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Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

5
Physics Laboratory

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

PANEL MEMBERS

Janet S.Fender, Air Force Research Laboratory, Chair

Neville V.Smith, Lawrence Berkeley National Laboratory, Vice Chair

Patricia A.Baisden, Lawrence Livermore National Laboratory

Anthony J.Berejka, Consultant, Huntington, New York

Gary C.Bjorklund, Bjorklund Consulting, Inc.

D.Keith Bowen, Bede Scientific Incorporated

Leonard S.Cutler, Agilent Laboratories

Ronald O.Daubach, OSRAM SYLVANIA Development, Inc.

Paul M.DeLuca, Jr., University of Wisconsin Medical School

Jay M.Eastman, Lucid, Inc.

Stephen D.Fantone, Optikos Corporation

Thomas F.Gallagher, University of Virginia

Tony F.Heinz, Columbia University

Jan F.Herbst, General Motors Research and Development Center

Franz J.Himpsel, University of Wisconsin

Daniel J.Larson, Pennsylvania State University

David S.Leckrone, NASA Goddard Space Flight Center

Thad G.Walker, University of Wisconsin

Frank W.Wise, Cornell University

Submitted for the panel by its Chair, Janet S.Fender, and its Vice Chair, Neville V.Smith, this assessment of the fiscal year 2001 activities of the Physics Laboratory is based on site visits by individual panel members, a formal meeting of the panel on March 8–9, 2001, in Gaithersburg, Md., and documents provided by the laboratory.1

1  

U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology, Physics Laboratory: Technical Activities 2000, NISTIR 6590, National Institute of Standards and Technology, Gaithersburg, Md., February 2001, and U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology, Physics Laboratory: Annual Report 2000, National Institute of Standards and Technology, Gaithersburg, Md., February 2001.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

LABORATORY-LEVEL REVIEW

Technical Merit

The NIST Physics Laboratory (PL) states its mission as supporting U.S. industry, government, and the scientific community by providing measurement services and research for electronic, optical, and ionizing-radiation technology. The laboratory carries out this mission via programs ongoing in six divisions: Electron and Optical Physics, Atomic Physics, Optical Technology, Ionizing Radiation, Time and Frequency, and Quantum Physics (see Figure 5.1). Of these six divisions, five are reviewed below under “Divisional Reviews.” The sixth, Quantum Physics, operates within JILA, a joint institute with the University of Colorado at Boulder, and will be reviewed by a special subpanel in 2002.

Based on its collective experience and expertise, the panel finds the programs ongoing in the laboratory to be of an extraordinarily high technical quality. This continues a long tradition of technical excellence at the laboratory. The Physics Laboratory is an indispensable national asset in terms of the technical capability that it maintains for the nation. Many of its capabilities are unique in the nation;

FIGURE 5.1 Organizational structure of the Physics Laboratory. Listed under each division are the division’s groups.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

some are unique in the world. Its world-class research aims at long-term goals in fundamental standards and metrology.

The panel spent a considerable amount of time at its meeting with laboratory management discussing four areas of science and technology that the laboratory has determined to be target areas for increases in investment. The four areas are nanotechnology, biophysics, medical physics, and quantum information. The panel had heard briefings on these areas at its 2000 meeting. The most recent discussions were intended to gauge Physics Laboratory progress in the last year toward building programs in these areas. At this point the panel comments briefly on the technical strength of the Physics Laboratory in the four areas. It comments in the next section, “Divisional Reports,” on the relevance and effectiveness of the laboratory’s work in these areas.

The laboratory has a strong capability in nanotechnology. Several laboratory researchers are considered by their peers as among the world’s leaders in fabricating and characterizing structures on the nanoscale. The laboratory recently completed assembly of specialized instrumentation, the Nanoscale Physics Laboratory, which integrates fabrication and characterization of nanostructured materials into one instrument and allows their characterization under conditions of low temperature and both fixed and variably oriented magnetic field. This gives the laboratory a unique technical capability. The panel anticipates that the next several years will bring continued outstanding results from the PL in nanotechnology.

