Journal of Research of the National Institute of Standards ... · Brazil (43). Twelve U.S. agencies notified the WTO of ... produce regular protrusions up to 6 nm wide with essentially

Volume 104, Number 6, November–December 1999Journal of Research of the National Institute of Standards and Technology

General DevelopmentsInquiries about News Briefs, where no contact personis identified, should be referred to the Managing Editor,Journal of Research, National Institute of Standardsand Technology, Building 101, Room E215, Gaithers-burg, MD 20899-2500; telephone: (301) 975-3577.

TRACE GAS METHOD BOOSTS SENSITIVITYBigger isn’t always better. NIST chemists recentlyproved this is true for trace gas measurements of watervapor or oxygen. The team found they could makemeasurements of gas concentrations that are only 1 %of currently measurable concentrations and with a test-ing chamber that is only one-tenth the size of previousmodels.

The semiconductor industry has rigorous require-ments for the purity of gases used in the fabrication ofintegrated circuits. One way to test for impurities suchas water vapor or oxygen is a technique known as cavityring-down spectroscopy. The conventional implementa-tion of this technique involves putting a sample of thegas to be tested into a chamber about one meter longand shining an infrared laser into the enclosure. Theinfrared light bounces back and forth between twomirrors at the ends of the chamber. The laser light istuned to a wavelength that is absorbed by the moleculeto be detected. By measuring the rate that light leaksfrom the chamber, scientists can determine the concen-tration of the contaminant.

Conventional wisdom has held that longer chambersshould provide better sensitivity. Longer chambers leaklight at a slower rate, so small changes in light levelsshould be easier to detect. However, the NIST groupobserved that light wave interactions within meter-longchambers compli-cated the detected signals.

To eliminate these interactions, the NIST researchersused a pulsed laser and made a chamber only 10 cmcavity length to produce the simplest pattern, the un-

News Briefs

long. They found that tiny changes in the distancebetween the two mirrors in the chamber generateddistinct wave patterns.

By carefully controlling the laser wavelength andwanted interactions were eliminated and sensitivity ofthe method was enhanced greatly.

For technical information, contact Roger van Zee,(301) 975-2363.Media Contact: Linda Joy (301) 975-4403; [email protected].

NIST CENTER DISTRIBUTES DRAFTTECHNICAL REGULATIONSDraft technical regulations concerning toys, electricalappliances, chemicals, dyes and telecommunicationsequipment topped the list of inquiries that NIST fieldedlast year in its role as the U.S. inquiry point for ques-tions on proposed domestic and foreign rules that mayaffect international trade.

Under the World Trade Organization’s (WTO) Agree-ment on Technical Barriers to Trade, governments of theinternational body’s 133 member countries are requiredto notify the WTO of prospective regulatory measuresthat may pose obstacles to market entry. The WTO, inturn, makes these one-page notifications available toNIST’s National Center for Standards and CertificationInformation (NCSCI) and to other inquiry points aroundthe globe. NCSCI and its counterparts distribute thenotifications to domestic industrial organizations,government agencies and other groups to encouragereview and comment. NCSCI also provides full-textcopies of the draft regulations.

To allow for adequate review, NCSCI explains in itsnewly issued annual report, the WTO recommends acomment period of at least 60 days. In 1998, the averagewas 36 days for the 615 notifications issued by 39 WTOmembers. At 89, the Netherlands issued the largestnumber, followed by Belgium (49), Israel (46) andBrazil (43). Twelve U.S. agencies notified the WTO ofa total of 33 proposed regulations in areas ranging from

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children’s sleepwear to spark ignition engines. Thecomment period for these proposals averaged 49 days.

In 1998, NCSCI staff responded to 240 inquiries onU.S. and foreign proposed regulations. The NIST centeralso provides translation services and transmitsU.S. industry comments on proposed regulations toforeign governments. The center offers a WTO Hotline,which provides a recorded summary of the latestnotifications of proposed foreign regulations. Thenumber is (301) 975-4041.

For more information on NCSCI and its responsi-bilities under the TBT Agreement, contact JoAnneOverman, Standards Information Program, (301) 975-4037. To get a copy of NCSCI’s annual report on TBTAgreement activities, contact NCSCI, (301) 975-4040,[email protected] Contact: Mark Bello, (301) 975-3776; [email protected].

NEW STANDARD DEBUTS AT SECOND eBOOKCONFERENCEElectronic books (also known as eBooks) are integratedproducts that combine features found in books andcomputers. For example, touch screen technologyallows a reader to touch an unfamiliar word to get animmediate dictionary definition. Touching the screenelsewhere can make the print larger or smaller.

The emerging industry’s second conference,Electronic Book ‘99, was held in September 1999, atNIST Gaithersburg. Highlighting the event for thenearly 600 attendees from book publishers, hardwareand software producers, and eBook manufacturers wasthe announcement of the first Open eBook PublicationStructure Specification.

The technical specification developed by industryleaders creates a universal way to format text forelectronic books. The use of a single format forelectronic books is expected to accelerate the availabil-ity of electronic reading material. For example, thespecification for eBook file and format structureis based on HTML and XML, the languages used toformat information for web sites. A publisher canformat a title once according to the specification and thecontent will be compatible with a wide variety ofreading devices.

To download the Open eBook Publication StructureSpecification, go to www.openebook.org on the WorldWide Web. For technical information, contact VictorMcCrary, NIST, 100 Bureau Drive, Stop 8951,Gaithersburg, MD 20899-8951, (301) 975-4321,[email protected] Contact: Philip Bulman, (301) 975-5661;[email protected].

VORTICES IMAGED IN BOSE-EINSTEINCONDENSATESNIST and University of Colorado researchers havecreated and imaged the first vortices ever seen in Bose-Einstein condensates, a form of matter first created in1995. The condensate is a tiny, spherical ball of mag-netically trapped rubidium gas atoms cooled to less than10–6 K, in which the atoms exhibit their quantummechanical wave-like properties and coalesce into akind of “superatom.”

All along the axis of the ball is a central region ofswirling motion that resembles aminiaturized tornado.The center of the vortex, like the “eye” of a tornado, isfilled with relatively calm, nonrotating gas. The conceptof vortices lies at the heart of scientific understandingof residual dissipation (i.e., resistance) in nominallyviscosity-free substances such as superfluids and super-conductors. Ongoing studies of the “captive” vortex willshed light on this complex problem.

This achievement was reported in the Sept. 27 issueof Physical Review Letters.Media Contact: Collier Smith (303) 497-3198; [email protected].

PHYSICISTS CATCH BEST WAVES EVERFROM IMPROVED SURF IIIUpgrades to the Synchrotron Ultraviolet RadiationFacility at NIST are yielding greatly improved calibra-tions for a wide variety of optic and photonic devicesfrom satellite instruments to medical lasers and environ-mental monitoring devices. The improved NIST syn-chrotron facility is designed to be the “nation’s standardlight bulb,” a resource for optical calibrations forU.S. industry as well as government and academicresearchers.

The facility, known as SURF III (which at more than180 tons of solid steel may be the world’s heaviest “lightbulb”) soon will be helping manufacturers improve avariety of processes. SURF III replaces SURF II, whichserved as the national synchrotron radiation standardfrom 1974 to 1998. Synchrotron radiation is the lightemitted by electrons as they are propelled around adonut-shaped ring in a strong magnetic field. The lightemitted from SURF III covers the infrared, visible,ultraviolet and extends into the x-ray region of theelectromagnetic spectrum. It is exceptionally pure, andscientists can tune it to a desired wavelength to probeand measure a wide variety of materials and devices.

Measurements at SURF III will be much more accu-rate due to several improvements in the magnetic field,which is more uniform and much stronger than previ-ously available in SURF II. Since variations in themagnetic field are extraordinarily small (only about 1 %

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of the variations of the field in SURF II’s magnet),electrons in the storage ring move in nearly perfectcircular orbits. The result is significant improvement inthe uncertainty of irradiance measurements at any givenwavelength. Additionally, SURF III has two more beam-lines than SURF II and a new accelerator control system.

More details on SURF III are available on the WorldWide Web at www.physics.nist.gov/SURF. For techni-cal information, contact Andrew Hamilton, (301) 975-6381, [email protected] Contact: Linda Joy (301) 975-4403; [email protected].

NIST MODELS OF ELECTRONICCOMPONENTS BENEFIT U.S. INDUSTRYAND SOCIETYIndustry and society are using mathematical codesdeveloped by NIST to design power electronic systemsfor automotive and consumer electronics. These mathe-matical models are providing important benefits tosociety, including decreased production costs, higherquality and lower prices for consumer goods andincreased energy efficiency. The benefits are detailed ina report recently completed by a research institute forNIST, which developed the models.

The models have resulted in improved productioncosts for systems utilizing a type of device known asinsulated-gate bipolar transistors (IGBTs). IGBTs areelectronic switches that enable sophisticated electroniccircuits to use small amounts of electricity to controldevices that require much larger amounts of electricity.Applications include:

• automotive ignition systems;

• “adjustable speed drives,” which enable electricmotors to run more efficiently and provide moreaccurate control of precision equipment such asrobotic machinery and x-ray machines;

• compressors for refrigeration and air conditioning;

• controls for household appliances;

• equipment used to ensure the smooth flow ofpower during severe storms and the efficient regu-lation of power in factories; and

• industrial technologiessuch as welding and elec-troplating.

The models are used in software to simulate howIGBTs perform, enabling manufacturers to design andperfect “virtual prototypes” before investing in theparts, material and labor needed to build the actualprototypes.Contact: Allen R. Hefner, Jr., (301) 975-2071; [email protected].

SCANNING PROBE MICROSCOPE OBSERVESSURFACE MODIFICATIONS BY EXOTIC IONBEAMSIon beams are a relative newcomer among the technol-ogy tools available to industry, but already numerousapplications have been developed in areas such asmicroelectronics, deep space propulsion, and medicine.In most cases, stripping a single electron from the con-stituent atom and then accelerating the ion to highvelocity using electric fields forms the ion beam. Thekinetic energy of the ions is then used to perform thetask at hand. A different approach is being explored atthe NIST Electron Beam Ion Trap facility, where ionsthat have a huge charge—10 to 100 times higher thanconventional ion beams—are being produced andstudied. These exotic highly charged ions producestrong electric fields themselves and utilize their largefree internal potential energy, instead of their kineticenergy, to produce changes in materials.

To explore these changes, NIST researchers havebombarded various surfaces under ultrahigh vacuumconditions and then observed them with atomic resolu-tion using a scanning probe microscope that is inte-grated into the same vacuum chamber. Recent resultson graphite, a semimetal, using 23- and 44-times ion-ized xenon, show that individual highly charged ionsproduce regular protrusions up to 6 nm wide withessentially 100 % efficiency. When the ion charge isvaried, while keeping the kinetic energy constant, theresearchers observe the size of the features to vary by afactor of 2. The NIST work extends similar Japanesework into a regime in which the available potentialenergy of the ion is 50 times stronger and the ion-in-duced features are large enough to be “mesoscopic” orbetween the atomic range (governed by quantummechanics) and the macroscopic range (governed byensemble averages).CONTACT: Ronaldo Minniti, (301) 975-3131;[email protected] or Laura Ratliff, (301) 975-6580; [email protected] or John Gillaspy,(301) 975-3236; [email protected].

UNRAVELING THE PUZZLE OF MOLECULARSIEVE CIT-1Zeolitic molecular sieves are made mostly of siliconand oxygen and have tiny, precise holes that will onlyfit some molecules, so for example, gasoline can fitinside, but not crude oil. They are used commercially tomake gasoline, separate air into oxygen and nitrogen,capture radioactive ions; they can be found between thepanes of double-pane windows and are even put inlaundry detergents to soften water. Making thesemolecular sieve materials is as much an art as a science

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because so little is understood about how these materialsform. One important question is why two reasonablydifferent trimethylammonium cations will coax silicon,oxygen, and other atoms into exactly the right positionsto make the molecular sieve CIT-1. In one cation, theammonium group is attached to a tricyclodecane ringand in the other cation, the ammonium group is attachedto a myrtanyl ring. However, moving the ammoniumgroup over by carbon atom along the myrtanyl ringmakes a cation that cannot be used to make a molecularsieve in the CIT-1 family. Researchers at NIST, alongwith collaborators at two universities, studied the CIT-1zeolite, while the holes were plugged with ammoniumcations. They used neutron and synchrotron diffractionas well as computer modeling and found that the shapeof the cations that make CIT-1 were matched perfectlyto the holes. However, when the researchers moved theammonium group one position, the subtle shape changewas just enough to keep the cations from fitting. Thiskind of information will help other researchers find newways to make molecular sieves.CONTACT: Brian Toby, (301) 975-4297; [email protected].

NCNR CONFIRMS SILICONE-FILLER MODELAND ACHIEVES A MEASURE BEYONDNIST researchers, in collaboration with a private com-pany, have completed a study of filled polymers usingsmall-angle neutron scattering (SANS) instrumentationat the NIST Center for Neutron Research (NCNR). Themeasurements probed the influence of fillers on thesilicone polymer chain dimensions as a function of fillerconcentration and polymer molecular mass. Siliconepolymers blended with particulate fillers are used com-mercially in rubber products and sealants. The interac-tions between the fillers and the polymers are key factorsthat influence product performance.

