7

Physics Laboratory

PANEL MEMBERS

Samuel Werner, University of Missouri, Chair

Peter R. Almond, University of Louisville

C. Denise Caldwell, University of Central Florida

William C. Eckelman, National Institutes of Health

Leopoldo M. Falicov, University of California, Berkeley

Charlotte Froese Fischer, Vanderbilt University

George W. Flynn, Columbia University

Andrew U. Hazi, Lawrence Livermore National Laboratory

Klaus B. Jaeger, Lockheed Missiles & Space Company, Inc.

Anthony M. Johnson, AT&T Bell Laboratories

Andrew Kaldor, Exxon Research and Engineering Company

James E. Lawler, University of Wisconsin

Sam V. Nablo, Energy Sciences, Inc.

David A. Shirley, Pennsylvania State University

Robert Vessot, Harvard-Smithsonian Astrophysical Observatory

Philip Wychorski, Eastman Kodak Company

Submitted for the panel by its Chair, Samuel Werner, this assessment of the fiscal year 1993 activities of the Physics Laboratory is based on site visits to the laboratory by individual panel members in March and April 1993, on a meeting of the full panel in Gaithersburg, Maryland, on May 3-4, 1993, on the annual report of the laboratory, and on many research papers and reports provided to individual panel members.

LABORATORY OVERVIEW
Functions and Mission

The Physics Laboratory conducts long-term research in measurement science; develops new physical standards, measurement methods, and reference data; and promulgates these standards, methods, and data by providing measurement services, conducting workshops, publishing research results, and collaborating with industry, universities, and other agencies of government. Specifically, the Physics Laboratory establishes spectroscopic methods and standards for infrared, visible, ultraviolet, x-ray, gamma-ray, and neutron radiation; investigates the structure and dynamics of atoms and molecules, singly and in aggregate; and develops and disseminates national standards of time and frequency and for the measurement of optical and ionizing radiation by means of calibrations, measurement quality assurance, and standard reference materials. The laboratory generates, evaluates, and compiles atomic, molecular, optical,



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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 7 Physics Laboratory PANEL MEMBERS Samuel Werner, University of Missouri, Chair Peter R. Almond, University of Louisville C. Denise Caldwell, University of Central Florida William C. Eckelman, National Institutes of Health Leopoldo M. Falicov, University of California, Berkeley Charlotte Froese Fischer, Vanderbilt University George W. Flynn, Columbia University Andrew U. Hazi, Lawrence Livermore National Laboratory Klaus B. Jaeger, Lockheed Missiles & Space Company, Inc. Anthony M. Johnson, AT&T Bell Laboratories Andrew Kaldor, Exxon Research and Engineering Company James E. Lawler, University of Wisconsin Sam V. Nablo, Energy Sciences, Inc. David A. Shirley, Pennsylvania State University Robert Vessot, Harvard-Smithsonian Astrophysical Observatory Philip Wychorski, Eastman Kodak Company Submitted for the panel by its Chair, Samuel Werner, this assessment of the fiscal year 1993 activities of the Physics Laboratory is based on site visits to the laboratory by individual panel members in March and April 1993, on a meeting of the full panel in Gaithersburg, Maryland, on May 3-4, 1993, on the annual report of the laboratory, and on many research papers and reports provided to individual panel members. LABORATORY OVERVIEW Functions and Mission The Physics Laboratory conducts long-term research in measurement science; develops new physical standards, measurement methods, and reference data; and promulgates these standards, methods, and data by providing measurement services, conducting workshops, publishing research results, and collaborating with industry, universities, and other agencies of government. Specifically, the Physics Laboratory establishes spectroscopic methods and standards for infrared, visible, ultraviolet, x-ray, gamma-ray, and neutron radiation; investigates the structure and dynamics of atoms and molecules, singly and in aggregate; and develops and disseminates national standards of time and frequency and for the measurement of optical and ionizing radiation by means of calibrations, measurement quality assurance, and standard reference materials. The laboratory generates, evaluates, and compiles atomic, molecular, optical,

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 and ionizing radiation data in response to national needs, develops and operates major radiation sources as user facilities, and maintains appropriate collaborations with other technical programs in NIST, the nation, and institutions throughout the world. The laboratory supports the research community and industry in communications, defense, energy, the environment, space, health, and transportation, as well as in specific technical areas such as lighting, microelectronics, and radiation. The reorganization of NIST in fiscal years 1990 and 1991 resulted in the creation of the Physics Laboratory, which is organized into eight divisions--electron and optical physics, atomic physics, molecular physics, radiometric physics, quantum metrology, ionizing radiation, time and frequency, and quantum physics (Figure 7.1). (The Quantum Physics Division, which consists mainly of researchers at the Joint Institute for Laboratory Astrophysics at Boulder, Colorado, is assessed biennially and is not included in this assessment.) The organizational structure and priorities of the laboratory have been carefully adjusted over the past 2 years to meet the needs of the changing mission of NIST. A gradually increasing emphasis on applied physics, technology, and service to industry is evident. In her presentation to the panel, the laboratory's director defined the laboratory's mission as follows: “The mission of the Physics Laboratory is to support U.S. industry, government, and the scientific community through strongly coupled, complementary programs of services and research in the physical sciences.” The panel concluded that the operating structure of the Physics Laboratory is sufficiently functional and adaptable to fulfill this mission in the current rapidly changing national environment. The program planning is well conceived and has been increasingly effective in capturing resources for new initiatives. Resources During fiscal year 1993, the Physics Laboratory had 218 full-time permanent staff, 8 part-time staff, 15 postdoctoral associates, 146 guest researchers, and 21 term and intermittent appointees. Its operating budget was $42.4 million, of which 63 percent, or $26.7 million, was direct congressional appropriations to NIST. Activities The Physics Laboratory Annual Report 1992, presented to the panel at its meeting, shows that the laboratory has been able to sustain and even enhance its level of productivity in high-quality fundamental and applied research while providing important advice and service to the many governmental,