The Physics Laboratory does not have a notable capability in biophysics. To have an impact in this area, it would need access to substantial expertise in the biological aspects of the relevant problems.

The laboratory currently has a strong technical capability in the medical use of radiation, one aspect of medical physics. It has been successful in developing new measurement capabilities and dosage standards to keep pace with the growing numbers and types of radiation therapies delivered to patients each year in the United States. The laboratory has access to unique facilities, one of which is the NIST Center for Neutron Research, that enable its capabilities in this area.

The laboratory is clearly well positioned technically to lead the country in attempts to use trapped atoms and ions and exotic states of matter such as the Bose-Einstein condensate to develop information storage systems based on the quantum properties of atoms. Of the dozen or so people in the world who are considered the experts in this rapidly developing area, NIST counts three on its staff, one a Nobel laureate. The technical knowledge and skills required to succeed in this area are well established in the laboratory, and groundbreaking work, such as the demonstration of a four-atom entangled state, or four “qubit” system, has already come out of this group. The team has set an extraordinarily challenging goal of a 10-qubit system by 2005, but its strength is so outstanding that it stands a very reasonable chance of achieving it.

Detailed comments on other technical programs ongoing in the Physics Laboratory are given below in “Divisional Reports.”

Program Relevance and Effectiveness

Many programs in the Physics Laboratory are clearly reaching their customers in industry and the scientific community. For example, the laboratory’s programs in optical radiation measurements (including derived photometric and radiometric units, the radiation temperature scale, spectral source and detector scales, and optical properties of materials such as reflectance and transmittance) are utilized by the aerospace, biotechnology, photographic, lighting, display, automotive, pharmaceutical, semiconductor, and scientific and optical instrumentation industries, among others. The laboratory’s measure-

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

ment services support important niche sectors of the economy—for example, its highly accurate measurements of the spectra of rare-earth elements have value to the commercial lighting industry. Although many technical programs were clearly targeted at current or anticipated industry needs, not all programs have such a clear focus. Assessing program relevance and effectiveness was difficult, since the panel did not hear a clearly articulated overall strategic vision for the laboratory’s impact. Clearly, articulating specific overall strategic goals for the laboratory would help improve alignment of individual programs with the laboratory mission and allow NIST stakeholders to better understand the value and effectiveness of the programs.

The panel strongly supports the laboratory’s planned emphasis on nanotechnology. Experts in science and technology predict that nanotechnology will lead the next industrial revolution. Advances are being made much more rapidly than had been anticipated when the field emerged. In the United States, Congress funded the National Nanotechnology Initiative to stimulate research by leading universities and industry in this important emerging area. The European Union is very well organized and intent on leading the world in the invention, development, production, and sales of nanobased technologies and devices. Standards and measurement capabilities are already needed in some key areas and will certainly be required as these technologies move closer to implementation. The laboratory has a strong technical base in place to begin such work. However, the panel did not find an articulated overall vision for the work, whose ultimate goals were not clear to it.

The panel supports near-term development of a NIST program in nanotechnology and high-level sponsorship by NIST management. First and foremost, the NIST program in nanotechnology needs to be defined. To develop the scope of its niche area, the NIST team should identify critical parameters and methods for measuring fabrication quality, performance, interfaces, and other aspects of nanotechnology devices. Since nano devices are atomic and molecular constructions, measuring bulk properties may not adequately characterize their performance. Interactions among individual atoms and molecules may produce effects that are not observed when properties of bulk materials are measured. Understanding what properties need to be measured will require a multidisciplinary team at NIST. A clear statement of vision and the niche that NIST will fill should be communicated to U.S. industry and all other stakeholders in the field.

