Volume 108, Number 5, September-October 2003 Journal of ...nvlpubs.nist.gov/nistpubs/jres/108/5/j85nbr.pdf · [email protected] or Stephen Hsu, (301) 975-6120; [email protected]

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

NIST ESTABLISHES REFERENCE FORMEASURING FREQUENCY DEPENDENCEOF CAPACITORSRecent work at NIST could lead to improvements in thecapacitance calibration services at NIST by a factor ofthree or four. The primary maintenance standard forNIST capacitance calibrations consists of a bank offour 10 pF fused-silica standards (referred to as theFarad Bank) which are maintained in an oil bath at25 °C. The Farad Bank is calibrated twice a yearagainst the calculable capacitor at a frequency of1592 Hz. The calculable capacitor provides an absolutedetermination of capacitance in terms of length onlyand is the ultimate reference for all impedance meas-urements in the United States. Until recently, there wasa lack of a well-characterized reference capacitor overthe audio frequency range, resulting in large assigneduncertainties for capacitance calibrations to account forthe uncharacterized frequency dependence of the FaradBank.

The value of a standard capacitor may vary slightlywith frequency because the imperfect medium betweenits electrodes has varying degrees of dielectric relax-ation over the frequency range and the leads and elec-trodes of the capacitor have residual inductance. Usinga combination of a 1 pF cross capacitor that has negli-gible frequency dependence due to electrode surfacefilms and a 10 pF nitrogen dielectric capacitor with avery small residual inductance as references, NIST staffhave measured the frequency dependence of two 10 pFtransportable fused-silica capacitors from 50 Hz to 20kHz. The relative standard uncertaintiesdetermined at 400 Hz and 100 Hz (0.15 × 10–6 and 0.32

× 10–6, respectively) are smaller than the uncertaintiespreviously assigned to frequency dependence at thesefrequencies by a factor of five. This will lead toimprovements in the capacitance calibration servicesat NIST by a factor of three or four.

The results were presented in an invited talk inAugust at the 2003 National Conference of StandardsLaboratories; an archival paper describing the work hasbeen published in the September issue of Review ofScientific Instruments. NIST plans to transfer thefrequency dependence data to the Farad Bank and otherreference capacitance standards, so that in the nearfuture, improved capacitance calibrations will beavailable from NIST for the entire audio frequencyrange.CONTACT: Jerry Stenbakken, (301) 975-2440;[email protected].

MEASUREMENT/CALIBRATION TECHNIQUEFOR NANOMETER SCALE AVERAGE FILMTHICKNESS ON ATOMICALLY ROUGHSURFACES DEVELOPEDCurrent magnetic hard disks are protected by ananometer-thick layer of alcohol functionalized per-fluoroakylether and carbon overcoat. Achievement ofhigher areal density requires further reduction in thespace between the head and the magnetic layer athigher speed. The possibility of occasional impactsfrom head disk collisions requires that the adhesivestrength of the organic molecules be increased whileretaining the mobility of some of the molecules. Onepossible solution is to use a mixed molecular assemblyin which two separate species are assembled togetherto impart both adhesive strength and mobility.Because of the poor solubility characteristics of per-fluoroakylethers, such mixed films are very difficultto achieve. Hydrocarbon molecules can be used for thispurpose. One technical barrier is the measurement ofaverage film thickness at 10 Å ± 1 Å on a surface with15 Å to 25 Å peak-to-valley distance. There is nowidely accepted analytical technique for measuring thisthickness accurately and consistently.

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News Briefs

To address this issue, a master calibration samplewas created by depositing a known mass of hydro-carbon molecules in a dilute solution on magnetic harddisk surfaces and allowing the solvent to evaporateslowly. Knowing the mass of the film and the bulkdensity of the material, the thickness of the film can becalculated. To achieve uniformity of deposition andevaporation, it was necessary to confine the solutionto a known area and to overcome the wetting andmeniscus forces during the deposition and evaporationprocesses. A barrier film was used to define the area.Then, the solution was frozen and the solventwas allowed to evaporate slowly under a controlledatmosphere. The procedure was carried out in a cleanroom to minimize potential contaminants.

