firms team with DOE labs to develop superchipThree of the largest computer-chip makers joined with DOE

laboratories to squeeze far more brain power into microprocessors.The unusual partnership aims to make computers a hundredtimes faster and bring features such as three-dimensionalgraphics to affordable machines. In addition to boostingcomputer speed, the memory chips will be able to store athousand times more information than they currently can.

In the biggest-ever corporate investment with the Departmentof Energy, the three firms—Intel Corp., Advanced Micro DevicesInc., and Motorola Corp.—are spending $250 million over fiveyears with three laboratories—Lawrence Livermore, SandiaNational Laboratories, and E. O. Lawrence Berkeley NationalLaboratory.

The partnership plans to design a new technique usingultraviolet light to etch ultrathin patterns (less than one-thousandththe width of a human hair) in silicon chips. These patterns willbe 60% smaller than the patterns in the most sophisticated chipsnow available. Another partnership aim is to cram one billiontransistors onto each thumbnail-size chip. Currently, Intel’smost powerful processor contains 7.5 million transistors.Contact: Rick Freeman (510) 422-3653 ([email protected]).

Zinc–air technology moves toward commercializationZinc–air fuel-cell technology, long a promising source of

clean energy and stored-energy recovery, begins a move towardcommercialization with the recent signing of a Memorandum ofAgreement between Lawrence Livermore and Power Air Tech,USA, a consortium of Australian companies. Discussions areunder way to bring other U.S. companies into the consortium.

The next step is a Cooperative Research and DevelopmentAgreement between the Laboratory and private industry, whichcould mean about $100 million of industry funding—$30 millionfor further research and development on a zinc–air fuel cell andits zinc recovery unit at Lawrence Livermore over the next fourto five years and an estimated $70 million for commercializationand manufacturing applications of the refuelable zinc–airtechnology and recovery unit.

Zinc–air fuel cells mix zinc pellets and electrolyte with airto create electricity. They create five times as much power aslead–acid batteries of the same weight. The Livermore designis unique because it is refuelable, and the spent zinc can berecycled into zinc pellets.

The agreement initially is intended to commercialize severalkinds of units: large units for utilities to meet peak power demand,small units as an alternative to gasoline and diesel generators

for uninterruptable power supplies, units for heavy andlightweight vehicles, and large uninterrupted power suppliesfor hospitals and airline reservation systems.

John Landerer, on behalf of Power Air Tech, USA, noted,“We will make every effort to have this technology ondisplay in Sydney by the time of the 2000 Olympic Games.” Contact: John Cooper (510) 423-6649 ([email protected]).

NIF construction contracts awardedNielsen Dillingham Builders, Inc., of Pleasanton, California,

has been awarded an $11.35-million contract to construct thestructural steel shell of the building that will house LawrenceLivermore’s National Ignition Facility (NIF), the world’slargest laser. Walsh Pacific Construction, based in Monterey,California, has won a separate $4.7-million award forfoundation work.

NIF is a stadium-sized, $1.2-billion, 192-beam lasercomplex now under construction. The NIF design requiresthat its high-tech laser components be tightly encapsulated inthe surrounding building. Slated for completion in 2003, thefacility will create—for the first time in a laboratory—briefbursts of self-sustaining fusion reactions similar to thoseoccurring in the sun and stars. The resulting data will helpthe Department of Energy maintain the safety and reliabilityof the nation’s nuclear stockpile without underground testingwhile providing benefits in basic science, astrophysics, andcommercial fusion power production.Contact: LLNL Media Relations (510) 422-4599([email protected]).

FAA looks to Lawrence Livermore for flight safetyResearchers from Lawrence Livermore and three companies

have been awarded $1.5 million to develop a new standardtool to assist the U.S. aviation industry in studying ways toprotect against uncontained jet engine debris.

As envisioned, a Livermore computer code written tomodel weapons systems would be adapted to examine howto mitigate engine fragments and reduce aircraft hazardsfrom any escaped debris. The unclassified code, DYNA3D,models collisions lasting thousandths of a second bysimulating how stress moves through structures.

The two-year Federal Aviation Administration agreementteams Lawrence Livermore with two engine manufacturers—AlliedSignal Engines and Pratt & Whitney—and the BoeingCommercial Aircraft Group.Contact: Rich Couch (510) 422-1655 ([email protected]).

many years, we facilitated productive interaction between thescientific community and the marketplace, providing insightfrom industry to Laboratory programs while gaining greaterexternal recognition for our capabilities and achievementsin the process. The following article, for example, illustrateshow the NDE staff couples the Laboratory to other externalcollaborators, especially the Department of Energy, with itsnoninvasive assays of waste drums.

In Engineering, as in other Laboratory directorates andprograms, we routinely must sort through our toolbox ofintellectual and physical resources to provide what’s neededtoday and what scientists and conceptual engineers will needtomorrow. We find that one key to the next success is theflexibility of the tools that are chosen. For example, most ofus discarded the analog world of pocket protectors and sliderules for the digital realm of computers some years ago.Today Engineering’s tools include:

• A staff having diverse and specialized skills.• Operational ability to move people rapidly from program

to program as needs change.• A technology base that is robust and diverse, backed

with Laboratory institutional support for continuingtechnology development.

• Access to and experience with world-class and uniquefacilities on site, in industry, and at leading academic centers.

• Participation in multiple programs and scientific disciplines. • Ability to successfully collaborate with various partners.In fact, these tools look surprisingly like tools elsewhere

around our Laboratory and in successful companies. Ourbiggest ongoing challenge in Engineering is developing thenext generation of tools to enable programmatic successwhile sustaining the most appropriate level and breadth ofour expertise with these tools.

■ Spiros Dimolitsas, Associate Director, Engineering.

Flexibility for Future TechnicalSuccesses

5


amplification slabs, 0.8- by 0.4-meter,42-kilogram pieces of glass used toamplify the light and achieve energygain.

The perimeters of these slabs arebonded with epoxy to cladding glass toabsorb any stray light that could reduceamplification efficiency. In the delicateworkings of lasers, however, thecladding-glass bond presents problemsif it is imperfect and contains bubblesor voids. Those imperfections can reflectstray light right back into the slab anddiminish amplification. Furthermore,bonding defects located on oppositesides of the slab could work together tocreate a conflicting pattern of back-and-forth light reflection that also disruptsamplification and ultimately can damagethe slab itself.

Laser researchers have specificationsfor slabs that define the sizes, volumes,and patterns of bond imperfections thatcan have adverse effects during laseroperation. In the past, the size of adefect was determined by “eyeballing”it against a sizing chart. Clearly, abetter inspection method for these slabswas needed, so Skip Perkins and DianeChinn designed one: an automated,optical inspection system consisting ofa staging platform to hold the slab, a

CCD (charge-coupled device) camera,light sources, and a computer to storedigital image data (Figure 1). Theyexperimented with different opticalconfigurations of camera and lightsources before finding the best onefor recording epoxy bond images.

A more crucial part of their projecthas been to develop software algorithmsfor processing the acquired digitaldata. The algorithms must accuratelydistinguish flaws from other opticalirregularities, for example, to locatescratches in the bond, categorize theflaws by size and other attributes, andfinally, classify the amplifier slab asacceptable for use or not.

According to the researchers, oncesoftware algorithms have beencompletely developed, the automatedinspection system will providestandardized, repeatable inspectionsthat assure a consistent level of laserslab quality. Perkins says that becausesystem data can be archived, there willbe a record of bond conditions that canbe used to identify and assess flawsthat are made by laser operation.

Technological advances in materials and

products pose great challenges for

inspection methods used to evaluate their

quality, efficacy, and safety. Livermore’s

nondestructive evaluation techniques

provide fast, accurate, quantitative

analyses of exotic devices and solve

complex evaluation problems.

HEN a shopper uses smell to assess the ripenessof a peach and when a homeowner taps on a wall

to figure out where the studs are, they are practicingeveryday varieties of nondestructive evaluation—thetechnique of inspecting something without destroying ordamaging it.

The most common nondestructive evaluation (NDE)methods used to characterize materials and inspectproducts are visual, operator-dependent, subjective, andqualitative. Those methods can be slow, imprecise, andinconsistent—and quite unsuited for inspections requiredduring the course of Lawrence Livermore’s scientificprojects. That’s why researchers in the Laboratory’sNondestructive and Materials Evaluation Section developspecially tailored evaluation methods that deliver exact,quantitative results. The methods use automated, digital,breakthrough technologies implemented through suchtechniques as computed tomography, digital radiography,ultrasonics, machine vision, and infrared thermography.Because the data are digital, the information can beprocessed and reconstructed into images that areamenable to computational analysis. These NDEmethods are more quantitative and sensitive than humansensory perception; they provide researchers a preciselook inside the object of interest.

Digital NDE systems have these components incommon: an energy source used to probe an object; areceiver or detector that measures how the energy hasbeen changed by the object; and a way to record, process,and interpret the measurement data. To configure thisbasic system for specific applications, system designersmust solve a plethora of problems. Among them are how

W to deal with interfering noise andnonlinear effects when energy is beingdelivered and detected; how to acquiredata for the best spatial and contrastresolution (that is, how small and howclearly resulting images can be seen);how to mathematically describe featuresand objects for detection as well as howto distinguish among variations in theirsize, shape, and intensity; and how toreconstruct digital data into imagesthat can be easily understood and used.

