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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Chapter 5

Physics Laboratory

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

PANEL MEMBERS

David H. Auston, Rice University, Chair

Janet S. Fender, Air Force Research Laboratory, Vice Chair

Anthony J. Berejka, Consultant, Huntington, N.Y.

Gary C. Bjorklund, Bjorklund Consulting, Inc.

D. Keith Bowen, Bede Scientific Incorporated

Shirley Chiang, University of California, Davis

Gregory R. Choppin, Florida State University

Stuart B. Crampton, Williams College

Leonard S. Cutler, Hewlett-Packard Company

Ronald O. Daubach, OSRAM SYLVANIA Development, Inc.

Paul M. DeLuca, Jr., University of Wisconsin–Madison

Daniel J. Larson, Pennsylvania State University

David S. Leckrone, Goddard Space Fight Center, NASA

Harold Metcalf, State University of New York, Stony Brook

David W. Pratt, University of Pittsburgh

Neville V. Smith, Lawrence Berkeley National Laboratory

Winthrop W. Smith, University of Connecticut

Robert G. Wheeler, Yale University

Submitted for the panel by its Chair, David H. Auston, and its Vice Chair, Janet S. Fender, this assessment of the fiscal year 1999 activities of the Physics Laboratory is based on site visits by individual panel members, a formal meeting of the panel on March 11–12, 1999, in Boulder, Colo., and documents provided by the laboratory.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

LABORATORY-LEVEL REVIEW

Laboratory Mission

According to laboratory documentation,1 the mission of the NIST Physics Laboratory is to support U.S. industry by providing measurement services and research for electronic, optical, and radiation technologies.

This mission is consistent with the overall mission of NIST. It is broad and encompasses a wide range of activities compatible with the core competencies of the laboratory. Specific programs are generally appropriate for the laboratory's mission, as discussed in detail in the divisional reports below. The laboratory is organized into six divisions: Electron and Optical Physics, Atomic Physics, Optical Technology, Ionizing Radiation, Time and Frequency, and Quantum Physics. (Quantum Physics, that component of the laboratory at JILA, a joint NIST-University of Colorado research institute, is reviewed in alternate years by a separate subpanel and so is not treated here.)

Technical Merit and Appropriateness of Work

Overall, the panel found the work of the laboratory to be of high technical merit. In many cases, NIST Physics Laboratory researchers are at or define the state of the art in their area of research. Research programs and projects are generally appropriate to the mission of the laboratory and of NIST.

The panel heard detailed presentations on two special topics: the laboratory's work in databases and measurement services, and its proposed initiative in optical technology.

The Physics Laboratory plays a very active role in the NIST database portfolio, currently maintaining eight databases in the areas of fundamental constants, resonance ionization mass spectroscopy, atomic energy levels and transition probabilities, spectral line broadening, molecular data, ionizing radiation, and neutron cross sections. Providing high-quality, evaluated data on basic atomic and molecular properties is a long-standing activity at NIST and represents a very fundamental response to the NIST mission. This information is regarded worldwide as the most authoritative and reliable data available, and NIST data have many users in industry, academia, and government. However, resources devoted to database activities have been at best flat and, in most cases, have decreased dramatically in real terms in the past 15 years. The level of effort devoted to database activities has consequently dropped. The panel applauds the Physics Laboratory's plan to bring new personnel into this program by a temporary infusion of laboratory discretionary funds over the next 5 years. This will allow training of new personnel before current experts in these areas retire. However, there appears to be a lack of ownership of responsibility for database activities at NIST and insufficient commitment to what is a core function of the institute. Cohesive management of database activities is necessary, including a comprehensive review of the need for the various categories of evaluated data, a better understanding of the users of the data, and an evaluation of how well users and potential users are being reached and their data needs met. The panel has in mind the sort of central

1  

U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology, Physics Laboratory: Annual Report 1997, National Institute of Standards and Technology, Gaithersburg, Md., 1998.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

coordination the NIST Office of Microelectronics Programs provides for NIST research programs that provide measurements, measurement methods, and standards relevant to the microelectronics industry. Sufficient stable funding for NIST database activities must be assured to avoid the loss of critical resources for the nation's economy and scientific enterprise.

The laboratory presented the panel with an overview of its planned initiative in optical technology. This initiative is in response to the needs and developments in this area predicted by the National Research Council (NRC) report Harnessing Light: Optical Science and Engineering for the 21st Century.2 It was clear from the presentation that some of the laboratory's current programs map well onto the needs and growth areas identified in Harnessing Light, and the laboratory recognizes that it can play an even greater role in this area, which the NRC report predicts to be as important in the next 20 years as semiconductors were in the 1980s and 1990s. Since the proposal is at an early stage in its development, the presentation given to the panel did not contain well-developed goals. The panel recommends that as the proposal develops, the specific projects envisioned be closely tied to the laboratory's mission.

The panel offers some suggestions for the optical technology initiative. First, Harnessing Light emphasizes the interdisciplinary nature of developments in optics and optical technology. The Physics Laboratory initiative, to be successful, should have an interdisciplinary strategy, including, for example, expertise and participation from the NIST Materials Science and Engineering, Chemical Science and Technology, Electronics and Electrical Engineering, and Information Technology Laboratories. The initiative should emphasize the importance of sensors and their applications for real-time, high-speed process monitoring. For example, the use of such sensors in the chemical processing industry alone has a huge potential for economic benefit. Potential projects in telecommunications are lacking any reference to wavelength division multiplexing technology, which is seen as key to achieving large, broad-bandwidth fiber-optic networks for practical applications. The laboratory can also use its expertise in near-field scanning optical microscopy to characterize important devices and materials types such as vertical cavity surface-emitting lasers and photonic bandgap materials. Harnessing Light: Optical Science and Engineering for the 21st Century also emphasizes the importance of education programs to ensure that the skill base necessary to lead in this area is available to the country. Although education is not a primary mission of NIST, the Physics Laboratory might highlight how it participates in meeting this need through its Summer Undergraduate Research Fellowships Program.

Impact of Programs

The Physics Laboratory's programs are generally effective and very important to those customers that the laboratory reaches. Examples of impact are found in the divisional reports below. Overall, the panel was very satisfied with the impact of the laboratory's programs.

Laboratory management did not seem to comprehend the panel's observation in its previous assessment that “it was not clear . . . whether program priorities had been chosen based first on industry needs, rather than on laboratory capabilities. ” In other words, it often appears that programs are chosen based on expertise available and the potential industrial use considered only secondarily. This probably generates a different set of programs than a process that first

2  

National Research Council, Harnessing Light: Optical Science and Engineering for the 21st Century, National Academy Press, Washington, D.C., 1998.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

identifies industry needs in an area of technology and then considers which of those needs can be addressed with laboratory expertise and are appropriate to NIST. Consideration of this distinction might assist the laboratory as it seeks to maximize the impact of its programs.

Laboratory Resources

Funding sources3 for the Physics Laboratory (in millions of dollars) are as follows:

 

Fiscal Year 1998

Fiscal Year 1999 (estimated)

NIST-STRS, excluding Competence

31.2

33.6

Competence

1.9

1.6

ATP

1.8

1.8

Measurement Services (SRM production)

0.2

0.2

OA/NFG/CRADA

9.5

9.9

Other Reimbursable

3.5

3.3

Total

48.1

50.4

As of January 1999, staffing for the Physics Laboratory included 204 full-time permanent positions, of which 172 were for technical professionals. There were also 56 nonpermanent and supplemental personnel, such as postdoctoral research associates and part-time workers.

The facilities problems noted in the last several assessments continue, including the need for greater air cleanliness, temperature control, and vibration isolation for critical experiments. The planned Advanced Measurement Laboratory, if built, would meet these needs for the laboratory's most sensitive experiments. In the meantime, methods that try to work around these problems divert resources, such as the time and energy of the highly trained and educated staff, from more productive uses.

Overall the quality of the staff of the laboratory is excellent. The staff of the Physics Laboratory represent one of the world's finest assemblies of talent in many areas of physics. Staff morale is good and contributes to the high level of accomplishment witnessed by the panel.

3  

The NIST Measurement and Standards Laboratories funding comes from a variety of sources. The laboratories receive appropriations from Congress, known as Scientific and Technical Research and Services (STRS) funding. Competence funding also comes from NIST's congressional appropriations, but it is allotted by the NIST director's office in multiyear grants for projects that advance NIST's capabilities in new and emerging areas of measurement science. Advanced Technology Program (ATP) funding reflects support from NIST's ATP for work done at the NIST laboratories in collaboration with or in support of ATP projects. Funding to support production of Standard Reference Materials (SRMs) is tied to the use of such products and is classified as Measurement Services. NIST laboratories also receive funding through grants or contracts from other government agencies (OA), from nonfederal government (NFG) agencies, and from industry in the form of Cooperative Research and Development Agreements (CRADAs). All other laboratory funding including that for Calibration Services is grouped under Other Reimbursable.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

DIVISIONAL REVIEWS

Electron and Optical Physics Division
Division Mission

According to division documentation, the mission of the Electron and Optical Physics Division is to develop measurement capabilities needed by emerging electronic and optical technologies, particularly those required for submicron fabrication and analysis.

Technical Merit and Appropriateness of Work

In pursuit of its mission, the division maintains an array of research, measurement, and calibration activities, including the following: (1) the central national basis for absolute radiometry in the far ultraviolet and extreme ultraviolet (EUV) regions of the electromagnetic spectrum, spanning the photon energy range of 5 eV to 250 eV, using a combination of ionization chambers, calibrated transfer standard detectors, and the Synchrotron Ultraviolet Radiation Facility (SURF) III electron storage ring, which provides a dedicated source of radiation over this spectral range; (2) world-class capabilities in scanning electron microscopy for polarization analysis (SEMPA) and scanning tunneling microscopy (STM) for imaging surface magnetic structures relevant to the magnetic recording industry and for surface structure and measurement techniques necessary for atomic-level device fabrication; (3) EUV optics characterization facility to perform measurements of EUV optical components and systems and to support application of such optics in microlithography, microscopy, and telescopy.