The panel was unable to divine the role that the Physics Laboratory believes it can fill in biophysics. For the laboratory to have an impact, its role must be determined early and driven toward. A solid base of technical expertise does not yet exist in the laboratory in biophysics, so the laboratory must consider carefully whether the role it can play merits diverting the resources necessary to establish such a base in the current flat budget situation.

As noted above, NIST already has a strong presence in medical radiation dosimetry, one aspect of medical physics. It was not clear to the panel what the NIST goals were for broader expansion into medical physics. A long-range vision is needed to guide the effort and to engage both staff scientists and stakeholders.

The panel was very impressed with laboratory plans in the Quantum Information Program. While this is a highly speculative effort, it is critical to both U.S. commerce and defense that the United States be the leader when and if this technology comes to fruition. The laboratory already has on its staff many of the world’s leading experts in science relevant to this area and is extraordinarily well-positioned to succeed in this effort. Despite the long-term, high-risk nature of the program, the team has set very specific, definable goals (10 qubits by 2005) for its work, and it communicated these goals effectively to the panel. These clearly defined goals and vision, coupled with the tremendous laboratory expertise in this area, bode well for the future success of the program. This program is a model of clear vision and organization that can be followed as PL defines its programs in other emerging areas.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

TABLE 5.1 Sources of Funding for the Physics Laboratory (in millions of dollars), FY 1998 to FY 2001

Source of Funding

Fiscal Year 1998 (actual)

Fiscal Year 1999 (actual)

Fiscal Year 2000 (actual)

Fiscal Year 2001 (estimated)

NIST-STRS, excluding Competence

31.2

33.0

33.0

33.9

Competence

1.9

1.6

1.8

2.2

ATP

1.8

1.9

1.9

2.3

Measurement Services (SRM production)

0.2

0.2

0.1

0.1

OA/NFG/CRADA

9.5

10.1

10.6

12.5

Other Reimbursable

3.5

3.6

4.2

4.0

Total

48.1

50.4

51.6

55.0

Full-time permanent staff (total)a

207

204

200

205

NOTE: Funding for the NIST Measurement and Standards Laboratories 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 is allocated 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.”

aThe number of full-time permanent staff is as of January of that fiscal year.

Laboratory Resources

Funding sources for the Physics Laboratory are shown in Table 5.1. As of January 2001, staffing for the Physics Laboratory included 205 full-time permanent positions, of which 170 were for technical professionals. There were also 51 nonpermanent or supplemental personnel, such as postdoctoral research associates and temporary or part-time workers.

The onset of construction of the NIST Advanced Measurement Laboratory is a positive sign and should significantly alleviate the facilities deficiencies that the panel has noted for a number of years. In general, the laboratory has adequate capital equipment, although specific needs in both capital equipment and facilities are noted in some of the divisional reports below.

The greatest resource of the Physics Laboratory is its staff. The panel takes great pleasure in once again noting that the assembled scientific talent constitutes a world-class team that any institution would be hard pressed to rival. It is a pleasure and an honor for the panel to interact with this staff during its assessment process.

The laboratory has been operating under a basically level budget for several years, and when mandatory cost of living increases for staff are taken into account, the budget has actually been in

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

gradual decline. This situation is reducing the laboratory’s capability to renew staff skills by replacement hiring and is of great concern to the panel since the staff is the laboratory’s most valuable asset. The laboratory must focus its programs even more tightly and articulate its vision and goals even more clearly. The panel reiterates that such articulation is key to bringing and keeping key stakeholders on board as the laboratory seeks to maintain the vitality of its programs and move into important new areas.

DIVISIONAL REVIEWS

Electron and Optical Physics Division

Technical Merit

The Electron and Optical Physics Division states that its mission is to develop measurement capabilities needed by emerging electronic and optical technologies, particularly those required for submicrometer fabrication and analysis. The division is organized into three groups: Photon Physics, Electron Physics, and Far UV Physics.