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 FIGURE 7.1 Organization and structure of the Physics Laboratory.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 university, and industrial “customers” of NIST's services and facilities. During fiscal year 1993, the Physics Laboratory received NIST's Stratton Award for an unusually significant contribution to scientific research, its Astin Award for outstanding achievement in the advancement of measurement science, and its Slichter Award for important contributions in building ties with industry. Three members of the staff were elected to fellowship in the American Physical Society, and one was elected to the National Academy of Sciences. One division chief received the Meritorious Executive Award from the Office of Personnel Management, and the Federal Laboratory Consortium Award was given to another staff scientist for transferring to industry an important optical-mechanical gravimeter. In addition, scientists in the Physics Laboratory won three Silver Medals and three Bronze Medals of the Department of Commerce. This long list of awards attests to the laboratory's high level of scientific and technological productivity and to its success in fulfilling its mission as judged by people and committees outside the laboratory. The Physics Laboratory collaborates directly with approximately 100 U.S. firms. Eleven of these collaborations were established through the Advanced Technology Program (ATP), and about 25 are Cooperative Research and Development Agreements (CRADAs). Many of these interactions with industry involve scientists who also are carrying out fundamental research. Collaborations with industry span a wide range of companies and address many subjects, such as characterization of alternative refrigerants by high-resolution molecular spectroscopy, study of magnetic materials, advances in temperature controllers and solid-state lasers, and research in nuclear reactor dosimetry, mercury-free fluorescent lighting, and x-ray mammography. During fiscal year 1993, the NIST director's office awarded the Physics Laboratory more than half of the funds available for the director's Competence Building Program ($800,000 per year). These funds went to programs in atom optics, diode lasers, and laser polarization of neutrons. These awards represent 5-year investments in areas of basic research likely to yield results and techniques important to future advanced technologies. The importance of diode lasers to atomic clocks, spectroscopy of pollutants, and communications is discussed below. The Laser Polarization of Neutrons Program will make the Advanced Neutron Source (a $2.5 billion Department of Energy program scheduled to come on-line in the early part of the next century at Oak Ridge National Laboratory) much more useful in the study of magnetic materials, biological materials, and polymers. Work in atom optics may yield a new type of Sagnac gyroscope. (The Sagnac effect is the shift in interference fringes from two coherent light beams traveling in opposite directions around a ring when the ring is rotated about an axis perpendicular to the ring.) The panel concludes that these long-term investments are well placed and utilize extremely talented people.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 In fiscal year 1992 and the first part of fiscal year 1993, the Physics Laboratory submitted 10 proposals for core support from NIST. Three of the proposals were included in the President's fiscal year 1994 budget for NIST: (1) “Atomic Scale Structure and Standards,” which will address the challenges of metrology for nanotechnology; (21) “Magnetic Measurement Technology,” which will address the improved measurement and standards needs of the information storage industry as it uses ever more sophisticated recording materials and devices; and (3) “Advanced Algorithms, Software, and Applications,” which will address problems related to portable computational libraries. The third proposal provides a unique opportunity for the Physics Laboratory to have an impact on the federal High Performance Computing and Communications (HPCC) initiative. The panel is particularly encouraged by indications of improved interlaboratory activity. Such activity includes a joint proposal for evaluating reference data with the Chemical Science and Technology Laboratory. The proposed data evaluation would be important to most industrial support activities authorized by HR 4848, the Technical Competitiveness Act, which created NIST from the National Bureau of Standards in 1988. The laboratory proposed an exciting “umbrella” initiative on advanced optical technology, involving staff from many of its divisions. NIST is the only laboratory in the United States where the broad range of necessary expertise exists in optical measurement and instrumentation techniques to pursue the proposed advances in optical technology. NIST's expertise spans the electromagnetic spectrum from the infrared through the ultraviolet and up to soft and hard x-rays. The proposal includes developments in advanced optical devices, x-ray technology, infrared technology, display technology, and optical manufacture and measurement. In its fiscal year 1992 program review, the panel was briefed on the changing scene in international standards and laboratory accreditation, especially developments in the European Community (EC). According to EC-92 regulations, U.S. industry must register, accredit, and comply with international standards such as those set down by the International Organization for Standardization (ISO) in order to have its products accepted by EC member nations. The quality of products made in the United States must be demonstrated to comply with these regulations. The panel expressed considerable: concern in its fiscal year 1992 assessment report that the United States was not prepared to meet this challenge for certification of products and accreditation of processes and laboratories. This year (fiscal year 1993) the panel was briefed by the chief of NIST's Calibration Program on NIST's progress in meeting the EC-92 and National Laboratory Accreditation Program challenges. Progress has been made, particularly in the area of laboratory accreditation, where three new hires were made. ISO issues are particularly important for industries needing optical and radiometric calibrations and