The division's Photon Physics Group is pursuing a well-motivated program in the area of EUV and soft x-ray physics that exploits the unique character of the SURF facility while also pursuing cognate techniques at the Advanced Photon Source at the Argonne National Laboratory. The primary areas of relevance are x-ray microscopy, microlithography, and x-ray astronomy. The program in EUV optics (reflectometry, optical constant determination, figuring by deposition, and multilayer manufacture and characterization) is of considerable value to the microelectronics industry, especially in view of the emergence of EUV technology as a potential choice for use as the next lithographic technique in the Semiconductor Industry Association (SIA) National Technology Roadmap for Semiconductors (NTRS). Work on the determination of optical constants of in situ deposited films is important and will permit the division to establish a database allowing the design of efficient normal incidence EUV multilayer mirrors. The group's calibration of instrumentation on x-ray astronomy satellites is of importance to the National Aeronautics and Space Administration (NASA). Its activities in EUV/x-ray microscopy include the development of a photon-to-electron conversion microscope and the development of a Schwarzchild water-window microscope.

The Photon Physics Group, in collaboration with the Optical Technology Division, has established a new radiometric facility for the calibration of photodetectors in the 50 to 400 nm wavelength range. The panel encourages the plan to extend these methods and to improve accuracy in the 11 to 13 nm range. This range is of interest to the EUV Lithography-Limited Liability Corporation (EUVL-LLC), which is a cooperative venture between Lawrence Livermore National Laboratory, Lawrence Berkeley National Laboratory, Sandia National

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

Laboratories, Intel Corporation, Motorola Corporation, and Advanced MicroDevices. For more facile transfer of calibrations, it is important that the group also develop new detector materials and configurations that are resistant to the deleterious effects of radiation and contamination.

The group uses the Advanced Photon Source to perform tomographic reconstructions of integrated circuit interconnections. The ability to examine three-dimensional buried structures and their defects will be directly applicable to future generations of integrated circuits. The potential to combine this technique with x-ray spectroscopy to produce three-dimensional maps of elemental composition of samples is particularly exciting.

The Far Ultraviolet Physics Group's upgrade of SURF from SURF II to SURF III is well advanced. The critical parameter is an azimuthal uniformity of the magnetic field, and an impressive uniformity of 1 part in 104 has been achieved. The ring itself is operating routinely (typical a current of 25 mA at 205 MeV), and now the beam lines are to be reinstalled. The group's principal goal is to assert world leadership as a primary standard for spectral irradiance measurement, consistent with the mission of NIST. Because of its low energy, SURF also fills a special niche in the nation's portfolio of synchrotron radiation facilities. Its capability for infrared microscopy is especially exciting and should attract use by local industry and other federal agencies if vigorously promoted. The SURF director has recently retired, and his replacement has not yet been found. Other retirements within the group may be pending. As SURF comes out of the upgrade phase and goes into operation, the division should give serious consideration to using this opportunity to restructure its management in order to integrate the facility more fully into the division's scientific program.

The Electron Physics Group continues to be a world leader in high-resolution imaging of magnetic materials by both STM and SEMPA. The group is working on novel fabrication methods for nanowires and nanotrenches by reactive-ion etching of laser-focused chromium. Theorists in the group have worked on models of magnetic exchange bias, magnetic reversal on vicinal surfaces, and interlayer magnetic coupling, all topics relating to the surface magnetic experimental studies in the group. The magnetic ordering and interlayer exchange coupling for the growth of Mn/Fe(001), Fe/Mn/Fe(001), and Fe/Cr/Fe(001) were probed using SEMPA. The group's two current SEMPA instruments are now scheduled to be replaced by one higher resolution (~10 nm) instrument.

The nearly complete Nanoscale Physics Facility will be the centerpiece of the group. It has capabilities unique in the world. The facility is centered on the measurement capability of a cryogenic, ultrahigh vacuum STM that will operate at temperatures as low as 2 K with the ability to apply magnetic fields of varying orientation up to 1.5 T, or of fixed orientation up to 10 T. The facility also has two molecular-beam epitaxy chambers, one for metal deposition and one for semiconductor III-V deposition, with capability for in situ transfer of fabricated samples among the chambers. Measurements will have both atomic-scale positional resolution and high resolution of electronic state spectroscopic features. Excellent progress has been made on construction of this state-of-the-art facility in the last year, and experimental results are expected soon on topics such as electron confinement and transport in nanoscale structures and devices, magneto-transport devices, quantum electronics, and autonomous atom assembly of nanostructures. The division should also consider using this facility to study artificially created photonic bandgap materials and phenomena.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
Impact of Programs

The Photon Physics Group has established a collaborative program with Intel, the University of Maryland, and J-Mar (a laser manufacturer) to develop x-ray microtomography for metrology of buried interconnects. This tool will be needed for the proper inspection of microcircuits with the critical dimensions anticipated in near-future generations. The group is also setting up a collaboration with the EUVL-LLC to develop metrology for multilayer mirrors, for EUV mask inspection, and for determining EUV radiation exposure levels. In November 1998, seven specific action request items were received from EUVL-LLC. Given the importance of this emerging technology, it might be a good idea to put in place some form of coordination activity, such as workshops, a steering committee, and the like.

The Electron Physics Group continues its close collaborations with industry and other government laboratories by using SEMPA to work on various magnetic characterization problems. Some recent investigations included the following: magnetic and compositional depth profiling of giant magnetoresistance magnetic multilayers for IBM, analysis of coatings for McDonnell Douglas, and magnetic domain imaging of submicrometer patterned nonvolatile magnetic memory elements produced at Motorola Corporation and the Naval Research Laboratory (NRL). The group has also responded to the information storage industry 's needs for higher spatial resolution imaging of ever-shrinking devices and media by designing and beginning the development of the next generation SEMPA apparatus capable of better than 10 nm spatial resolution, which has been enthusiastically applauded by IBM and Motorola. The work of the group in characterization of magnetic thin films and in fabrication of nanowire structures is extremely important to U.S. industry in magnetic storage technology and next-generation integrated circuit manufacturing and also completely in accordance with the division, laboratory, and NIST missions.

Division Resources

Funding sources for the Electron and Optical Physics Division (in millions of dollars) are as follows:

 

Fiscal Year 1998

Fiscal Year 1999 (estimated)

NIST-STRS, excluding Competence

4.6

5.6

ATP

0.2

0.1

OA/NFG/CRADA

0.5

0.6

Other Reimbursable

0.1

0.1

Total

5.4

6.4

As of January 1999, staffing for the Electron and Optical Physics Division included 23 full-time permanent positions, of which 20 were for technical professionals. There were also three nonpermanent and supplemental personnel, such as postdoctoral research associates and part-time workers.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

Progress has been made on some facilities issues, such as painting the walls and replacing floor tiles in the Radiation Physics Building, but the staff still report leaks in some offices during rainstorms.

Atomic Physics Division
Division Mission

According to division documentation, the mission of the Atomic Physics Division is to carry out a broad range of experimental and theoretical research in atomic physics in support of emerging technologies, industrial needs, and national science programs. The mission includes critical evaluation and compilation of spectroscopic reference data.

Technical Merit and Appropriateness of Work

The Atomic Spectroscopy Group's capabilities in atomic spectroscopy and plasma radiation studies are widely recognized as world class, primarily because of the competence and professionalism of the individuals on its relatively small staff. Moreover, world-class laboratory spectroscopic facilities exist at NIST. Other organizations engaged in basic research rely on NIST as a source of unique and accurate laboratory data, particularly wavelengths, energy levels, and the absolute and relative strengths of atomic transitions (including branching ratios).

The NIST Atomic Spectroscopy Group has taken several important steps in the dissemination of critical data evaluation and compilation. Most significant is the development of a comprehensive online database, which is currently being tested and is expected to be available for customer use shortly. The easy availability of the entire set of critically evaluated atomic data on the Internet will facilitate the work of scientists and technologists around the world. It is especially noteworthy that the data can be continuously updated with more complete and more accurate values, adding to the usefulness and currency of the database beyond what was possible with published versions. Several members of the subpanel visited the Electronic Commerce in Scientific and Engineering Data office and were impressed with how well this NIST-wide Web-based data and bibliographic service is now working. Frequent revisions are needed to keep this vital service up-to-date.

The Atomic Spectroscopy Group has also begun a modest program to critically evaluate the accuracy of some of the large atomic databases created outside of NIST that are used to calculate opacities needed in the theoretical modeling of the interiors of the sun and stars. The evaluation has begun with Fe I and Fe II, and already potentially serious systematic discrepancies have been identified such as disagreement between theory and experiment of greater than 50 percent for transitions with oscillator strengths smaller than 0.1. This has instigated an urgent reevaluation by the atomic physicists responsible for the Iron project and Opacity project databases. These large databases are widely disseminated and used for a variety of theoretical computations in areas of great importance to astrophysics. It is essential that NIST play its traditional role of critical evaluation of atomic data, even within the context of such enormous databases. Further linkages between the Atomic Spectroscopy Group and these large database projects would be of great value to the world community of data users.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

Over the past decade, the needs of the scientific and technological communities for atomic data have evolved rapidly. High-speed computers have enabled the development of complex theoretical codes in a variety of physical and chemical subfields, requiring calculations with enormous databases of atomic parameters. In these applications, data must be statistically as complete as possible, covering as many energy levels as possible over a wide range of elements and ionization states. New instrumentation has also enabled ever-more-precise observations of individual spectral transitions in nature, in the laboratory, and in other settings. The scientific and commercial exploitation of such new capabilities has created a need for order-of-magnitude improvements in the accuracy of data for spectral transitions in a wide-ranging variety of atoms and ions.