Photon Physics. The Photon Physics Group’s research in extreme ultraviolet (EUV) physics and measurement technology is high-quality, state-of-the-art work that clearly supports important national goals in the emerging technology of EUV lithography. The group is also carrying out important and highly innovative work in EUV and x-ray microscopy.

In EUV lithography, the group maintains several strong programs. It has constructed a laser-produced plasma source of pulsed EUV radiation. This source, which generates plasma by the laser irradiation of inert gas clusters produced by supersonic expansion, provides superior repeatability, and, compared with commonly used solid-state laser plasma sources, is relatively free from degradation and contamination after multiple irradiations. The group is currently using this source to characterize optical components. The group has also upgraded its EUV reflectometry facility with a larger sample chamber. This enlarged chamber is capable of holding EUV mirrors as large as 40 cm in diameter and weighing 50 kg. A large mirror from the Sandia-developed engineering test stand, the C-1 mirror, has been sent to the NIST facility for characterization. This new instrument is the only one in the world that can make reflectometry measurements on such large mirrors. The first sample EUV mirrors for calibration in this facility were to arrive shortly after the panel met. The panel looks forward to reviewing the results of these new calibration capabilities in its next report.

The group has in place several capabilities that position it to study the contamination that degrades the EUV mirrors used in lithographic processes because:

  • It can produce high-quality, sputter-deposited EUV multilayer mirrors.

  • Its Synchrotron Ultraviolet Radiation Facility, SURF III, can provide high fluences over extended times at the lithographically relevant 13-nm wavelength.

  • It also has the reflectometery capabilities to measure mirror reflectivities before and after exposure to this radiation.

The three processes that limit the lifetime of EUV mirrors are deposition of debris from the laser plasma source, EUV-induced oxidation, and EUV-induced carbonization. The group could conduct

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

long-term studies of these contamination problems and of the cleaning phenomena that have been proposed as solutions.

In the area of EUV and x-ray microscopy, the Photon Physics Group has performed x-ray nanotomography of integrated circuits using the Advanced Photon Source at Argonne National Laboratory. Using 1800-eV photons, the first three-dimensional reconstruction of an integrated circuit interconnect (aluminum/tungsten technology) was achieved, with 400-nm resolution. The group is following up on this success with an experiment on the Advanced Light Source at Lawrence Berkeley National Laboratory, which will provide even greater image resolution. The group will have full access to a beam line dedicated to tomography experiments and anticipates beginning experiments using 4000-eV photons and hollow-cone illumination by the end of 2001. Images with a resolution of 80 nm should be obtained.

An interesting possibility for another application of the x-ray nanotomography technique is the study of the three-dimensional structure of photonic devices such as integrated optical circuits. In many cases significant amounts of dopants are used to modify the index of refraction to define channel waveguides. These dopants might provide sufficient contrast to be imaged, provided that the x-ray wavelength is properly chosen at the appropriate absorption edges.

Electron Physics. The research programs pursued by the members of the Electron Physics Group are in all cases state of the art and in some cases unique.

The group has been a longtime leader in the area of magnetic microscopy, and its current projects bode well for extending that leadership into the future. The group has upgraded its capabilities in scanning electron microscopy with polarization analysis (SEMPA) by installing a new, ultrahighvacuum, field-emission scanning electron microscope in the facility. This new microscope provides a higher-intensity field-emission electron source and state-of-the-art optics compared with the units it is replacing. This upgrade has improved the resolution of magnetic images obtained from the SEMPA apparatus from 50 nm to 20 nm. The group plans to couple this new instrument with its polarized detection system. This system, based on the detection of circularly polarized light emitted by polarized electrons tunneling from a ferromagnetic sample into a GaAs tip, gives a well-defined, quantitative signal compared with other spin detection schemes. When this detection system is in place, the group hopes to achieve 10-nm resolution of its images, which would be the best of any SEMPA system in the world. This instrument has been of great interest to industrial customers such as Seagate and IBM, since the width of a bit in state-of-the-art hard disks is 50 nm and the size of a magnetic storage particle is about 10 nm. The SEMPA facility also has capabilities for in situ thin-film growth and nanoscale compositional and structural analysis. Structures such as trilayer wedges can be grown and characterized with techniques such as reflection high-energy electron diffraction.