Molecular simulations have predicted that polymerchain dimension in the presence of fillers is a functionof the filler particle size and concentration. However,tests of these predictions have not been available.

The SANS measurements showed that polymerchains which are approximately the same size as thefiller particle in the unfilled material experience adecrease in chain dimensions at all filler concentrations.In contrast, for larger chains, at low filler concentra-tions, an increase in chain dimensions relative to theunfilled chain dimensions is observed. Both results arein agreement with existing predictions from molecularsimulations.

However, at even higher filler contents, which arebeyond the scope of the molecular simulations, the chaindimensions reach a maximum value before decreasingto values that are still larger than the unfilled chain

dimensions. A qualitative excluded-volume model wasproposed to account for the experimental results. Theextension of the experimental data beyond the existingcalculations provides researchers with the necessarydata to supplement current predictions. Furthermore,the measurements suggest that changes in chaindimensions in filled polymers should be consideredwhen predicting their mechanical performance.CONTACT: Alan I. Nakatani, (301) 975-6782; [email protected].

MOLECULAR ORIENTATION FOUND TOAFFECT WEAR IN ARTIFICIAL JOINTSUltrahigh molecular weight polyethylene (UHMWPE) isthe material of choice for artificial joint replacement inorthopedic practice. Cobalt and chromium alloy is com-monly used as the counterface against the UHMWPE.This material pair is currently used for hip and kneereplacements and has proven to be durable and biocom-patible. In the search for improved biomaterials, NISTand four private companies have teamed together toconduct research on understanding the wear mecha-nisms of these materials.

UHMWPE used in joints has an average relativeatomic mass of 4 million to 6 million. Cross-linking ofthis material has produced extremely low wear. Themechanism of why cross-linking reduces wear is notunderstood. Using the Brookhaven Synchrotron ultra-soft beam line, NIST scientists have been able to mea-sure quantitatively the degree of molecular orientation ofUHMWPE as a function of rubbing direction andcycles.

Results suggest that the polymer is easily oriented byshear at the surface layer. If the motion is unidirectional,all the chains would align along the direction of motion,producing a semi-glassy solid which is prone to frac-ture. By cross-linking the amorphous region of the poly-mer, the molecular orientation from rubbing is reducedseverely, producing much better wear resistance.CONTACT: Stephen Hsu, (301) 975-6119; [email protected].

SILVER-BASED SUBSTITUTE FORMERCURY-CONTAINING DENTAL ALLOYSAs a result of a 4 year long program supported by theNational Institute of Dental Research, NIST researchershave concluded the development of a mercury-freemetallic alternative for conventional dental amalgams.

The use of mercury-containing dental restoratives isrestricted severely in Japan and much of Europe. Severalalternative materials are in use, but none of them iscompletely satisfactory. While mercury-containingrestoratives are still in use in the United States, there has

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often been discussion of restricting their use, and it is,therefore, desirable that a better alternative materialshould be available.

The technology developed at NIST is based on theability of silver surfaces to adhere (cold weld) to eachother after being treated in dilute fluoboric acid. Silverparticles that have been immersed in such acid can behand-consolidated into cohesive solids (78 % theoreticaldensity) using conventional dental tools. Over the courseof the program, several forms of silver powder wereevaluated, and it was determined that the best source ofsilver was obtained from a two-solution chemical pre-cipitation process (patent pending). The silver powdercharacteristics required for optimum hand consolidationproperties also were determined.

Two of the most important parameters are theagglomerate size and individual particle size of thesilver powder. Dramatic increase in both the transverserupture strength and density of hand consolidatedsamples was achieved by optimizing the precipitationprocess and annealing the silver powder. Acid-assistedconsolidation (three patents, two issued and one pend-ing), however, was the major finding, which makessilver powder possible as a mercury-free metallicrestorative because the acid removes the silver surfaceoxide and thereby promotes cold welding.

Using the current technology, hand consolidatedsilver equals or exceeds the transverse rupture strength,shear strength, creep, toughness, corrosion resistance,microleakage, cyclic contact fatigue, and wear proper-ties of conventional amalgam. The results of in vitrobiocompatibility testing have shown the mercury-freerestorative to equal or exceed the biocompatability ofmercury amalgams. Licensing of this technology isavailable through the Office of Technology Partnerships.CONTACT: Christian E. Johnson, (301) 975-6409;[email protected].

THE DISPUTED DISCOVERY OF ELEMENT43: A RE-EXAMINATION OF AN ELEGANTEARLY USE OF WAVELENGTH DISPERSIVEX-RAY MICROANALYSISTypical modern histories of the discovery of the chemi-cal elements report that element 43 was discovered in1937 by Perrier and Segre. According to these accounts,the discovery was made by chemical separation in asample of deuteron-bombarded molybdenum, suppliedby E. Lawrence, and thus represents the first discoveryof an element produced artificially and is the reason forthe name “technetium” (Tc) chosen by the investigators.Some accounts might note in passing that the elementwas reported as discovered in 1925 by Noddack, Tacke,and Berg utilizing x-ray emission spectroscopy in

natural samples and called “masurium” (Ma). Thesereports, however, invariably call this discovery erro-neous and sometimes refer to the investigators (typicallyleft unnamed) as “deluded.”

The fate of this early investigation has become anobject of study by historians of science. Recently,Van Assche concluded that the experiment of Noddacket al. seemed self-consistent and valid. His conclusionshave been the subject of some debate, with supporterson both sides.

To test if the claims of Noddack et al. are plausible, aNIST scientist utilized the NIST x-ray database andspectral analyzer program DTSA to simulate the 1925data. The experimental configuration was deduced fromthe original paper and simulations were made for arange of compositions for the residue suggested byVan Assche. The relative intensities of the various x-raylines and the peak-to-background ratios were deter-mined and compared to the original spectrum.

The x-ray database in DTSA showed no interferencesfor lines at the Tc/Ma K-series wavelengths that wereconsistent with the Noddack et al. spectrum. The linesattributed to Ma appear consistent with element 43 at avalue of at least five times the detection limit. The bulkcomposition (mole fractions) of a sample consistent withNodack’s spectrum is: 70 % Nb, 20 % Mo, 7.6 %Ma(Tc), and 2.3 % Ru. The mass of Ma(Tc) calculatedfrom the peak-to-background ratios is consistent withthe amount expected from spontaneous fission of the Upresent in their starting material. The NIST simulationprovides compelling support for the 1925 spectralclaims and demonstrates the forensic capabilities en-abled by recent advances in measurement science.CONTACT: John T. Armstrong, (301) 975-3929; [email protected].

TRANSITION-EDGE X-RAYMICROCALORIMETERS ACHIEVE NEWBEST-IN-THE-WORLD ENERGYRESOLUTIONSNIST researchers have successfully fabricated new x-raymicrocalorimeters with best-in-the-world energy resolu-tion for nondispersive detectors. An energy resolution of4.5 eV60.1 eV at 5.9 keV was achieved for x rays froman Fe55 radioactive source using a microcalorimeter witha newly developed Mo-Cu superconducting transition-edge thermometer. This detector was fabricated using afully photolithographic process on a Si3N4 membranestructure micromachined in a “flyswatter” geometry tocontrol the thermal conductance. The ability to pho-tolithographically fabricate detectors will allow the con-struction of microcalorimeter arrays for imaging or forincreased area and total count rate. In addition, another

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best-in-the-world energy resolution of 2.0 eV60.1 eVat 1.5 keV was achieved using a low-energy-band transi-tion-edge microcalorimeter fabricated with the groupsoriginal shadow-mask lithography process. This detec-tor is designed for use in low-beam-voltage x-ray micro-analysis, particularly to identify small contaminantparticles in the semiconductor industry. It already hasbeen used to observe the x-ray chemical shift in Albetween particles of Al and Al2O3, and the Ti chemicalshift between Ti and TiN in thin films.CONTACT: Kent Irwin, (303) 497-5911; [email protected] or David Wollman, (303) 497-7457;[email protected].

NEW SINGLE-ELECTRON TUNNELINGCAPACITANCE STANDARDA prototype of a new capacitance standard based oncounting electrons was recently developed by NISTscientists. The new “SET capacitance standard” wascreated by combining single-electron tunneling (SET)devices, which allow precise manipulation of electrons,with a cryogenic vacuum-gap capacitor having nearlyideal properties. The current prototype has a fractionalrepeatability of 3310–7 and agrees with NISTs primarycapacitance standard within the 2310–6 relative uncer-tainty of the comparison. The researchers expect that atotal relative uncertainty of 1310–7 or less will be pos-sible with further work. By exploiting the quantizationof the electron charge, the SET capacitance standardoffers a natural or quantum basis for capacitance metrol-ogy, analogous to the voltage standard based on theJosephson effect and the resistance standard based onthe quantum Hall effect. The new standard was de-scribed in an article in the Sept. 10, 1999 issue ofScience.CONTACT: David Rudman, (303) 497-5081; [email protected].

NEW MEASUREMENT SERVICE ANNOUNCEDFOR 193 nm LASER POWER METERCALIBRATIONSNIST is now offering measurement services for thecalibration of laser power and energy meters used withargon fluoride (ArF) excimer lasers emitting radiationat 193 nm. The explosive growth of ArF excimer laser-based systems for eye surgery and for high-resolutionphotolithography have resulted in an urgent needfor better measurement standards and techniques forcharacterizing the pulsed, ultraviolet radiation producedby these lasers. Current computer microprocessor andmemory chips require feature sizes that can be achievedonly by using the short-wavelength radiation produced

by sources such as excimer lasers. Corneal sculptingtechniques (e.g., PRK [photo-refractive keratectomy]and LASIK [laser in situ keratomileusis]) use the ArFlaser radiation to correct or improve certain visionimpairments. NIST scientists designed and built twoelectrically calibrated calorimeters, which are used asprimary standards in a specially designed, beamsplitter-based measurement system to perform the calibrationmeasurements in a purged-enclosure environment.CONTACT: Thomas R. Scott, (301) 975-3651; [email protected].

JOINT EXPERIMENT ESTABLISHESCONFIDENCE IN TEMPERATURE PROBESA joint experiment between NIST and a private com-pany established confidence in both NIST’s and thecompany’s temperature probes used to measure shortduration, small magnitude temperature changes of amolecular beam epitaxy (MBE) grown compound semi-conductor sample with a sensitivity of about 18C.Knowledge of these dynamic growth conditions ismissed by conventional thermocouple temperatureprobes. This experiment provided the company withinformation vitally needed to evaluate future markets fortheir products, and may lead to improved device perfor-mance.

Last spring, the company installed one of their emis-sivity-corrected pyrometer temperature sensors NIST’sMBE chamber. The sensor works by measuring lightemitted from the wafer during growth, while a compara-ble sensor already in place on the NIST MBE deter-mines temperature by measuring light absorption andreflectance during sample growth. The sensor improveson existing pyrometers by self-calibrating as the opticalproperties of the wafer change during deposition. Thejoint experiment demonstrated compatible results withboth approaches, which boosted confidence in eachmethod.

The company is a leading materials science companyin the field of compound semiconductors. Compoundsemiconductors are materials fundamental to the manu-facture of a broad range of commercial devices, such ashigh-speed transistors for cellular phones, solar cells forsatellites, laser diodes for telecommunications, and highbrightness light-emitting diodes. The company leads theworld in the sales and manufacture of metal organicchemical vapor deposition (MOCVD) systems used toprepare mainstream compound semiconductor thinfilms (such as gallium arsenide, indium phosphide, andgallium nitride) on four- and six-inch wafer substrates.CONTACT: Jonathan Guyer, (301) 975-5329; [email protected].

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NIST RESEARCHERS COMPARE ANDCHARACTERIZE DIELECTRICMEASUREMENT METHODS FOR CIRCUITBOARDS, PRINTED WIRING BOARDS,AND SUBSTRATESNIST staff have evaluated a wide range of dielectricmeasurement methods used on thin materials such ascircuit boards, printed wiring boards, and substrates.Dielectric measurements are extremely important tomanufacturers of circuit-board and substrate materialsespecially as the frequency of operation increases. Inmost applications it is important to measure the dielec-tric constant with a relative uncertainty of 2 %. It alsois important to characterize the loss in these materialssince in electronic applications loss produces unwantedheating. In this study, the most commonly used tech-niques used for measurements of thin dielectric materi-als were compared and uncertainties calculated. It wasfound that the full-sheet resonance technique workswell for the dielectric constant but not for the loss in thematerial. The re-entrant cavity method works well forboth the dielectric constant and loss but is limited tomaterials of thickness greater than 1 mm. It was con-cluded that dielectric-resonator techniques produce themost accurate results. The results of NIST’s study ondielectric measurement methods on thin materials havebeen summarized in NIST Technical Note 1512.CONTACT: Robert M. Judish, (303) 497-3380;[email protected].

NIST RESEARCHERS DEVELOP BROADBANDMEASUREMENT METHOD TOCHARACTERIZE THIN FILMSTo improve the electrical performance of interconnects,the semiconductor industry is replacing traditionalsilicon dioxide thin films with lower permittivity(low-k) thin films. Reducing the permittivity of thedielectric separating the interconnects decreases theparasitic capacitive effects. As a result, smaller inter-connects that operate at higher frequencies are feasible.Although many candidate low-k thin film materialsexist, the permittivity of many of these new materialsremains relatively unknown, especially at high frequen-cies.