There is a demonstrable need for the NIST atomic data evaluation, compilation, and atomic spectroscopy functions to grow and evolve in order to keep pace with growing and evolving demands for data and services, but core staff in these areas is aging and has had significant attrition. One key leader recently retired, and several other senior scientists are within a few years of retirement. The atomic data staff has dropped to about one-third of its level of 15 years ago. There is now only single-point staffing (or less) supporting many programs. In some cases, key retiring staff members may return as contractors, providing a brief window of opportunity for them to train their replacements. However, this opportunity will be lost if new scientists capable of both independent research and data evaluation are not hired in a timely fashion. Decisions must be made very soon about the future of the atomic data functions at NIST.

The Laser Cooling and Trapping Group continues to flourish as one of the world leaders in the burgeoning field of optical manipulation of atoms. It has three permanent staff members who work in different experimental areas (cold collisions, optical tweezers, and Bose-Einstein Condensation [BEC] and optical lattices), but the boundaries are not sharp and there is considerable overlap and interaction. The panel notes that in 1998 one member of the group received the Schawlow Prize for Laser Science from the American Physical Society (APS) and another member of the group was elected a Fellow of the APS. This group collaborates closely with the Quantum Processes Group on cold collision theory and with the Electron and Optical Physics Division on topics related to BEC. Although the group was not among the first to achieve BEC, it has moved the study of this state of matter into new areas. One of the most spectacular results was the extraction of atoms from the BEC by Raman transitions between different momentum states. This enables the control of atomic motion to an unprecedented degree, leading to the production of the world's best-controlled “atom laser” atomic beam that occupies only one size cell of phase space. This is related to Bragg diffraction of deBroglie waves and has led to additional studies of atomic diffraction in the Raman-Nath regime and in the boundary region between them. The group is also studying the transport properties of the BEC and the possible production of vortices.

Theoretical studies by the Quantum Processes Group prompted the experimentalists in the Laser Cooling and Trapping Group to investigate the nonlinear matter wave optical effects, analogous to four-wave mixing in nonlinear optics, which were predicted to occur in a BEC as a result of atom-atom interactions. Bragg diffraction pulses were used to produce condensates in the appropriate momentum states for observation of four-wave mixing in atom optics in a BEC for the first time. The fourth wave of as much as 12 percent of the initial number of condensate atoms was demonstrated to depend on the product of the atom densities in the three initial

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

momentum states. This research appears to open up some exciting new possibilities for the optical manipulation of ultracold atoms.

The group benefits enormously from the continuous flow of visitors supported by a variety of programs. There are NRC postdoctoral research associates, visiting faculty on sabbatical, researchers connected as independent contractors, guest researchers, and others. This steady flow of talent and expertise results from a conscious decision to use some of the group's budget for visitors rather than hiring additional permanent staff. Many vibrant new ideas and approaches have been brought to the research of this group as a result of its use of short-term visiting researchers in this way.

The Quantum Processes Group has been the world leader in the theory of cold collisions for many years. The superb corroboration with Na measurements performed elsewhere in the division serves as a paradigm for advances in collisions, molecular studies, determination of dipole moments (e.g., atomic state lifetimes), and so on. The group's effort in near-field optics and nanostructures spans nanostructures such as quantum dots, clusters, and wave optics. Special funding has been awarded to the group for near-field diagnostics of optical waveguides. The group's development of theory and modeling of near-field scanning optical microscopy (NSOM) is an important effort. NSOM is an emerging technology that has application to materials science, cellular and subcellular biology, thin film studies, and a host of other topics that benefit from microscopy with resolution below 100 nm. The group has made important contributions to the detailed study of the fields near the tip of the NSOM probes, and these have had considerable impact on experiments in the Optical Technology Division. This is one of many examples of collaboration across divisional lines. This group also benefits by a flow of visitors and postdoctorals, again financed through multiple channels.

In last year's report, the panel noted the Quantum Metrology Group's ambitious new competence project in subnanometer metrology. This project, a collaboration with NIST's Manufacturing Extension Laboratory, involves simultaneously measuring a displacement with Michelson, Fabry-Perot, and x-ray interferometries to improve the accuracy of displacement measurements. The project has so far achieved reduction of periodic errors associated with heterodyne Michelson interferometry and a digital phase meter with fringe splitting of 32,000. The group 's efforts in high-energy gamma-ray wavelength measurements with calibrated Si crystals have led to new precision determinations of the neutron mass. The previous assessment discussed the so-called “silicon kilogram ” project, which aims to develop a means of realizing the kilogram without using artifactual means, as is the current method. A possible resolution of the molar volume anomaly between Si samples grown in Europe and Japan was realized by using high-resolution x-ray imaging to detect what appear to be small voids, possibly filled with hydrogen. This study continues, although at a reduced level of funding that threatens to become subcritical. The group has also collaborated with the Ceramics Division of the NIST Materials Science and Engineering Laboratory in providing calibration of new powder diffraction Standard Reference Materials (SRMs). This is of direct benefit to some 10,000 x-ray powder diffraction scientists in U.S. industry and universities.

A major achievement since the previous assessment was the compilation of a revised atomic x-ray emission wavelengths table combining state-of-the-art theory, selected accurately measured x-ray transitions, and corrected values for less-well-measured transitions. In addition to providing the best available x-ray data of this type, the work has uncovered small deficiencies in the theory for inner-shell transitions. This project includes measurement of x-ray standard

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

lines such as the Sc K alpha line that is needed for an improved absolute mass measurement for the pi-minus meson.

Other agency funding in this group from NRL, NASA, and Harvard-Smithsonian allows scientists access to NIST's x-ray spectroscopy expertise. Available services include providing spectrometry components and calibrations.

There has been turnover in the Plasma Radiation Group with the retirement of the group leader and the internal promotion of a replacement. The group currently has four full-time PhD-level staff, each with different focus, augmented by two postdoctoral research associates, two full-time technicians, and a variety of short-term guest researchers. The group is doing a number of significant projects on plasma radiation and industrial plasma processing standards, the physics of highly charged ions, atomic spectroscopy of these ions, ion-surface interactions, and nanotechnology. These projects range from very basic (spectroscopy and surface physics of highly charged ions) to applied (physics of plasma etching of semiconductors and deep UV materials characterization for lithography).

The group continues its long-term basic research in precision x-ray spectroscopy and lifetime measurements of highly charged ions on the electron beam ion trap (EBIT). High-quality curved crystals of mica and quartz have been developed in collaboration with Russian scientists, enabling a new type of x-ray spectrometer designed for use on EBIT. It features both high collection efficiency and relative insensitivity to drifts in source position. Demonstration spectra from neon-like Ba46+ and helium-like Ar16+ have been obtained. In addition, x-ray wavelengths in H-like and He-like vanadium have been measured with an accuracy of 20 to 30 ppm, sufficiently high to challenge recent atomic structure calculations, including quantum electrodynamic corrections.

In ion-surface physics, the group has recently made molecular dynamics simulations on nanoscale modification of silicon surfaces via Coulomb explosion due to the impact of highly charged ions. Experimental measurements have been carried out on x-ray emission from low-energy Ar17+ ions impacting on silica, on nonkinetic damage from the impact of ions such as Xe44+ on other insulating materials, and most recently on masked ion beam lithography of silicon surfaces coated with poly(methyl methacrylate) (PMMA) or photoresist material. The etching of a 1 µm array of squares with better than 100 nm edge resolution was demonstrated by exposure of the surface to highly charged ions. The new in situ atomic force microscope recently added to the facility also showed some effects in PMMA; the impact of a single Xe44+ ion produced 24-nm-wide holes in the surface. Related work has been done to pattern an ultrathin resist consisting of self-assembled monolayers of alkane thiolates. Many more useful studies in this area are possible.

Studies of the physics, dynamics, ion orbits, and ion density optimization for the EBIT trap itself are now under way. This work is being performed in parallel with related studies at Lawrence Livermore National Laboratory, which has the only other EBIT facility in the United States.

This group continues its work on use of nonintrusive optical measurement techniques on emitted and absorbed radiation to determine the properties of radio frequency (RF) inductively coupled and arc discharge plasmas. The group maintains a standard high-vacuum reference chamber with a pair of parallel-plate electrodes, originally developed by participants in the 1988 Gaseous Electronics Conference. The specifications and mechanical drawings for this chamber can be downloaded from the NIST Web site to allow the detailed time and space mapping of RF plasmas widely used in the manufacturing of semiconductors and integrated circuits. Recent

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

research has included studies of plasma etching with less surface damage by using positive and negative “ion-ion” plasmas. The same RF standard cell is used as a radiometric standard for the vacuum UV region (see comments under Spectroscopy above on the vacuum UV [VUV] index of refraction measurements for optical materials used in semiconductor lithography).

Impact of Programs

Enlightened research efforts nurture basic curiousity-driven research even while aggressively pursuing the immediate rewards of applied research. They confront the issues of the proper balance between these two approaches and of funding basic research that may not fully pay its own way in the short term. The NIST atomic spectroscopy and plasma radiation groups and laboratories reside at an intersection of “basic” and “applied” research, serving the needs of both science and commerce.