NDE developers benefit fromLawrence Livermore’s expertise inengineering, materials science, andcomputations. In return, NDEtechnologies support Laboratoryscience, first, by providing thespecialized inspections required ofunique projects and, second, bydeveloping new technologies thatexpand NDE concepts and uses.

Looking into Laser SlabsLooking at the preparations under

way for the construction of the NationalIgnition Facility, to be the world’slargest laser, one can easily see that theproject is complex, having a multitudeof components that must be carefullyinspected before they can be used.Among those parts are 3,100 laser

Advancing Technologies and Applications inNondestructive Evaluation

Advancing Technologies and Applications inNondestructive Evaluation

7


Nondestructive Evaluation

One manufacturing-line inspectionstudy, still under way, will determine howto implement an ultrasonic system todetect porosity defects in pistons. Suchdefects cause piston surfaces to deteriorateduring finish machining. If defectivepistons could be culled before themachining process, production costswould be reduced.

Another inspection occurs aftermachining. Especially critical are thegrooves in the piston walls, into whichmetal piston rings must fit snugly forefficient operation. Grooves containingpits or other low-density spots provide apathway for combustion gases to leakaround the rings.

NDE researchers experimented witha prototype ultrasonic scanning system(Figure 2) for this inspection. Theultrasonic evaluation of metal–matrixcastings presents many technicalchallenges. Very small defects must bedetected reliably and, once detected,must be characterized to distinguishbenign or noncritical attributes (such asreflections of solid masses) from criticaldefects (such as air-filled bubbles).Development is under way for advancedsignal-processing algorithms and atransducer design that will provide therequired spatial and depth resolutions.The NDE researchers have, in themeantime, used the prototype systemto demonstrate the feasibility of acomputer-controlled, automatedinspection on the manufacturing floor.Thomas will work with his private-industry collaborators and a privateultrasonic system manufacturingcompany to design and build theproduction version of the LawrenceLivermore prototype system.

This technical know-how is alsoused for other Laboratory projects. Forexample, the NDE researchers are nowapplying ultrasonic evaluation to inspectand characterize castings of specialnuclear materials.

Assaying Waste ContainersAt Department of Energy facilities

around the U.S., radioactive andhazardous wastes generated duringscientific experimentation have beenpacked into waste drums and awaittreatment, storage, or disposal. Wasteregulations are stricter and dispositionmore costly for wastes that have higherlevels of radioactivity.

Opening the sealed drums for anassay is a risky, time-consuming, andexpensive proposition. Traditionally,the drums are inspected by real-timeradiography, a technique in which an x ray is viewed on a monitor during x-ray exposure of the waste drums.This method allows a partial identificationof drum contents. It is limited in thatit provides only two-dimensionalinformation; it misses overlappingfeatures, does not “see” depth, andcannot count radioactive quantities.Without an accurate quantification ofthe radioisotopes, waste regulators musterr on the side of safety and designatewaste disposal based on higher-endestimates of radioactivity.

Nuclear physicist/chemist Harry Martzand his NDE colleagues have developed

hardware and software technology toperform quantitative, noninvasive assaysof waste drums. They use a two-stepapproach called gamma-ray active andpassive computed tomography, orA&PCT.

Like radiographic techniques, whichproduce the familiar medical x rays,computed tomography measures radiationenergy that travels from a source throughan object to a detector and records theintensities that result from the interactionof the energy with the object. But unlikeradiography, tomographic measurementsrequire the acquisition of many differentimages of an object. In medicaltomography (i.e., CAT scans), thesource and the detector move aroundthe patient; in industrial tomography, theobject is usually rotated, elevated, andtranslated (moved in parallel motion).

Martz’s A&PCT system takes twodifferent tomographic measurements.For the first, called the activemeasurement, an external radiationsource emits gamma rays (instead of x rays), and a gamma-ray spectrometersystem measures the gamma radiationthat passes through and outside theobject being measured. Gamma-ray

6



Light source Laser slab Rail

Polarizing filters

Figure 1. (a) Photo and schematic of anautomated, optical inspection system developedby nondestructive evaluation researchers Skip Perkins and Diane Chinn. (b) Raw and (c) processed image data from the system.

(b)

(a)

(c)

Improving the Total ProcessGraham Thomas, group leader for

ultrasonics and surface techniques, hasalso instituted an automated inspectionmethod, using ultrasonic technology, toreplace “eyeball” inspections. He did thisas part of a collaboration with privateindustry in work that also includedproduct development monitoring, rawmaterial evaluation, and investigations ofmanufacturability issues. Interestingly,the ultrasonic technology developedduring this project is now being appliedto other Laboratory programs.

Thomas was working with an enginepiston that had been designed for betterfuel efficiency to meet increasinglystringent federal pollution guidelines.It is made by a metal–matrix compositecasting process: molten aluminum isforce-injected into a refractory metal

mold that contains reinforcing ceramicfibers (called a preform). Theperformance of the finished pistonsdepends on the quality of the preform.During fabrication of the pistons, unevenfiber concentrations can cause densityvariations in the casting, and cracks,voids, or other surface abnormalitiescan appear.

Thomas and his colleagues’ first taskwas to select an inspection techniqueto assure the quality of the preforms.They tried five techniques (x-raycomputed tomography, digitalradiography, optical imaging, ultrasonictesting, and infrared imaging),discovering that while all can effectivelydetect flaws, each one has differentstrengths and weaknesses. For example,computed tomography provides the bestcharacterization of internal features.

Digital radiography is the fastest andhas the highest resolution, but it is lesssensitive to voids and cracks. Theyselected digital radiography to screenthe preforms during the project’sdevelopment and demonstration phase.

For the production phase, a differentinspection technology was needed, onethat is fast, inexpensive to implement,and requires no shielding to protectworkers (as the radiographic techniquedoes). Thomas is adapting ultrasonicsources to send out pulses of high-frequency sound waves, which thenradiate into the material of interest.Detectors measure how much soundattenuates using specially designedtransducers, devices that convert soundpulses into electrical signals. Theresulting pulses—the detected electricalsignals—are processed and interpreted.

Figure 2. Prototype ultrasonic scanning system (with sample pistons atop the monitor) that willbe used for detecting very small casting defects.

9



quantitate the images. Results fromscanning the simulated samples willidentify the optimum scanning conditionsand parameters for the real samples.

Lawrence Livermore and UC Davisresearchers will also compare and refinethe three-dimensional visualizationtechniques that both groups havedeveloped. They are planning a majorsoftware improvement—providingdynamic visualization—to show themicroscale soil transport changes in time.

Dual Bands More PreciseAnother method that is pushing the

envelope of NDE technology is dual-band infrared (DBIR) thermography.This method measures apparent surfacetemperature patterns to detect subsurfaceflaws, based on the fact that flawedmaterials or structures heat and cooldifferently than those without flaws.Normally, heat measurements are takenin one range of infrared wavelengths, butthose measurements do not distinguishbetween real structural defects and“clutter,” surface-reflected infrared noise.

Nancy Del Grande has developed adual-band measurement technique thatsimultaneously uses short wavelengths(4.5 to 5.5 micrometers) and longwavelengths (8.5 to 11.5 micrometers)

8



been adapted for a commercial mobilewaste inspection system developed byBIR Inc. of Lincolnshire, Illinois, that isproviding services at waste sitesthroughout the U.S.

Measuring TransportBecause high spatial resolution

imaging capabilities are now availablewith x-ray computed tomographicsystems, the technique is being viewed asan attractive tool for obtaining rock andsoil property measurements. Investigatorsfrom the Environmental ProgramsDirectorate at Lawrence Livermore—aided by Pat Roberson, Dan Schnebert,and other NDE researchers—have usedx-ray tomography to measure watercontent in rocks from The Geysersgeothermal reservoir in northernCalifornia. Concurrently, NDE x-raycomputed tomography specialists beganplanning work with researchers from theUniversity of California at Davis to studycontaminant transport mechanisms in soil.The goals are to design a viable methodfor estimating groundwater contaminationrisks and to plan remediation.

Early x-ray tomographic studies ofGeysers rock were conducted in alaboratory. Lawrence Livermore

scientists took a variety of x-raytomographic scans of preserved coresamples.

Pairs of cylindrical core samples,each with different water content, weremeasured for the extent of their fluidsaturation, how fast they dried, andhow fractures influenced bothsaturation and drying. The experimentsdemonstrated that tomographic scanscould be used to monitor moisturedistribution and movement in rockshaving at least 8% porosity. Scanningwas less definitive for measuring rockwith lower porosity, such as graywacke,a typical Geysers rock.

With a higher-energy x-ray imagingsystem that provided better spatial andcontrast resolution than medical scannersand also included specialized imagereconstruction software, the scientistswent on to scan rock samples. At thesite of a completed drilling operation,they sealed off sections of core with analuminum cylinder to preserve andprotect each one from furtherdisturbance. Multiple views of thesamples were radiographed and three-dimensional tomographs were thenreconstructed (Figure 4). Thetomographs clearly show changes at

different depths in the reservoir andmajor structural features useful fordeducing reservoir processes. Theexperimenters conclude that, with furtherrefinements to this spatial and contrastresolution, quantitative measurementsof mineralogy, porosity, water content,and distribution may be possible.