NIST researchers, in collaboration with SEMA-TECH, have developed a new measurement method forcharacterizing the permittivity of dielectric thin films.The method utilizes printed microstrip transmission linetest structures that incorporate the low-k thin film. Frommeasurements of the test structures propagation con-stant and characteristic impedance, the thin film permit-tivity is determined over a frequency range of 50 MHzto 40 GHz. By measuring both the propagation constant

and characteristic impedance, they demonstrated theability to separate the electrical properties of the dielec-tric thin film from the metal conductors. Recentmeasurements on both low-k and silicon dioxide thinfilms confirm that the relative uncertainty of themeasurement of permittivity is within the goal of65 %.CONTACT: Jim Baker-Jarvis, (303) 497-5621; [email protected].

THINNEST CYLINDRICAL ARTIFACTS EVERMEASURED BY NISTNIST scientists recently completed diameter measure-ments on a set of ultra-thin nickel-alloy fibers, only13 mm in diameter. These artifacts will be used toprovide traceable calibrations that will improve manu-facturing of a new generation of carbon fibers. Thefibers are the thinnest cylindrical artifacts ever mea-sured by NIST; this measurement is indicative of newand expanding traceability requirements of emergingindustries.

Measurement of the artifacts was made possiblethanks to a unique contact micrometer designed byNIST scientists. A 50 mm section of fiber was mountedwith wax in a thin aluminum frame to allow for easymanipulation of the artifacts. Each fiber was twistedapproximately two rotations between the wax mountsallowing for sampling of two-point roundness errors ofthe fiber. Measurements were made at three appliedforces on one of the samples to determine the elasticdeformation of the material. The expanded uncertainty(coverage factork= 2 ) for the measurements was calcu-lated to be 90 nm, with the primary source ofuncertainty being the fiber taper and roundnessgeometry.CONTACT: John Stoup, (301) 975-3476; [email protected].

NIST COOLS IT AGAIN!A NIST researcher has observed a new form ofmatter—a Fermi degenerate gas. Every particle innature can be classified as either a fermion—possessinga half integral value for spin—or a boson—possessingan integral value of spin. Fermions are subatomic mattersuch as the proton, neutron, electron, and neutrinos.Their behavior is described by Fermi-Dirac statistics.The most common example of the boson is a photon,and Bose-Einstein statistics describe the behavior oftheir systems. Atoms are composed of these fundamen-tal particles and also can be either fermions or bosonsdepending upon their resultant spin.

Using techniques and insight gained with the discov-ery of the Bose-Einstein condensate (BEC), a NIST

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researcher and a graudate student from the University ofColorado cooled approximately 1 million potassium-40fermions to 290 nK—the coolest kinetic temperature forfermions ever observed. Unlike the boson, which willfall readily into the lowest energy state and condense,the fermion is an unwilling participant due to the Pauliexclusion principle, which prohibits two identical parti-cles from occupying the same state and, therefore, stopsthe collisional thermalization process. The cooling offermions is, in a way, more difficult than the cooling ofbosons.

To overcome the Pauli exclusion obstacle to coolingfermions, the40K atoms were magnetically trapped intwo different spin states and microwave radiation wasused to selectively enable the evaporative coolingprocess. The resultant ultracold, nearly ideal, Fermi gasprovided an environment ripe for observing quantumstatistics.

Possible long-range applications of this work includeatomic superconductivity and more accurate clocks.

This work was first reported inScience,Sept. 10,1999, and likely will be named one of the most signifi-cant achievements in physics in 1999.CONTACT: Jim Faller, (303) 492-8509; [email protected].

TWO NEW PRECISION MEASUREMENTGRANTS AWARDED FOR FY 2000Two new $50 000 NIST Precision Measurement Grantshave been awarded for fiscal year 2000. The recipients,Elisabeth G. Gwinn of the University of California,Santa Barbara, and Protik Majumder of WilliamsCollege, were selected from an initial group of 26candidates. NIST sponsors these grants to promotefundamental research in measurement science in U.S.colleges and universities and to foster contacts betweenNIST scientists and researchers in the academiccommunity actively engaged in such work.

The aim of Gwinn’s project, “Combining the Quan-tum Hall and AC Josephson Effects for Electric CurrentMetrology,” is to develop a new quantum standard ofelectric current by combing the ac Josephson effect (JE)and the quantum Hall effect (QHE) in an integrated,unique way. Further, this will allow one to check theinternal consistency of the value of the elementarycharge e that is characteristic of a single electron tunnel-ing device and the combined JE and QHE. An importantaspect of this work is the development of a new kind ofJosephson junction array based on a superconductor,semiconductor-quantum-well, superconductor tunnel

ing device or S/QW/S, and a cryogenic semiconductorswitch.

The aim of Majumder’s project is to develop a high-finesse laser ring-cavity and to use it to search for long-range electron-nucleon forces in atomic thallium thatviolate time-reversal symmetry (T) but conserve parity(P). The proposed experiment would improve limits onpossible T-violating (but P-conserving) forces of thistype by four to five orders of magnitude. In this work,the signature for T-violation is a shift of the phase ofcounter propagating laser beams in the special ring-cavity when the optical path length for the beams ispossibly changed when the direction of an electric fieldthrough which the beams pass is reversed. Observationof T-violation in atomic thallium would clarify thepoorly understood observation of charge symmetry (C)violation and P-violation in the decay of the kaon andtest the standard model of particle physics.CONTACT: Barry N. Taylor, (301) 975-4220;[email protected].

NIST CONTRIBUTES TO RUSSIAN-AMERICANSOLAR NEUTRINO EXPERIMENTFor more than 30 years, one of the outstanding prob-lems in astrophysics has been the measured deficit ofneutrinos produced in the solar interior. Several experi-ments have now confirmed this deficit. Since January1990, the Russian-American Solar Neutrino Experi-ment (SAGE) has carried out measurements of the cap-ture rate of neutrinos in 60 metric tons of ultrapureliquid gallium as a measurement of the solar neutrinoflux. The reaction71Ga(n,e–)→ 71Ge provides the onlypresently feasible means to measure the predominantneutrinos produced by the fusion of protons in the sun.A NIST scientist is one of the U.S. collaborators on thisexperiment. The detector resides in an undergroundlaboratory in the Caucasus Mountains of southernRussia.

In an article to appear inPhysical Review C,theSAGE team present the analysis of 8 years of measure-ments of the solar neutrino flux. NIST has participatedin the calibration of the detector using a 19 PBq,51Crradionuclidic source along with analysis of the data.The result represents only about half of the predictedflux given by the Standard Solar Model. Although thismodel describing the processes of nuclear fusion in thesun has been very successful in explaining numeroussolar features, the deficit in the solar neutrino flux stillremains one of the unresolved problems.CONTACT: Jeffrey Nico, (301) 975-4663; [email protected].

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HELP TOOLBOX USER’S GUIDE PUBLISHEDNIST Technical Note 1428 has been published as auser’s guide to the High Dimensional Empirical LinearPrediction (HELP) Toolbox, which was developed as asoftware optimization tool designed specifically to meetthe requirements of test and measurement engineers.The approach is based on a simple mathematical modelthat relates the device response at all candidate testconditions to a set of underlying variables. Once anaccurate model has been developed, algebraic opera-tions on the model are used to:• select an optimal set of test points that will minimize

the effort to achieve a specified level of confidence,

• estimate the parameters of the model from meas-urements made at the selected test points,

• predict the response of the device at all candidatetest points (from measurements made at the selectedtest points) as a basis for accepting or rejectingunits, and

• compute statistical intervals (uncertainty bounds)for the predicted response, and test the validity ofthe model, on-line.

The entire process, including model development,can be performed with the HELP Toolbox, which is agraphical software package for use with a commercialmathematical programming language. While a generalunderstanding of the underlying principles is desirable,no mathematical programming is required of the opera-tor. HELP places special emphasis on empirical model-ing using measurement data collected previously ondevices similar to the units under test. In addition to testoptimization, the HELP Toolbox is also useful forexploring the structures that underlie the behavior of thetested devices.

For many electronic devices and instruments, it is notphysically or economically feasible to perform exhaus-tive testing. Therefore, test engineers must formulateabbreviated test plans that are economical to executebut still yield accurate measures of the overall perfor-mance of the tested products. Examples of products thatcan benefit from using the HELP approach range fromprogrammable filters to analog-to-digital (A/D)and digital-to-analog (D/A) converters to multirange,multifunction precision instruments.CONTACT: Barry A. Bell, (301) 975-2419; [email protected].

NIST HOSTS WORKSHOP ON PRESSINGNEEDS IN UV METROLOGYA NIST physicist jointly organized and conducted aWorkshop on the Pressing Needs in UltravioletMetrology in July 1999, with Rad Tech International.

Rad Tech is an industry association with more than 700members that supply and use ultraviolet (UV) andelectron beam (EB) equipment, raw materials, andformulated products. Over 60 people attended, includ-ing manufacturers of UV sources and metrology instru-mentation, UV curing and coating processors, andrepresentatives from the photolithography and semi-conductor industries.

The goal of the meeting was to identify the industrialneeds for ultraviolet metrology. The UV curingproces-sors and photolithographers detailed their urgent needfor improved UV standards and measurement methods.UV curing is a rapidly growing technology because iteliminates the need for volatile chemicals. UV, alongwith EB and visible light, are proven technologiesthatinstantly “cure” or polymerize inks, coatings, and ad-hesives, making industrial processes more efficient,while virtually eliminating the air pollution and wastegenerated by traditional methods. UV/EB is used in awide range of applications to protect, decorate, or bonditems such as wood, fiber optics, compact discs, creditcards, beverage cans, food packaging, magazine covers,and automotive parts.

Representatives from the semiconductor industryexpressed the need for improvements in metrology forthe measurement of optical constants and UV radiationfor photolithography processing. Photolithography is theprocess used for building microelectronic componentson top of silicon wafers. A photoresist coating is appliedto the wafer that reacts to UV light and is an integral stepin the process.

A follow-up took place at the fall meeting of RadTech in October in Arlington, VA. It is anticipated thata NIST metrology program will be developed to addressthe needs of the UV/EB industries.CONTACT: Jonathan Hardis, (301) 975-2373; [email protected] or Rajeev Gupta, (301) 975-2325;[email protected].

WORKSHOP HELD ON CHARACTERIZATIONOF NUCLEAR REACTOR PRESSURE VESSELSTEELSA workshop entitled “Nondestructive Characterizationof Embrittlement in Reactor Pressure Vessel Steels” washeld at NIST Boulder in July 1999. The workshop waspart of an ongoing NIST research program sponsored bythe Nuclear Regulatory Commission. Experts in assess-ing radiation embrittlement of reactor pressure vesselsprovided overviews of the programs for monitoringembrittlement in the United States, Europe, and Japan.Researchers from universities and government laborato-ries in Germany, France, Belgium, and Japan describedtheir R&D programs for developing nondestructivetechniques for detecting embrittlement in the steels

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used for pressure vessels in their countries. Many of theinvestigations used very sophisticated microscopy tech-niques to elucidate the mechanisms of embrittlement onan atomic level and thus defined the conditions that thenondestructive methods must detect. NIST scientistspresented the results of their research on eight physicalproperties that were found to be sensitive to themicrostructures associated with embrittlement andwhich could form the basis for non-destructive testingprocedures. On the last day of the workshop, attendeesaddressed the preparation of a roadmap to guide futureresearch toward the development of non-destructiveevaluation methods that could be introduced into themaintenance programs of existing nuclear power plantsto increase their safety and extend the useful life of theirpressure vessels.CONTACT: George Alers, (303) 497-7899; [email protected].

CIPM WORKING GROUP FOR FLOWMEASUREMENTS ESTABLISHEDAt its Fall 1999 meeting, the International Committeefor Weights and Measures (CIPM) officially establisheda Working Group for Flow (WGF) within its Consulta-tive Committee for Mass. In 1998 the international flowmeasurement community formed an Ad Hoc Group forFlow (AHGF) that could evolve into a WGF to conductkey comparisons of the flow standards in nationalmeasurement institutes (NMIs). The AHGF was con-vened in Denver, CO, in conjunction with the recent 4thInternational Symposium for Fluid Flow Measurement.A NIST scientist was elected by this international groupto serve as chairman of the proposed WGF. A structurefor the proposed WGF was arranged, and the first meet-ing of the WGF is now scheduled for June 2000 inconjunction with the FLOMEKO 2000 Symposium inSalvador, Brazil. The central issues will be to initiatespecific key comparisons of flow standards for the wideranges of fluid and flow conditions needed by theworld’s NMIs to quantify equivalencies.CONTACT: George Mattingly, (301) 975-5939; [email protected].

BIOTECH NOLOGY HOLDS WORKSHOP ONSCANNING PROBE MICROSCOPY OF SOFTMATERIALSA NIST postdoctoral researcher organized and con-ducted a Workshop on “Scanning Probe Microscopy ofSoft Materials” in August 1999. The workshop was

attended by more than 40 researchers from NIST, otherDC area government labs, and universities as well asrepresentatives from the scanning probe microscopeindustry (molecular imaging and digital instruments).The workshop consisted of a series of talks on the usesof scanning probe microscopy to image biological,polymer, and self-assembled systems. This was followedby a discussion of issues preventing progress in the fieldthat focused on gaining a better understanding of phasemeasurements and the physical characterization ofprobe tip.CONTACT: John Woodward, (301) 975-5495; [email protected].