In the 1980s, NIST atomic spectroscopists were commissioned by the Goddard High Resolution Spectrograph (GHRS) team, which was developing an instrument for flight on the Hubble Space Telescope (HST) to measure the UV spectrum of platinum with unprecedented resolution and accuracy. The HST and GHRS were launched in 1990, and the new NIST data on the platinum spectra were subsequently published and also made available to the public on a NIST Web site. Throughout the 1990s, NIST continued to collaborate scientifically with the HST/GHRS team, providing highly accurate new measurements of the wavelengths of ions of heavy elements such as zirconium, mercury, lead, and bismuth for use in the analysis of the UV spectra of stars with grossly peculiar chemical abundances. This work unexpectedly found immediate application in the commercial sector. One company manufacturing spectrochemical instrumentation containing spectral databases obtained the NIST data on the platinum spectrum over the Internet and used it to solve spectral discrepancies on one of its product platforms. In another instance, a difficulty with the bismuth spectrum observed on the company's instrument was resolved through direct interactions with the NIST atomic physicists who had originally measured the bismuth spectrum for the analysis of chemically peculiar stars. A second company, the leading manufacturer of excimer lasers for deep-ultraviolet lithography in the manufacture of densely integrated circuit chips, used the NIST HST/GHRS platinum spectrum to detect large systematic errors in previous calibrations of a laser wavemeter being used to measure the wavelength and stability of ArF lasers under development.

The Atomic Spectroscopy and the Plasma Radiation Groups have recently brought on line two Fourier transform spectrometers (FTSs), one of which is capable of measuring spectra at VUV wavelengths. These instruments provide an order-of-magnitude improvement in the wavelength accuracy and resolution with which spectral transitions can be measured. The VUV FTS was used to measure the temperature-dependent index of refraction of CaF, which is used in the manufacture of optical components needed by the microchip industry for laser etching. It is also potentially very important for the measurement of far-VUV wavelengths and transition probabilities for astrophysics and other areas of basic research. The second FTS was used to measure branching ratios (relative line strengths) needed to calculate transition probabilites of the rare-earth element dysprosium. This work was motivated in part by its applications to astrophysics, specifically the study of stellar evolution and the chemical evolution of the galaxy. However, the data are also very important in the development of high-pressure mercury arc lamps containing metal halide salts, which provide high-quality, energy-efficient lighting. A

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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major lighting manufacturer is already using the NIST data on the dysprosium spectrum to model and design a new generation of high-intensity lamps.

The calibration of thin film standards is an important new service for the electronics industry. About 200 specimens were calibrated in 1998. U.S. industry uses these critically important standards for process development. A new high-accuracy x-ray diffractometer has been funded and will be available for use in these calibrations in 1999, enabling the calibration of epitaxial materials and thin amorphous films with certified traceability to NIST. This service is in response to SEMATECH (semiconductor manufacturing technology) needs and will likely be the basis of ISO-9000 certification of materials for wireless and fiber-optic communications. However, future funding to continue development of this project appears to be in doubt. An application for ATP funds failed, perhaps because of insufficient support from Physics Laboratory management for thin film characterization. The panel recommends that the laboratory affirm its commitment to this important and practical field.

Division Resources

Funding sources for the Atomic Physics Division (in millions of dollars) are as follows:

 

Fiscal Year 1998

Fiscal Year 1999 (estimated)

NIST-STRS, excluding Competence

5.7

6.9

Competence

0.7

0.3

ATP

0.2

0.2

OA/NFG/CRADA

1.2

0.9

Other Reimbursable

0.2

0.2

Total

8.0

8.5

As of January 1999, staffing for the Atomic Physics Division included 32 full-time permanent positions, of which 27 were for technical professionals. There were also 12 nonpermanent and supplemental personnel, such as postdoctoral research associates and part-time workers.

Optical Technology Division
Division Mission

According to division documentation, the mission of the Optical Technology Division is to provide high-quality national measurement standards and support services to advance the use and application of optical technologies spanning the UV through microwave spectral regions for use by diverse customers in industry, government, and academia.

The division programs described to the panel conform in all respects to the above-stated mission and to the broader missions of the Physics Laboratory and NIST itself.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
Technical Merit and Appropriateness of Work

The Optical Technology Division maintains the national standards for optical radiation measurements and ensures their relationship to the International System of Units. These measurement responsibilities include the photometric units of the candela and lumen, the radiation temperature scale, spectral source and detector scales, and optical properties of materials such as reflectance and transmittance. To ensure that the United States has the best available measurement infrastructure, the division maintains a research and development program designed to furnish high-quality services to meet the needs of rapidly evolving scientific and technological applications. Industries that rely on their services include the aerospace, photographic, lighting, display, automotive, pharmaceutical, and scientific instrumentation industries.

The division also has research programs to develop optical and spectroscopic tools for future applications in industrial and environmental processes. These tools include a Fourier transform microwave (FTMV) instrument, several infrared (IR) spectrometers, a high-resolution UV spectrometer, and tunable, ultrafast IR, visible, and UV lasers; these are being used to identify transient species, molecular complexes, and other chemical species, in either homogeneous or inhomogeneous environments (e.g., material interfaces). This provides the basis for new reference materials and optical calibration methods for the 21st century. New programs using the NIST synchrotron radiation source, SURF III, and exploring the uses of nonlinear optical processes in materials to perform fundamental radiometric measurements, also are being pursued.

The diversity of activities within the division ranges from basic research on light-matter interactions, to applications of light scattering as a metrological tool for the characterization of solid surfaces, to repeated and ongoing interactions with scientists and engineers to establish methodologies and standards for industries that are using optical technologies in their everyday work. The division comprises five different groups, each with a different focus. In what follows, the panel provides an assessment of some of the activities in each of these groups.

The Optical Temperature and Source Group maintains the national scales for spectral radiance and irradiance, the international temperature scale above the freezing point of silver, and the standards for highly diffuse reflectance and transmittance measurements. Calibration facilities include the Facility for Automatic Spectroradiometric Calibrations (FASCAL), the Facility for Advanced Radiometric Calibrations (FARCAL), the spectral trifunction automated reference reflectometer (STARR), pyrometry, diffuse transmittance, and aperture area measurement facilities.

STARR currently provides SRMs for specular reflectance, diffuse reflectance, and reflectance factor measurements as a function of wavelength. In addition, STARR has served as the prototype for instruments designed to measure an extended range of optical appearance attributes. An example is a reflectance colorimeter that will enable the group to produce robust color standards accurately and rapidly. A Color and Appearance Task Group has been formed in collaboration with personnel from the Building and Fire Research Laboratory, the Manufacturing Engineering Laboratory, and the Information Technology Laboratory to develop an entire area of metrology that will be made available to U.S. industry in the near future.

The group has the capability of making gloss measurements in compliance with American Society for Testing and Materials (ASTM) D253 and International Organization for Standardization (ISO) 2813. Although the development of a new, more reproducible, and stable

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

SRM is very significant and will be widely used, the documentation of the gloss evaluation method (especially of spectral effects on gloss value) also will be of value to the customer base. Evaluation of haze is closely tied to gloss. The group is nearing completion of upgrades that will permit accurate haze evaluations.

Progress in FARCAL significantly adds to the group's ability to provide radiometric calibrations for NASA's Earth Observing System (EOS) and the Department of Defense's space-based measurements. The technical implementation incorporates technology and skills unique to the division. The facility's medium background chamber is designed for flexibility. Calibrations are performed in the temperature range of 80 to 325 K. In combination with the portable thermal-infrared transfer radiometer under development, FARCAL allows this project to meet the group's vision of improving uncertainties and simplifying calibrations by providing the customer with the shortest possible calibration chains, in this case by making calibration possible at the customer site.

The FASCAL, which provides the basis for spectral irradiance measurements for U.S. industry, is in desperate need of upgrading. The group is designing an upgraded FASCAL. This effort needs higher priority if the group is to remain world class in its services.

High-accuracy aperture measurements represent an important enabling technology. The availability of apertures with accurately known areas is essential to the accuracy of the optical scales maintained by the group. The group intends to serve as a pilot laboratory for an international intercomparison of aperture measurements in conjunction with the Consultative Committee for Photometry and Radiometry.

Retroreflectance measurement technology would benefit from direct NIST funding to develop the necessary hardware for producing SRMs and providing the roadmap needed by industry. This is an important area for standardization and calibration. Group personnel have been very active in bringing together those entities with a stake in the development of this metrology by the division. Their efforts to ensure that an important area of metrology receives the necessary attention are strongly commended and deserve reinforcement.

The instrumentation for step tablet SRMs is an example of an innovative response to industrial customers' needs, providing improved accuracy and timeliness while making optimal use of limited means.

The Rapid Thermal Processing (RTP) project, which focuses on development of advanced methodologies for accurate temperature measurements in RTP tools using radiation thermometers, is clearly an example of a forward-looking, industry-driven project. Interlaboratory participation (Chemical Science and Technology Laboratory, Electronics and Electrical Engineering Laboratory) and the incorporation of regular interactions with an industry advisory group have led to rapid realization of technological impact and economic advantages for firms adopting the technology.

The development of radiation pyrometry based on absolute detectors is an area of research that will lead to reduced uncertainty in temperature measurements and improved maintenance of the temperature scales. The group is developing a 3000 K high-temperature black body (HTBB) to replace the freezing point of gold as the basis for the spectral irradiance and radiance temperature scales. The spectral irradiance of sources such as FEL lamps used as working standards can be directly assigned by comparison to the HTTB. The final uncertainties in the spectral irradiance of issued FEL lamps will be reduced by the new, more direct scale assignment. The old source-based scale and new detector-based scale are in agreement to better than 0.5 K at 800 K and higher temperatures. Work is in progress to extend the comparison to

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

the gold freezing point (1337.33 K). This project applies division research to bootstrap the metrology of radiation temperature measurements to a higher level of performance. This represents a real advance in metrology for radiation temperature and should be strongly encouraged. The panel commends the group for its strong commitment to the vision of providing world-class metrology to the nation.