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 metrological standards. The panel discusses these issues further in the assessment of the Radiometric Physics Division. In discussions with a number of scientific staff members, panel members raised concerns about the efficiency and usefulness to the Physics Laboratory of the Manufacturing Engineering Laboratory's Fabrication Technology Division machine shops. NIST is being asked to respond to the needs of U.S. industry and therefore must be able to rapidly make devices for specialized use. Adequate and responsive machine shop services are critical. In response to its inquiries, the panel was given a report by an internal NIST committee that reviewed this matter in fall 1992. The panel endorses the internal report's main conclusions and recommendations, which are as follows: (1) Research on computer-aided design/computer-aided manufacturing (CAD/CAM) should be separated from services provided to shop users. (2) The important role of the instrument maker to the cadre of expertise at NIST, which historically has helped to make its scientific research unique, should be renewed. (3) The number and quality of small “contact shops” reporting to and controlled by the divisions should be increased. (4) Engineering Services, which presumably does design and drafting work for various NIST programs, should be eliminated. In its fiscal year 1992 assessment the panel expressed concern that metrological standards, especially those for length and mass, were not receiving the level of attention needed to serve the high-technology industries of the next century. Because length is now derived from the standard second using the defined velocity of light, there is a need for a practical and transferable manifestation of this definition. This issue is discussed further in the panel's assessment of the Time and Frequency Division. With regard to career development and personnel matters of its technical staff, the Physics Laboratory is strengthening its diversity. Last year, it hired two African Americans and one woman among its 13 new National Research Council (NRC) postdoctoral fellows. The panel also recognizes that NIST has additional opportunities, and perhaps responsibilities, to better use the special talents of Russian and Eastern European scientists. In summary, the panel finds that the Physics Laboratory is very productive in a broad spectrum of research and development, including fundamental physics research, applied physics, instrumentation and metrological standards work, services to industry, and technology development.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 ASSESSMENT OF DIVISIONAL PROGRAMS Electron and Optical Physics Division Far Ultraviolet Physics Group at the Synchrotron Ultraviolet Radiation Facility Most noteworthy among the activities of the Far Ultraviolet Physics Group that manages the Synchrotron Ultraviolet Radiation Facility (SURF) was completion of the alteration of SURF's physical layout. The removal of a wall, relocation of the power supply for the ring, and rewiring of the electrical supply to the experimental stations provides a much-needed facility improvement. The x-ray spectrometer is awaiting installation, as is discussed in the section below on the Photon Physics Group. With regard to efforts on the various beamlines around the SURF ring, installation of new slits on the 2-m normal incidence monochromator (NIM) is complete and operational, and a University of Nebraska researcher is setting up a gas-phase experiment, taking advantage of the new areas for guest users that were allocated as part of the facility reconstruction. The assignment of a staff member to work with the University of the District of Columbia on the 6.65-m NIM should help move this program along. This instrument should be able to deliver a highly accurate (probably the most accurate to date) high-resolution determination of the absorption cross section of N2. Progress is being made in the development and analysis of silicon detectors (as discussed in the panel's fiscal year 1992 report). This work accompanies the progress of industrial collaborators in fabricating these detectors. A beamline is used to calibrate detectors for the National Aeronautics and Space Administration's use. The spectrometer necessary for using the SURF facility as a primary radiometric standard is now functioning. Calibration comparisons with a thermopile have given good results. Since one area of the laboratory is now responsible for radiometric calibration standards at all wavelengths, an overlap of optical and infrared wavelength calibrations is possible for wavelengths where calibrations were previously weakest. One of the most desirable characteristics of the SURF facility is the extent to which its radiation can be described analytically, making SURF radiation extremely useful for experiments using vacuum ultraviolet (VUV) optics. SURF's comparative advantage over more recently constructed synchrotron radiation sources is its broad spectrum of wavelengths of light suited for research and calibrations. SURF is more than competitive in its absolute flux reference capabilities. Moreover, it is extremely cost-effective. For these reasons, SURF can continue to occupy a useful niche among the nation's storage rings.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 Electron Physics Group The Electron Physics Group is recognized worldwide for its innovative approaches, its path-breaking research, and its outstanding technical skills and accomplishments. Its main areas of research are electron-surface interactions; electron microscopy; surface, thin-film, and multilayer magnetism; laser-focused atom deposition; electron-polarization phenomena; electron optics and instrumentation; and electron-interaction theory. The group's major accomplishments during fiscal year 1993 have been in magnetic properties of surfaces and, in particular, phenomena related to magnetic (micro) structure. Highlights include the following: Scanning electron microscopy with polarization analysis (SEMPA) studies of the antiferromagnetic ordering of chromium thin films; SEMPA studies of the domain structure of cobalt single crystals; SEMPA studies of the structure of domain walls at surfaces; SEMPA studies of the nature of coupling between two ferromagnetic films--iron, in particular--separated by a thin layer (or a shallow wedge) of a normal metal, in particular, chromium and silver; Deposition of chromium atoms on a silicon surface in a well-defined pattern--thin, 50-nm-wide lines spaced periodically by 213 nm--controlled by a laser (laser focusing); Scanning tunneling microscopy (STM) studies of the electronic properties of cesium structures--one-, two-, and three-dimensional--deposited on indium antimonide surfaces; STM studies of the initial stages of film growth, in particular, iron on iron and chromium on iron; Initial stages of the development of a scanning tunneling microscope with magnetic sensitivity; Studies of polarized electron-atom scattering, in particular, scattering from sodium atoms that were spin polarized by optical pumping; Theoretical studies of exchange coupling in magnetic heterostructures, in particular, magnetic layers separated by a nonmagnetic spacer; and Theoretical studies of the isotope effect in high-temperature superconductivity and the constraints it imposes on the various theoretical models. The group is well balanced with respect to age distribution, theoretical versus experimental effort, and basic research versus instrumentation development. Despite its considerable strengths, the group could benefit from longer-range planning, a steady budget, and a steady influx of postdoctoral fellows.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 Photon Physics Group A major accomplishment of the Photon Physics Group since the panel 's fiscal year 1992 assessment is the completion of a monochromator (including the toroidal gradient mirrors) for the NIST/Advanced Research Projects Agency (ARPA) soft x-ray reflectometry facility, which improves wavelength and spatial resolution and expands wavelength coverage. The next step is to construct and commission a new reflectometer chamber that permits measurements on large optical components (up to 35 cm in diameter). A valuable radial scanning mode will also be made an option. Joint NIST, ATP, and ARPA funding for this program attests to its perceived value to the x-ray community for “at wavelength ” analysis of optical elements. Work utilizing the x-ray fluorescence spectrometer at the National Synchrotron Light Source is continuing, although it is anticipated that these experiments will move to the Center for Advanced Microstructures and Devices in Louisiana in the near future. The greater propagation in matter of photons produced in x-ray decay allows probing of matter at greater depths. Also, the probing is less sensitive than longer-wavelength probing to the sample's surface features. Measurements to date have been primarily for use in the analysis of high-critical-temperature (high-Tc) superconductors. The panel supports future plans that call for measurements to analyze buried interfaces, with more emphasis on the solid-state physics phenomena. A similar spectrometer is being constructed for one of the beamlines at the new Advanced Light Source at the University of California, Berkeley. The continuing multiphoton process experiments are an excellent mix of applied and fundamental physics. One achievement since the fiscal year 1992 assessment was the determination of the configuration-dependence of the alternating current Stark shifts in calcium. One discovery from these measurements was that the level shift in a high field can be up to half as large as the ponderomotive shift. Experiments on calcium are expected to continue in an effort to determine a suitable multiphoton excitation mechanism, which could lead to an isotope enrichment program. A cost-effective calcium isotope separation scheme is needed for medical research; calcium isotope experiments are essential in the study of bone decalcification caused by extended periods of weightlessness during space travel. This effort is being conducted in cooperation with a small industrial company. Measurements on two-photon processes in helium are continuing, although conducted largely by a postdoctoral research fellow. The helium experiment is a potentially important fundamental project. The high-precision calculations of the ground state of neutral atomic helium have never been tested against a high-accuracy, high-precision laser experiment. Since helium is the simplest and the most fundamental multielectron