WORLDWIDE COMPARATIVE ASSESSMENTOF MOLECULAR MODELING ANDSIMULATIONNIST has joined with the National Science Foundationand the Department of Energy to fund a worldwidecomparative assessment of molecular modeling andsimulation. The study will focus on the development ofnew modeling and simulation technologies and thetransfer of those technologies to industry. The study willbe conducted by a blue ribbon panel of experts fromacademe and industry. Observers from NIST, theNational Science Foundation, and the Department ofEnergy will accompany the panel as it visits nationallaboratories, universities, and industries in Europe andAsia. The panel will prepare a written report that will bereleased to the public at a workshop to be held nextsummer.

Advances in computing technology and the develop-ment of new modeling and simulation methods over thepast two decades have created a significant scientificand technological resource that is becoming widely usedin industry as a source of fundamental physicochemicaland engineering properties for product and processdesign and optimization. The study, which is being runby the World Technology Evaluation Center of LoyolaCollege, will compare the state of advance in molecularmodeling and simulation in academia and nationallaboratories of the United States, Japan, the UnitedKingdom, Germany, and France. It also will assess theextent and effectiveness of transfer of this knowledge tovarious types of industries, primarily process andproduct-based ones such as chemical, energy, andmaterials. This information will be of value to U.S.researchers, academicians, strategic planners, and deci-sion makers.CONTACT: Walter J. Stevens, (301) 975-5968; [email protected].

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STANDARD FOR AUTOMATED ACROSS-THE-ROAD RADAR SYSTEMSTraditional speed enforcement involving traffic stops ondensely traveled, fast-moving urban roads is dangerousfor police officers and creates a potentially hazardousdistraction for other motorists. A better method is toautomatically photograph vehicles exceeding a specifiedamount above the posted speed and then to ticket theviolators by mail. The automated across-the-road radarsystems, popularly called “photoradars” and beginningto appear along U.S. roads, are capable of determiningthe directions, speed and type of vehicle (truck, car, ormotorcycle) crossing its radar beam and then recordingthe speed-violating vehicle along with the time, date,location speed, and other information on photographicfilm as evidence. Systems requirements and methods oftesting the performance of photoradar units appear inthe standard “Model Minimum Performance Specifica-tions for Automated Across the-Road Doppler RadarSystems” recently prepared by NIST for the NationalHighway Traffic Safety Administration.CONTACT: George Lieberman, (301) 975-4258;[email protected].

A NEW PERFORMANCE STANDARD FORPOLICE TRAFFIC RADAR DEVICESAs early as 1947, police officers began using Dopplerradar devices to enforce traffic speed laws. Alongsidethe subsequent worldwide proliferation of radar devicesamong police departments, the need arose to ensurereliable and accurate speed measurements. In 1977, theU.S. Department of Transportation’s National HighwayTraffic Safety Administration (NHTSA) entered into aninter-agency agreement with NIST to develop compre-hensive performance requirements and methods of testfor speed measuring devices, including police trafficradars. The radar performance specifications, firstpromulgated by NHTSA in 1981, have undergoneseveral revisions to keep up with the technology.The current embodiment, “Speed Measuring DevicePerformance Specifications: Radar Module” is nowbeing readied for distribution by NHTSA.CONTACT: George Lieberman, (301) 975-4258;[email protected].

CONFERENCE PROCEEDINGS PUBLISHEDON ULTRATHIN SIO 2 AND HIGH- kMATERIALS FOR ULSI GATE DIELECTRICSUltrathin SiO2 and High-k Materials for ULSI GateDielectrics, the proceedings of a recent Materials

Research Society (MRS) Symposium, was published inSeptember 1999 (highk refers to high permittivity). Thesymposium was part of the April 1999 meeting of theMRS in San Francisco, CA. The plenary speaker at thismeeting noted that at the current pace (of dimensionalshrinkage in integrated circuits) the industry wouldreach the limits of what can be accomplished with SiO2

by about 2005. The symposium is believed to be themost comprehensive to date detailing the latest researchon the potential showstopper issue of identifying a suit-able production-worthy replacement material for SiO2

as a MOS transistor gate dielectic.The 615-page proceedings gives an account of

fundamental research into the materials, processes, andmanufacturing challenges that must be resolved beforethe high-k gate stack module can be used in mainstreamIC manufacturing. The symposium, co-organized by aNIST researcher provided a means for leaders in thetechnical areas of ultrathin and high-k materials to shareresearch on critical problems in technology associatedwith present-day and near-future MOS gate dielectrics.

The proceedings contains 81 published papers fromthe more than 100 presenters at the symposium. Thesymposium was truly international, with participantsrepresenting six different continents and 34 of the 81published papers coming from countries other than theUnited States.CONTACT: Curt A. Richter, (301) 975-2082; [email protected].

NIST-DEVELOPED STANDARD BULLETSPREDICTED TO HAVE A WORLDWIDEIMPACTThe 1999 IBIS (Integrated Ballistics IdentificationSystem) users group meeting was held in August 1999,in Dallas, TX.

NIST developed prototype standard bullets in 1998.Those bullet signatures tested at NIST showed highuniformity and reproducibility. NIST standard bulletstesting results showed highly repeatable and repro-ducible IBIS scores when compared to the quality assur-ance bullets now being used. Bullet examiners believethat the unique properties of the NIST standard bulletswill make it very useful for instrument calibrations andmeasurement quality control and have a potential use forenabling nationwide and worldwide ballistics measure-ment traceability and unification.CONTACT: Junfeng Song, (301) 975-3799; [email protected].

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REALLY LARGE SCALE METROLOGY—GLOBAL POSITIONING SYSTEMMEASUREMENTS AT WASHINGTONMONUMENTAs part of a cooperative effort with the National ParkService and the National Geodetic Survey (NGS),NIST’s large scale coordinate metrology groupdesigneda metrology stand to aid in conducting a GlobalPositioning System (GPS) survey from atop theWashington Monument. A NIST machinist fabricatedthe metrology stand.

This GPS survey is part of the Height ModernizationInitiative and will determine the height of the nationalmonument. These surveys are performed on a regularbasis by NGS, usually by using conventional surveyinginstrument. This survey took advantage of the fact thatthe monument top was accessible because of currentcleaning/restoration operations. The last time that thetop of the monument was accessible was in 1934.CONTACT: Charles Fronczek, (301) 975-4079; [email protected].

NIST PUBLISHES TREC-7 PROCEEDINGSNIST published the proceedings of the seventh annualText REtrieval Conference in August 1999 as NISTSpecial Publication 500-242, The Seventh TextREtrieval Conference (TREC-7). The TREC workshopseries is sponsored by NIST and the Department ofDefense to support the text retrieval industry by provid-ing the infrastructure necessary for large-scale evalua-tion of text retrieval methodologies.TREC-7, the mostrecent workshop in the series, was held at NIST inNovember 1998, with 150 participants. Fifty-six groupsfrom 13 different countries and 19 companies attended.

The proceedings contain an overview summarizingthe retrieval tasks and main results of the conference,papers that were presented at the conference, and com-plete evaluations of individual group results. The pro-ceedings also contain “track” reports, where a track isfocused work on a particular retrieval subproblem. Thisyears reports include a summary of the “Very LargeCorpus” (VLC) track in which participants searched100 GB of web pages. VLC systems not only wereforced to handle much greater amounts of data (standardTREC collections are approximately 2 GB) but alsoto accommodate the different genre of data representedby web documents. An electronic version of theproceedings is available on the TREC web page athttp://trec.nist.gov.

In other TREC news, the Japanese National Center forScience Information Systems held the first NTCIRWorkshop on Research in Japanese Text Retrieval theend of August in Tokyo. The evaluation leading to this

workshop was based heavily on the NIST TREC modelof evaluation; NIST supported this effort with adviceand tools during the year. A NIST staff memberpresented the keynote for this workshop, which wasattended by 28 participating groups, including the majorJapanese companies involved in text retrieval and threeU.S. groups.CONTACT: Ellen Voorhees, (301) 975-3761; [email protected] or Donna Harman, (301) 975-3569;[email protected].

NIST SPONSORS INDUSTRY USABILITYREPORTING WORKSHOPThe NIST Industry USability Reporting (IUSR) projectseeks to improve the testing and reporting of softwareproduct usability, thereby reducing the uncontrolledcosts of poor usability. As part of this effort, NISTsponsored a 2 day Industry USability Reporting (IUSR)project workshop in September to begin a pilot trial tovalidate the value of reporting usability data in decision-making processes. Attendees included prominent indus-try representatives from software suppliers as well asorganizations who are large software purchasers. Thegoal of the pilot trial is to determine how well theCommon Industry Format (CIF) for usability reportingworks and to determine the value of using the format insoftware procurement.

At the meeting, vendors and consumers discussedtheir responsibilities during the pilot trial and definedthe metrics for NIST to use in measuring the effective-ness of the CIF. Participants also reviewed the CIF forreporting usability results and outlined how and whenrevisions will be made during the pilot study. Additionalrepresentatives from major corporations, not initiallyinvolved in the project, attended and many othersexpressed interest in participating in the trials, furtherpublicizing this effort to trade publications and organi-zations, and planning for including future drafts of theCIF into their business processes. For more information,see http://www.nist.gov/iusr.CONTACT: Sharon Laskowski, (301) 975-4535;[email protected].

NIST LAUNCHES CONFORMITY ASSESSMENTWEB SITEConformity-assessment issues, programs, and proce-dures are featured on a newly launched NIST web site(http://ts.nist.gov/ca). This will provide one-stop shop-ping for conformity assessment information. Thesite contains the 1999 edition ofNIST’s Directoryof Federal Government Certification and RelatedPrograms,which summarizes requirements issued by

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federal departments and independent agencies. Entriesinclude the purpose of each requirement, whethermandatory or voluntary, and methods used to ensurecompliance. sources of documentation, reciprocityarrangement, enforcement approaches, and other itemsalso are listed.

The new web site was developed in cooperation withthe recently formed conformity Assessment Network, agovernment and private-sector partnership for improv-ing business and consumer understanding of the some-times confusing procedures used to assess the worthi-ness of products and services. Testing, sampling,inspection, certification, and other conformity assess-ment methods are intended to verify that a particularproduct meets a specified level of quality or safety or toaccomplish other aims. They also can influence marketentry and business competitiveness.

The site also includes sources for information on theinternational environment management standards(International Organization for Standardization (ISO)14000), the international quality management standards(ISO 9000), certification programs related to fair laborpractices (i.e., Social Accountability 8000), a large listof acronyms, and many links to other relevant con-formity assessment sites.CONTACT: Maureen Breitenberg, (301) 975-4031;[email protected].

NIST DIGITAL MATH LIBRARY PROJECTRECEIVES NATIONAL SCIENCEFOUNDATION AWARDNIST recently received funding from the NationalScience Foundation (NSF) to support the developmentof the NIST Digital Library of Mathematical Functions(DLMF). The NIST proposal entitled “MathematicalFoundations for a Networked Scientific KnowledgeBase” was awarded $1.3 million over 3 years through theNSF Knowledge and Distributed Intelligence (KDI)program.

The DLMF will provide NIST-certified referencedata and associated information for the higher functionsof applied mathematics. Such functions possess awealth of highly technical and critically importantproperties that are used by engineers, scientists, statisti-cians, and others to aid in the construction and analysisof computational models in a wide variety of applica-tions. The DLMF will deliver this data over the WorldWide Web within a rich structure of semantic-basedrepresentation, metadata, interactive features, and inter-nal/external links. It will support diverse user require-ments such as simple lookup, complex search and

retrieval,a formula validation and discovery, automaticrule generation, interactive visualization, custom data ondemand, and pointers to software and evaluated numeri-cal methodology.

The DLMF was conceived as the successor for theNBS Handbook of Mathematical Functions (AMS 55),edited by M. Abramowitz and I. Stegun and publishedby NBS (National Bureau of Standards, now NIST) in1964. AMS 55 is possibly the most widely distributedand cited NBS/NIST technical publication of all time.(The U.S. Government Printing Office has sold morethan 150 000 copies, and commercial publishers are es-timated to have sold several times that number). TheDLMF is expected to contain more than twice as muchtechnical information as AMS 55, reflecting the contin-uing advance of the intervening 40 years.

Further information on the project can be found athttp://math.nist.gov/DigitalMathLib/.CONTACT: Ronald Boisvert, (301) 975-3812; [email protected] or Charles Clark, (301) 975-3709;[email protected] or Daniel Lozier, (301) 975-2706; [email protected].

NEW NIST LASER MEASUREMENT SERVICEHAS USERS BEAMINGArgon-fluoride excimer lasers are shining brightly inboth the medical and manufacturing worlds. Theselasers, which produce pulsed, ultraviolet radiation at awavelength of 193 nm, are commonly used in cornealsculpting techniques such as photorefractive keratec-tomy and laserin situ keratomileusis (abbreviated PRKand LASIK respectively) that correct vision impair-ments. The excimer laser’s short wavelength also makesit perfect for the high-resolution photo-lithographyneeded to manufacture faster microprocessors andlarger memory chips.