The Optical Properties and IR Technology Group establishes and disseminates primary standards for transmittance and reflectance measurements in the IR. It also studies the optical properties of materials from the microwave to the UV and develops theoretical models to interpret these behaviors for further standards development. The group also is developing superconducting materials for components used in optical sensor applications. The core metrology programs within the group push the envelope in developing characterization techniques and standards for parameters of emerging importance. Unmet needs are being addressed through pioneering work in the characterization of transmission and absorbance of diffuse materials. For example, a multidisciplinary effort to develop optical techniques to characterize and set standards for biological measurements is forward thinking and responsive to contemporary advances in a field of tremendous national interest. Continued work on standards of this sort should be encouraged. The group's principal facilities include the Low Background IR Calibration Facility, which has recently been used to develop several sensitive NIST transfer standard detectors. Industry has voiced the need for broadband spectral radiometric standards. NIST scientists can address the shortfall if provided the resources. Spectral radiance calibration of black-body sources should be a NIST priority.

Certification of calibration sources to be used in future venues such as space for emerging NIST functions could significantly extend the scope of NIST activities and services with minimal or no impact on the budget. Fresh ideas and approaches are applauded in this area and should be encouraged through aggressive outreach programs. An example of such efforts is the group's collaboration with the Scripps Institution of Oceanography in the NASA-funded Triana mission. The group was selected by Scripps to build a radiometer to measure total Earth reflected and emitted light viewed from the L1 point in space. Providing calibrated radiometry from space positions the group to play a significant role in the Space Station program and to share in NASA Space Station funding through its user programs. This extends the role of NIST by providing first-time NIST-calibrated measurements of important sources from space. Similarly, new outreaches of this type in the biological arena are highly encouraged.

The Optical Sensor Group establishes the national measurement scale for the candela, a fundamental SI unit. It also provides measurement and calibration services for the absolute spectral responsivities of optical detectors in the spectral region from 200 nm through the IR and performs research and development work on new detectors for applications in radiometry, photometry, colorimetry, and spectrophotometry. Its principal facilities include the high-accuracy cryogenic radiometer (HACR), the detector Spectral Comparator Facility, spectral irradiance and radiance calibration with uniform sources (SIRCUS), and the SURF III radiometric facility.

The HACR is the basis for the national standard for optical power measurements. It is the foundation of the radiometric measurement chain and is used to maintain the scales of spectral radiance, spectral irradiance, and absolute detector responsivity from 200 nm to the far IR, with a maximum uncertainty in optical power of +/- 0.02 percent. Over the last decade, the performance limitations of this once state-of-the-art instrument have become more significant relative to other sources of uncertainty. The group is developing a new instrument (HACR 2) to

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

increase the dynamic range of power measurements from a lower limit of 1 µW to an upper limit of 70 mW while reducing the maximum uncertainty in comparison with the original instrument. The response time also will be improved by nearly an order of magnitude, which may improve the division's ability to respond to requests for calibration services and will enable more direct comparisons to be made to HACR 2 than is possible on HACR. Finally, there will be relaxed restrictions on the size of detectors that can be directly compared with HACR 2. The proposed upgrade of HACR is highly desirable and urgently required. For example, the semiconductor industry is crucially dependent on such technology for the calibration of its ultraviolet light sources, used in the new narrow-line lithographic projection chip fabrication process.

The panel commends the division for placing HACR 2 in the laboratory where SIRCUS is located. Here, laser sources covering the full spectral range at power levels as high as 1 W are available for calibration services. SIRCUS will be the preeminent spectral irradiance and radiance calibration facility in the world and will make calibrations of detectors over a continuous spectral range from 200 nm to the far IR possible. Combining the capabilities of HACR 2 with SIRCUS allows for a more direct measurement of spectral radiant power and an improved accuracy of the candela and other photometric units.

The development of pulsed source photometry responds to a long-standing need for accurate calibration of pulsed navigation and warning lighting, especially important for aviation.

The group's work on colorimetry of displays will greatly improve the measurement capabilities of existing test facilities. The coincident development of a matrix algorithm to improve the performance of color evaluation instruments leverages the benefits of this program for end users. The group will also be involved in the color aspects of a project to produce color and appearance standards.

The detector comparator facility continues to expand and enhance its capabilities, most recently in the IR. HACR/SIRCUS/SURF III intercomparisons using the new high-accuracy apertures will provide a foundation for future projects such as “smart” sources. The group is continuing its expansion of wavelength coverage while simultaneously improving uncertainty and reducing calibration chains. This effort is strongly supported by the Panel. There is great benefit to multiple approaches for the realization of these important bases for measurements for U.S. industry.

The Intrinsically Absolute Radiometer Using Correlated Photons project has been transferred to the Laser Applications Group. This project seeks to use correlated photons to realize a technique for measuring radiance directly. The 1997 and 1998 Assessment Panels expressed enthusiasm for this technique. The initial comparison results were encouraging, and the project was attracting notice from the community. The panel urged that the research be pursued with considerable vigor as it might provide a physically distinct method of calibration (i.e., an independent check on the electrical energy substitution method as embodied in HACR). A full-time postdoctoral research associate is engaged in the project, which the panel will monitor for appropriate progress in the next year.

The Laser Applications Group develops and applies state-of-the-art pulsed laser diagnostics to applications in industrial and environmental processes; uses tunable, ultrafast IR, visible, and UV lasers to identify transient chemical species involved in molecular reactions in gases and liquids and at semiconductor or metal surfaces; and probes the performance of semiconductor interfaces related to device fabrication, reliability, and function in biological and chemical sensing. Its principal facilities include a laser-based bidirectional reflectance distribution function instrument, several ultrafast laser systems, including a new terahertz (THz)

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

spectrometer, and two near-field scanning optical microscopes, one being developed for single-molecule studies.

The group is commended for its significant programmatic decisions in the past year. It has terminated activities in three recent areas of excellence (gas phase molecular dynamics, dynamics of molecules on metal single-crystal surfaces, and vibrational relaxation of molecules in liquids) in order to focus on the emerging area of surfaces and interfaces and their application to semiconductors, biotechnology, and optoelectronics. A recent application is the study of subpicosecond interfacial electron injection in dye-sensitized TiO2 films. The group has obtained new competence funding for advanced THz applications and ATP funding for DNA diagnostics, catalysis, tissue engineering, and organic electronics. THz laser technology is being used for imaging and applications to DNA, DNA chip technology, and protein folding in real time. A new method of vibrationally resolved sum-frequency generation with broad-bandwidth IR pulses has been developed and is being used to study the incorporation of different chromophores in cell membranes, with eventual application to tissue engineering. NSOM methods are being developed to extend the measurements and standards infrastructure to nanoscale optical characterization of thin films and interfaces. The new techniques include a wet-cell NSOM suitable for investigating biological or biomimetic films, a near-field probe preparation and evaluation facility, and a confocal scanning microscope for single molecule imaging and spectroscopy. Locating and sizing particles and defects on silicon wafers is the current focus of the optical scattering group, using a goniometric optical scattering instrument, extensive theoretical modeling calculations, and a prototype production-line light-scattering inspection tool. Defect detection plays an important role in maintaining high production yields on semiconductor chip fabrication lines, highlighted in the 1997 NTRS.

The Spectroscopic Applications Group improves spectroscopic instrumentation and measurement methods and standard reference frequencies, data, databases, and theoretical models for determining the fundamental properties, energetics, and internal dynamics of stable molecules, molecular complexes, and reactive species like radicals and ions. Activities are focused on emerging technologies in the microwave, IR, and UV spectral regions. Principal facilities include a Fourier transform microwave (FTMW) instrument, an IR cavity-ringdown spectrometer (CRDS), Fourier transform infrared (FTIR) instruments, and a new high-resolution UV-Vis spectroscopy facility.

A miniaturized version of the FTMW instrument has been developed and used to demonstrate detection of physiologically significant species in chemical warfare agents. A patent for this instrument was awarded in November 1998; the group is currently seeking a company to license the technology. New THz sources have been developed and are being applied to plasma-processing chemistry. The CRDS has detected fundamental modes in the mid-IR with 100X improved sensitivity. The new UV-Vis facility is now fully operational, demonstrating a resolution in the ~300 nm spectral region approaching 1 part in 109, sufficient to resolve the underlying eigenstate structure in large organic molecules for the first time, revealing thousands of previously undetected lines in a single scan. A key feature of this instrument is the actively locked laser stabilization system, unique to instruments of this type.

The panel is disappointed in the lack of progress on the development of a molecular data center comparable to that for atomic spectral data. The group has devoted significant time and effort to plan a center that would critically evaluate the entire world's output of high-resolution spectral data for different classes of molecules in different spectral regions. A workshop to focus the efforts of this group was held at NIST in late 1996; their efforts are summarized in an internal

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

report and were published by American Institute of Physics. Despite this, no resources have been committed to the further development of this worthy project.

Impact of Programs

In general, the efforts by the Optical Technology Division continue to meet the needs of U.S. industry and its scientific communities. Especially noteworthy are the establishment of radiometric scales traceable to HACR, the rebuilding of FASCAL, the emerging development of uniform color and appearance standards, improvements in international comparisons, services to the IR user community via electrical substitution radiometry, new measurement scales for transmission and reflectance of materials, the development of HACR 2 and SIRCUS, programmatic changes in the Laser Applications Group, and the construction of a world-class high-resolution UV-Vis facility.

Also noteworthy are recent short courses produced by the division on Temperature Measurement by Radiation Thermometry (on site), Photometry (on site), and Ultraviolet Radiometry for Lithography (presented at the 23rd annual meeting of the Society of Photo-optical Instrumentation Engineers [SPIE]). Earlier workshops on color and appearance and on retroreflection lead to clear identification of industry needs. These efforts fill a need by combining scientific and technical instruction on the metrology with information on the measurement standards upon which each metrology relies. The division can greatly assist its customers through continued support and expansion of training of this type.