This technique has been used successfully to depositfilms with a range of hydrocarbon thickness from 3 Åto 25 Å, using disks of different roughness (isotropicand anisotropic), different carbon overcoat thickness,and different carbon overcoat chemistry (hydrogenatedcarbon, nitrogenated carbon, and a mixed hydrogenate/nitrogenated carbon). Consequently, this method can beapplied to a variety of engineering surfaces for filmthickness measurement, and it can be used to calibratedifferent analytical techniques used for suchmeasurements.CONTACT: Richard Gates, (301) 975-3677; [email protected] or Stephen Hsu, (301) 975-6120;[email protected].

NIST RESEARCHERS QUANTIFY CELLULARVIABILITY AND INFLAMMATORY RESPONSETO DENTAL BONDING RESINSImplanted biomaterials frequently evoke inflammatoryresponses, which are subsequently responsible for bio-medical implant failures. NIST researchers have devel-oped a metrology for the analysis and quantitation ofcellular inflammatory responses in vitro. The techniquewill accelerate biomedical device development byminimizing or eliminating the need for expensive invivo animal testing.

Real-time polymerase chain reaction (RT-PCR) andflow cytometry were used to quantify elevated cytokineproduction as an indicator of inflammatory responses tofour commercial dental resins. (Cytokines are proteinsthat are responsible for regulating both the duration andintensity of immune responses and for mediatingintercellular communication.) Murine macrophagescells exposed to resins containing Bis-GMA(2,2-bis[p-(2'-hydroxy-3'-methacryloxypro-poxy)phenyl]propane) and HEMA (2-hydroxyethyl metha-crylate) had the most adverse responses, as indicated by

the relative proportion of live cells to dead cells.Moreover, the other resin systems displayed inter-mediate levels of viability when compared with theuntreated control. The results demonstrate that cellularresponse to toxic leachables follows a distinct pathway,starting with up-regulation (elevated production) ofproinflammatory cytokines and, depending on thestrength of the response, terminating in extensivenecrosis (localized death of living cells).

For additional information, visit the PolymersDivision Web site at www.nist.gov/polymers.CONTACT: Newell Washburn, (301) 975-4348;[email protected] or LeeAnn Bailey,(301) 975-6803; [email protected].

NIST RESEARCHER DEVELOPS PROTOTYPEAUTOMATED COMMISSIONING TOOL WITHFRENCH SCIENTIFIC AND TECHNICALBUILDING CENTER (CSTB)A NIST researcher participated in a 3 month collabora-tion with CSTB in Paris, France, to develop an auto-mated commissioning tool for building air handlingunits. After developing the concept for an automatedcommissioning tool, NIST partnered with CSTBto code the fault detection algorithm, develop thegraphical user interface, and test the prototype tool ona real system. The retro-commissioning project tookplace in the ARIA Building at CSTB where none of thethree constant air volume air-handling units had beenpreviously commissioned. By interfacing the automat-ed commissioning tool to the building energy manage-ment system, test scripts can automatically commandchanges to system setpoints to achieve various operat-ing states and document system responses. In prelimi-nary results, several faults having significant impactson energy consumption and occupant comfort wereidentified, including sensor errors and impropersetpoints.CONTACT: Natascha Castro, (301) 975-6420; [email protected].

NIST PARTICIPATES IN DEMONSTRATIONOF FIRST RESPONDER TECHNOLOGIESTO FIREFIGHTERSOn July 16, 2003, NIST hosted a meeting of fire-fighters and rescue personnel to demonstrate technolo-gies under evaluation by the NIST Distributed Testbedfor First Responders. In attendance were firechiefs/commissioners and their associates from com-munities in Phoenix, Ariz.; New York City; Wilson,N.C.; King of Prussia, Pa.; Arlington, Charlottesville,


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Fairfax, and Prince William, Va.; and Fort Meade andMontgomery County in Maryland. A discussion on theneeds and priorities of first responders followed thedemonstration.

The technologies demonstrated included access tobuilding information database and dynamic buildingstatus from sensors, sensor-driven fire model using theNIST Virtual Cybernetic Building Testbed simulator,standardization of communications interface forsensors, biometrics for identification and authentica-tion, dynamic self-organizing wireless networks forvoice and data, voice over Internet, and emergencypersonnel localization and tracking.