Although only a small part of thereservoir can be studied through coresampling, data from these studies maybe useful for extrapolating informationto a scale as large as several squarekilometers. Geophysical properties,such as seismic velocity and electricalconductivity, depend on water saturation;if these properties could be calibratedto water content, they could be used toprovide measures of water saturation.

The soil studies, in collaboration withUC Davis, require microscale x-raycomputed tomography with a spatialresolution of 15 to 30 micrometers.The objective is to use the microscaledata to better understand transportmechanisms associated with themigration of contamination. Thisinformation will be used to verify andimprove pore-scale models that predictmigration. For dynamic cases, researchersobtain a sequence of highly detailedradiographs of water and contaminatesflowing through the soil and observethe changes. For static cases, two three-dimensional computed tomographyimages are acquired, one from a referencesample that is not contaminated andone from a contaminated sample. Bysubtracting the reference image, theyobtain a three-dimensional, pore-scaledistribution of the contaminant. Gettingthe high-resolution data requires a new,microfocus, in-line CT scanning systemthat is being developed by NDE.

First, however, the investigators mustsimulate porous-media (i.e., soil) flowsystems by taking computed tomographyscans of spherical glass beads in differentcombinations of fluids. The well-definedshapes of the beads make it easy to

to create three-dimensional thermalimages of materials for NDE projects.Del Grande knew that hotter defect spotsshow the same patterns at differentwavelengths, whereas clutter shows verydifferent patterns (emitted light andreflected light obey different physicallaws). She thus surmised that bycomparing the two image data sets,she would be able to analyze heat flowpatterns precisely and separate structuralflaws from surface emissivity variations.Del Grande has already applied the dual-band technology to detect flaws such asaircraft skin corrosion and bridge deckdelamination (see S&TR, May 1996).

The very high precision of DBIRtemperature measurements can beapplied to uses other than detection ofmaterial weaknesses and flaws. ForLawrence Livermore’s National IgnitionFacility (NIF), DBIR technology issupporting efforts to determine whatthermal controls and recovery times willbe needed to avoid damaging potassiumdihydrogen phosphate (KDP) lasercrystals that will be used to boost laserenergy. Scientists need to know how longthe pulsed crystals will take to return toambient temperature so they can besafely pulsed again. Because the crystaltemperature changes in question are

Figure 3. Assaying a container suchas this transuranic waste drum ismade easier with LLNL’s active andpassive computed tomography(A&PCT). Here, data are shown inrendered views of (a) a typicalindustrial transmission tomographat high spatial and energy resolution,(b) the active data set, and (c) thepassive data set, which gives thedistribution of plutonium-239 in thedrum. When the measurements arecombined, radioisotopes can beidentified, located, accuratelymeasured, categorized, and certifiedfor disposition.

(a) (b) (c)

Figure 4. Radiographsof 1.5-meter cores ofGeysers rock withinsealed aluminumcoring tubes showdiffering degrees ofmineralization, texture,and fracturing.

spectroscopy offers several advantagesfor waste characterization, one beingthat gamma rays are emitted at discreteenergies, making it possible to determinethe attenuated gamma-ray energy foreach volume element in the three-dimensional space of the object. Thisinformation is vital for an accurate wasteassay (Figure 3).

The second measurement is a passivemeasurement. The gamma-ray sourceis shuttered, and the waste container ismoved through the same positions usedto collect the active measurements. Thistime, the detector records gamma-rayemissions from the radioactive materialinside the waste container. The passivemeasurement localizes the radioactivitydistribution in the container.

By combining active and passivemeasurements, corrections can be madeto account for the effect that the wastecontents have on the internal radioactiveemissions. The corrected gamma-rayspectra can be used to identify, localize,and assay all measured radioisotopespresent in the container, and the wastescan thus be categorized and certifiedfor disposition.

This waste assay system is mobile aswell as accurate. The technology has now

11


Nondestructive Evaluation10



crystals inside the Beamlet (once its fullcapability is online), one pulsed andone not, to determine the initialtemperature rise and required recoverytime for the pulsed crystal.

In yet another Laboratory project,the DBIR technique helped the HeavyIon Fusion Group to determine theextent of temperature uniformity ofhigh-temperature zeolite (aluminumsilicate), a material used as a sourceof ions for a prototype inductionaccelerator (Figure 7). The image dataindicated that high-temperature andtemperature-gradient measurementsmay also provide useful informationabout zeolite aging so scientists willknow when the zeolite source shouldbe replaced, thereby assuring continuedaccelerator performance.

Aging zeolite can be identified bythe uneven distribution of silicate,one of its components, on the zeolitesurface. Because silicate ions have abroad infrared resonance (from 9 to 11 micrometers), they cause the zeolitetemperature to appear much lower inthe long band than in the short band.Nevertheless, making the dual-bandzeolite heat measurements waschallenging: most of the target isrelatively unaffected by the silicatebuildup, so measurements had to bevery precise to “see” the unevendistributions. In addition, themeasurements were made in a vacuumenvironment, and they were detected

minute and the measurementenvironment (a hard-to-access vacuumchamber) is both complex and delicate,tracking crystal cool-down is not easy.DBIR offers a feasible means for takingthe necessary measurements.

To demonstrate the capability of thetechnique to measure temperatures nearroom temperature to a precision within0.07°C, Del Grande first acquired dual-band measurements of two KDP crystals(Figure 5), one heated in an oven andone kept at room temperature. Then sheheat-imaged KDP crystals through azinc–selenide vacuum window. Thegoals were to reproduce the effect of theactual vacuum environment in whichcrystals will be pulsed and measured,to demonstrate that heat images can betaken through the window, and todetermine the corrective calibration

measurements for the DBIR systembefore its use in the actual NIFprototype laser, the Beamlet.

In the next part of the study, heatimages were taken of an actual fused-silica Beamlet window, without thecrystals. The window was externallyheated and allowed to cool down.Cool-down was very slow, indicatingthat temperatures in the vacuum chamberenvironment were well controlled andnot susceptible to external influences(Figure 6). The comparison of emissivitydifferences between fused silica andaluminum at 20°C indicated thatdifferences were slight, and windowtemperatures were unaffected by vacuumchamber walls and aluminum structures.

With these assurances that heat-imagemeasurements are possible and accurate,Del Grande expects to measure two KDP

indirectly. That is, the coffin-likechamber of the ion beamline meant thatthe zeolite infrared signals had to bereflected at right angles off a silvermirror and then transmitted through thevacuum window to reach one detectorcamera and then the other. Therefore,corrections had to be made for theeffect of the silver mirror and for thetransmissions of the reflected infraredsignals through the window, in additionto corrections for the dual-band,wavelength-dependent emissivityvariations. Despite the difficulties,the results demonstrate that suchmeasurements are feasible and, in fact,show uncertainties as small as 3°C attemperatures as high as 915°C.

Technology for the FutureTo follow the course of NDE

developments is to anticipate ever moreinnovative and far-reaching uses forits technologies. The NDE researchers’work already demonstrates diverse newareas of NDE applicability. For example,it can be used as an environmental tool(as seen in the work on tomographicwaste assays and tomographiccontaminant studies) and in uniquescientific applications (as in the workfor the KDP laser crystals and forzeolite ion sources). With continuingadvances in radiation physics, computeralgorithm development, and computervisualization, NDE technologies willundoubtedly provide still other usesand applications.

— Gloria Wilt

Key Words: computed tomography,contaminant transport, digital radiography,dual-band thermography, gamma-rayspectroscopy, infrared computedthermography, inspection, nondestructiveevaluation (NDE), nondestructive wasteassay (NDA), optical inspection, ultrasonics.

For further information contact ClintLogan (510) 422-1888 ([email protected]).

Figure 5. A dual-band infrared (DBIR) experimentmeasured KDP crystals. (a) The photo shows the setup,and (b) an image demonstrates the different temperaturesof the experiment elements. Inset numbers denote (1) anoven-heated crystal, (2) an unheated crystal, (3) a heatedblackbody calibration plate, and (4) a calibrated resistancethermometer.

(a) (b)

(a) (b)

Figure 6. Temperature images of the Beamlet vacuum chamber experimentat (a) 2 minutes and (b) 200 minutes after the heater was turned off. Insertnumber (1) denotes a fused-silica window, and (2) denotes an aluminum wall.

(a) (b)

Figure 7. (a) DBIR cameras face the vacuum-chamber port of the Livermore prototype recirculatinginduction accelerator. Red cursor marks show measurements of the aged 2-centimeter-diameterzeolite heavy-ion sources at (b) a long wavelength band (8.5 to 11.5 micrometers) at 911+3°C and(c) a short wavelength band (4.5 to 5.5 micrometers) at 915+3°C.

(c)

CLINT LOGAN joined Lawrence Livermore National Laboratoryin 1963 after receiving a B.S. in mechanical engineering fromMontana State University that year. He received an M.S. inmaterials from the University of California at Davis in 1972.Logan’s first job assignment at the Laboratory was in theMechanical Engineering Department’s Apparatus Division.Since that time, he has had experience in the fields of weaponstesting, experimental physics, magnetic fusion, x-ray lasers, and

digital mammography (also see the article on mammography, pp. 23–25 of thisissue). Logan is currently the section leader for nondestructive and materialsevaluation.