Engaging the community is essential to the architecture and implementation of an effective NIST research, services, and technology transfer program. NIST's initiation of the Optical Properties and Materials Consortia with SPIE is commendable. More outreach programs of this type are encouraged. Furthermore, NIST scientists should consider a more substantial flow of technology from academia, industry, and other government laboratories into NIST where appropriate. Resistance to adopting technologies developed elsewhere may be limiting the breadth of NIST capabilities. Technology flow into NIST could extend the budget and increase the portion available for research and expansion into new areas.

Transfer standards are tremendously important to the technical community, and the precision calibration of blocked impurity band detectors across unprecedented spectral and dynamic ranges provide an important contribution to IR technology developers and users. Similarly, work on electrical substitution radiometers holds promise in the area of transfer standards beyond the conventional laboratory environment. With the proper radiation hardening, they could be calibration standards for space and other future venues.

In the 1998 assessment, the panel commented favorably on the rapid response of the division to the needs of lens designers for the value of the optical index of refraction to an accuracy of better than one part in 105 for materials that are useful as lens elements in the UV. These measurements have been improved as well as extended to shorter wavelengths. This work is a timely response to the evolving needs of the semiconductor industry.

All groups in the division play key roles in the development of defense technology, capabilities, and the assurance of military system effectiveness. Partnerships with NASA are equally successful. These are important relationships that NIST has done well to cultivate and are encouraged to continue. More opportunities for commercial industry and academia to partner with NIST would be welcomed in the optical technology community.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

The panel is concerned at the lack of a formal external review process specific to each instrument and calibration method developed to provide U.S. and international standards. This concern is mitigated by the fact that instruments and products developed with customer funding or by outside sources for NIST are reviewed according to contractual agreements. Nonetheless, the responsibility of NIST is of such great national importance that the instruments and products need serious peer review prior to and beyond that occurring in the course of publication in journals.

The division has assumed an expanded role in the development of international standards related to optical technology. Although it is essential that U.S. industry take the lead in such development, the support of the division is absolutely crucial. To enhance these interactions, the division should actively seek contacts with U.S. industry groups for the purpose of preparing responses to international organizations on standards issues. The Consultative Committee on Photometry and Radiometry key comparisons are especially important. The division also should maintain close liaison with other divisions active in the accreditation of calibration and testing laboratories.

The division can participate directly in a myriad of emerging areas of national significance. The panel identified four target goals that, if met, would greatly enhance the activities of the division:

  1. Greatly expanding its exchange programs with academia and industry, making its facilities available for use by a wider variety of young researchers, and enhancing the productivity and experiences of existing staff members. Undergraduate and graduate students working at other institutions would especially benefit from such opportunities.

  2. Creating onsite visitor facilities (such as dormitories) at Gaithersburg that could be used on a regular basis by students, scientists, and engineers during research visits to NIST.

  3. Improving interactions with other laboratories at NIST, especially the Chemical Science and Technology Laboratory and its Biotechnology Division.

  4. Taking advantage of research roadmaps such as the National Research Council report Harnessing Light: Optical Science and Engineering for the 21st Century to aggressively pursue new research opportunities in optical technology.

Attention to multidisciplinary activities such as these and the transfer of capabilities beyond the physical boundaries of NIST will have a positive impact on industry, government partners, and the national competitive advantage.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
Division Resources

Funding sources for the Optical Technology Division (in millions of dollars) are as follows:

 

Fiscal Year 1998

Fiscal Year 1999 (estimated)

NIST-STRS, excluding Competence

5.3

5.3

Competence

0.6

1.0

ATP

1.0

1.0

Measurement Services (SRM production)

0.1

0.1

OA/NFG/CRADA

3.7

3.7

Other Reimbursable

0.5

0.6

Total

11.2

11.7

As of January 1999, staffing for the Optical Technology Division included 44 full-time permanent positions, of which 40 were for technical professionals. There were also 15 nonpermanent and supplemental personnel, such as postdoctoral research associates and part-time workers.

Ionizing Radiation Division
Division Mission

According to division documentation, the mission of the Ionizing Radiation Division is to provide national leadership in promoting accurate, meaningful, and compatible measurements of ionizing radiation (x rays, gamma rays, electrons, neutrons, energetic charged particles, and radio activities).

The mission statement adequately embraces the overall goals and objectives of the division. However, the division mission statement should indicate that to become a world-class laboratory implies attaining preeminence not just through technical achievements, but also through world-class resources such as state-of-the-art equipment.

The Ionizing Radiation Division epitomizes the ideal of a strong relationship between NIST and the industrial scientific community. The three groups in this division (Radiation Interactions and Dosimetry, Neutron Interactions and Dosimetry, and Radioactivity) enjoy deep and long-standing interactions with their constituent communities. The division has been responsive to national needs as defined by the Council on Ionizing Radiation Measurements and Standards (CIRMS), a coordinating council involving industry, government, and academic constituencies. Moreover, NIST routinely takes a leadership role in establishing appropriate metrology standards and identifying and developing measurement procedures to ensure the highest level of metrology. These contributions are nicely complimented by fundamental research activities, especially those employing the cold neutron facility.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
Technical Merit and Appropriateness of Work

The Radiation Interactions and Dosimetry Group has done outstanding work in developing calculation methods and codes that expand the ability to postulate radiation effects in areas ranging from medical applications such as brachytherapy to the space environment and for radiation protection purposes. Such postulations and calculated dose profiles, however, require far greater attention to empirical verification when possible. The scientific and technical quality of this work is diminished insofar as calculated effects are not verified by experimental results.

The alanine dosimetry technique has been enhanced by the development of an alanine-containing film. This dosimetry method can now be used in a manner similar to the more historical method of film dosimetry. The recent reorganization of the film supplier means a viable commercial source for such film needs to be identified and qualified. Excellent dosimetry comparisons have been conducted with other national and international laboratories such as the National Physical Laboratory, Bureau International des Poids et Mésures (BIPM), and Pacific Northwest Laboratory, but protocols are needed before the dosimetry group can improve its outreach to secondary laboratories and to the general user community. Laboratory personnel should seek leadership positions in recognized standards groups, such as ASTM. The ASTM Standard Practices use of statistically based uncertainties for dosimetry needs to be resolved with the more common use of empirically based precision and bias statements as required for Standard Methods of Test.

Incremental progress continues on remote Internet-driven electron paramagnetic resonance (EPR) alanine pellet dosimetry. The local site (NIST) controls the remote site data acquisition. After up-loading the results to NIST, data are qualified and analyzed and the results issued as an encrypted signature of compliance and calibration. An industrial test site is now essential to advance the program by fully testing the performance of the Web transaction. This project has potential but needs to move beyond proof of principal.

The group's success in establishing standardization procedures for mammography exposures, calibrating brachytherapy seeds, and performing reference calibrations of dosimeters has generated a diverse range of what are now routine operations. Such operations should be managed more as a routine service, with greater use of laboratory technicians. This would improve response times and enable research staff to engage in more exploratory work.

During 1998, the division greatly expanded its online interactive database. This included an elegant graphical display capability that significantly enhances usability and communication. Currently, the data warehouse includes partial photon interaction coefficients for all elements and numerous compounds and mixtures. Several dosimetry-related quantities are also available. Stopping power data for a similar range of materials are available for electrons, protons, and alpha particles. These well-presented data are extremely useful and valued for their evaluation over a long term. Although measuring the impact of this database would be challenging, some effort is needed to track utilization. A survey of users might be appropriate. In addition, given that Oak Ridge National Laboratory work in radionuclide information, especially dosimetry-related data, is only being weakly supported, NIST may consider acting as a resource for all such data. Such a NIST source could easily achieve world prominence and serve as a huge resource for the industrial and academic communities.

Through the Neutron Interactions and Dosimetry Group, NIST continues to strongly participate in the determination of neutron cross sections and the evaluation of neutron interaction data for the Evaluated Nuclear Data File (ENDF). Such work can seem abstract

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

compared with other activities, but recent national initiatives on the transmutation of nuclear waste, the breeding of tritium from a spallation neutron source, and the development and application of neutron tomography and other medical applications give the work relevance. NIST activities include leading the effort in measurement of the important H(n,p) cross section up to 100 MeV neutron energy —this cross section serves as the most fundamental metric for neutron fluence determinations. NIST staff members are participating in designing the experiments, data interpretation, and evaluation of the results as part of the U.S. Cross Section Evaluation Working Group, the International Nuclear Data Committee, and the Nuclear Energy Agency Nuclear Science Committee. Any measurement of the neutron lifetime is a formidable challenge. Several years of extraordinary effort are now showing substantial and positive results. In collaboration with several major research groups, NIST staff are actively pursuing two related strategies: (1) the traditional decay-in-flight technique and (2) a containment configuration. Numerous experimental challenges are gradually being resolved. The panel anticipates considerable progress during 1999. Evaluation of new high-energy fission cross sections in 235U, 238U, and 208Bi are proceeding in the context of the ENDF effort and the International Atomic Energy Agency. This is an international effort with excellent dissemination and widely used by the scientific community. NIST' s presence in this community is essential. NIST might consider a more defined program in this area by assuming full responsibility for some specific mass regions or reaction channels. A tighter connection to the programs at the NIST research neutron reactor might also be productive.

Closely related to the neutron lifetime measurements are the 3He neutron polarization experiments. Hyperpolarization of 3He is perhaps the most efficient technique for cold neutron polarization. The NIST program in 3He polarization is maturing rapidly and becoming prominent internationally, with numerous recent publications. NIST uses two approaches to polarization. One employs metastable 3He, transferring polarization to ground state 3He by thermal collisions. The other technique uses spin exchange from optically pumped rubidium. Both processes work well and provide usable quantities of polarized 3He. Beyond efficient production of hyperpolarized 3 He, the pragmatic difficulty of mechanically pumping the He to significant and useful absolute pressures was also accomplished. The resulting pumping system is inexpensive and very functional but most importantly allows the straightforward distribution of He to remote sites. An offshoot of these efforts is the use of polarized 3He for human lung scanning. Using the “breath hold” technique, polarized 3He fills the lung space and is well imaged by conventional magnetic resonance (MR) techniques. A strong collaboration with the University of Pennsylvania and the University of Virginia is yielding very positive results. These experimental programs indicate strong fundamental science with active collaborations with users throughout the United States. The balance between applications and basic science and the progress of the work is impressive. The continuing competitive support by the U.S. Department of Energy is a strong marker of the significance of this programmatic effort.