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 system, this experiment offers the possibility of a discovery of profound importance to physics. Atomic Physics Division Atomic Spectroscopy Group Atomic data generation and evaluation continue to be an important part of the mission of the Atomic Spectroscopy Group. Recent accomplishments include the improved measurements of wavelengths for the prominent spectral lines of Cr XVI to Cr XXII. The spectra of transition metals are of particular interest to the fusion community. In support of the VUV spectroscopy being carried out by NASA Goddard using the high-resolution spectrometer on the Hubble Space Telescope, the group has obtained high-accuracy laboratory wavelength data for the different isotopes of Hg III. The laboratory measurements enable the proper interpretation of the Hubble data, which in turn will have a significant impact on various theoretical models of young, hot stars. A general thrust of the spectroscopy research has been to extend the availability of high-quality data to more highly ionized systems and heavy elements, where information is sparse or nonexistent. The group has used a variety of sources of experimental spectra, such as laser-produced and magnetically confined plasmas, and will soon have access to the electron beam ion trap. This novel ion source, which is discussed further in the assessment of the Plasma Radiation Group, will provide new opportunities to obtain high-resolution spectra of highly charged ions in an environment free of plasma effects. The productivity of the Atomic Spectroscopy Group is reflected in its number of high-quality publications and the receipt of the 1992 William F. Meggers Award by one of its members. Collaborations with external organizations appear to have strengthened since the panel's fiscal year 1992 assessment. The group plans to develop a computer-accessible database for atomic energy levels, transition probabilities, and lifetimes and to network it to the Astrophysical Data System supported by NASA and to ALADDIN, which is sponsored by the International Atomic Energy Agency and the Department of Energy. This effort is timely in view of the current federal emphasis on high-speed computer networks as components of an “information superhighway.” Computer-accessible spectroscopic data would also benefit U.S. industry. One current need is for atomic data involving rare-earth elements for the development of new lighting technologies. The group is a valuable scientific resource for other federal agencies with specific atomic data needs.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 Atomic Radiation Data Group The Atomic Radiation Data Group develops fundamental atomic theory and maintains state-of-the-art computational capabilities for atomic phenomena. Experimental studies are carried out to resolve discrepancies in the theory and thus increase understanding of the underlying atomic physics. Research focuses on effects of relativity in electron-ion collisions and on the quantum electrodynamical theory of electronic structure. A recent accomplishment is the calculation, with unprecedented precision, of nuclear size effects on the self-energy contribution to energy levels of heavy, highly charged ions. The Atomic Radiation Data Group is small, and the panel believes it could benefit from having an NRC postdoctoral fellow. Past concerted efforts to recruit the best available young atomic theorists from good schools have not been successful. This group also assists in critical evaluations of atomic data for the Atomic Energy Level Data Center and the Data Center on Atomic Transition Probabilities and Line Shapes. During fiscal year 1993, the group added a part-time scientist with major responsibility for building a database readable from widely available platforms such as personal computers and workstations. This effort is parallel to the networking of the Atomic Physics Division's critically evaluated spectroscopic data to NASA's Astrophysical Data System. The Atomic Radiation Group shared in the development of an interdivisional proposal for the federal HPCC initiative. Should this proposal be funded in fiscal year 1994, it would provide the group with an opportunity to exploit massively parallel computers for frontier atomic structure calculations and to make a major contribution to computer-based dissemination of critically evaluated atomic databases. The group could also expand the scope of its work to include computational physics, an area that appeals to many young scientists. Plasma Radiation Group Significant progress has been made by the Plasma Radiation Group during fiscal year 1993 on the development of the electron beam ion trap (EBIT). EBIT is now almost fully assembled, and component testing is well under way. The development of EBIT is extremely important in NIST's continuing world leadership in basic atomic spectroscopy and to its becoming a world leader in the basic atomic spectroscopy of highly ionized atoms. Spectroscopy of highly ionized atoms is important for diagnosing fusion plasmas and for fundamental tests of plasma theory. NIST's work in this field is now being performed using laser-produced plasmas and Tokamak plasmas at remote sites. Along with greater productivity due to an in-house capability, EBIT has the potential to provide sharp, unperturbed spectral lines that are unaffected by the turbulence and the high collisional rates found