The explosive growth in ArF excimer laser usedemands that better measurement standards and tech-niques be available for calibrating these instruments.NIST scientists have designed and built two electricallycalibrated laser calorimeters to accomplish the task. Ac-curate assessments of the ArF excimer laser beam’senergy are made in an enclosed environment using aspecially designed, beamsplitter-based measurementsystem.

For technical information on this new 193 nmmeasurement service, contact Marla Dowell, MC815.01, NIST, Boulder, CO 80303; (303) 497-7455;[email protected] Contact: Fred McGehan (303) 497-3246;[email protected].

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STUDY SHEDS LIGHT ON DEGRADATION OFSELF-ASSEMBLED MONOLAYER FILMSSelf-assembled monolayer films are the basis forpromising new sensors and diagnostics currently undercommercial development for a variety of uses—every-thing from detecting genetic diseases in humans to pin-pointing pathogenic microbes in food or water.

These sensors are made of alkanethiol molecules thatorganize themselves spontaneously on a gold surface toform a uniform crystalline film just one molecule thick.Single-stranded DNA molecules are tethered to thislayer and used to latch onto complementary DNA froma solution washed over the sensor.

Until recently, self-assembled monolayers werethought to be stable in an ordinary lab environment.However, studies have shown that ozone in the air candegrade these monolayers by oxidizing the thiol portionof the alkanethiol molecules.

A team of NIST scientists examined this processusing scanning tunneling microscopy (STM) and photo-electron spectroscopy. To follow the time evolution ofthe reaction, they exposed monolayer films to increasingdoses of pure ozone while recording STM data. Thisrevealed that ozone attacks the crystalline monolayerspreferentially at the network of domain boundariesbetween the molecules. As ozone exposure increases,the reaction spreads into the domains.

The images also provided evidence of an unexpectedoccurrence: the crystalline monolayer melts and formseither a liquid or noncrystalline solid.

The NIST study points to possible strategies toimprove the monolayer’s stability in ozone, such asdecreasing the density of the domain boundaries ordecorating the boundaries with molecules that areozone-inert. The study will be reported in an upcomingissue of theJournal of the American Chemical Society.

For more information, contact Gregory E. Poirier,(301) 975-2603; [email protected], or check outwww.nist.gov/sams on the World Wide Web.Media Contact: Linda Joy (301) 975-4403; [email protected].

LONG-DISTANCE WELD MONITORINGNOW FEASIBLEQuality control has gone remote. In a recent paper, aNIST researcher in Boulder, CO, reports that he moni-tored the quality of welds made in Gaithersburg, MD,via the Internet. The welds joined a mounting bracket tothe shaft of an automobile suspension strut. A pair of 2 swelds were made with an approximately 1 s delay be-tween welds. The monitoring was done through the arcsensing monitor (known as ASM), a through-the-arcsensing system.

In both cases, the network speed was adequate totransmit the data between welds and have the ASM beready to process the next weld.

Approximately 3 kbit of data need to be transmittedfor each second of weld. The web server, the engineer-ing workstation and the database server all can run on asingle personal computer.

Quinn says that remote monitoring has the advantageof allowing informed decisions to be quickly made—from anywhere—about maximizing a welding station’sproductivity or solving operating problems that occur.The only requirement is that a reliable TransmissionControl Protocol and Internet Protocol (known as TCP/IP) network must be installed in the factory.

For a copy of the paper, 43-99, “Internet BasedManagement of Data from Welding Sensors,” contactSarabeth Harris, MC 104, NIST, Boulder, CO 80303-3337; [email protected] Contact: Fred McGehan (303) 497-3246;[email protected].

NIST TURNS OVER CMRL MANAGEMENTAFTER 70 YEARSNIST is transferring management of the ConstructionMaterials Reference Laboratory (CMRL) to the privatesector after 70 years of growth. At the same time, theCMRL’s link to NIST research is being strengthened.

Stewardship of the two CMRL program components,the Cement and Concrete Reference Laboratory (abbre-viated CCRL) and the American Association of StateHighway and Transportation Officials (AASHTO)Materials Reference Laboratory (abbreviated AMRL),changes this month. Taking over for NIST are thesponsoring organizations: AASHTO for AMRL and theAmerican Society for Testing and Materials for CCRL.Both the CCRL and AMRL will continue to operatefrom NIST.

Launched in 1929 because of concerns about thequality of cement used in the construction of federalfacilities, the CMRL now includes more than 1200laboratories that test materials used by the constructionindustry.

Participants use a variety of AASHTO and ASTMstandard test methods to help assure that high-qualitymaterials will be the norm in the American constructionindustry. These labs test everything from concrete toasphalt and serve many private-sector firms, as well asstate and local governments.

Participation in the CMRL programs is voluntary.They have grown steadily over the decades to keep upwith the demand for quality assurance in the testing ofbuilding materials such as concrete, cement, soil andasphalt. The CMRL now carries out on-site assessment

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programs for over 700 testing labs. It evaluates testequipment, identifies testing deficiencies and suppliesproficiency samples.

Currently, the CMRL distributes more than 13,000proficiency samples annually to laboratories in theUnited States, Canada, Mexico and more than a dozenother countries. The CMRL’s role in the constructionindustry is significant because inadequate testing canlead to good materials being rejected, poor materialsbeing accepted, construction delays and even structuralfailures.

Participating laboratories should not see any signifi-cant changes in the CMRL or either of its componentsas a result of the management change.

For more information, contact James Pielert, NIST,100 Bureau Drive, Stop 8622, Gaithersburg,MD 20899-8622, (301) 975-6704, [email protected] Contact: Philip Bulman (301) 975-5661; [email protected].

INTERNATIONAL MEASUREMENTS WILL NOLONGER BE BEYOND COMPAREThe United States and 37 other nations agreed recentlyto launch a system for assessing the accuracy andreliability of measurements made worldwide, aidingefforts to resolve technical and regulatory differencesthat impede global trade flows.

Efforts to link national measurement standards withina global framework were formalized in a “mutual recog-nition arrangement” signed by a NIST representative andrepresentatives of other countries participating in the21st quadrennial meeting of the Conference on Weightsand Measures earlier this month.

The arrangement calls for a systematic series of “key”measurement comparisons among the signing countries’national metrology institutes (known as NMIs). Thesecomparisons will establish how closely a particularmeasurement (of voltage, for example) performed at oneNMI agrees with results achieved in other countries.Levels of agreement among NMIs establish the basis forlinking measurements across international borders.

Such measurement traceability should make it easierfor exporters to demonstrate compliance with measure-ment requirements embodied in nations’ regulations andvoluntary standards.

Results of key comparisons will be recorded near anInternet-accessible database hosted by the InternationalBureau of Weights and Measures (BIPM) near Paris.All nations can participate in the new system. Throughits membership in one of the world’s six regionalmetrology organizations, any NMI can list its measure-

ment capabilities in a portion of the database, subject toreview by expert committees.

The database system was developed at NIST, a strongproponent of efforts to strengthen measurement trace-ability on a global basis. NIST will maintain and furtherdevelop the system.

Information on the mutual recognition arrangement isavailable on the World Wide Web at www.bipm.fr/enus/8_Key_Comparisons/key_comparisons.html.

For more information on the International Compari-sons Database, contact NIST’s Robert L. Watters, Jr.,Senior Scientific Advisor, (301) 975-4122; [email protected] Contact: Mark Bello, (301) 975-3776; [email protected].

STEPS TO STEP DOCUMENTED IN NEWPUBLICATIONNot long after manufacturers first got a taste of com-puter-aided design and computer-aided manufacturingin the 1970s, they recognized that a key to the newtechnology’s success would be the development of auniversal, unambiguous language for exchangingproduct information. The chronicle of the public-privateeffort that brought that language to life and standardizedits use can be found inSTEP: The Grand Experience,anew publication from NIST.

STEP (the STandard for the Exchange of Productmodel data also known as ISO 10303) enables compa-nies and suppliers to digitally express and share aproduct’s design, manufacturing and support processesvia computer in a standard format. The new 185-pagebook takes its readers from the definition of a drawingexchange capability (the Initial Graphics ExchangeSpecification, or IGES) in 1979 through to the futureplans for the international STEP specification. In be-tween, the story of STEP’s emergence and worldwideacceptance is divided into topical areas such as“Modeling,” “Conformance and Interoperability Test-ing” and “Managing the Process to Achieve the Product-Standards.”

Other milestones and accomplishments detailed in thetext include:

• the formation, work and contribution of PDES Inc.,the joint industry/government consortium set up toaccelerate the development and implementation ofSTEP;

• the creation of the Integrated Product InformationModel (or IPIM) in 1988, described in the book asthe “grand big daddy” summarizing all models up tothat point;

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• the first product manufactured using STEP—anautomobile connecting rod—in 1993; and

• the initial publication of ISO 10303 in 1994.

Additionally, the book features a detailed glossary ofSTEP-related terminology and an extensive biblio-graphy.

A single copy of NIST Special Publication 939 isavailable from NIST’s Manufacturing EngineeringLaboratory by sending an electronic message [email protected]. An Adobe Acrobat version on theWorld Wide Web is expected in the near future.Media Contact: Michael E. Newman (301) 975-3025;[email protected].

NIST X-RAY PATENT LICENSEDOn Aug. 12, 1999, a private company received anexclusive license to a joint invention with NIST,“Method and Apparatus for Diffraction MeasurementUsing a Scanning X-Ray Source,” NIST Docket[97-026US. The concept came from a combination of thehigh-energy x-ray diffraction technology that has beendeveloped at NIST during the past 5 years with theunique area-scanned x-ray tube developed by the privatecompany, which will take over the responsibility fordeveloping the method into commercial products.CONTACT: Tom Siewert,(303) 497-3523; [email protected].

EXCLUSIVE LICENSE GRANTED FOR SOLARWATER HEATING SYSTEMA novel system that uses the power of the sun to heatwater is about to become commercially available afteryears of development and testing at NIST. An exclusivelicense has been granted to a private company to use theNIST patented technology. Thecompany is in a uniqueposition to make use of NIST’s solar hot water heatingsystem by the use of integrated photovoltaic panels intheir sun room and skylight products.

The solar water heating system is the first to usephotovoltiac cells and computer chips to harness anddirect the sun’s energy. Photovoltaic (PV) cells are usedto convert energy from sunlight into electricity. TheNIST system was developed to use an array of PV cellsto transfer solar power to specially designed heatingelements inside a hot water tank.

The system was developed and tested at NIST’sGaithersburg campus. Several other successful pilotprojects have shown that the system works well indifferent climates.CONTACT: A. Hunter Fanney, (301) 975-5864; [email protected].

AMERICAN CONCRETE INSTITUTEACKNOWLEDGES NIST RESEARCHERSIn September 1999 the American Concrete Institute(ACI) published provisional standard ACI-ITG/T1.1-99“Acceptance Criteria for Moment Frames Based onStructural Testing.” With this standard in place, the con-struction industry has now moved forward swiftly tomake use of novel structural systems in earthquake-prone regions of the country. The most notable of thesenew structures is a 40-story high-rise office in SanFrancisco that uses precast moment-resisting concreteframesa technology that was pioneered at NIST.CONTACT: Bill Stone, (301) 975-6075; [email protected].

NEW MEASUREMENT SYSTEM FOR TESTINGTHE EFFECT OF FATIGUE ON THE CRITICALCURRENT OF SUPERCONDUCTORSA new measurement system for testing the effect ofcyclic transverse compressive stress on the criticalcurrent of superconducting wires and tapes has beendeveloped by NIST staff. The system is capable of cyclicapplication of transverse stress over 100 MPa to super-conductor samples at low temperatures, while simulta-neously applying currents of up to 300 A in magneticfields of 11 T. The system is being developed to testsuperconductors for use in large magnet systems thatwill be energized repeatedly and consequently be sub-jected to several thousand stress cycles in actual opera-tion. Static stress tests have been performed on many ofthe candidate superconductors for these systems, butpreliminary data from the new fatigue system suggeststhat additional critical-current degradation can accumu-late from cyclic loading. Because of the expense oflarge superconductor magnet systems being proposedfor particle accelerators and electric utility power condi-tioning, the apparatus will provide a unique, butrelatively inexpensive, testing capability for qualifyingsuperconductors for use in their construction.CONTACT: Jack Ekin, (303) 497-5258; [email protected].

NIST DEVELOPS KEY MEASUREMENTSFOR OPTICAL TELECOMMUNICATIONSINDUSTRYThe growth of wavelength-division multiplexing inoptical fiber systems has resulted in new measurementrequirements for a variety of optical components fortelecommunication systems. In particular, the measure-ment of group delay, or the propagation time delayamong the various wavelengths, has become increas-ingly important for dispersion management in lightwave

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systems. In response to industry requests for thesemeasurements, NIST researchers have developed anddemonstrated a low-coherence interferometric methodfor measuring dispersion and group delay in waveguidedevices. Fiber Bragg grating group delay has beenmeas-ured with 1 ps repeatability, and this methodshows 1.5 ps agreement with the more commonly used,but much slower, modulation phase-shift method.Dispersion, the change in group delay with wavelength,can be measured with better than 1 % repeatability(0.02ps/nm standard deviation for a grating with 7ps/nmdispersion).