Continuing and in some cases dramatic progress occurred during the last year in the area of the Neutron Interferometry and Optics Facility (NIOF). These accomplishments range from fundamental experiments investigating quantum entanglements of nuclear states in H20 and D20 mixtures to development of a sophisticated neutron-imaging facility. The recent advances are creating new opportunities in neutron imaging. In the last year, imaging of water distribution in fuel cells with 100 µm resolution was accomplished in collaboration with an industrial partner. This portends the extension to high-resolution neutron tomography and the applications in industry and biological sciences. An exemplary feature of this program is the high degree of

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

programmatic integration including various experimental apparatus and excellent utilization of beam lines and scientific talent. At this juncture, the NIST NIOF facility is certainly positioned to take international leadership in this area.

The Radioactivity Group develops, maintains, and disseminates radioactivity standards, develops and applies radioactivity measurements and techniques, and engages in research on radiation interactions and nuclear decay schemes to meet the requirements for new standards. The panel examined the group's efforts in radionuclide metrology, development of standards for nuclear medicine and environmental monitoring, calibration services, and basic research for new standards.

Basic research is focused on standards development and on calibrations for nuclear medicine. Short-life isotopes of potential use in positron emission tomography are produced in-house. This is a useful activity that is well managed. Of particular interest is research to reduce restenosis after balloon angioplasty. To accurately measure the dose being delivered to the artery in this therapy, this group is developing an approach to relate the delivered dose to the amount of the radioactivity present in the delivery system. Strontium-90 seeds, 32p stents, and other sources are being used to improve the calibration and characterization. A method has been developed to perform direct and nondestructive measurements of contained radioactivity in balloon catheter sources. This technique uses an ionization chamber and a special radiation shield designed by the members of the group. The shield allows only response by the dose calibrator to the activity contained in the balloon. This calibration was an essential part of the development and involved the use of 133Xe. It is a significant development and reflects extremely well on the high professional quality of the members of the group involved in this research.

Another interesting development involved the glow discharge-initiated resonance ionization mass spectrometry (RIMS) system. This system allows the direct analysis of soil and sediments for radioactive trace elements. The soil or sediment samples are vaporized using a glow discharge source and a laser, and the vaporized material is analyzed using RIMS. The ability to handle a variety of sources reduces the measurement time considerably, since so little source preparation is needed. This technique should be applicable in environmental monitoring and remediation as well as in nuclear medicine for measurement of radionuclides and biological tissue.

The efforts in metrology include improved liquid scintillation techniques, calibrations by gamma-ray counting, alpha and beta measurements of large-area sources, and comparisons for calibration activity measurements. All of these efforts are being conducted quite capably and will be significant improvements in these areas of analysis and measurement.

In summary, the dedication as well as the quality of the scientists is impressive. They are studying significant problems and enjoying quite good success. It was obvious that these researchers are making important contributions to the national good through their research and development studies. NIST is to be congratulated on the quality of the work and on the morale evident in the enthusiasm of the staff.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
Impact of Programs

The division has been responsive to measurement programs and priorities as outlined by the independent Council on Ionizing Radiation Measurements and Standards. The CIRMS Executive Committee indicates that programs have been completed or significant progress has been made on most of the programs defined in the 1995 CIRMS National Needs in Ionizing Radiation Measurements and Standards.4 The division interacted with its constituents from academia, industry, and other government bodies to help in the development of the second CIRMS National Needs in Ionizing Radiation Measurements and Standards,5 issued in 1998. Other measures of output such as publications in leading scientific journals are excellent. The ever-increasing group of users and industrial partners is very encouraging and indicative of the high regard for NIST research and capabilities.

5 Council on Ionizing Radiation Measurements and Standards, National Needs in Ionizing Radiation Measurements and Standards, Council on Ionizing Radiation Measurements and Standards, Duluth, Ga., 1998.

Although responsive to longer-term program demands, the division needs to institute a more business-oriented tracking system for its service activities. Some calibrations have been known to languish.

Division Resources

Funding sources for the Ionizing Radiation Division (in millions of dollars) are as follows:

 

Fiscal Year 1998

Fiscal Year 1999 (estimated)

NIST-STRS, excluding Competence

4.3

4.5

ATP

0.2

0.2

Measurement Services (SRM production)

0.1

0.1

OA/NFG/CRADA

1.5

1.7

Other Reimbursable

0.8

0.8

Total

6.9

7.3

As of January 1999, staffing for the Ionizing Radiation Division included 36 full-time permanent positions, of which 32 were for technical professionals. There were also six nonpermanent and supplemental personnel, such as postdoctoral research associates and part-time workers.

Budgetary allocations within NIST have constrained the Ionizing Radiation Division such that its growth has not kept up with demands of industry and the professional community. Sources for outside funding, such as Department of Energy, Department of Defense, and NIST's National Advanced Manufacturing Testbed, have been used to bring the division merely back to a zero-growth state.

4 Council on Ionizing Radiation Measurements and Standards, National Needs in Ionizing Radiation Measurements and Standards, Council on Ionizing Radiation Measurements and Standards, Duluth, Ga., 1995.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

Unlike many other areas of technology being developed at NIST, ionizing radiation tends to be very capital-intensive in its research and in its industrial use. In some areas there has been an astute use of modest capital expenditures, such as in the development of the beams needed to establish the national standards for mammography testing. However, the division still requires some capital overhaul. For example, when replenishing a 60Co source, the division would be prudent to swap or to exchange its old receptacles with more state-of-the-art equipment for these national reference sources.

Lacking a high-current electron beam accelerator, the division cannot fully relate to the major industrial use of ionizing radiation as a process technology. With over 1,000 high current industrial electron beam accelerators in use on a worldwide basis, the division can neither provide high-dose-rate calibration services nor adequately determine the effects of dose rate and beam current on materials. The existing Medical and Industrial Radiation Facility (MIRF) electron linac and the low-energy electron electrostatic accelerator are useful for low-intensity dosimetry but are not adequate to address the needs for very high level dosimetry in many industrial applications. A clear plan to resolve this issue is needed. To be a world-class facility, the division needs to develop a capital plan to replace the MIRF accelerator with state-of-the-art equipment. This may call for a one-time expenditure of a few million dollars.

The panel was impressed by the progress made in modernizing many of the photon calibration facilities. The x-ray beam lines and related data acquisition apparatus are greatly improved. This is not true for the 60Co facilities. Facilities have also been improved by clearing work areas and having new paint and lighting in corridors, especially in basements and subbasements where vaults are located. The age profile of the division has been improved by adding younger, very qualified new hires to replace retirees.

The division would greatly benefit from a 3-year plan of activities, improvements, and budgetary planning. This would also greatly improve the panel's ability to assess the programs.

Time and Frequency Division
Division Mission

According to division documentation, the mission of the Time and Frequency Division is to support U.S. industry and science through provision of measurement services and research in time and frequency and related technology.

To fulfill this mission, the division engages in the development and operation of standards of time and frequency and their coordination with other world standards; the development of optical frequency standards supporting wavelength and length metrology; the provision of time and frequency services to the United States; and basic and applied research in support of future standards, dissemination services, and measurement methods. The programs of the division are well aligned with and strongly support its stated mission and the missions of the Physics Laboratory and NIST.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
Technical Merit and Appropriateness of Work

The frequency and time program continues to rank overall as probably the best in the world. The high quality of the technical work is continually increasing, and the division is extremely fortunate in the excellent quality of its people. The quality of both the research and the staff helps attract the very best scientists and visiting scientists, and the division has a bright future as long as it maintains expertise and vitality in these important areas. The technical staff have demonstrated outstanding ability to create and develop new ideas and techniques and have demonstrated the capability of acting on external ideas and getting up-to-speed and to the technical forefront of such areas quickly.

The division currently maintains an excellent operating primary frequency standard, NIST-7, and has brought its new cesium fountain into operation. It also has effective means of both frequency and time dissemination and research and development directed towards new, much higher performance standards in both the optical and microwave frequency ranges. Some of this work is important to the development of commercial frequency standards, which are widely used in time-scale generation in national standards laboratories. Commercial standards, consisting of five hydrogen masers and several cesium standards, are used in the division to generate a carefully optimized time scale that is disseminated via a number of means. There continues to be very good work on time dissemination via networks and time and frequency comparison via the Global Positioning System (GPS) and two-way satellite time transfer. This is important for industry because of the increasing accuracy requirements for time synchronization in digital communications systems. The division continues its excellent effort in the area of lasers. It is developing a new, highly practical frequency chain connecting the optical range to the microwave range. Low-flicker noise amplifiers and oscillators and spectrally pure frequency sources being developed are important for the high-performance frequency standards and have commercial importance as well. The division has finalized an agreement with the United States Naval Observatory (USNO) on the equivalence of time and frequency between NIST and USNO. This is an important and long-sought-after accomplishment.

The accuracy of the optically pumped NIST-7 cesium beam standard is currently still evaluated at 5 × 10-15. Further improvement is promised as well as a detailed publication of the evaluation. The copy of NIST-7 made for the Communications Research Laboratory in Japan has been delivered and is operating successfully. Some of the improvements made to it and its electronics are being retrofitted to NIST-7. These improvements, along with new software to make evaluations much less labor-intensive, should improve the accuracy considerably. However, it is not clear how much effort should be put into improving NIST-7. It is probably more reasonable to put effort into replacing it with the cesium fountain standard as soon as feasible.