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 these standards programs, which serve large segments (nuclear power, industrial radiation processing and radiography, and nuclear medicine) of U.S. industry. Timely responses are needed for national standards and data for radionuclides with new applications, especially in nuclear medicine. As the panel pointed out in the fiscal year 1992 report, this group's resources are subcritical for fulfilling the group's responsibilities under NIST's congressional mandate and, in particular, the group's broad responsibilities for providing traditional standards for U.S. industry and public health and safety. Deliberate support of the group's programs now would preclude costly duplication of the group's capacity by other agencies in pursuing cleanup programs for radioactive sites. Neutron Interactions and Dosimetry Group The Neutron Interactions and Dosimetry Group (1) maintains primary national neutron radiation standards, (2) develops neutron measurement techniques, (3) develops improved dosimetry techniques, (4) provides neutron radiation calibration and measurement technique services to industry, universities, and other government agencies, and (5) carries out basic neutron-related research in support of the above missions. The work of this group is done mainly at the NIST research reactor in Gaithersburg, Maryland. Collaborative research is also carried out at the Oak Ridge Electron Linear Accelerator, the University of Missouri Research Reactor, and the University of Michigan's reactor (Ford Nuclear Reactor, or FNR). Over the past several years, the group's Fast Neutron Research Program has established the Materials Dosimetry Reference Facility at the FNR. This effort is in direct support of the materials neutron dosimetry needs of the nuclear power industry and the needs of the metallurgical community engaged in the study of radiation damage in steel structures such as reactor pressure vessels. This facility, which is still in its early stages of operation, will provide fast neutron fluences an order of magnitude greater than those currently available at NIST's research reactor. Two different spectra are available to investigate detector response characteristics and to validate dosimetry measurements. The importance and usefulness of this facility will be discussed by the panel in its fiscal year 1994 assessment. Other fast-neutron-related programs involve neutron transport through iron shells, a fast neutron calibration spectrometer of interest to the Defense Nuclear Agency, and calculations related to correction factors for fast neutron measuring instruments due to neutron reflections from the walls, floor, and ceiling surrounding the instrument. Calibration work on detection of fast neutron radiation is difficult, important (especially at research reactors and neutron spallation sources), and appropriate for NIST to pursue.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 A new experiment aimed at detecting a correlation between the direction of the spin angular momentum of a decaying neutron and the momentum of the decay particles (proton and electron) was begun, and its feasibility was demonstrated, by the Weak Interaction Physics Program at the national Cold Neutron Research Facility (CNRF) since the panel's fiscal year 1992 assessment. Such a correlation would require a violation of a fundamental principle of physics known as time-reversal symmetry. Also since the fiscal year 1992 assessment, a reconstructed neutron lifetime apparatus was installed at the end position of the CNRF beam guide NG6. All of the major components of the apparatus have now been debugged and tested. Its aim is measurement of the neutron lifetime to a precision of 0.1 percent. An accurate value for the neutron lifetime is necessary to create a unified theory for the strong, weak, and electromagnetic interactions of nature. The panel will review this long-term experiment in more detail in its fiscal year 1994 assessment. Of all the experimental techniques available for studying the structure and dynamics of materials and their surfaces, the scattering of thermal neutrons is perhaps the most versatile and powerful. To take full advantage of this technique, methods for polarizing the incident beam and analyzing the polarization of the scattered beam are often necessary. This technique is particularly important for studying magnetic, superconducting, and hydrogen-containing materials. The Laser Polarization of Neutrons Program takes advantage of the high flux of neutrons from NIST's research reactor and NIST's high level of laser expertise to polarize the nuclei of 3He gas by optical pumping. This program polarizes the 3He gas by spin exchange; i.e., anoptically polarized rubidium vapor sample polarizes the dense 3He gas by collisions. Spin-up neutrons (with respect to the 3He nuclear spin) suffer little absorption, whereas spin-down neutrons experience a large neutron absorption cross section in the 3He gas cell. Thus the transmitted beam will be highly polarized (a polarization of the order of 80 percent is possible). The 3He gas cannot be polarized directly with a laser because of the unavailability of tunable ultraviolet lasers. There are other excellent ways to polarize monoenergetic beams of neutrons, such as by Bragg reflection from magnetic crystals and by mirror reflection by magnetic multilayers, but these techniques are not useful for a broad energy band of incident neutrons. They also require a substantial change in the geometry of the spectrometer in switching from unpolarized to polarized neutrons. A polarized 3He gas cell can be placed in an unpolarized neutron beam, allowing only spin-up neutrons to pass through it, thus providing a polarized beam without change of spectrometer geometry. For time-of-flight neutron spectroscopy at the new pulsed spallation neutron sources, the incident beam has a broad (Maxwellian) energy spectrum. The polarized 3He cell is well suited for such beams.