About the Engineer


of about 10 millionths of an inch. Therepeat distances in the multilayers, thatis, the thickness of two adjacent layers,can be purposely selected to be identicalto the interaction lengths characteristicof important physical properties (e.g.,magnetic interaction lengths) to yieldnew properties. In this context, saysLaboratory material scientist TroyBarbee, Jr., one of the pioneers ofmodern multilayer technology, “it isgenerally accepted that one shouldexpect the unexpected when multilayersare fabricated and experimentallycharacterized.”

Multilayers are part of a larger,established scientific field of so-calleddesigner or “nanostructured” (fromnanometer, a billionth of a meter)materials that represent the currentlimits of materials engineering and thatare currently impacting numerousLaboratory research programs. Indeed,multilayers are among the first materialsto be designed and fabricated at theatomic level, a capacity termed “atomicengineering” by Barbee. “We’re buildingmultilayer materials atom by atom andmolecule by molecule,” he says. Theresult is tremendous potential forimproving the performance of large

numbers of products through eithernew or enhanced mechanical, optical,magnetic, thermal, and other physicalproperties.

To date, Barbee’s team of materialscientists, engineers, and technicianshas synthesized multilayers from 75 of the 92 naturally occurringelements in elemental form or as alloysor compounds. With that wealth ofexperience, the team has emerged asone of the world leaders in multilayerscience and its applications. The teamhas also forged partnerships with othernational laboratories, U.S. industries,universities, federal agencies such asthe Department of Defense and NASA,and researchers worldwide.

The first applications of multilayerstructures were demonstrated more than50 years ago for such uses as opticalinterference filters and reflectioncoatings. During the 1970s, “macro”multilayer films became essential tothe semiconductor industry for makingeverything from computer chips to harddisk drives. In the late 1970s, Barbeepioneered significant advances infabrication technology in the developmentof multilayers for a wide variety ofapplications in the x-ray, soft (lower

energy) x-ray, and extreme ultraviolet(EUV) regions of the electromagneticspectrum. For example, high-reflectivitymultilayer mirrors have made possible anew class of telescopes for solar physicsand astronomical research. Multilayeroptics also have found applications inelectron microprobes, scanning electronmicroscopes, x-ray lasers (especially inlaser-fusion diagnostic systems), andparticle beamlines in accelerators.

To Save Airlines MillionsLivermore researchers are currently

pioneering new kinds of multilayers—beyond optical uses—that take advantageof their extraordinary properties. Theseapplications include high-performancecapacitors, ultrahigh-strength materials,thermo-electric devices, and coatingsfor gears and bearings, aircraft andautomobile engines, and cutting andmachine tools.

Products incorporating multilayerspromise higher strength-to-weight ratios,less friction and wear, higher temperatureoperation, corrosion resistance, fracturetoughness, and low electrical resistivity.Multilayer technologies can also havea profound impact on manufacturingprocesses by decreasing the amount of

common adage goes, “thin is beautiful.” To agrowing number of researchers—and intrigued

companies—the saying is especially true for a uniqueclass of materials called multilayers. Composed ofalternating layers of two different materials as thin asa few atoms, multilayers offer extraordinary strength,hardness, heat-resistance, and unexpected newproperties. At Lawrence Livermore NationalLaboratory, researchers are pioneering entirely newapplications for these materials, which many nowbelieve to constitute an essentially new state of matter.

Multilayers’ alternating layers can vary in numberfrom a few to more than 200,000. Individual layerthicknesses range from a few atoms to a few thousandatoms, corresponding to a maximum structure thickness

A

Alloys

Plasma spray

Electron beam

500

300

100

Base

1960 1980Year

2000

Tem

pera

ture

, °F

Figure 1. (a) Multilayermaterials in aircraftengines withstandgreater temperatures,which allow engines todevelop greater thrust.(b) A turbine’s airfoilthermal barrier coatingprolongs engine lifetime.

1312 (a)

(b)

Atomic Engineeringwith MultilayersAtomic Engineeringwith MultilayersThe future looks bright for multilayers, exceedingly thin alternating layers of

materials that often demonstrate remarkable—and unpredictable—properties

for a host of applications.

15


Multilayers

reflection angles and x-ray wavelengthsfor which they can be used. To retainthis range of reflected light, one can usea series of multilayers to replace thenatural crystals. An added advantage ofmultilayers is that they can be smoothlydeposited on curved substrates, arequirement for high-performanceoptical systems.

Barbee’s work on multilayer opticsbegan in the 1970s at Stanford University,where he was laboratory director of theCenter for Materials Research. He leddevelopment of multilayers using atechnique called magnetron sputterdeposition, now the most commontechnique for depositing multilayers onsubstrates (see box, p. 18). In 1976, thetechnique was reported to Congress bythe National Science Foundation as amajor breakthrough in material science.

Barbee and his staff at Stanforddesigned a set of magnetron sputteringsources to produce multilayers based oncopper layered with the transition metalsniobium, tantalum, molybdenum, andtungsten. From analyzing these earlymultilayers, they found that the structuresmight be of x-ray optical quality.

An effort was begun to explore thisopportunity with the material pairtungsten and carbon. These elementswere selected because only a minimumnumber of layers were required to achievesignificant reflectivity, minimizing thedemands on the stability of the maturingsputtering process. These materialsproved to be very effective and havebeen a staple of the internationalmultilayer x-ray optics field ever since.In addition, the development effort wasaided by the appearance of new tools,namely the scanning transmissionelectron microscope (STEM) forcharacterizing multilayer structuresand synchrotron x rays forcharacterizing mirror performance.

When Barbee came to Livermore in1985, he set out to advance the sputteringprocess, develop more advanced

multilayer optics, and explore a widerrange of multilayer applications. Today,Livermore is known internationally forthe design and manufacture of optics forobtaining high-resolution images of theSun and astronomical objects in the x-ray to EUV spectrum. The Livermoreteam made the multilayer optics for aCassegrain telescope on the StanfordUniversity/Marshall Space FlightCenter sounding rocket launched onOctober 23, 1987. The images (Figure 4)

clearly resolved features, such as loopsand plumes, of the Sun’s corona for thefirst time in this region of theelectromagnetic spectrum. One of thephotos appeared on the September 20,1988, cover of Science magazine.

Since then, Livermore researchershave manufactured multilayer opticsused in several satellites by the U.S.,the U.K, and France. Livermoremultilayer optics for an x-ray telescopewill be onboard a new NASA research

14


Multilayers

material. This multilayer is composedof 7,100 individual layers of materials—3,550 layers of copper (each layer is325 angstroms, or 156 atoms, thick) and3,550 layers of a copper–zirconium mix(each layer is 100 angstroms, or 38 atoms,thick). All told, the multilayer measuresabout 142 micrometers thick, equivalentto the thickness of about two human hairs.Although only about three atoms in everyhundred are zirconium, the material hasa tensile strength of about a billionpascals (160,000 pounds) per squareinch, more than six times the strengthof commercial copper. With their highstrength, nonmagnetic nature, and moreenvironmentally friendly materials,copper–zirconium multilayers could beused to replace beryllium– copper alloyscommonly used in springs and tools.

Seeing the Sun in New WaysOne of the most important applications

of multilayers is astronomical imaging.High-performance multilayers have beenused as mirrors to focus light in the x-ray,soft x-ray, and EUV regions. Imagestaken by telescopes using multilayermirrors reveal important features thatcannot be captured by standard imaginginstruments operating at longerwavelengths. Furthermore, becausemultilayer mirror surfaces are reflectiveonly within a certain wavelength range,they can be used to isolate a particularregion of the spectrum of interest toastronomers (Figure 3).

Barbee notes that standard opticaltechniques cannot be used in x-rayimaging devices because x rays aresubstantially absorbed by the materials.As a result, reflective optics based oncollective scattering of the individuallayers in a multilayer solid are used tocollect and image the x rays. X rays arereflected only if they hit a metal surfaceat a very shallow, or grazing, angle.However, natural crystals have spacingbetween their planes on the order of afew angstroms, which limits the

diameter. As a result, the layers arestronger and less likely to fail understress. Multilayers made of metals getstronger and harder, while multilayerceramics become less brittle. Thestrongest materials are those with thethinnest layers because they have themost uniform structure.

Barbee says it is a complex task tochoose materials to make up amultilayer because a researcher mustunderstand metallurgy as well as thephysics of the intended application.Indeed, combinations of two materialssometimes result in surprising newproperties. A multilayer fabricated byLivermore scientists and composed ofcopper and Monel (copper–nickel alloy)(Figure 2) has more than 10 times thestrength of copper alone and is highlyresistant to chemical corrosion.Sometimes materials with differentproperties can be combined in multilayersto eliminate or mitigate some of theirindividual drawbacks. For instance, veryhard materials can be combined withthose that are very tough to producesomething, such as copper–Monel, thatis both hard and resistant to cracking.

One multilayer designed by Barbeeillustrates the advantages gained byadding even a small quantity of a different

machining necessary between rawmaterial and finished product.

The enormous commercial potentialof multilayers has not gone unnoticedby U.S. industry. A recently completedthree-year Cooperative Research andDevelopment Agreement (CRADA)joined scientists from LawrenceLivermore, Pratt & Whitney, and RohrInc. to develop high-performancemultilayer coatings for aircraft engineblades and high-strength engine parts(Figure 1). Such advances could safelyincrease the operating temperatures ofgas turbine engines by 10 to 38°C, therebypermitting the engines to develop greaterthrust. The coatings would also prolongthe life of many parts throughout theengine, conceivably saving commercialairlines and the Department of Defensetens of millions of dollars annually.