The completion of the Nanoscale Physics Laboratory was discussed in the panel’s previous report. Its centerpiece is a cryogenic, ultrahigh-vacuum scanning tunneling microscope (STM) capable of operating at temperatures as low as 2.3 K in a fixed-orientation applied magnetic field of 10 T or a variable-orientation field as large as 1.5 T. With its two molecular beam epitaxy chambers, field-ion microscopy apparatus, and integrated design, the system is truly unique. The first results from this facility were presented to the panel this year. Initial experimental results include an STM image and measurement of the tunneling conductance for a single-atom Kondo system comprising an isolated Co atom on a Cu (111) substrate. These atomic-level images were obtained at temperatures as low as 2.3 K and in magnetic fields as high as 10 T. This new facility positions the group to be a leader in the fabrication and characterization of nanoscale magnetic materials.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

Room-temperature STM was used to study the growth and morphology of epitaxial Mn films grown on Fe (100) single-crystal whiskers, enabling elucidation of interlayer exchange coupling mechanisms. In Fe/Mn/Fe (100) trilayers an interesting spiral spin structure was found that is connected with a 90° magnetic coupling different from the 0°, 180° coupling through antiferromagnetic Cr in Fe/Cr/Fe (100) wedges.

In a fascinating extension of the work on laser-focused deposition, the concept of “atom on demand” is beginning to be explored. The idea is to capture a single atom in a trap, creating a source of individual atoms that might be used to build a precise microstructure.

An important contributor to the overall success of the group is its strong theoretical contingent. The theorists interact with the experimentalists in the group and with other researchers within and outside of NIST. The presence of theoretical expertise in the group provides an enhanced opportunity for cross-fertilization of ideas and brings a second perspective to problem solving. Recent theoretical activities include work on exchange-bias bilayers, calculation of spin-dependent interface resistance, and investigation of magnetization reversal in ultrathin films.

Far UV Physics. The Far UV Physics Group operates SURF III. This recently upgraded facility has provided its users with improved capabilities, such as an increase in beam current from 200 mA to 700 mA, a remarkable achievement given the low energy of the synchrotron ring. This capability, coupled with its available instrumentation for absolute optical and radiation measurements makes SURF III unique in the United States. The facility has a well-defined customer base that requires high-precision radiometry and optical measurements in the near and extended ultraviolet frequencies. Customers include NASA (characterization of space-based probes), Lawrence Livermore National Laboratory (as part of its activities for the EUV LLC consortium2), and industrial firms examining the use of UV radiation to cure organic compounds with less release of VOCs.

Further enhancements to the facility are under way, including the addition of a beam line for UV Fourier transform interferometry. Other areas for possible expansion include infrared microscopy and photoemission microscopy. The low energy of SURF III is uniquely suited for producing tunable near-UV photons (3 to 6 eV) that are used for obtaining work function contrast in photoemission microscopy. Both potential options are well matched to the qualities of the SURF III light source. For full implementation of infrared microscopy, an improved beam stability at higher frequencies needs to be pursued. For successful development of photoelectron microscopy, a clear tie into a specific scientific application is essential to motivate and guide the work.

The facility is well managed, and the panel noted pride and enthusiasm among the small but competent staff.