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 Funding is assured for 5 years. The goal is to develop prototype devices for use in neutron scattering research at the new spallation sources and at the Advanced Neutron Source scheduled to become operational at the Oak Ridge National Laboratory in the early part of the next century. This program, along with the Weak Interaction Physics Program and the neutron interferometry research, represents some of the most fundamental physics research under way within the Physics Laboratory. Division-wide Issues The Physics Laboratory Annual Report 1992 that was provided for reference during the fiscal year 1993 annual assessment documented steps taken by the Physics Laboratory, and involving the Ionizing Radiation Division, toward stronger interlaboratory collaboration. Examples are the Physics Laboratory's collaboration with the Chemical Science and Technology Laboratory in (1) developing a joint proposal for a 1994 NIST budget initiative on physical and chemical measurements, and (2) sponsoring the Conference on Metrology for Environmental Management on April 14 and 15, 1993. Other documents that were helpful during the program review and in arriving at the following comments were “Physics Laboratory Highlights, 1992,” an informal summary paper on the technical activities of the Radiation Interactions and Dosimetry Group, and the Ionizing Radiation Division's 1992 strategic plan. Although the Council on Ionizing Radiation Measurements and Standards was set up in 1992, it has yet to assist the Ionizing Radiation Division in program planning and priority setting. More workshops like the Ionizing Radiation Division's March 1992 “National Voluntary Laboratory Accreditation Program (NVLAP) Personnel Dosimetry Workshop” are recommended to stimulate industrial input for planning and priority setting. The panel found a much-improved morale in the Ionizing Radiation Division staff, which is no doubt partly attributable to the expected increase in support and staff over the next 4 years. This division provides unique and essential support to a U.S. industry that has $50 billion in annual billings. The division's role will increase in importance as the magnitude of U.S. radiological health and safety issues continues to increase. Time and Frequency Division The Time and Frequency Division (1) develops and operates standards of time and frequency and coordinates them with other world standards, (2) provides time and frequency services for U.S. clientele, and (3) performs basic and applied research in support of future standards, in ways to disseminate services, and in measurement methods.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 The division has a full-time staff of 40, and it hosted 20 long-term guest researchers and 5 postdoctoral associates in fiscal year 1993. The division collaborates with 18 industrial companies. The division 's research is unquestionably first-rate. The morale is strong, and there is a pride of achievement and a sense of common mission among the staff. The division is reviewed here according to major programs rather than according to groups. New Cesium Frequency Standard; NIST-7 Program During fiscal year 1992, NIST-7, an optically pumped cesium-beam atomic clock, became operational and was put “on the air.” It is designed ultimately to operate at an uncertainty level of 1 × 10-14. It is already performing at an uncertainty level of 4 × 10-14. NIST-7 is the most accurate optically pumped primary frequency standard in the world. Previous cesium clocks have been based on magnetic state selection and detection. The fundamental advantage of this new standard clock is its greatly enhanced signal-to-noise performance, which allows for more rapid evaluation of its accuracy. Time Dissemination and Transfer Program The time scale stability will be improved to hold to Coordinated Universal Time (UTC) to within 100 nanoseconds. The resources and talent necessary to realize this goal are available within the division. Input from NIST will help the International Bureau of Weights and Measures to reduce the time lag between receipt of data and issuance of time differences from UTC. This improvement in stability will benefit the telecommunications industry. The Time and Frequency Division has an excellent record of dissemination and transfer of time standards, as evidenced by the following: The Automated Computer Time Service operated by the division has experienced substantial growth since its inception in 1988, with a doubling of its activity in a period of well under 1 year. The current level of use is more than 4,000 calls per day. The division operates two radio stations (WWV and WWVB) in Fort Collins, Colorado, and in Hawaii (WWVH) that provide time and frequency broadcasts. It also provides a time code broadcast from the GOES weather satellite operated by NOAA. It is a credit to the division that WWVH stayed on the air and survived the damage from Hurricane Iniki in September 1992. A two-way satellite time transfer is being implemented using a NIST-developed time transfer modem that could become the world standard.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 The Global Positioning System common view technique will be continued and improved by enhancing the NIST-designed receiver to measure the ionosphere delay. Work on time jitter or phase stability has substantially helped the telecommunications industry. The division has developed secondary standards that can be transported from laboratory to laboratory and into industry. This is a previously neglected area of work that supports the division and the outside world. The high level of outside funding is proof that this effort has been beneficial. Diode Lasers Program The panel pointed out in its fiscal year 1992 report that diode laser technology development was vital to the development of the next generation of optically pumped atomic and ionic frequency standards. Funds from the NIST director's Competence Building Program were used to hire another professional staff member for the development of diode lasers. Present development involves a number of collaborations within NIST and with industry; however, the work would benefit from better technical coordination throughout NIST. There are many applications for tunable diode lasers of high stability, e.g., in laser manipulation of atoms on surfaces in nanostructures, optical pumping for frequency standards,a transferable standard for length, and in spectroscopy for chemical analysis, analysis of pollutants, and similar applications. Development of high-stability tunable diode lasers is an important new technological development at NIST based on cooperation with U.S. high-technology industry. New Initiative in Cryogenic Oscillators (Proposed) Because of the extraordinarily narrow frequency discrimination capability that has resulted from development of trapped ion capabilities, it is appropriate for NIST to develop oscillators to serve as “frequency-maintaining flywheels” to provide signals to be steered by the discriminators. Although new crystal oscillator developments can still offer improvements, these devices are limited by their mechanical nature and are sensitive to vibration. It is well known that low-temperature operation offers considerable advantages for realizing highly stable oscillators. These advantages include reduced levels of additive white thermal noise, very small loss tangents in dielectric materials such as sapphire, improved mechanical and thermal characteristics, superconductivity, and superfluidity. The panel notes that NIST's growing emphasis on creating generic technologies provides an opportunity to promote low-temperature device development within the Time and Frequency Division.