Such coatings work becauseextremely thin slices of matter exhibitnew and sometimes unanticipatedproperties. Scientists believe the reasonis their extensive “boundary structure.”In a multilayer with layers only fouratoms thick, half of the atoms lie at aninterface between the layers. They donot develop the conventional molecularstructure and bonding found in pieces ofmatter greater than 100 nanometers in

Theoretical strength (2.1 gigapascals)

Copper–Monel 400

Multilayer period, millimeters

1.0

0.5

1.5

010110–110–3

Ten

sile

str

engt

h, g

igap

asca

ls

Copper

Figure 2. Strength testsshow the difference betweencommercial copper and thecopper–Monel multilayermaterial.

Figure 3. (a) Multilayers ofmolybdenum carbide and amorphoussilicon (Mo2C/Si) are shown in atransmission electron microscopyimage at 4 million magnification afterannealing at 500°C. (b) Reflectivitymeasurements of Mo2C/Si, taken byLawrence Livermore and the NationalInstitute of Standards andTechnology (NIST), are extremelyclose to the theoretical calculation ofa perfect structure at the wavelengthsshown.

NIST

LLNL

Calculation

0170 180

Wavelength, angstroms190 200 210 220

0.1

0.2

0.3

0.4

0.5

Ref

lect

ivity

(a)

(b)

17


Multilayers

capacitors because they could createentirely new markets.

Another application that may soon seecommercial use is a multilayer foil madeof reactive materials such as aluminumand nickel that would act as a highlyportable welding tool. A piece of themultilayer could be slipped into a breakor crack of metal, for example, and thefoil would be lit with a match. Themultilayer would quickly reach atemperature of up to 2,000°C to repairthe crack. The multilayer materialswould be chosen to produce differenttemperatures and rates of heat release tocorrespond to the material being welded.

Replacing Loud CompressorFurther away from commercial

realization than multilayer capacitorsor welding materials, yet with as manypotential applications, are multilayerthermo-electrics. The thermo-electric

16


Multilayers

Extensive Effort Under WayThe Laboratory-wide multilayer

development effort consists of more than 15 senior researchers and 25 technicians at work in fivelaboratories. The results of their workcan be seen across LawrenceLivermore’s directorates—Chemistryand Materials Science, Engineering,Defense and Nuclear Technologies—and especially in the Laboratory’sLaser Programs. Barbee’s teamproduced more than 250 multilayeroptics last year for laser applications,particularly for laser-fusion research.

“Using multilayer technology,we’ve been imaging high-energy-density plasma of the Sun and thenturning around and imaging the samekinds of phenomena in laser fusion,”Barbee explains.

Multilayer optics make possible x-ray interferometry for characterizingplasmas created by high-power lasers.The technique provides the onlyworkable diagnostic tool to directly

look at extremely hot, high-electron-density plasmas of matter produced ininertial confinement fusionexperiments (Figure 5).

Researchers in Lasers’ AdvancedX-Ray Optics Group are usingmultilayer mirrors in recentlydeveloped soft x-ray lasers. Onepotential use of a laboratory x-ray laseris in imaging biological samples. Aspherical multilayer mirror is used tocondense x-ray laser light onto livingorganisms to obtain a high- resolution(greater than 800 angstroms) image.

Barbee’s team is also collaboratingwith researchers in Lasers’ AdvancedMicrotechnology Program to makepossible computer chips with 10 timesthe performance yet one-tenth the sizeof today’s devices. Achieving thesebreakthroughs will be possible onlywith lithography using EUV light. Thenew EUV technology is the focus of amajor CRADA announced in September1997 by Department of Energy SecretaryFederico Peña. As with today’s deep-ultraviolet-light-based technology, EUVlithography will employ multilayersin creating computer chips and theirmaster patterns, called masks.

Capacitors around a CornerOne research avenue of significant

potential is using multilayers as ultra-compact, high-energy storage, andextremely cost-effective capacitorsmade up of alternating metal (conductor)interdigitized with dielectric (insulator)layers. Power electronic “snubber”capacitors, normally made of ceramicor polymer dielectrics, and similar insize to a C battery, are usuallyconnected to much smaller solid-stateswitching devices. These capacitorstypically store 0.1 to 0.2 joules per cubiccentimeter capacitor volume and arewidely considered the limiting factor inmany applications. In contrast, multilayercapacitors the size of a postage stampwould store 10 joules per cubic

satellite scheduled to be launched by aPegasus spacecraft in December 1997.The x-ray telescope is designed to havethe highest spatial resolution of any suchinstrument ever flown. Livermoremultilayer optics are also beingconsidered for two other U.S. spacemissions and for satellites for theJapanese and European space programs.The popularity of the multilayer opticsis a significant factor in the growinginterest in x-ray imaging of astrophysicalphenomena from stellar sources.

The outstanding properties ofLivermore’s x-ray optics can be seen inSTEM images of multilayers containingalternating layers of molybdenum carbide(Mo2C) and amorphous silicon (Si).The image (Figure 3a) shows that theinterfaces between the multilayers arevery smooth and abrupt in contrast, withno intermediate chemical reaction layer atthe interfaces of the two layers. Figure 3bshows that the measured reflectivity ofthe multilayer is essentially equal to thatpredicted for a perfect structure.

centimeter while costing perhaps one-twentieth that of their ceramic forebears.

Project leader Gary Johnson, anelectronics engineer, says that the firstcommercial multilayer capacitors willlikely be targeted at power electronics,computers, and communication devices.Compact multilayer capacitors, forexample, would be highly useful inpower conditioners that convert dc toac (or vice versa) and for adjustable-speed motor drives.

Johnson says longer-term multilayercapacitor applications includetemporary energy storage for physicsexperiments such as high-energylasers. Other potential applicationsinclude electric motor controls andenergy ballasts for batteries in electricvehicles. Multilayer capacitors coulddeliver at least 100 times more powerper unit of volume than anythingavailable today for electric vehicles.Multilayer capacitors have the potentialto be especially useful in regenerativebraking, in which the considerableenergy dissipated in braking isconverted by a generator back intoelectricity to recharge capacitors (seeS&TR, October 1995, p. 12). Realizingthe potential of these large storageapplications, however, is dependentupon substantial advances in multilayercapacitor fabrication processing, thenext major research and developmentthrust of this work.

The present multilayer capacitoreffort focuses on honing themanufacturing process, in particular,eliminating sources of contamination.When a layer is only a few atoms thick,even the tiniest dust particle can severelycompromise capacitor performance,Johnson notes. The Livermore team isin early discussions with capacitormanufacturers and tooling companiesto license this technology. Johnsonsays capacitor companies areparticularly enthusiastic about the highenergy density offered by multilayer

effect uses heat transported by electronsto produce cooling with electricalcurrent. Conversely, thermo-electricmaterials can also take advantage ofdiffusion of electrons in a thermalgradient to produce a current. Thermo-electric materials have no moving parts,so they can be miniaturized and may bevery reliable. Current applicationsinclude temperature-sensingthermocouples, electric powergenerators for spacecraft, and portablefood and beverage coolers.

The application of thermo-electricdevices for cooling or heating largeequipment is primarily limited by theirefficiency, which is lower than that ofconventional gas cycle refrigeration.However, the development of multilayershas sparked interest that multilayerthermo-electric materials may be thekey to taking these devices into thecommercial mainstream.

Figure 4. Early advancesin multilayer technologiesbrought images of theSun with higherresolution than previousgrazing incidencetelescope images. Thereason: multilayerlaminates in the x-rayoptics allow the use of anormal incidence opticssystem for whichaberrations can beminimized.

Figure 5. Where no other systems have worked, multilayered optics allowan x-ray interferometry measurement of electron-density, colliding-plasmaexperiments relevant to inertial confinement fusion.

Distance, micrometers

200

0

200

400

400

1200600 800 1000400

Dis

tanc

e, m

icro

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19


Multilayers18


Multilayers

“Multilayers may have the potentialto increase the efficiency of thermo-electric materials by a factor of three orfour,” says Livermore material scientistAndrew Wagner. He notes that anefficient multilayer thermo-electriccooling system could replace theconventional large, heavy, and noisyrefrigerator compressor that often cycleson and off. A multilayer thermo-electricdevice would be silent, operatecontinually, and not requireenvironmentally unacceptablehydrofluorocarbon gases.

Wagner, together with researcherJoseph Farmer and technicians RonaldForeman and Leslie Summers, hasconducted basic research on thefeasibility of producing multilayerthermo-electric materials, which, in thatapplication, would require millions ofalternating layers of conducting andinsulating materials.

Another area of active developmentis using multilayers as optics for imagingsources of neutrons. This applicationhas important implications for theDepartment of Energy’s StockpileStewardship and Management Programbecause high-energy neutron radiographycan be used to image low-densitymaterials for surveillance of stockpilenuclear assemblies. For physics researchapplications, the Livermore team iscollaborating with the University ofIllinois on a new neutron beamline thatmakes use of multilayers as optics forneutrons from a variety of sources.