NIST established the Distributed Testbed for FirstResponders to evaluate different technical approachesand to carry out the NIST mission of assisting industryin the development of standards for interoperability andopen systems. The testbed, which builds on workalready under way at NIST, will enable collaborativeresearch at NIST on issues relating to improving thesafety and effectiveness of first responders. Researchwill be conducted on a variety of topics, includingdeveloping and demonstrating highly capable commu-nication and localization systems, increasing thequality and quantity of information available to firstresponders, improving information display anddecision support systems, and the seamless integrationand interoperability of smart wireless sensor networksin buildings.CONTACT: George Kelly, (301) 975-5850; [email protected] or Kang Lee, (301) 975-6604; [email protected] or Nader Moayeri, (301) 975-3767; [email protected].

NIST UPDATES HEALTH CARE COMMUNITYON IT SECURITY WORKOn July 29, 2003, the Security Health Care Certi-fication and Accreditation Work Group met at NIST toreview the latest work at NIST regarding IT securitystandards and guidelines. Approximately 60 peopleparticipated in the meeting, of which about 90 % wereprivate-sector health care service/support providers.The participants were interested in learning and assess-ing relevant NIST IT security standards and guidelinesthey could draw upon to aid the community in comply-ing with requirements of the Health InsurancePortability and Accountability Act (HIPAA) FinalSecurity Rule that was issued by the U.S. Departmentof Health and Human Services (HHS) in February2003. The HIPAA Final Security Rule identifies NISTand several IT security documents as sources ofinformation.

NIST provided presentations on draft NIST SpecialPublication (SP) 800-37, Guidelines for the SecurityCertification and Accreditation of Federal InformationTechnology Systems; draft Federal InformationProcessing Standard 199, Standards for Categorizationof Federal Information and Information Systems;the status and overview of forthcoming draft NISTSP 800-53, Guidelines for Selection and Specificationof Security Controls for Information Systems;and draft SP 800-50, Building an InformationTechnology Security Awareness and Training Program.(For copies of the draft documents, see http://csrc.nist.gov/publications/drafts.html.) NIST personnelalso briefed the group on a joint NIST and Center forMedicare and Medicaid Services/HHS project toproduce a resource guide of NIST information forsupporting implementation of the HIPAA SecurityRule.

URAC (also known as the American AccreditationHealthCare Commission), a 501(c)(3) non-profitcharitable organization founded in 1990 to establishstandards for the health care industry, is helping tocoordinate the health care community in assessingsecurity standards and best practices for health careinformation systems through the Security Health CareCertification and Accreditation Work Group.Ultimately, the workgroup hopes to develop a commonset of health care security standards that will coversecurity policies, procedures, controls, and auditingpractices for IT security in health care informationtechnology systems.CONTACT: L. Arnold Johnson, (301) 975-3247;[email protected].

NIST ISSUES REFERENCE MATERIAL 8457TO AID ORTHOPEDIC IMPLANTMANUFACTURERS AND RESEARCHERSReference material (RM) 8457, which consists of0.5 cm cubes of orthopedic-grade ultra-high molecularweight polyethylene that are well suited for measure-ments of cross-link density by a new ASTM Inter-national swell-test method, has been issued. Scientistsat NIST produced the RM in response to recent interestamong manufacturers and researchers of orthopedicimplants to improve wear performance by ionizingradiation treatments. These treatments are known toproduce new chemical bonds (cross-linking) betweenthe polymer molecules. The extent to which cross-link-ing occurs during the radiation treatment is an impor-tant design variable. In recognition of its importance,ASTM International issued a new standard test methodfor cross-linking, F2214-02: Standard Test Method for


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In Situ Determination of Network Parameters ofCrosslinked Ultra-High Molecular-Weight Polyethylene.The standard test method references RM 8457, alongwith results of a round-robin analysis of the method.NIST supplied specimens for the round-robin testingthat were manufactured from the same material—RM 8456—as RM 8457.

The RM can be purchased at the Standard ReferenceMaterial/RM Web site: www.nist.gov/srm.CONTACT: Bruno Fanconi, (301) 975-6769; [email protected] or John Tesk, (301) 975-6799;[email protected].