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 Assignment for Development of Length Standard Because length is now derived from the unit of time, the second, through the defined velocity of light, the Time and Frequency Division has the expertise but only a secondary responsibility for developing the standard of length. The primary responsibility for a standard of length resides with the Precision Engineering Division of the Manufacturing Engineering Laboratory. The Time and Frequency Division, with its laser expertise, could be assigned responsibility for developing and implementing a unified time-length standard. The essential aspect of this standard would be a laser-generated light source at a frequency directly related to the NIST primary frequency standard. Development of techniques for determining distance standards based on the laser-generated light source should not necessarily be the responsibility of the Time and Frequency Division. Opportunities in Nationwide Initiatives in Computers and Information (Panel Comments) Time synchronization in telecommunications is an increasingly important factor in schemes to link computers across the country, across the oceans, and in space. Such challenges in the development of a “national information highway” are more formidable than originally thought. There are opportunities, and perhaps responsibilities, for the Time and Frequency Division to assist in the rapidly emerging telecommunications industry in the synchronization of signals. Fundamental Basic Physics Research (a Panel Comment) The research within the Time and Frequency Division is extremely well structured to support the time and frequency standards mission of the division; however, it also stands on its own as high-quality fundamental physics research. An example of the division's fundamental research is the recent experiment in which π-polarized light scattered from two trapped atoms was shown to give rise to “Young's-like” two-slit interference fringes, while σ-polarized light did not. This experiment, carried out by the division's Ion Storage Group, has ramifications for the study of the fundamental nature of quantum mechanical phenomena.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 PANEL RECOMMENDATIONS--FISCAL YEAR 1993 Laboratory-wide Recommendations The panel recommends that the Physics Laboratory extend the “Advanced Algorithms, Software, and Applications” proposal to include the development of on-line visualization and a state-of-the-art physics computational center to support the database effort. This extension could have a major impact on NIST's general responsibilities to provide to industry such scientific and technical data as plasma radiation data and atomic energy level data. The panel recommends more interlaboratory proposals such as the joint evaluation of reference data (with the Chemical Science and Technology Laboratory) for coordinating NIST's support of U.S. industry. The panel recommends that the advanced optical technology initiative be pursued as a high-priority program, not only because it supports the mission of NIST and will strengthen NIST's ability to interface properly with its extramural Advanced Technology Program, but also because NIST is the only place in the United States where the necessary expertise exists in optical measurement and instrumentation techniques to significantly advance optical technology. The panel recommends that the laboratory's name be changed to the Physical Sciences and Technology Laboratory. This name not only would more accurately reflect the laboratory' s activities and responsibilities but also would be more in parallel with the names of other NIST laboratories. Division-level Recommendations Electron and Optical Physics Division The panel recommends additional emphasis on making the toroidal gradient monochromator operational. As new synchrotron radiation facilities come on-line, the panel recommends that managers of the Synchrotron Ultraviolet Radiation Facility (SURF) project elucidate the advantages that make SURF a unique measurement tool. In particular, future plans for SURF should capitalize on the unique advantages of the optical quality of SURF's radiation. The panel recommends that long-range planning be undertaken for the Electron Physics Group. The panel recommends that x-ray fluorescence measurements using existing instruments be focused on problems that do not require the high brilliance of the Advanced Light Source.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 Atomic Physics Division The panel recommends that the Atomic Radiation Data Group secure the assistance of a computer scientist with expertise in database software for the efficient implementation of its database efforts. The panel recommends that final assembly and testing of the electron beam ion trap (EBIT) be accelerated. Because the Gaseous Electronics Conference (GEC) reference reactor program has direct applications to the U.S. semiconductor industry, the panel recommends additional support for the program. Molecular Physics Division The panel recommends that the Molecular Theory Group play an active role in and fully support the Physics Laboratory's effort to be part of the federal High Performance Computing and Communications (HPCC) initiative. Radiometric Physics Division Because the ambient background infrared (ABIR) facility has several challenges to meet, the panel recommends that the Radiometric Physics Division prepare a detailed time line to track the various facets of the planned improvements. The panel recommends that (1) a well-thought-out plan and time line be developed for the optical Properties of Materials Program on the basis of customer input, (2) two additional full-time professionals be hired and adequate Scientific and Technical Research and Services (STRS) funding be secured for this program, and (3) a high priority be placed on implementing International Organization for Standardization (ISO) Guide 25 policies. The panel recommends that the Radiometric Physics Division examine all of the scales to be integrated with the high-accuracy cryogenic radiometer (HACR) and prepare a master plan to address the tasks required to achieve this objective, associated funding required, and the proposed time line for completion. Several papers and presentations have been prepared since the fiscal year 1992 assessment; however, the panel recommends that dissemination of the technologies being developed within HACR be intensified. Work on measurement aperture areas should continue to be given high priority by the Radiometric Physics Division. The Detector Metrology Group should emphasize technology transfer, e.g., by conducting periodic workshops or seminars. The Radiometric Physics Division should emphasize updating SP 250 publications and developing an official manual for laboratory personnel on International Organization for