The neutron work is anotherapplication for multilayers. Butmultilayers have that way about them:they force new thoughts about makingmaterials—this time on the atomicscale—and finding applications thatwill benefit society.

—Arnie Heller

Key Words: multilayers, nanostructuredmaterials, sputtering, thermo-electrics, x-ray optics, x-ray lasers.

For further information contact Troy W. Barbee, Jr. (510) 423-7796([email protected]).

TROY W. BARBEE, JR., is a materials scientist at the Laboratory,focusing on the science, technology, and application of multilayers.Before arriving at Livermore in 1985, Barbee was at StanfordUniversity, where he was a senior research associate in theDepartment of Materials Science and Engineering and laboratorydirector at the Center for Materials Research. Barbee also was avisiting professor in San Jose State University’s Materials ScienceDepartment and at the Stanford Research Institute. Barbee received

his B.S. in metallurgical engineering and his M.S. and Ph.D. in materials scienceengineering from Stanford.

About the Scientist

Making Multilayers by SputteringIn manufacturing multilayer materials, the Livermore

team uses a process called sputtering, a technique createdmore than a century ago. Livermore materials scientistTroy W. Barbee, Jr., applied an advanced form ofsputtering, called magnetron sputtering, to fabricatingmultilayers in the 1970s. Today, the semiconductorindustry, for example, uses magnetron sputtering todeposit thin films on computer parts, and the machinetool industry uses the technique to apply hard coatings tocutting tools. It is even used to tint windows by forming

thin, optically active interference coatings of metal uponglass and to coat jewelry with gold-appearing coatings.

Most of the sputtering work at Livermore takes placeat the vapor-phase deposition laboratory. Here,technicians secure a substrate to a table that rotates overtwo magnetron sputter sources of material for themultilayer. The table rotates at a predetermined speed,and the alternating layers are quickly built up as thesubstrate passes over first one material source and thenthe other. The sputter sources operate by bombardingplates of the material to be deposited with high-energyargon gas ions. The impact of these ions blasts atomsfrom the surface of the sources into the vapor and ontothe substrate. As the multilayers revolve frommagnetron source to magnetron source, the alternatinglayers, ranging from a few to many thousand, aresequentially formed.

Sputtering gives a constant deposition rate in whichthe thickness of each layer is precisely determined by thedistance of the substrate from the sources and the timethe substrate spends over each source. The techniqueenables layer thickness control of one-hundredth of anatomic diameter for up to one thousand layers. Thisprocess can also achieve a layer thickness uniformity ofbetter than 0.7% (approximately one-thirtieth of anatomic diameter) over a 10-centimeter-diameter substrate(see photo at left).

To help evaluate the performance of multilayers,researchers use a soft x-ray diffractometer that wasdesigned and built at Livermore. It is contained in avacuum chamber and scans the surface of a sample undercomputer control to provide a map of reflectivityuniformity. In addition, samples are sectioned and thinnedfor electron microscope analysis to inspect interfacesharpness, layer-to-layer uniformity, and layer smoothness.

Dan Noecker of Livermore’s vapor-phase deposition laboratoryadjusts atom-by-atom fabrication of a new class of materials forhigh-strength and high-temperature applications.

21


Astrophysics

Lawrence Livermore’s current leadership position inmodeling x-ray sources is a result of its work to understandhigh-energy-density physics, which is required to predict thebehavior of weapons.

“In short, theory draws from computer simulation, andcomputer simulation draws from experiment,” Liedahl says.“Livermore’s computational modeling for the SSMP willbenefit from the improved atomic models that allow us toverify the accuracy of our computational models.”

Liedahl also works closely with Peter Beiersdorfer ofLawrence Livermore’s Electron-Beam Ion Trap (EBIT)facility. At EBIT, measurements of electron-impact ionization,excitation, and recombination can be made that are crucial tounderstanding high-temperature plasmas. These experimentsyield data that can be used to verify the completeness andaccuracy of atomic models of the emission properties ofvarious elements involved in astrophysical processes. Liedahland his colleagues use these improved atomic models, alongwith data from space-borne experiments, to calibrateastrophysical models. In turn, these improved models allowscientists to refine theories about the behavior of plasmas andhighly charged ions—essentially, our basic understanding ofmatter in extreme environments.

Science Born by Chance“The science of x-ray astronomy was born in 1962 during

a rocket-based experiment to detect x-ray-induced fluorescenceon the lunar surface,” Liedahl says. “By chance, the Moon’s

Works in Both DirectionsThe goal of Liedahl’s project is to improve and experimentally

benchmark a sophisticated suite of computational tools formodeling the radiative properties of astrophysical plasmas.Liedahl and his colleagues are approaching solutions toproblems in astrophysics along four avenues: astronomicalobservations, laboratory experiments, computer simulations,and theory (see figures for the interplay of these approaches).Historically, laboratory experiments have been performed toidentify elements by measuring wavelengths that can bematched to stellar spectra. But the interaction of computersimulations and laboratory experiments works in bothdirections. Data from experiments are used to refine thecomputer models, and the computer models help scientistsunderstand the problem and develop theories.

Especially now, in the Department of Energy’s nuclear-test-free Stockpile Stewardship and Management Program(SSMP), x-ray astrophysical observations and relatedmodeling will play an essential role in benchmarking ourability to understand the physics of thermonuclear weaponsbecause much of the physics is common to both fields. Forexample, high-quality x-ray observations from satellites maywell be the source of future data supporting the SSMP.

20


Marrying Astrophysics with the Earth

STROPHYSICISTS, it could be said, have the universe fora laboratory. And what a laboratory it is, with conditions

that cannot be duplicated in an earthly setting—nearly perfectvacuum, extraordinary temperatures and pressures, and enormousdistances. But the very vastness that provides these conditionsmakes study of astrophysical phenomena difficult.

The observable phenomena in the universe often are the resultof complex interplay between several physical processes, each ofwhich operates over a scale that cannot be controlled or modifiedby the experimenter. Obviously, a researcher cannot performany type of controlled experiment on objects outside the solarsystem. Theory and computer simulations must be called uponto fill the void left by the absence of controlled experiments.

To complement their observations, astrophysicists must leavetheir laboratory of the universe and return to the more modestfacilities on Earth. Lawrence Livermore, with its advancedcomputational resources and laser plasma research capabilities,is a natural place to conduct this research.

Occupying that particular spot on Earth is astrophysicistDuane Liedahl. Along with astrophysicist Christopher Mauche,Liedahl is working to shed some light on the properties of cosmicx-ray sources while also using the data from space-borneexperiments to refine and improve the accuracy of computersimulations of these phenomena.

A

Research Highlights

20 3 4Energy, keV

5 6 7 8

25

20

15

10

5

0

S XVI RRC120 eV

S XVI Lyå

cts

s–1 k

eV–1

ModelData

0–0.5–1.0–1.5–1.5

–1.0

–0.5

0

5 eV

30 eV

50 eV ~500 eV

>1 keV

Fe XXVI

Fe XXVSi XIV

Mg XII0.5

1.0

1.5

0.5 1.0 1.5z/a, units of binary separation

y/a

Neutron star/ blackhole

S XVI Ca XX

Ar XVIII

Companion

14126 8 1040

2

4

6

8

10

12

14

16

16 18 20Wavelength, Å

XMM (1999)

ASCA (1994)

Pho

ton

flux,

a.u

.

1,500

1,000

500

eV

Fe XX n = 3,4 668 levels 67,176 rad rates 9,512 coll rates

Is2 2p5

Is2 2s 2p4

Is2 2s2 2p3

The interplay ofastrophysicalresearch atLawrenceLivermorebenefits fromunique facilitiesand capabilities.

Astrophysical observations

Analysis

Predictions

Astrophysicalmodel

Atomic models

National Ignition Facility

Electron-BeamIon Trap facility

2322


orbit passed close to the position of the star Scorpius X-1, anda dramatic increase in flux—changes in the radiation emitted—was detected. This discovery indicated that x-ray observationscould reveal new and exotic cosmic phenomena that are largelyinvisible to conventional optical and radiotelescope techniques.”

Our solar system is inside a million-degree ball of gas—purportedly carved out by an ancient supernova—that isradiating x rays. The Sun, because of its proximity to Earth,is our brightest source of x rays. However, most objects inthe universe—stars, supernova remnants, galaxies, and blackholes—also produce x rays. Scorpius X-1 is a much brightersource of cosmic x rays, 100 billion times stronger than ourSun. But it is also 100 million times more distant than our Sun,and the apparent brightness decreases with the distance squared.

“We’ve found that x-ray spectroscopy is a very usefulmeasuring tool for cosmic plasmas,” Liedahl continues.“However, its real usefulness in astrophysics depends onsignificant improvements in its sensitivity and capabilities. Thisusefulness will be realized only after we can make significantimprovements in our spectroscopic modeling tools. Some ofthe unique characteristics of cosmic plasmas include ultralowdensity (down to 10–3 atoms per cubic centimeter, roughly amillion times better than the best vacuum achievable on Earth),high radiation-energy density, ultrahigh magnetic fields,relativistic gas flows, and very-high-temperature shock waves.”