NIST HELPS DEVELOP NEW METHOD TOATTACH LONG-CHAIN ALIPHATICMOLECULES TO SILICONNIST scientists have developed an improved solution-based method for the direct attachment of long-chainaliphatic molecules to Si. In this method, ultravioletradiation is used to assist the attachment of alcohols tothe hydrogen-terminated Si(111) surface to success-fully form molecular monolayers. To investigate thequality of these organic monolayers, they werephysically and chemically characterized with infraredspectroscopy, spectroscopic ellipsometry, and contactangle measurements. The electrical properties of theseorganic films were probed by using current-voltage andcapacitance-voltage (CV) measurements obtainedfrom a metal-organic-silicon test structure fabricated bypost-monolayer metal deposition. The effect ofdiffering alkane chain length on the electrical proper-ties was investigated, and the CVs are in agreementwith traditional theory for a metal-insulator-semi-conductor. Initial results of this research were present-ed at the 2003 meeting of the American ChemicalSociety.

Direct attachment of organic molecules to the siliconsurface is of increasing importance for emergingmolecular electronics applications as devices incorpo-rating molecules chemically bonded to silicon areamenable to integration with existing Si processingtechniques. In addition, the chemical bond between Siand organic molecules is stronger and, therefore,expected to be more stable than the metal-moleculebond typically used in the assembly of molecularelectronic devices. However, forming this Si-moleculebond to create self-assembled monolayers can bedifficult. Costly and time consuming ultra-highvacuum techniques are often used to attach moleculesto Si.CONTACT: Christina Hacker, (301) 975-2233; [email protected].

NIST MEASURES DIPOLE MOMENT OFSEMICONDUCTOR QUANTUM DOTSNIST researchers have developed a new measurementtechnique for the characterization of semiconductorquantum dots (QDs), which are used in quantumcomputing, optical communication, and quantumcryptography applications. Little detailed knowledge ofthe transition dipole moment of QDs previously hadbeen available, although it is critical in determininggain for QD laser design and in implementing thecoherent manipulation of the QD state in quantum logicgates that may be part of future-generationoptical computers.

A NIST researcher developed a new technique todirectly measure the dipole moment of QDs and hasapplied it to self-assembled InGaAs/GaAs dots. It relieson the measurement of pulses of light that exit anoptical waveguide containing the QDs as the lightreflects multiple times from the waveguide facets.Light that is coupled out of the waveguide is mixedwith a variably delayed gating pulse in a non-linearcrystal to time resolve the output. The absorptionco-efficient is determined by comparing the energy ofsuccessive pulses and taking into account the measuredwaveguide facet reflectivity and background absorp-tion, as determined from measurements of a waveguidethat does not contain QDs. The dipole moment isderived from the ground state absorption and the QDareal density, which was determined from transmissionelectron micrographs generated by collaborators at theNational Renewable Energy Laboratory. Quantum dotdensity variation in the samples proved to be the largestsource of uncertainty in the measurement.

The NIST dipole moment measurement techniqueovercomes the large uncertainties of other measure-ment techniques which were based on thresholdcurrents of laser diodes, had large background materialabsorption, or had difficulty estimating couplingefficiency into and out of the QD region. Techniquesare now being developed to directly measure theabsorption of a single, isolated quantum dot.CONTACT: Kevin Silverman, (303) 497-7948; [email protected].

NIST DELIVERS HIGH ACCURACYCALIBRATION INSTRUMENT FOR NAVYOPTICAL FIBER SENSORSA NIST scientist designed, characterized, and recentlydelivered a calibration instrument for optical fiberBragg grating (FBG) strain and temperature sensors tothe Naval Research Laboratory (NRL). This instrumentwill be used to calibrate the Navy’s strain sensor read-

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out units that will be deployed throughout the Navyfleet. The project was funded by the Navy’s Coordinationand Calibration Group.

FBGs are a periodic modulation of refractive indexwritten directly into the core of optical fiber. Thisperiodicity causes a narrow spectral bandwidth of thelight traveling in the fiber to be selectively reflectedfrom the FBG. The center wavelength of the reflectedlight changes as the FBG is subjected to strain andtemperature changes, making FBGs attractive as small,lightweight, networkable sensors.

The calibration instrument delivered to the NRLcontains four stabilized FBGs whose center wave-lengths were accurately measured using both a tunablelaser measurement system and low-coherence inter-ferometry. Careful uncertainty analysis on bothtechniques yielded a 2 pm expanded uncertainty onthe calibration instrument. It was found that the“stabilized” FBGs actually drift slightly with time(a few picometers per year). This instability illustratesthe need for accurate metrology related to FBG charac-teristics. FBG sensors have potential uses in medicalapplications and as strain sensors to measure thestructural integrity of buildings, bridges, and aircraft.NIST researchers are investigating FBG metrologyneeds for these applications.CONTACT: Shellee Dyer, (303) 497-7463; [email protected].