The cesium atomic fountain standard is now in preliminary operation. Although the division is still a little behind the French standards laboratory team, recent progress has been excellent. The current accuracy evaluation is at about 2.8 × 10-15 with about 1.4 × 10-15 systematic error mainly due to uncertainty in the density shift and the correction for the local gravitational potential. The standard is noisier than expected, since a number of factors affecting the signal-to-noise ratio have not been optimized. Correction of these problems and the application of transverse cooling should provide a much better signal-to-noise ratio and smaller systematic errors.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

The division is engaged in a flight definition study for a laser-cooled, very-high-performance cesium beam clock in space. The project is aimed at an improved realization of the definition of the second, improved coordination of time and frequency standards on Earth, and tests of several aspects of special and general relativity. If the project remains on the present schedule, flight should occur aboard the International Space Station in 2003.

The division continues work on low-noise flywheel oscillators of various types, including a laser-pumped gas cell device. These are essential to realize the stability performance promised by the fountain and the other high-performance passive standards.

The trapped ion microwave frequency standard, which uses a linear string of seven cooled 199Hg ions, has demonstrated a stability of about 1 x 10-14 for an interrogation time of 100 s at an averaging time of 1,000 s. Increasing the number of ions should lead to record stability. Estimates are now that an accuracy of about 1 x 10-16 can be achieved. The limitation is currently due to magnetic fields at the trap drive frequency because of asymmetries in the quadrupole electrodes, producing unbalanced capacitive currents.

Since fractional frequency stability improves with increasing frequency, it is expected that substantially higher performance can be achieved using the optical, electric-quadrupole transition at 282 nm in the same mercury ion. Experiments on the optical frequency standard have been initiated using methods similar to those described above. In addition, the division is working on an optical standard based on a narrow resonance in calcium atoms cooled and trapped in a magneto-optical trap. The calcium frequency has very low sensitivity to electric and magnetic fields. Cooling and detection are both done with high-performance diode lasers, also developed by the group. Toward the goal of an optical mercury ion standard, the narrowest laser linewidth ever achieved, less than 1 Hz, was obtained in a pair of cavity-stabilized 563 nm dye lasers built by the division. Frequency doubling this type of laser will provide the required stable excitation for the 282 nm transition. This major technological achievement, and the extremely promising new methods for connecting optical and microwave frequencies, should open the way for full exploitation of the promise of the optical standard.

In the past, the measurement of optical frequencies in terms of the cesium microwave reference has required a very complex, unreliable system of phase-locked lasers and very fragile point contact detectors. The division is working on a new scheme using periodically poled lithium niobate crystals as nonlinear components for mixers and harmonic generators. These are used with lasers to subdivide optical frequency intervals. Several of these can be used to get a final interval small enough to be bridged with a comb of frequencies generated by the pulses from a broadband, mode-locked laser. Measurement of the mode-locked pulse rate in terms of cesium when two of the sidebands are phase-locked to the lasers at the ends of the interval, and knowing the number of sidebands between, provides the connection to the cesium frequency. This scheme is relatively simple and should be reliable.

A miniature ion trap has been constructed whose electrodes are formed from machined alumina substrates upon which metal electrodes have been deposited using lithographic techniques. This will provide strong confinement for a linear array of ions, which is very desirable for both frequency standards and quantum logic.

The division continues to investigate correlated states. Two beryllium ions have now been trapped with their quantum states entangled with high efficiency. This work has application not only to quantum computation but also to improving frequency stability over that achievable classically in trapped ion standards.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

Division staff have phase-locked the rotation of strongly coupled nonneutral plasmas to a well-controlled rotating electric field in a Penning trap. Bragg diffraction peaks from the rotating plasma crystal show that the crystal lattice can remain stable for longer than 30 minutes or 108 rotations, and the rotation is phase-locked to the rotating electric field without any slippage. Although the methods promise possible improvement for studies of plasma crystallization, the most significant practical implication is for future frequency standards. The uncertainty of the second-order Doppler shift for ions stored with this new technique can be greatly reduced compared with that in a conventional Penning trap. Accuracy approaching 1 part in 1017 may be achieved.

Work in the area of phase and amplitude noise and electronics for frequency standards and clocks continues to lead the world. Further progress has been made in understanding flicker-of-phase noise and its reduction in amplifiers, leading to improvements of better than 20 dB. This is important for amplifiers as well as low-noise oscillators. The group also has made headway in studying the noise of circuit components. In addition, good progress has been made in developing low-noise synthesizer chains and regenerative frequency dividers. The latest microwave synthesizer developed by the division has outstanding performance with regard to insensitivity of phase to ambient temperature, as well as very low added phase noise. The performance is due in large part to the use of carefully designed regenerative dividers at the highest frequencies and digital dividers at lower frequencies. A phase noise measurement technique for pulsed RF and microwave signals is a new and important development. The technique provides tens-of-decibels improvement over previously available instruments. Portable phase noise standards have been developed. In collaboration with the Politecnico di Torino, the group has developed a high-performance 100 MHz distribution amplifier. Many of the results from this group have direct and important applications in industry. The group also performs many calibrations for industry.

The stability of the NIST-coordinated universal time (UTC) scale with respect to the UTC disseminated by BIPM has improved greatly over the last several years. The use of five commercial hydrogen masers with cavity auto-tuning has contributed greatly in this respect. The stability of the time scale is now about 3 x 10-16 for 5-day averaging.

Time comparison by the division via advanced GPS common-view techniques is at the level of a few nanoseconds in 1 day. Common-view comparison of the GPS carrier phase allows frequency comparison to about 1 part in 1015 in 1 day. If cycle ambiguity can be resolved, time comparison to a few hundred picoseconds in 1 day can be achieved. This is similar to the results achieved by the division using two-way time transfer. The cycle ambiguity can be resolved in principle by using several receiving sites and adjusting the results to obtain consistency between the sites.

The Internet time dissemination service provided by the division is now receiving 6,000,000 calls per day, and the performance is 1 to 2 ms for long network paths and 100 to 200 µs for short paths. The division has also implemented a Y2K time/date service that allows users to test their software for the year 2000. Access to the service is by either telephone or Internet, and all common time formats are supported.

The upgrade of the 60 kHz transmitters at radio broadcast station WWVB is continuing. Upon completion, there will be 50 kW radiated power, compared with the 10 kW before modification. This is important, since there are now many clocks and watches as well as frequency standards in use that are automatically synchronized to the frequency signals broadcast by WWVB.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

Development is proceeding on a compact frequency standard based on the 3 GHz Raman transition in 85Rb. This could be 3 x 3 x 9 cm3 in volume, consume perhaps only 1 W of power, and have a stability of better than 1 part in 1010. It could fill the niche between high-performance quartz oscillators and high-accuracy atomic devices and thus have many applications.

In summary, the division's technical work, not all of which is mentioned here, is outstanding and leads the world in many areas. The leadership of the groups in the division appears to be excellent. In view of the number and quality of the results, the planning is certainly adequate.

Impact of Programs

The division has published more than 100 papers and given 37 invited talks in the last year. In addition, one invited talk at a Centennial Symposium at the prestigious APS meeting in March 1999 was given by a division staff member, and another Centennial Symposium was chaired by a division scientist. All these represent the division work very well.

The impact on industry continues to be strong. There are three active CRADAs on tunable external cavity lasers, software for GPS common-view processing, and optical and nonoptical pumping techniques for alkali-vapor frequency standards. The division's technical results as reported in publications and talks are widely used by industry. Its calibration services continue to be important. The division also sponsors workshops that are of direct interest to the time and frequency community. There is also staff participation in a number of standards committees.

The division continues to anticipate the future needs of industry. Its scientists are highly respected and recognized as leaders in most areas of the time and frequency field.

Division Resources

Funding sources for the Time and Frequency Division (in millions of dollars) are as follows:

 

Fiscal Year 1998

Fiscal Year 1999 (estimated)

NIST-STRS, excluding Competence

5.9

5.9

Competence

0.3

0.0

ATP

0.0

0.1

OA/NFG/CRADA

1.9

2.3

Other Reimbursable

0.7

0.5

Total

8.8

8.8

As of January 1999, staffing for the Time and Frequency Division included 40 full-time permanent positions, of which 36 were for technical professionals. There were also 10 nonpermanent and supplemental personnel, such as postdoctoral research associates and part-time workers.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×

The Time and Frequency Division is reasonably well supported and the resources are adequate, although the division is actively engaged in many frequency standard development programs at the moment and could make very good use of additional resources if they were available. There are recognized needs for more laboratory space, especially for the ion storage group, that should be addressed when NIST obtains space formerly occupied by the National Oceanic and Atmospheric Administration in Boulder. The disconnected nature of the division's space is also an issue. The activities of the division would benefit if they were not so widely dispersed throughout the building.

MAJOR OBSERVATIONS

The panel presents the following major observations.

  • The work of the Physics Laboratory is of high technical merit overall. Researchers often are at or define the state of the art in their field. Programs and projects are generally appropriate to the mission.

  • Laboratory staff represents one of the world's finest assemblages of talent in many areas of physics.

  • Facilities shortcomings noted in the previous assessment continue. The planned Advanced Measurement Laboratory, if built, would eliminate these problems for the most sensitive experiments.

  • More cohesive management of database activities is required to establish ownership and responsibility for this core Institute function. This should include a comprehensive review of the need for data, better understanding of its users, and how well user and potential user needs are met. Sufficient stable funding for database activities must be ensured to avoid loss of this resource.

  • The laboratory's planned initiative in optical technology should have a significant interdisciplinary component, involving substantial participation by other NIST laboratories.

Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
×
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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Suggested Citation:"Chapter 5 Physics Laboratory." National Research Council. 1999. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999. Washington, DC: The National Academies Press. doi: 10.17226/9685.
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An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 1999 Get This Book
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