Traditionally, spectroscopy has been used to identify elements.As data quality improves, the demands placed on spectroscopicmodels will become much more stringent because astrophysicistswill want to know the physical conditions of the plasmas inwhich the elements exist. Liedahl’s approach seeks to identifythe detailed behavior of atoms in a wide range of physicalenvironments. His team uses these data to build atomic modelsto hypothesize about the composition and physical conditionsof cosmic plasmas. Then the team uses these atomic models torefine the astrophysical models and improve accuracy.

“Atomic physics operates the same way on Earth as it does inspace,” Liedahl says. “By improving our atomic models underconditions we can control, we develop the confidence to applythem to more complex astrophysical environments, which wecan’t control.”

Liedahl’s work helps further our understanding of both therelevant atomic physics and the astrophysics of the sourcesthemselves. Unfortunately, acquiring high-quality x-ray spectraof cosmic sources poses experimental challenges because thesources are extremely faint, and observations must be conductedfrom space. Although the interstellar medium is an extremelygood vacuum, it is not perfect and thus is not entirely transparentto x rays. However, our ability to collect high-quality data willbe dramatically improved in the near future when new satellitesare launched. The U.S. project AXAF; the European XMM,for which Lawrence Livermore collaborated with the Universityof California at Berkeley to construct the grating arrays in thespectrometers; and Japan’s Astro-E will provide more thanorder-of-magnitude improvements in sensitivity and resolution.“We also are expecting to achieve great improvements in theversatility of x-ray spectroscopy analysis tools,” Liedahl adds.

The tremendous quantity of data expected from the newsatellites launched by the U.S., Europe, and Japan willprovide a basis for significant advances in our understandingof a wide range of phenomena. Lawrence Livermore’s abilityto coordinate large-scale technology, formidable computationalpower, and an experienced team of researchers can have amajor impact on the astrophysics community by helping tomaximize the scientific yield from major space missions.

—Sam Hunter

Key Words: astrophysics, astrophysical plasmas, atomic physics.

For further information contact Duane Liedahl (510) 423-9647 ([email protected]).

Astrophysics Research Highlights

Continuing Work in Breast Cancer Detection Technologies


EITHER cause nor cure is known for breast cancer, a seriousdisease that may affect one out of every nine women in the

United States. Early detection is the only known means forincreasing a victim’s chances for survival; mammography iscurrently the best means of cancer detection in women showingno symptoms.

The power of mammography is proven. Yet, some breastcancers are missed, usually because the cancer is not imaged orbecause its indications in the image are too subtle to berecognized. The difficulty of visually detecting the cancer’ssubtle warning signs (in particular, sorting out significantmicrocalcifications—the calcium-rich deposits that are clues tomalignant breast cancers) point to the need to improve imagequality and the means of interpreting mammograms.

In 1991, help for improved breast cancer detection came froman unexpected source—Lawrence Livermore scientists andengineers working on national defense projects. They began torecognize that their technologies had important medicalapplications. Clint Logan, an engineer with expertise in materialsimaging, an important aspect of nondestructive evaluations (seearticle on p. 4 of this issue), proposed using digital computeranalysis on film mammograms. His proposal was carried outin a three-part project, first described in Energy andTechnology Review, Nov.–Dec. 1992, pp. 27–36. The first part was to digitize mammograms, that is, to convert the data on the film record into numbers, applying a high spatialand contrast resolution to the entire mammogram. Whendigitized, data could be displayed with a variety of contrastsettings, which allow clearer viewing than film studied over alight box.

The second part of this work was to develop computeralgorithms to automatically detect microcalcifications in thedigitized mammograms. The objective was to provide a“mammographer’s assistant” that would quickly andobjectively detect and flag microcalcifications for radiologistsand doctors. The algorithm, developed by biomedical imageprocessing specialist Laura Mascio, first performs two types

N

recently, however, there has been no way to compare thedifferent algorithms because each research group has testedits own algorithms on different sets of film images that havevarying degrees of diagnostic difficulty. Comparison of theirrelative performance is important because, in many cases, onlypartial records have been digitized.

To provide a standardized algorithm evaluation tool, Mascioand other Lawrence Livermore scientists began collaboratingin 1995 with researchers from the University of California atSan Francisco (UCSF) to compile a library of mammogramsthat could be used to test detection sensitivities and specificities.They used UCSF screening data of patients whose identities hadbeen obscured. A total of 50 patient cases were selected torepresent different categories: 5 normal, average, healthy cases;5 normal but difficult cases (e.g., with implants, asymmetrictissue); 20 cases with obviously benign microcalcifications; 12cases of suspicious but benign microcalcifications; and 8 casesof a biopsy-proven, malignant cluster of microcalcification. Aradiologist then worked with the Livermore team, using allavailable clinical information, to annotate the mammograms.

The library is a first step toward a meaningful comparisonof microcalcification-detection algorithms. The completelydigitized mammograms have been put onto a CD/ROM inbinary data format (see photos, p. 24) to make them availablefor other researchers. Images will be available soon onLawrence Livermore’s Web site (http://www.llnl.gov/).

Another problem with digital mammography is that its verylarge data files can present storage and processing problems,especially for small clinics with limited computer resources.Digital mammography usually records four views per patient,each taking up 200 megabytes of computer memory. To makethis technology more efficient and practical, Mascio hasproposed a way to compress mammogram files by factors of10 to 30 without sacrificing image detail or diagnosticaccuracy. Furthermore, it requires no decompression time whendata are retrieved for viewing or analysis.

Generally, the more data are compressed, the more thedata values differ from their original form once they aredecompressed. Mascio’s approach, called dynamically losslesscompression, avoids wholesale data compression and insteadselectively assigns the most data space (i.e., provides thehighest spatial resolution) to the features that must be depictedin the most detail, such as detected microcalcifications.Less important features—such as background, healthy,nonglandular tissue—are given coarser resolutions. Thus, animage may contain many different spatial resolutions, eachappropriate to the significance of the particular feature, and all

based on mammogram-specific knowledge. This compressionapproach parallels human visual inspections of mammogramfilm—radiologists use a magnifying glass to get a higher-resolution view for studying microcalcifications, but theyinspect larger abnormalities without the magnifier and bystanding at a distance from the mammogram.

For the Next-Generation SystemAs a result of this collaboration, four direct-digital

screening systems produced by Fischer Imaging Corp. havebeen installed at sites around the U.S. Even as they are beingintroduced to the general population, Jeff Kallman, aLawrence Livermore engineer, is starting research on thesensors for a new generation of mammography screening. Heproposes to generate three-dimensional images of soft breasttissue speedily and painlessly with linear ultrasonic diffractiontomography. Because breast tissue has neither large sonicvariations nor appreciable multiple scattering, linear imagingtechniques can be used. There is some evidence that canceroustissue has sound speed and attenuation properties differentfrom normal tissue; the hope is that such an imaging systemwill be able to distinguish between them.

Data collection would be done while the breast isimmersed in water or gel, bypassing the breast compressionthat makes conventional mammography uncomfortable andeven painful for some women. Furthermore, it would involveno ionizing radiation, thus eliminating concerns about x-rayexposure. With appropriate data-acquisition technology,which Kallman is investigating, breast cancer screening in thefuture would be done quickly as well as safely.

— Gloria Wilt

Key Words: breast cancer, data compression, detection algorithms,digital mammography, linear ultrasonic diffraction tomography,mammogram library, microcalcifications.

25


Breast Cancer Update24


Breast Cancer Update

film-based system, yet it would require a lesser x-ray dose tothe patient. In collaboration with Fischer Imaging Corp.,Logan and Jose M. Hernandez, another Livermore engineer,developed a digital screening unit with a novel x-ray sourcethat can be adjusted for each patient’s body size and an imagedetector that uses a charge-coupled device camera. Early trialsindicate that this system yields images with better signal-to-noise ratios than conventional x rays. And because the imagesare digital, they can be manipulated in terms of contrast,magnification, and area of interest for the best view.

Improving Detection AlgorithmsAlgorithms having better sensitivity lead to earlier

diagnosis of breast cancer and improved long-term survival.Algorithms having improved specificity (that is, they canseparate suspicious spots that turn out to be benign from those that are malignant) mean fewer unnecessary biopsiesand thereby less cost and less patient anxiety. However,sensitivity must be retained when improving specificity;otherwise, early, curable cancers could be missed.

In recent years, several other institutions have developedalgorithms for computer detection of breast cancer. Until

of high-frequency analysis on a digitized image. Oneprocedure extracts contrast (intensity difference) information,saving structures that have abrupt changes in brightness (fromedges, for example) and are larger than several pixels in size.The other procedure extracts spatial, or size, information andthus saves small, textured structures.

Adding together what has been preserved by the two high-frequency analyses produces an image that is brightest whereit contains detail common to both. When a selective erosion orenhancement (SEE) filter is applied over this image, it furtherreinforces image pixels that show strong evidence of belongingto a microcalcification and erodes pixels that show otherwise.The method developed by Mascio forms the basis of a computeralgorithm that distinguishes between microcalcifications andmimicking spots, such as specks and flecks on the film. It wasthe first microcalcification-detection algorithm to use a gray-scale morphology for extracting frequency and textureinformation. It served as a model for further development ofmammography screening algorithms.

The third part of the project was the design of a filmless,directly digital mammography system. Such a system wouldprovide information and detection superior to the conventional

For further information contact J. Patrick Fitch(510) 422-3276 ([email protected]).