ULTRA-SMALL-ANGLE X-RAY SCATTERING(USAXS) IMAGING OF HUMAN ANDARTIFICIAL TISSUESUSAXS imaging is a high-contrast imaging techniquebeing developed by NIST researchers. It providesdirect images of the shapes and three-dimensionalarrangement of the scattering objects within a samplethat is unobtainable using conventional x-ray imagingmethods. USAXS imaging, combined with USAXSanalysis, provides information on the size distributions,shapes, and three-dimensional arrangements of scatter-ing objects. When applied to human and artificialtissues, these techniques improve the understanding ofthese materials and assist in the development of newman-made biomaterials. The goal of this research isnondestructive observation of the critical structuresresponsible for the properties of natural and man-madetissues.

The following paragraphs describe our most recentresults from USAXS imaging and USAXS analysis onhuman ankle cartilage and man-made tissue scaffolds.

USAXS images and USAXS scans were made ofhuman ankle cartilage mounted in a wet cell to forestall

dehydration. Images were recorded at locations nearthe bone/cartilage interface, in the center, and near thecartilage surface. Images taken with the scatteringvector parallel to the cartilage surface showed fewstructures. Images taken with the scattering vectorperpendicular to the surface showed copious structuresboth near the surface, where the collagen fibers areparallel to the surface, and on the opposite side near thebone where the collagen fibers are perpendicular to thebone. The middle of the sample showed few distinctstructures supporting the model of “disorder” in thisregion.

Polymer-based tissue scaffolds for growing tissuesare under development, but the degree of crystallinityon the pore surfaces can strongly affect cell growth. Toexplore this effect, a polymer scaffold (porous Poly-Capraloactone, PCL) was produced with an additionalannealing/cooling step to alter the degree of crystallini-ty. USAXS scans from the tissue scaffolds containeda pronounced peak produced by the lamellar structureof the polymer. The density difference between theamorphous and crystalline phases of the scaffold leadsto enhanced scattering at the boundaries. Comparisonand superposition of the images made in radiographicmode and USAXS imaging mode allowed researchersto determine the locations of the crystallites relativeto the pore surfaces, and an analysis of the scatteringcurve enabled them to extract the crystallite sizedistribution.CONTACT: Gabrielle Long, (301) 975-5975; [email protected] or Lyle Levine, (301) 975-6032;[email protected].

SUBSCRIPTIONS TO ONLINE JOURNAL OFPHYSICAL AND CHEMICAL REFERENCE DATAINCREASE GREATLYIn December 1999, NIST changed to a sole partnershipwith the American Institute of Physics (AIP) inpublishing the Journal of Physical and ChemicalReference Data (JPCRD). Since that time, AIP hasvigorously marketed the journal and the number ofprint subscribers has stabilized. More importantly, AIPhas included the journal in package offerings toconsortia of academic and non-profit organizationinstitutions. In late September 2003, AIP announcedthat the number of online subscribers had risen from470 to today’s total of 1128 institutions. The greatincrease dramatically improves the availability of NISTstandard reference data and once again demonstratesthe revolutionary nature of online dissemination.

The Journal of Physical and Chemical ReferenceData is an internationally renowned publication

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featuring articles evaluating published scientific data.Subjects include thermodynamics, thermophysics,atomic and molecular spectra, electron, atomic andmolecular collisions, surface science and solubilities ofsubstances. Articles in the journal are not subject topage constraints and contain comprehensive tables ofrecommended data values as well as detailed explana-tions of evaluation criteria and reviews of data genera-tion procedures. About 50 % of the journal articles areauthored by NIST data experts and the remaindercome from scientists throughout the world. Since itsinception in 1972, the journal has published over 626articles, nine monographs, and 12 supplements,making it one of the largest ongoing handbooks ofevaluated chemical and physical data in the world.CONTACT: Geraldine Dalton, (301) 975-2214; [email protected].