Concurrently, there was a round robin of dispersionmeasurements among industrial laboratories. This setof dispersion measurements showed a 16 % rangefor the same grating, indicating the real need for theseimproved measurements. A key benefit of the low-coherence interferometric method is the fast measure-ment time. Measurements with 7 pm wavelength resolu-tion can now be made in 1 min compared to the hoursrequired to obtain measurements with reduced wave-length resolution using current methods. This may provevaluable for commercial measurements of the largenumber of fiber Bragg gratings being used in fibertelecommunications systems.CONTACT: Kent B. Rochford, (303) 497-5170;[email protected].

INTERNATIONAL ROUND ROBIN TESTINGCOMPLETED ON CERAMIC POWDERSNIST completed an international round robin study onproperties of advanced ceramic powders. Thirty-fourlaboratories participated, including those in Belgium,Germany, Japan, Sweden and the United States. Theultimate goal of this activity, conducted under the aus-pices of the International Energy Agency (IEA), is todraft uniform standard test methods in each participat-ing country and through the ISO. The propertiesmeasured included those used for characterization ofpowders suspended in water (particle dispersion andrheology), characterization of spray dried powders (flowrate, particle size distribution, moisture and binder con-tent), and green body evaluation (bulk density and greenstrength). The compiled data were analyzed to deter-mine the repeatability of the data within each laboratoryand to examine variations in the data obtained by differ-ent laboratories. In general, no significant variationsoccurred within the laboratories. However, significantvariations between laboratories were observed for a fewmeasurement procedures, even though the procedureshad been predefined. The meas-urement procedures thatresulted in unacceptable variation will need furtherevaluation and improvement before establishing national

and international standard test methods for characteriza-tion of ceramic powders.CONTACT: Lin-Sien Lum, (301) 975-3674; [email protected] or Said Jahanmir, (301) 975-3671;[email protected].

NEW VOLTAGE STANDARD ATTACHED TOWATT EXPERIMENTNIST researchers have completed the first program-mable Josephson voltage standard system and have madeit available for the moving coil watt-balance experiment.The latter may eventually lead to a new definition of thekilogram, the unit of mass in the International System ofUnits (SI). The system operates as an instrument thatcan be commanded over the IEEE 488 bus to produceany voltage within its output range of61.1 V. When notbeing used as a voltage reference, the system automati-cally executes a variety of self-tests to confirm correctoperation and to evaluate uncertainties. Once set up, thesystem can operate unattended 24 hours a day. It will beconnected directly as the voltage reference for the Wattexperiment and is expected to eliminate uncertaintiesassociated with a chain of voltage comparisons usedpreviously.

The new system has attracted much interest inter-nationally and is a prospect for replacing dc voltagestandards around the world.CONTACT: Sam Benz, (303) 497-5258; [email protected].

MODEL DEVELOPED FOR BONDING OFSUPERALLOYSA model has been developed by NIST researchersdescribing the process of transient liquid phase (TLP)bonding, which can be used to make high-quality jointsin superalloys and other materials. An important appli-cation of this process is to make large, complex single-crystal components by joining together smaller singlecrystals, since defect-free small single crystals can beproduced more easily than large ones. In TLP bonding,the pieces to be joined are fitted together, with a thin foilof a lower-melting alloy between them. When theassembly is heated, the foil melts but then resolidifiesisothermally as its constituents diffuse into the adjoiningcrystal, leaving a virtually invisible joint.

The model is based on a thermodynamic model of thesingle crystal and bonding foil materials, a matrix ofdiffusivities, and a reaction path model describing thediffusion process. A major consideration in the designof a TLP bonding process is the possibility that unde-sired crystallographic phases will form in the vicinity ofthe joint, causing unacceptable weakness. Use of the

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model enables a designer to analyze how the formationof such undesired phases will be affected by the bond-ing foil composition and the thermal cycle to which theassembly is exposed, and thus to design a process toavoid formation of the undesirable detrimental phase.

Application of the model has been demonstrated fora simple Ni-based alloy with a bonding foil containingboron. Application to a more complex superalloy systemwill require incorporation of additional thermodynamic data. With successful application of TLP, indus-try will be able to create stronger, more complex partgeometries enabling higher efficiency engines.CONTACT: Carelyn Campbell, (301) 975-4920;[email protected].

POLYMER CHAIN MOTIONThe first experiments on the nation’s only neutron spinecho (NSE) spectrometer recently have been performedat the NIST Center for Neutron Research (NCNR). Thiscold neutron spectrometer allows measurements of keydynamic process in macromolecular systems essentialto researchers in polymer, biomedical, and colloidscience. The instrument covers a combination of time—(0.01 ns to 100 ns) and length-scales (0.2 nm to 20 nm)previously inaccessible in the United States. Uniquemeasurements of slow dynamics in other areas ofmaterials and chemical engineering—including, forexample, giant magnetoresistance materials and super-critical fluids—are also expected. The measurement ofdynamic processes out to 100 ns is 1000 times longerthan previous U.S. capabilities.

This new instrument was developed in partnershipwith a private company and a research institution inGermany. Work on the spin echo spectrometer isexpected to allow more realistic models of why andhow molecules move. Thus scientists will be able tobetter predict and improve macromolecular properties.A general call for experiment proposals from the re-search community will be issued at the end of 1999.CONTACT: Nicholas Rosov, (301) 975-5254;[email protected].

NIST DATABASE ON COMPOSITEREINFORCEMENTS NOW AVAILABLEON WWWA NIST database for composite reinforcements is nowavailable on the World Wide Web. A critical manufac-turing variable of reinforcements used in structuralcomposites is their permeability, which is the ability ofpolymeric resins to flow through their porous struc-tures. The database was developed to report permeabil-ity data from NIST measurements. Companies in the

automotive and other industries have been purchasingthe database since it was released in 1998 in disk formatand they use the data in process design activities. Theavailability of the database on the World Wide Web willimprove industry access as well as provide the opportu-nity for expansion through additional data from externallaboratories.CONTACT: Richard S. Parnas, (301) 975-5805; [email protected].

NIST DEVELOPS A NEW MAGNETICRESONANCE SPECTROMETER BASED ON AMICROMECHANICAL CALORIMETERSENSOR FOR MEASUREMENTS OFTHIN-FILM MAGNETIC SAMPLESWork at NIST on an atomic scale magnetism has led tothe development of a new type of ferromagnetic (FMR)resonance spectrometer. The instrument is a result ofongoing research that focuses on new types of scannedprobed microscopes (SPMs) for high-resolution imag-ing of nanometer scale magnetism. In particular, theresearch aims to develop SPM technologythat combinesatomic force microscopy with the essential features ofmagnetic resonance imaging (MRI).

The project responsds to the need to develop instru-mentation for nanometer scale microscopes and magne-tometers for metrology of disk drive components.Currently, the data storage industry is producing thinfilm recording heads with reader and writer dimensionsbelow 100 nm. Recorded bits on hard disk media have60 nm lengths and 1 mm widths, and there is a substan-tial economic pressure to reduce these dimensions withthe growing demand for higher density digital datastorage devices.

The FMR spectroscopy probe is based on a calorime-ter sensor. The sensor is an atomic force microscope(AFM) cantilever coated with a ferromagnetic thin filmthat serves as a bimaterial thermal sensor to measureabsorption of microwaves. Spectra show a peak in thecantilever deflection as a function of applied magneticfield corresponding to a peak in the absorbed microwavepower that occurs under FMR conditions for the ferro-magnetic film. The saturation magnetizationMeff,and the damping factora , determined from the FMRmicrowave absorption spectra for Co, NiFe, and Ni thinfilms correlate well with conventional FMR spectrataken with a tuned cavity spectrometer. The instrumentcan detect magnetic moments as small as 1.3310–12

A ? m2 (1.3310–9 emu) with prospects for sensitivityimprovements to the 1310–16 A ? m2 (1310–12 emu)level.

The technique provides a potentially superior wayto make quantitative measurements of the saturation

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magnetization of thin-film samples with very small totalmagnetic moments. The Brownian motion of thecantilever sensor fundamentally limits its ultimate sensi-tivity—at room temperature it should be possible tomeasure 1 pW. This corresponds to the FMR powerabsorbed by a 30 nm thick magnetic sample with anarea of 2.6310–16 m2 (16 nm316 nm). In the future,the group plans to combine microtorque magnetometrywith FMR calorimeter spectroscopy in one apparatus.In this way they will be able to performM-H loops onthin-film samples and calibrate the saturation magne-tization directly with FMR.CONTACT: John Moreland, (303) 497-3641;[email protected].

NIST TAKES LEAD ON VIDEO QUALITYANALYSISNIST is helping to conduct a multilaboratory, multi-national examination of objective methods for themeasurement of video quality through the VideoQuality Experts Group (VQEG), a joint working partyof the International Telecommunications Union (ITU).Traditionally, subjective measurement studies are usedin the television industry for evaluation of video sys-tems, however such methods involve the assembly ofgroups of viewers to evaluate carefully selected videosequences displayed on special equipment and undercontrolled conditions. Such tests are costly and imprac-tical for the frequent, or even continuous “in-service”measurement of video quality. Accordingly, the VQEGhas undertaken a study of proposed computationalmodels that mimic subjective tests. The study consistedof assembling appropriate source material, rating thatmaterial using the 10 proposed objective models, andanalyzing the correlation of the model scores to previ-ously determined subjective scores. NIST, as an impar-tial participant, was responsible for the study logisticsand data analysis, preparing a report that was presentedat the latest VQEG meeting in the Netherlands. Themost significant outcome of the testing was the unex-pectedly poor correlation of all objective measures withthe subjective scores. The group decided that the modelproponents would improve their models based onthe information derived from this test and then anadditional round of testing would be conducted.

A constrained monotonic cubic fitting functionformulated and implemented by NIST proved to beexceptionally useful for the analysis. The objective testplan had recognized that non-linearities were likely tooccur in the data and specified that prior to correlation,each objective data set could be transformed usingeither a four-parameter logistic function or a cubic

polynomial, provided that the cubic was constrained tomonotonicity.CONTACT: Bruce F. Field, (301) 975-4230; [email protected].

POWER CALIBRATION SERVICE FOR 2.4 mmCOAXIAL CONNECTORSNIST has established a new calibration service for2.4 mm coaxial power standards. The service covers afrequency band of 0.05 GHz to 50 GHz. The newcalibration service addresses an industry need for powermeasurements in 2.4 mm coaxial line (0.05 GHz to50 GHz) that are traceable to NIST. Previously industrytraceability was achieved through adapters and multiplewaveguide and coaxial power standards. Makingmeasurements in this fashion not only degrades theaccuracy but is also a laborious time-consuming processthat involves measurements in four different connectortypes.

The 2.4 mm calibration service is based on a newtype of detector specifically developed for calorimetricmeasurements. The detector is unique in that it is con-structed using semiconductor fabrication techniques andthe microwave power is measured using a dc substitutionmethod. NIST collaborated with a commercial companyin the development and testing of the 2.4 mm detector.A 2.4 mm microcalorimeter, which measures the effec-tive efficiency of the 2.4 mm detectors also wasdesigned, built, and evaluated. The new detectors arecalibrated in the microcalorimeter and then are used astransfer standards to calibrate other devices.

Currently, industry uses either thermoelectric ordiode detectors for 2.4 mm power measurements. Thesedetectors cannot be measured in the microcalorimeter.In order to transfer the measurement services to indus-try, two automated direct comparison transfer systemswere developed and constructed to calibrate 2.4 mmpower meters and thermoelectric electric and diodepower meters. These systems also can calibrate powersensors in other connector types such as Type N and3.5 mm. A typical expanded (2s) uncertainty in effec-tive efficiency for the direct comparison system variesfrom 0.005 at 50 MHz to 0.023 at 50 GHz.CONTACT: Robert M. Judish, (301) 975-3380; [email protected].

EXPANDED WR-15 NOISE-TEMPERATUREMEASUREMENT SERVICE REOPENEDNIST has reopened its measurement service for thenoise temperature of WR-15 waveguide noise sourcesfor the frequency range 50 GHz to 65 GHz. The service

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originally covered only 55 GHz to 64.5 GHz, but it wasclosed about 5 years ago because of concerns about therepeatability of the measurements and the histories ofthe check standards. To recertify the system, criticalsystem checks were performed, the software for thesix-port reflectometer was improved, the uncertaintyanalysis was checked and updated, and the checkstandards were remeasured and compared to previousresults. Typical expanded uncertainties (coverage factork = 2) for the revived service are expected to be about1.9 % for noise temperatures of 5000 K to about12 000 K. The WR-15 band extends from 50 GHz to75 GHz. Principal applications are cross links betweenor among satellites around 60 GHz and short-rangeterrestrial wireless local area networks.CONTACT: Robert M. Judish, (301) 975-3380;[email protected].

SWITCHING IN SUB-MICROMETER DEVICESON SUB-NANOSECOND TIME SCALESNIST researchers completed a study of high-speedswitching in 0.5mm to 0.8mm wide “spin valves.”These devices are similar to those being developed for“giant magnetoresistive” (GMR) read heads and mag-netic random access memory (MRAM) elements fordata storage. The devices were repeatedly switchedwith pulses whose widths ranged from 0.2 ns to 2 ns.