The panel on the left is a mammogramwith calcifications. The area containingcalcifications is magnified in the twopanels on the right, (top) withoutannotation marks and (bottom) with theoverlying annotation marks.

26


Each month in this space we report on the patents issued to and/orthe awards received by Laboratory employees. Our goal is toshowcase the distinguished scientific and technical achievements ofour employees as well as to indicate the scale and scope of thework done at the Laboratory.

Patents

Patent issued to

Anthony F. BernhardtRobert J. ContoliniVincent MalbaRobert A. Riddle

Abraham P. LeeM. Allen NorthrupPaul E. AhrePeter C. Dupuy

Anthony F. BernhardtRobert J. Contolini

Jerald A. Britten

Thomas E. McEwan

Patent title, number, and date of issue

Repairable Chip Bonding/InterconnectProcess

U.S. Patent 5,653,019August 5, 1997

Polymer Micromold and FabricationProcess

U.S. Patent 5,658,515August 19, 1997

Method of Forming a Spacer for FieldEmission Flat Panel Displays

U.S. Patent 5,658,832August 19, 1997

Moving Zone Marangoni Drying of WetObjects Using Naturally EvaporatedSolvent Vapor

U.S. Patent 5,660,642August 26, 1997

Window-Closing Safety System

U.S. Patent 5,661,385August 26, 1997

Summary of disclosure

A chip-on-sacrificial-substrate technique, using laser processing, for mounting andinterconnecting chips. Transmission lines or leads are formed on the top or horizontalsurface and the sides or vertical surfaces of a chip, ending in a gull wing configurationinterconnect at the bottom of the chip for subsequent solder or compression bondingto a substrate or board. The leads or lines may be coplanar transmission lines. Thechip or die attachment and lead bonding are repairable so that chips can be removedwithout damage to any component.

An extrusion micromold, i.e., a singular, hollow device that can be tailored to bethermally uniform and has micrometer-sized features. The mold is a metal shell with apassageway having an inner contour profile with diameters on the order of tens tohundreds of micrometers, and an outside diameter of 1 to 8 millimeters. The featuresof this mold are made by using a sacrificial mandrel that is machined to define thedesired contour profile of the mold, coated to form an outer shell or mold body, andthen selectively etched away, leaving a mold in the form of a hollow tube with thedesired inner contour profile.

A method for forming spacers that uses a dielectric mold formed on a substrate andmold release agent. The spacers are formed of dielectric-containing aerogels orxerogels. A gel precursor is applied to the mold, filling holes that expose thesubstrate. A release agent is applied to the mold prior to precursor application, toease removal of the mold after formation of the dielectric spacer. The shrinkage of thegel during solvent extraction also improves mold removal. The final spacer material isa good dielectric, such as silica, secured to the substrate. The resulting spacers havethe capability to withstand atmospheric pressure, which tends to collapse the spacebetween the phosphor faceplate and the field emitter cathode or baseplate in a flatpanel display, provide standoff against high voltage imposed between the two plates,and are inexpensive to fabricate.

A contactless drying process whereby a surface tension gradient driven flow (aMarangoni flow) is used to remove the thin film of water remaining on the surface ofan object following rinsing. The process passively introduces minute amounts ofalcohol (or other suitable material) vapor in the immediate vicinity of a continuouslyrefreshed meniscus of deionized water or another aqueous-based, nonsurfactantrinsing agent. Used in conjuntion with cleaning, developing, or wet etchingapplications, the rinsing coupled with Marangoni drying provides a single-stepprocess for cleaning, developing or etching, rinsing, and drying objects such as flatsubstrates or coatings on flat substrates without using heat, forced air flow, contactwiping, centrifugation, or large amounts of flammable solvents.

A safety device with a wire loop embedded in the glass of a passenger car windowand routed near the closing leading edge of the window. The wire loop carriesmicrowave pulses around the loop to and from a transceiver with separate output andinput ports. An evanescent field, an inch or two in radius, is created along the wireloop by the pulses. Just about any object coming within the evanescent field willdramatically reduce the energy of the microwave pulses received by the transceiver.Such a loss in energy will cause electrical interlocks to halt or reverse a powerwindow motor that is actively trying to close the window.

Patents

27


1997 Index

Science and Technology Review 1997 Index Page

January/February 1997The Laboratory in the News. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Commentary: Accelerators at Livermore: Back to the Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Features

The B-Factory and the Big Bang . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Assessing Exposure to Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Research HighlightsThe Next Generation of Computer Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22A Powerful New Tool to Detect Clandestine Nuclear Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Patents and Awards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

March 1997The Laboratory in the News. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Commentary: The Contained Firing Facility in a Changing Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Features

Site 300’s New Contained Firing Facility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Computational Electromagnetics: Codes and Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Research HighlightsErgonomics Research: Impact on Injuries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18The Linear Electric Motor: Instability at 1,000 g’s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21


April 1997The Laboratory in the News. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Commentary: Shaping Nuclear Materials Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Feature

Dealing with a Dangerous Surplus from the Cold War. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Research Highlights

Volcanoes: A Peek into Our Planet’s Plumbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Optical Networks: The Wave of the Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17


May 1997The Laboratory in the News. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Commentary: Using Physics Research to Help Cure Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Feature

PEREGRINE: Improving Radiation Treatment for Cancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Research Highlights

The Unitized Regenerative Fuel Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Better Flash Radiography Using the FXR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Nuclear Weapons Information Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Patents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

June 1997The Laboratory in the News. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Commentary: The Critical Roles of Energetic Materials Science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Features

Transforming Explosive Art into Science. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4On the Offensive against Brain Attack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Research HighlightLaser Targets: The Next Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22



28


1997 Index

July/August 1997The Laboratory in the News. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Commentary: The Vital Role of Nuclear Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Features

Assuring the Safety of Nuclear Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4The Microtechnology Center: When Smaller Is Better . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Research HighlightsSpeeding the Gene Hunt: High-Speed DNA Sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Microbial Treatment of High Explosives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21


September 1997The Laboratory in the News. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Commentary: Superlasers as a Tool of Stockpile Stewardship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Features

Nova Laser Experiments and Stockpile Stewardship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Sharing the Challenges of Nonproliferation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Research HighlightTaming Explosives for Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Patents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

October 1997The Laboratory in the News. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Commentary: A Measure of Excellence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Feature

Livermore Science and Technology Garner Seven 1997 R&D 100 Awards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4New Interferometer Measures to Atomic Dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Compact, More Powerful Chips from Virtually Defect-Free, Thin-Film System . . . . . . . . . . . . . . . . . . . . . . . . . . . 8A New Precision Cutting Tool: The Femtosecond Laser. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10MELD: A CAD Tool for Photonics Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12The Tiltmeter: Tilting at Great Depths to Find Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Smaller Insulators Handle Higher Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Computer Storage Management Software: The Next Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Patents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

November 1997The Laboratory in the News. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Commentary: The Evolution of a Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Features

A New World of Biomedical Research: The Center for Accelerator Mass Spectrometry. . . . . . . . . . . . . . . . . . . . . . . . 4Isotope Tracers Help Manage Water Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Research HighlightsLANDMARC: Making Land-Mine Detection and Removal Practical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Improved Detonation Modeling with CHEETAH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21


December 1997The Laboratory in the News. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Commentary: Flexibility for Future Technical Successes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Features

Advancing Technologies and Applications in Nondestructive Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Atomic Engineering with Multilayers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Research HighlightsMarrying Astrophysics with the Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Continuing Work in Breast Cancer Detection Technologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Patents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Advancing Technologies and Applicationsin Nondestructive Evaluation

The methods used to inspect and evaluate materials,devices, and products are now based on imaging systemsthat collect digital data and process and interpret themthrough specially developed computer algorithms. LawrenceLivermore’s Nondestructive and Materials EvaluationSection has been developing a wide range of imagingsystems, implementing them through a range oftechnologies, including digital radiography, computedtomography, machine vision, ultrasonics, and infraredcomputed thermography. Applications of these varioustechnologies are described in the article. They demonstratethe range and increasing flexibility of the concept ofnondestructive evaluation.Contact: Clint Logan (510) 422-1888 ([email protected]).

Atomic Engineering with Multilayers

Composed of alternating layers of two different materialsas thin as a few atoms, multilayers offer extraordinarystrength, hardness, heat resistance, and unexpected newproperties. At Lawrence Livermore National Laboratory,researchers are pioneering new applications for thesematerials. They have synthesized multilayers from 75 of the92 naturally occurring elements in elemental form or as alloysor compounds. The team has emerged as one of the worldleaders in multilayer science and its application and hasforged partnerships in government and industry to developand apply multilayer materials. The article describes currentand future applications of multilayers, including high-strengthaircraft engine parts, mirrors for astronomical imaging, high-energy capacitors, and thermo-electric devices.Contact: Troy Barbee, Jr. (510) 423-7796 ([email protected]).

Abstracts

© 1997. The Regents of the University of California. All rights reserved. This document has been authored by the The Regents of the University of California under Contract No. W-7405-Eng-48 with the U.S. Government. To request permission to use any material contained in this document, please submit your request in writing to the Technical Information Department,Publication Services Group, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551, or to our electronic mail address [email protected].

This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of Californianor any of their employees makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information,apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service bytrade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or theUniversity of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California andshall not be used for advertising or product endorsement purposes.

U.S. Government Printing Office: 1997/683-051-60036

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