ABSOLUTE SURFACE COVERAGEMEASUREMENT DEMONSTRATEDUSING VIBRATIONAL OVERTONESUsing evanescent-wave cavity ring-down spectroscopy(EW-CRDS), a technique pioneered at NIST, measure-ment of absolute surface coverage with submonolayersensitivity has been demonstrated. The first C-Hstretching overtones of trichloroethylene (TCE),cis-dichloroethylene, and trans-dichloroethylene wereprobed for the gas- and adsorbed-phase species using aseeded optical parametric amplifier. Polarized absoluteadsorbate spectra were obtained by EW-CRDS using ahigh-finesse fused-silica monolithic optical resonator,while absolute absorption cross sections for the gas-phase species were determined by conventional CRDS.A measure of the average transition moment orientationon the surface, which is required for monolayer cover-age determination, was derived from the polarizationanisotropy of the surface spectra. As the vector-charac-ter of absorption yields only an average tilt angle tocharacterize the orientation distribution, the methodis accurate for highly oriented, unimodal surfacedistributions. For such well-ordered systems, cover-age uncertainties of ±0.1 monolayer are possible. TheEW-CRDS technique also was shown to providea significant advance in sensitivity for chemicaldetection of TCE, which is a major environmentalcontaminant.

This work, performed collaboratively by NIST andthe Eindhoven University of Technology in theNetherlands, has been supported by the EnvironmentalManagement Science Program of the Department ofEnergy.CONTACT: Andrew Pipino, (301) 975-2565; [email protected].

NEW CD-ROM RELEASEDNIST has just released a new CD-ROM, entitled NISTSpecial Publication 1001, Basic Mass Metrology,specifically aimed at training metrologists in concepts,procedures, and mathematics (including simplestatistics) needed for basic mass metrology. Created byNIST staff and contractors, the CD-ROM represents theculmination of a 3 year effort to provide an interactive,multimedia supplement/reinforcement for a basic massmetrology seminar.

A paper describing NIST efforts to create an effec-tive CD is also available. The paper is posted atwww.nist.gov/labmetrology. The paper shared the BestPaper Award at the 2003 Measurement ScienceConference and was discussed at the 2003 NCSLIWorkshop and Symposium.

The Basic Mass Metrology CD-Rom will supple-ment the training that is offered to weights andmeasures officials and ensure that they have the samebasic knowledge when attending the NIST trainingsessions.CONTACT: Georgia Harris, (301) 975-4014; [email protected].

NIST PUBLISHES NEW INFORMATIONSECURITY GUIDELINESNIST recently released five new information securityguidelines as NIST special publications (SPs):• NIST SP 800-35: Guide to Information TechnologySecurity Services. The guide provides assistance withthe selection, implementation, and management of ITsecurity services by guiding organizations through thevarious phases of the IT security services life cycle.The factors to be considered when selecting, imple-menting, and managing IT security services include thetype of service arrangement; service provider qualifi-cations, operational requirements and capabilities,experience, and viability; trustworthiness of serviceprovider employees; and the service provider’s capabil-ity to deliver adequate protection for the organizationsystems, applications, and information.• NIST SP 800-36: Guide to Selecting InformationSecurity Products. The selection of IT securityproducts is an integral part of the design, development,and maintenance of an IT security infrastructure.The guide defines broad security product categories,specifies product types within those categories,and provides a list of general characteristics andquestions an organization can ask when selecting aproduct.• NIST SP 800-42: Guideline on Network SecurityTesting. The guide stresses the need for an effective

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security testing program within federal agencies. Itidentifies network testing requirements, discusses howto prioritize testing activities with limited resources,and describes several network security testingtechniques and tools. Also presented is a framework forincorporating security into the information systemdevelopment life cycle (SDLC) process. The guideseeks to help organizations select and acquire cost-effective security controls by explaining how to includeinformation system security requirements in the SDLC.• NIST SP 800-50: Building an Information TechnologySecurity Awareness and Training Program. The publi-cation provides detailed guidance on designing, devel-oping, implementing, and maintaining a comprehen-sive awareness and training program as part of anorganization’s IT security program. It provides guide-lines that can help federal agencies meet their securitytraining responsibilities as contained in the FederalInformation Security Management Act and Office ofManagement and Budget guidelines.• NIST SP 800-64: Security Considerations in theInformation System Development Life Cycle. The guidepresents a framework for incorporating security into theinformation system development life cycle (SDLC)process. It seeks to help organizations select andacquire cost-effective security controls by explaininghow to include information system security require-ments in the SDLC.