While the low-frequency characterization showedthat the devices were bistable, many of the devicesactually exhibited long-lived metastable states whendriven by fast magnetic field pulses. Micromagneticsimulations indicate that the devices should be revers-ing by domain wall motion for the low amplitude pulsesand by magnetization rotation for the large field pulses.The simulations, at present, do not predict the existenceof long-lived metastable states or an observed oscilla-tion of the switching probability.

The data suggest that there are given field rangeswhere different reversal mechanisms are efficientlydriven. If the system is overdriven, it can get stuck in ametastable state accessible only by the large transientenergy that is available during a high-speed switch.This work is one of the first to analyze the details ofdynamical switching in sub-micrometer devices onsub-nanosecond time scales. The results are importantfor the development of MRAM, where reproducibleswitching of 100 billion sub-micrometer elements willbe required, and magnetic read heads, where the switch-ing studies provide a much more rigorous test of theaccuracy of micromagnetic simulations.CONTACT: Ron Goldfarb, (303) 497-3650; [email protected].

FIRST OBSERVATION OF TRANSIENT SPINWAVES IN MAGNETIC FILMSNIST has an active program to measure the speed ofmagnetic switching for application to problems in datastorage. Using a new technique of vectorial second-harmonic magneto-optic Kerr effect, NIST scientistsdetected the transient generation of spin waves duringmagnetic field step excitations in Permalloy Ni-Fe films.

The effect manifests itself as a 50 % reduction inaverage magnetization during the first few nano-secondsof dynamical magnetization response. This is the firsttime that experimental measurements have shown thatcoherent magnetization response to an applied fieldpulse can result in efficient spin wave generation.

A key aspect of the experiment is creating in thesample a highly “rippled” state through the applicationof a bias field orthogonal to the preferred anisotropyaxis. When the bias field is equal to the anisotropy field,the magnetization falls into a relaxed state that is highlysusceptible to spatial variations in the anisotropy, result-ing in magnetization ripple. The ripple state acts tonucleate the spin waves during the dynamical responseto an applied field pulse, much as vortex generators onthe leading edges of commercial aircraft wings induceturbulent airflow along the wing surface, preventing stallat low air velocities.

This discovery will lead to further understanding ofthe fundamental limits of high-speed switching in datastorage devices. Further work will address how to con-trol spin wave generation in response to the applicationof pulsed magnetic fields. A paper has been submittedto Physical Review Letters.CONTACT: Ron Goldfarb, (301) 975-3650; [email protected].

NIST RELEASES INTERACTIVE NISTCGM TEST SUITENIST recently released the NIST Computer GraphicsMetafile (CGM) Test Suite, which is available in aninteractive format from the NIST CGM web sitehttp://www.itl.nist.gov/div897/ctg/cgm.htm. In the AirTransport Association (ATA) CGM CertificationProgram, ATA Recognized Laboratories use the CGMTest Suite to determine conformance to the ATA Speci-fication 2100. The updated test suite utilizes the Exten-sible Markup Language (XML), the Document ObjectModel (DOM), and JavaScript to create an interactiveenvironment allowing users to control the access andview of the test suite. The interactive test suite can bequeried for specific versions, category, or by individualfile.CONTACT: Jacki Schneider, (301) 975-4454;[email protected].

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NIST’S LINE SCALE INTERFEROMETERMEASUREMENT ASSURANCE NOTEDThe “International Meter bar” S.N. 12924 was on loanfrom the Bureau International des Poids et Mesures(BIPM) for 2 years, and extensive measurements wereconducted with NISTs Line Scale Interferometer (LSI).This bar was used from 1975 to 1988 for the round robinmeasurements conducted by BIPM among 12 nationallaboratories around the world, including NIST. At thattime, the NIST measured value was within 30 nm of themean of the international values including BIPM’svalues. The last time the bar was measured by BIPMwas in June 1992, and the correction to the nominal 1 mwas +823 nm. If that value is used as the reference forNISTs recent measurement, the measured value waswithin 13 nm to the BIPM value, or +810 nm. TheBIPM’s value has a great importance, because theirvalue is the average of three different methods used todetermine the bar’s length.CONTACT: Bill Penzes, (301) 975-3477; [email protected].

NIST TAKES DELIVERY OF XCALIBIRNIST has completed installation of the X-Ray OpticsCalibration Interferometer (XCALIBIR). XCALIBIR isa general-purpose 300 mm aperture interferometer formeasuring surface figure error of precision optics witha measurement capability target of 0.25 nm standarduncertainty for flats, spheres, and mild aspheres. Theoptical table for the instrument, a 16 metric ton slab ofgranite, was delivered in July, followed by the finalstages of laboratory construction. The interferometeris housed in an environment-controlled enclosure, andpreliminary evaluations show temperature stability asgood as 0.018C. The interferometer itself was installedduring the months of August and September.CONTACT: Angela Davies, (301) 975-3743; [email protected].

MAGNETIC FIELD CONTROL OFCOLD ATOMSResearchers at NIST have constructed a model toexplain the response of a pair of cold, trapped atomsto a time-dependent magnetic field. This is importantbecause variable magnetic fields offer a means tomanipulate the interactions between atoms in thisunique environment. These interactions play a crucialrole in Bose-Einstein condensation (BEC), a phasetransition which occurs due to quantum statistics whena dilute gas of bosonic atoms approach near zerotemperature and all the atoms occupy a single quantumstate. BEC provides a source of coherent matter for a

variety of applications in metrology and fundamentalphysics.

The stability and dynamics of a condensate dependson whether the effective interactions between the atomscomprising it are attractive or repulsive. It was proposedsome time ago that magnetically tunable resonantscattering states of the atom pair could be used to varythese effective interactions over a wide range. The effectwas demonstrated recently on a sodium atom conden-sate at a U.S. university but was accompanied by a largeloss of atoms when the field was tuned near theresonance condition. The NIST researchers constructeda highly quantitative model for calculating the proper-ties of two colliding sodium atoms in a magnetic field.The model is an extension of one previously constructedfrom precise spectroscopic data obtained at NIST. Themodel predicts the magnetic fields for which suchresonance tuning occurs.

By introducing the effect of a time-varying magneticfield into the model, the NIST group found that such afield could cause large changes in the number conden-sate atoms. The field tunes the energy of a specialresonance state of the atom pair so that it is nearly thesame as the energy of two separated atoms. Thisresonance state is one where the two colliding atoms aretemporarily bound tightly together as a diatomicmolecule before they separate again. If the time-varyingmagnetic field raises the energy of the resonance state,the resonant scattering process can convert initially coldatoms to hot atoms. On the other hand, if the time-vary-ing field lowers the energy of the resonance state,unbound atoms can be converted to cold diatomicmolecules. In either case, atoms are rapidly lost from thecondensate. Although such a mechanism is harmful to acondensate, magnetic tuning of cold atom scatteringmay find applications in cold molecule production oreven in novel forms of quantum information processing.CONTACT: Paul Julienne, (301) 975-2956; [email protected].

CHROMIUM ATOMS TRAPPEDBuilding on expertise developed over the past few yearson laser manipulation of chromium atoms, researchersat NIST recently have demonstrated, for the first time,the cooling and trapping of chromium atoms in amagneto-optical trap. Using laser light tuned to the7S3–7P84 Cr atomic transition at 425 nm, they were ableto cool and collect over 106 atoms in a sub-millimetersized cloud. Because Cr has an intermediate metastable5D level, extra care was needed to make the cooling andtrapping effective. Two extra laser frequencies, gener-ated by laser diodes at 654 nm and 663 nm, had to beintroduced and locked on the transition to pump atoms

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back into the cooling process. Once the atoms weretrapped, observations of the trap lifetime revealed inter-esting results: non-exponential, density-dependenttrap loss was seen, indicating a surprisingly high levelof excited-state collisions. Applications of this workinclude forming a highly coherent source of atoms foratom-optically controlled nanofabrication, generating aprecursor to creating a quantum degenerate gas in asystem with either fermionic (53Cr) or bosonic (52Cr)particles, or providing a new arena for studying ultra-cold collisions.CONTACT: Jabez McClelland, (301) 975-3721;[email protected].

OPTICAL FREQUENCY MEASUREMENTUSING MODELOCKED LASERSThe measurement of frequencies in the optical domainis a challenging problem due both to the large differ-ence between optical frequencies and the 9.192 GHzcesium standard and to the difficulty in comparing twooptical sources to one another. Recently, several groupsaround the world began exploiting the regularly spacedcomb of frequencies produced by a modelocked laser toproduce a “ruler” of optical frequencies.

Researchers at NIST have spectrally broadened (inoptical fiber) the output from a Ti:sapphire laser thatproduces 10 fs pulses. The resulting comb was used tomeasure the 104 THz gap between a single frequencyTi:sapphire laser locked to rubidium and a Nd:YAGlaser locked to iodine with a relative uncertainty of2310–11. The measurements using a modelocked laserwere significantly simpler than those performed previ-ously.

Techniques using modelocked lasers are under devel-opment that will allow the measurement of opticalfrequencies directly from a cesium clock.CONTACT: Steve Cundiff , (303) 497-7858;[email protected] or Jan Hall, (303) 497-3126; [email protected].

NEW SI UNIT ADDEDThe 21st General Conference on Weights and Measures(CGPM, Conference Ge´nerale des Poids et Mesures),which met in Paris in October 1999, added a newderived unit with a special name and symbol to theInternational System of Units (SI, Syste`me Interna-tional d’Unites), the modern metric system. The unit isthe katal, symbol kat.

These are, respectively, the special name and symbolfor the coherent, SI derived unit mold per second and itssymbol mol/s for use in the fields of medicine andbiochemistry to express values of enzyme catalytic

activity in terms of the rate of conversion of a specifiedindicator reaction. Although the CGPM recognizes thatthe proliferation of special names and symbols forderived units could undermine the universality and easeof understanding of the SI, it also recognizes the need tomake exceptions in matters related to human health andsafety. In the case of the katal, a non-SI unit called“unit,” symbol U, equal tommol/min, which is notcoherent with the SI, has been used widely in medicineand biochemistry for the past 35 years for expressingvalues of enzyme catalytic activity. furthermore, thelack of a special name and symbol for the coherent SIderived unit mole per second has led to results of clinicalmeasurements being given in various local units, eventhough the use of SI units in medicine and clinicalchemistry is strongly recommended by the internationalunions in these fields.

The CGPM is one the international bodies establishedby the Meter Convention (Convention du Me`tre), whichwas signed in Paris in 1875 by 17 countries, includingthe United States (nearly 50 countries are now membersof the convention). The SI was established by the 11thCGPM in 1960; one of the responsibilities of the CGPMis to ensure that the SI is disseminated widely and thatit reflects the latest advances in science and technology.CONTACT: Barry N. Taylor, (301) 975-4220; [email protected].

ASTROPHYSICISTS BRING NEWHIGH-RE SOLUTION, BROAD-BANDX-RAY DETECTOR TO THE NISTELECTRON BEAM ION TRAP FACILITYX-ray detection is an essential tool for the study ofhighly charged ions, whether in the laboratory or inastrophysical environments. To date researchers typi-cally have had two types of x-ray detectors to choosefrom: solid-state detectors and x-ray crystal spectro-meters. Solid-state detectors are very efficient and havebroad spectral bandwidth, but suffer from poor energyresolution. Crystal spectrometers offer unprecedentedresolution, but they have poor efficiency and havelimited spectral bandwidth. Recent advances in singlephoton calorimetry have produced x-ray detectors,which for the first time combine the strengths of thesetwo devices. The resulting x-ray microcalorimeters havenearly 100 % detector efficiency, a broad energy band-width that allows the simultaneous observation ofphotons from a few hundred eV to tens of keV, and anenergy resolution better than 5 eV, approaching that ofcrystal spectrometers.

Recently, a group of scientists from a U.S. universityand an Italian observatory brought a microcalorimeterto the NIST electron beam ion trap (EBIT) facility to

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study the x rays emitted by highly charged ions. Origi-nally developed for space bound x-ray observatories, themicrocalorimeter is ideal for studying the photons emit-ted by highly charged ions in an EBIT. The EBIT,in turn, provides a well controlled environment for“laboratory astrophysics,” allowing the study of ener-getic atomic processes occurring in many astrophysicalenvironments and in a wide variety of Earth-basedplasmas such as tokamaks.

In a preliminary study, the scientists measured thex-ray spectra from highly charged nitrogen, oxygen,neon, argon, and krypton, with photon energies thatdiffer by more than a factor of 10. The teams madepreliminary measurements of the electron densitydependence of the line ratios in helium-like oxygen, asystem that has potential use as an electron diagnosticin land-based plasmas and in the solar corona. Futureexperiments will continue to provide atomic data ofinterest for plasmas and will be extended to include thestudy of highly charged ion/surface interactions.CONTACT: Trey Porto, (301) 975-3238; [email protected] or Endre Takacs, (301) 975-8244; [email protected] or John Gillaspy, (301) 975-3236; [email protected].