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 Standardization (ISO) quality requirements as defined in ISO Guide 25. In addition, seminars should be organized for the benefit of personnel that would bring in representatives from outside organizations who are familiar with the standardization process and with the quality requirements. The panel recommends that the Radiometric Physics Division develop long-term (10- to 15-year) goals and document plans. The Radiometric Physics Division should increase its emphasis on dissemination of information regarding optical calibration techniques and measurement techniques and the dissemination of routine measurement techniques. Quantum Metrology Division The Quantum Metrology Division should expand into a broad-based x-ray technology effort, following the example of the mammography tubes project. Ionizing Radiation Division The Committee on Interagency Radiation Research and Policy Coordination should help develop priorities for the Office of Radiation Measurement 's services. In its fiscal year 1992 assessment the panel recommended that a senior scientist be sought to lead standards activities in the Radioactivity Group. It reiterates that recommendation here. The panel recommends that the strategic plan for the Ionizing Radiation Division be updated annually. The panel recommends an integration of the Office of Radiation Measurement and the Radioactivity Group in view of their overlapping missions. The identities of the two groups could be preserved under a new “radiation standards group.” The panel recommends that the Council on Ionizing Radiation Measurements and Standards interact with relevant trade organizations to provide feedback for the Ionizing Radiation Division's planning. In view of the Ionizing Radiation Division chief's plan to retire in June 1994, the panel recommends that a nationwide search begin immediately to recruit a senior scientist of international reputation as a replacement. Time and Frequency Division The panel recommends that the Time and Frequency Division invest in the personnel and equipment necessary to develop precommercial cryogenic oscillators.

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An Assessment of the NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY PROGRAMS: Fiscal Year 1993 The panel recommends that NIST formalize, in some useful way, a new definition of the meter in terms of the velocity of light.

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