The five security guidelines are available fordown-load at http://csrc.nist.gov/publications/nistpubs/index.html.CONTACT: Edward Roback, (301) 975-3696; [email protected].

NIST RESEARCHERS DEVELOPHIGH-TEMPERATURE SUPERCONDUCTINGMICROWAVE POWER LIMITERSuperconducting electronics are being explored formany high-performance communications applicationsthat require very low insertion loss, or unsurpassedsensitivity or dynamic range. However, such high-performance superconducting components are vulner-able to damage if exposed to high-power transientsignals, such as lightening strikes or unintentional radarillumination and thus need to be protected by an inputmicrowave power limiter. Conventional power limiterswould increase the insertion loss or significantly reducethe dynamic range of the system, thereby compromis-ing the advantages of using superconducting compo-nents.

In order to address these issues, researchers havedesigned, fabricated, and tested a microwave power

limiter based on high-temperature superconductor thin-film technology. In order to be compatible with thehighest performance superconducting digital circuits,researchers have designed a limiter for minimuminsertion loss and maximum possible bandwidth. Thepower limiter takes the form of a 50 Ω coplanar wave-guide (CPW) transmission line fabricated from aYBa2Cu3O7–δ film grown on a sapphire substrate. TheCPW transmission line is reversibly driven from thelow-loss superconducting state to the high-loss normalstate when the microwave currents within the deviceexceed a critical value. When operated at 70 K, thesignal limiter displays very low insertion loss andextremely wide bandwidth in the nonlimiting state withconstant impedance over the entire microwave range,making it essentially “transparent” to the system. Whenthe input power exceeds the designed limit, the deviceswitches into the normal state, effectively blocking thesignal above the critical value. The device providesonly the amount of attenuation that is needed andcontinues to pass a portion of the incident signal duringthe overpower event.

One of the key parameters of a microwave powerlimiter is its switching time. In order to protectsensitive components from high-power signals, thelimiter must turn on in a sufficiently short period oftime. The researchers have demonstrated that the super-conducting limiter switches from the non-limiting tothe limiting state in less than a nanosecond, with nodetectable leakage through the device on this timescale. The superconducting limiter is now being evalu-ated for use in a variety of high performance communi-cation systems.CONTACT: James Booth, (303) 497-7900; [email protected].

NIST RESEARCHERS MODELANTI-REFLECTION STRUCTURESFOR PHOTON NUMBER RESOLVINGOPTICAL DETECTORSNIST researchers have successfully modeled anti-reflection structures that could be used with tungstensuperconducting transition-edge sensors (TES) toincrease the quantum efficiency of detection of a1.55 µm photon from 20 % to 98.5 %. By using areflecting layer underneath the detector metal layer(tungsten) and a single layer anti-reflection coatingabove the tungsten, the quantum efficiency of a photonbeing absorbed in the tungsten can be significantlyenhanced. After carefully measuring the optical proper-ties of thin films of tungsten, silicon oxide, and siliconnitride fabricated in a NIST cleanroom, optical meas-

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urements of anti-reflection structures agreed withnumerical calculations for their performance. A struc-ture with >98.5 % absorption of photons in a tungstenfilm was fabricated. In principle, >99 % absorptionshould be possible with better control of thicknesses ofthe various films.

Improvements in the quantum efficiency of detectionfor tungsten films fabricated into TES sensors will havea significant impact on several areas of research,including metrology for quantum key distributionsystems, quantum optics, and linear optical quantumcomputing.CONTACT: Sae Woo Nam, (303) 497-3148; [email protected].

NIST PHOTON NUMBER RESOLVINGDETECTORS CONTRIBUTE TO QUANTUMKEY DISTRIBUTIONIn collaboration with a team of researchers atLos Alamos National Labs (LANL), researchers atNIST have, for the first time, combined the fiber-basedquantum key distribution system demonstrated by theLANL team with the photon number resolving detec-tors developed by NIST. The fiber-based system usedlight from a weak coherent laser pulse at 1310 nm totransmit key material and attenuators between thetransmitter and receiver to simulate fiber losses overlong distances.