MAPPING PHASE DYNAMICS OFCONDUCTING POLYMER BLENDFILMS WITH NEAR-FIELD SCANNINGOPTICAL MICROSCOPYConventional methods to fabricate small structures andpatterns (e.g., electronic devices, and chips for analyz-ing biological molecules such as DNA and proteins)mainly employ high-resolution lithographic techniques,which are costly. More recently, innovative techniquesare being investigated that involve the control and use ofthe “molecular microenvironment” in polymer blendsfor generating submicron patterns and devices. Self-assembly of macromolecules using phase separation inpolymer blends is one technique. Some aspects of phaseseparation in these multicomponent polymer systemshave been studied by conventional optical techniques.However, these techniques have resolution that isdiffraction limited so there is still little informationavailable on the nanoscale electric, mechanical, oroptical properties of phase separated films.

NIST researchers, using NIST-built near-field scan-ning optical microscopes (NSOMs), have completed astudy mapping the phase dynamics of polymer blendfilms in which one of the polymer components is con-ducting. NSOM uses the near-field interaction of lightfrom a sharp fiber-optic probe with a sample of interestto image surfaces at a resolution beyond the diffractionlimit of conventional optics. Simultaneous topography,

transmission, and fluorescence NSOM images taken onthese polymer samples at different annealing stagesrevealed many previously unobserved details of phaseseparation that are relevant for the manufacture of opto-electronic and organic-electronic devices. The resultsshowed that conducting polymer molecules in the blendare mobile even under the glass transition temperatureof the conducting component alone. High-resolutionNSOM measurements revealed many other details ofrestructuring dynamics during the annealing process.Further investigation in this line of research will greatlybenefit the industry of polymer processing and devicefabrication.CONTACT: Jeeseong Hwang, (301)975-4580; [email protected] or Lori Goldner, (301) 975-3792;[email protected].

ICFRE3 FIRE CONFERENCE A SUCCESSNIST and the International Association of Fire SafetyScience hosted 129 delegates from 145 countries atthe Third International Conference on Fire Safety andEngineering in Chicago. The bi-annual conference, heldthis year in October, provides a venue for interchangebetween practicing engineers and fire researchers.Approximately two-thirds of the presentation during thefour day conference featured results that utilized NISTcomputer fire models and/or data from the Web site(fire.nist.gov). This web site has become so well knownby the fire research and engineering community that itwas acknowledged to be the first source looked to forinformation by this audience. The conference proceed-ings are available from SFPE (www.sfpe.org).CONTACT: David Evans, (301) 975-6897; [email protected].

SECOND WORKSHOP HELD ON HEAT FLUXTRANSDUCER CALIBRATIONA second workshop on heat flux transducer calibrationwas held recently in Gaithersburg. Questions wereposed to ascertain how the heat flux measurement needsof industry had changed since the first workshop held in1995, what the implications were for the transducermanufacturers and calibration services, and what wouldbe the best way for NIST to interact with manufacturers,university researchers, and government laboratories.

More than 40 attendees were drawn from U.S. indus-try, academia, and government organizations. Repre-sentatives of a spectrum of industries that rely uponaccurate measurement of heat flux described theirapplications and calibration needs. The effort beingundertaken in Europe to standardize heat flux calibra-tion methods for fire safety standards was discussed.

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Discussions involving all the workshop participantswere organized around special considerations andcalibration needs of heat flux measurement devices forthree different situations: (1) convection dominated,moderate temperature, quasi-steady environments withsize and cost as major constraints; (2) convection domi-nated, high temperature, transient environments withsmall size and accuracy highly desirable; (3) radiationdominated with high flux levels, with applicationsconstrained by government regulations. A summary ofthe workshop is available in NISTIR 6424.CONTACT: William Grosshandler, (301) 975-2310;[email protected].

CIRMS HOLDS EIGHTH ANNUAL MEETINGAT NISTThe Council on Ionizing Radiation Measurements andStandards (CIRMS) held its eighth annual meeting atNIST in October 1999. The organization representsthousands of users of ionizing radiation and radioactivesources engaged in industrial radiation processing andsterilization, medical radiation diagnostics and therapy,nuclear power generation, worker radiation protection,and environmental measurement programs. CIRMSprovides a forum for discussing ionizing radiationissues; identifying, defining, and prioritizing neededwork; disseminating information on standards; andorganizing workshops and meetings to advance ionizingradiation technology.

More than 160 participants from industry, federal andstate agencies, and national laboratories attended themeeting and presented lectures and posters in fourparallel workshops that addressed the specialties of thefour CIRMS subcommittees: Medical Applications,Occupational Radiation Protection, Public and Environ-mental Radiation Protection, and Industrial Applicationsand Materials Effects. Participants seem to prefer theparallel focus-workshop format for the meeting, as therewas a 50 % increase in attendance over last year. Themain issues in medical applications were needs forstandards and methods for radioactive sources used inradiation therapy. The environmental subcommitteefocused on a single topic: performance evaluationmaterials for use in quality control programs forradioactivity meas-urements. The occupational radia-tion protection subcommittee dealt with facilities,measurements, and standards for neutrons. This topicwas particularly timely in light of the recent criticalityaccident in Japan. The materials effects subcommittee

this year concentrated on radiation effects on materialsfor space applications.

The annual gathering of the radiation user commu-nity is a key element of the planning processes for stateand federal agencies. CIRMS encourages one-on-oneinteractions, open group discussions, and prioritizationof the national measurements and standards needsthrough consensus. These collective efforts help indus-try and government to solve short-term problems moreeffectively and to prepare adequately for the futureneeds of emerging radiation technologies.CONTACT: Bert Coursey, (301) 975-5584; [email protected].

45TH ANNUAL CONFERENCE ON BIOASSAY,ANALYTICAL, AND ENVIRONMENTALRADIOCHEMISTRYNIST organized and co-sponsored the 45th AnnualBAER conference in October 1999 with 15 industrysponsors. Over the past 45 years, the Annual Confer-ence on Bioassay, Analytical, and Environmental Radio-chemistry (BAER) has been a forum where profession-als can discuss works-in-progress and commonproblems encountered during the development of state-of-the-art methods and procedures for detecting,measuring, and analyzing radioactive materials found ina large variety of environmental and biological media.The unique objective of the BAER Conference is toprovide a test crucible for pre-publication ideas, assump-tions, and approaches. The participants engage inintense interactions to share new discoveries, challengeaxioms, gain insights, seek solutions to technical prob-lems and barriers, and examine the impact of newpolicies and regulations. Two hundred and twentyparticipants attended the conference from universities;federal and state national and defense laboratories;nuclear power stations; instrument manufacturing com-panies; commercial service laboratories; geoscienceinstitutes; and the International Atomic Energy Agency.The technical contributions highlighted new advancesthat were presented in 45 oral presentations, 33 posterpresentations, 14 topical and vendor workshops, and by25 exhibiting companies.

Selected highlights of the conference included newdevelopments in the areas of oceanographic radio-nuclide speciation, characterization of single particlehot spots and virtual gamma-ray calibrations for com-plex extended volume reference and biological sources.CONTACT: Kenneth G.W. Inn, (301) 975-5541;[email protected].

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NIST HOSTS WORKSHOP ON LUMINESCENCESTANDARDS FOR CHEMICAL ANALYSISAbout 35 scientists from the clinical and biotechnologycommunities, instrument and standards vendors, federalagencies, academia, and five national metrologyinstitutes (NMIs) attended a workshop on standards forfluorescence-based chemical analyses jointly sponsoredby NIST in September 1999. The goals of the workshopwere to assess the importance and needs for fluores-cence standards as well as to appraise new materialsand technologies that might be candidates for suchstandards.

Luminescence measurements have become themethods of choice for new clinical and biochemicalanalyses due to their extraordinary selectivity and highsensitivity. Reporter gene and green fluorescent protein(GFP) technologies now make itpossible to labelspecific bio-chemical entities with high specificity andthen to detect the marked species at near single moleculelevels in extremely heterogeneous environments such asliving cells. Luminescence measurements provide theanalytical grease for many current fast track chemicaltechnologies—today’s genetic engineering and high-throughput screening for drug discovery could not behappening without luminescence measurements. Formany years, luminescence has been a qualitative screen-ing technique—“does it or doesnt it glow?” However,now that many screening technologies havebeen auto-mated and new leads are easy to generate, the questionhas changed to assess the quality of new leads—“if itglows, how much does it glow?” To provide this sort ofanswer, standards are needed to calibrate luminescencemeasurement instruments and to validate the analyticalmethods themselves. In the highly regulated pharma-ceutical and clinical industries, such standards areneeded to satisfy the quality assurance and validationrequirements of regulatory agencies. The increasingimportance of drug and food testing is making the needsfor such standards increasingly important for trade andsparking collaborations and future intercomparisonactivities among the NMIs.

The workshop agenda and abstracts can be foundat http://www.cstl.nist.gov/nist839/839.04/index.html(click “Agenda”).CONTACT: Paul DeRose, (301) 975-4572; [email protected] or Gary Kramer, (301) 975-4132; [email protected].

WORKSHOP HELD ON VALIDATION OFMULTIPHASE COMBUSTION MODELSNIST sponsored a 1 day workshop in Gaithersburg inJune 1999, to address benchmark experimental needs ofindustry for input and validation of multiphase com-

bustion models. Thirty-five people attended the work-shop, representing industry (chemical, power, energy,and software developers), other government agencies,and academia.

All attendees were provided the alpha version of abenchmark database developed at NIST and publishedearlier this year (NISTIR 6286). The focus of the work-shop was to familiarize the participants with NISTsreference spray combustion facility, assess the informa-tion currently provided in the database, review prelimi-nary findings from simulations of the NIST facility,allow modelers to express their data needs, and providean opportunity for feedback concerning future measure-ments.

An overview of the benchmark experimental databasefor the baseline case was given by several NIST person-nel. Four invited speakers, involved in the developmentof spray combustion models for industry, described theirefforts to use the benchmark data.

Discussions focused on the industry needs and whatshould be the next phase of the NIST program. A widerange of needs were discussed with some topics priori-tized. Follow-up discussions are currently under waywith the participants to determine the most criticalindustrial needs and how NIST can provide the greatestimpact.CONTACT: Cary Presser, (301) 975-2612; [email protected].

WORKSHOP HELD ON SCANNING PROBEMICROSCOPY OF SOFT MATERIALSAtomic force microscopists met at NIST for a Workshopon Scanning Probe Microscopy of Soft Materials inAugust 1999. “Soft” materials include biologicalmolecules and assemblies, and the talks covered diversetopics such as the effect of infectious agents on livecells, polymer phase separation, the binding of water tolipid headgroups, and engineered hybrid cell mem-branes. Presentations were given by researchers fromNIST, National Institutes of Health, Naval ResearchLaboratory, and a private company. Reports on funda-mental studies such as the use of scanning probemicroscopy to determine the phase behavior of alka-nethiols on gold, and measuring friction at differentlength scales, led to discussions of the promises andpitfalls of using scanning probe microscopy on softsamples, and how to improve the information gained. Animproved understanding of phase imaging—the mea-surement of the phase lag between the drive signal andresponse during tapping or modulating imaging—wassingled out as a particularly important technique forthese materials. The workshop was capped with ademonstration by the private company of their magnetic

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AC (MAC) mode atomic force microscopea new tech-nologythat enhances the ability to image soft materialsunder fluids. Nearly 50 people from industry, govern-ment labs, and academia attended.CONTACT: John Woodward, (301) 975-5495; [email protected].

Standard Reference Materials

NEW PLATINUM SRM THERMOMETERThe International Temperature Scale of 1990 (ITS-90) isdefined over the range 13.8033 K to 1234.93 K throughthe use of standard platinum resistance thermometers(SPRTs). The scale is disseminated from NIST through-out this range through calibrations of customer SPRTsusing any one of 11 ITS-90 defined sub-ranges. Hereto-fore, a customer requiring a NIST calibration on one ofthe lowest sub-ranges, those spanning temperaturesbelow 83.8 K, would typically invest some $10 000 ormore in the combined costs of a suitable capsule SPRTand the calibration fee. In addition, customers wouldsometimes be required to wait up to 6 months before abatch calibration run could be scheduled. The combina-tion of this relatively high initial capital investment andthe relatively long lead-time had discouraged someprivate firms from using these types of standards to helpmaintain their quality control.

NIST has now addressed these problems through thepreparation of a set of Standard Reference Material(SRM) SPRTs. The SRM 1750 is a batch of 20 SPRTs,built to NIST specifications, which have been calibratedin two back-to-back batches over the ITS-90 sub-rangeof 13.8033 K to 429.7485 K. The economy of scaleproduced by fabricating, calibrating, and certifyingall 20 SPRTs in two batches of 10 devices each hasproduced a net savings that will be passed on to the endusers of the SRM 1750, the projected unit cost of whichwill be about $6000. In addition, the individual unitswill be available as an “off-the-shelf” item, for immedi-ate delivery for an end-user.

As a whole, the data produced for the SRM 1750 hasillustrated the exceptional uniformity in purity andannealing that is possible today in the fabrication offine-wire platinum elements. The high degree of corre-lation found in the resistance-ratio data throughout thetemperature range studied is a characteristic of a highsample-to-sample uniformity. These data, to be pub-

lished in an SP-260 series document, will be valuable toproducers of high-purity fine platinum wire elements asa benchmark for these properties.CONTACT: Weston Tew, (301) 975-4811; [email protected].

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