As part of the Defense Advanced Research ProjectsAgency’s Quantum Information Science and Tech-nology program, NIST researchers have designed andbuilt a prototype single photon detection system thathas demonstrated the ability to count the number ofphotons in a short pulse of light with no dark counts.The detectors are superconducting transition-edgesensors (TES), optimized for the detection of opticaland telecommunication wavelength photons. Eachphoton or group of photons absorbed by the TESdevices produces a signal that is a short current pulsewith a relatively fast rise time, <1 µs, and a decay timeof 20 µs.

With conventional detectors, the dark count rate isresponsible for an increased error rate and, consequent-ly, a loss of security over long distances. Because of theextremely low dark count rate with a TES detector, itshould be possible to securely transmit key materialover longer distances (≈100 km).CONTACT: Sae Woo Nam, (303) 497-3148; [email protected].

NIST SUCCESSFULLY MITIGATES NOISE INSUPERCONDUCTING THIN-FILM SENSORSNIST researchers are building large-format arrays ofcryogenic sensors for materials analysis and astronomy.The performance of these sensors has been limited byexcess noise sources not explained by existingtheories. Researchers recently measured sensors withdifferent geometric noise-mitigation features andidentified designs in which the excess noise is heavilysuppressed. The most interesting features implementnormal-metal bars across the sensor in the directionperpendicular to the current flow. These results provideclearer understanding of noise sources in super-conducting films. It is hoped that these designs willresult in improved detector performance.CONTACT: Joel Ullom, (303) 497-4408; [email protected].

FIBER LASER-BASED FREQUENCY COMBFOR FREQUENCY METROLOGY IN THEINFRARED DEVELOPED BY NISTNIST staff recently developed a phase-locked“frequency comb” in the 1100 nm to 2200 nm wave-length region using fiber optic technology. This novelfrequency comb should enable high-precision frequen-cy metrology experiments in the near infrared and, inparticular, across the telecommunications region of1300 nm to 1600 nm. Indeed, over the past severalyears, stabilized frequency combs have revolutionizedfrequency metrology and optical clocks. However,prior to the present work, all self-referenced, phase-locked frequency combs used bulk-optic solid-statelasers and covered only the visible and very nearinfrared. This fiber laser-based comb extends thiswavelength coverage 1000 nm further into the infrared.In addition, the fiber laser-based system can be muchmore compact, robust, power-efficient and lighter thana bulk optic solid state laser system, and can requireless alignment. Finally, it can be integrated easily into atelecommunication system.

The phase-locked frequency comb is based on amode-locked, erbium-doped, fiber laser whose outputis amplified and spectrally broadened in novel disper-sion-flattened, highly non-linear optical fiber to spanfrom 1100 nm to 2200 nm. This super-continuumactually comprises a comb of frequency lines, separat-ed by the laser repetition rate and with an arbitraryfrequency offset. Borrowing the now standardtechniques used with Ti:sapphire laser-based systems,researchers phase-locked both the comb spacing and


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offset to an RF oscillator. If the RF oscillator is phase-locked to an atomic frequency standard, the comb willform an accurate frequency ruler covering the entire

near infrared region from 1100 nm to 2200 nm. Anyunknown optical frequency then can be measured bysimply comparing its frequency to that of the nearesttooth of the stabilized frequency comb.CONTACT: Nathan Newbury, (303) 497-4227; [email protected].

PATENT ISSUED ON NIST INTEGRATINGSPHERE-BASED WEATHERING DEVICEPatent Number 6,626,052, “Method and Apparatusfor Artificial Weathering,” was assigned to two NISTscientists on Sept. 30, 2003, for the device known as theSimulated Photodegradation via High Energy RadiantExposure (SPHERE). It can uniformly irradiate testspecimens with a high-intensity ultraviolet radiant fluxwhile accurately and precisely controlling this flux, inaddition to other weathering elements such as tempera-ture and relative humidity, in order to predict theservice life of polymeric materials. The NIST SPHEREprovides a source of high-intensity, collimated UV radi-ation with a spatial uniformity greater than 95 %.Ultraviolet radiant fluxes equivalent to approximately22 “suns” of solar ultraviolet radiation can be achievedat 32 sphere exit ports. Temperature and relativehumidity in the specimen chambers attached to thesphere can also be independently and precisely con-trolled over wide temperature and relative humidityranges and over long exposure periods.

Additional information on the NIST SPHERE andthe NIST Service Life Prediction Program can be foundat http://slp.nist.gov.CONTACT: Joannie Chin , (301) 975-6815; [email protected].


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