Program Relevance and Effectiveness

As feature sizes in semiconductors shrink, optical lithography moves toward shorter and shorter wavelengths of light. EUV lithography at around 13 nm is a leading candidate technology for future semiconductor manufacturing. The division holds regular technical meetings with representatives of EUV LLC. The consortium has requested NIST assistance in nine areas, including EUV source, mirror, and detector calibrations. This collaboration has involved no funding, and the division has tried to offer

2  

A consortium founded by Intel, Motorola, and Advanced Micro Devices in 1997 and now including many additional industrial firms and three DOE national laboratories.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

assistance using its limited resources and staff. Additional staff in this area would allow the division to provide a more timely response and have a greater impact.

X-ray nanotomography of integrated circuits is another area with potentially significant impact. Clearly, the ability to form three-dimensional, element-specific images of conducting pathways in integrated circuits with 100-nm resolution is of great interest to the semiconductor industry. This technique could have some importance for the field of photonics if three-dimensional dopant-specific images could be formed of optical integrated circuits.

The frontier research of the Electron Physics Group in nanoscale science and technology assures its relevance to a broad customer base spanning the industrial, governmental, and academic communities. With its wide-ranging capability for fabricating nanostructures atom by atom and for investigating their electronic and magnetic properties, the Nanoscale Physics Laboratory will interest a broad spectrum of customers, ranging from those concerned with atom manipulation in specific nanostructures to those studying the intrinsic physics of atom-solid interactions.

As noted, the anticipated extension of the SEMPA capability to 10-nm resolution is attracting interest from the magnetic data storage industry, with manufacturers already sending samples for evaluation. The NIST MEL is utilizing laser-deposited nanoscale Cr line structures on Si substrates prepared in this facility as a standard for nanoscale length measurements.

The division’s results are communicated to customers through a variety of methods. Most significant is the substantial number of high-quality papers published in refereed external scientific literature.

Division Resources

Funding sources for the Electron and Optical Physics Division are shown in Table 5.2. As of January 2001, staffing for the Electron and Optical Physics Division included 24 full-time permanent

TABLE 5.2 Sources of Funding for the Electron and Optical Physics Division (in millions of dollars), FY 1998 to FY 2001

Source of Funding

Fiscal Year 1998 (actual)

Fiscal Year 1999 (actual)

Fiscal Year 2000 (actual)

Fiscal Year 2001 (estimated)

NIST-STRS, excluding Competence

4.6

5.0

5.4

5.4

Competence

0.0

0.0

0.0

0.2

ATP

0.2

0.2

0.1

0.2

OA/NFG/CRADA

0.5

0.6

0.5

0.8

Other Reimbursable

0.1

0.1

0.1

0.1

Total

5.4

5.9

6.1

6.7

Full-time permanent staff (total)a

27

23

23

24

NOTE: Sources of funding are as described in the note accompanying Table 5.1.

aThe number of full-time permanent staff is as of January of that fiscal year.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

positions, of which 21 were for technical professionals. There were also 4 nonpermanent or supplemental personnel, such as postdoctoral research associates and temporary or part-time workers.

The division staff is of high quality, and the panel observed generally good morale among its members. However the division appears to be understaffed relative to customer needs in key areas such as EUV lithography and EUV and x-ray microscopy. In a situation of flat budgets, there is little opportunity to hire new staff. The division chief perceives the NIST overhead rate as unusually high and believes that it impacts his budget sufficiently to inhibit his ability to maintain adequate staffing for existing projects. In addition, staff are concerned that the federal salary scale does not allow them to compete on a level playing field for the best researchers and postdoctoral fellows.

Equipment funding for the Electron and Optical Physics Division appears to be adequate.

Atomic Physics Division

Technical Merit

The Atomic Physics Division states its mission as carrying out a broad range of experimental and theoretical research in atomic physics in support of emerging technologies, industrial needs, and national science programs. It is organized into five groups: Plasma Radiation, Quantum Processes, Laser Cooling and Trapping, Atomic Spectroscopy, and Quantum Metrology.

Plasma Radiation. The Plasma Radiation Group is responsible for maintaining and operating the laboratory’s electron beam ion trap (EBIT), which produces and traps ions in charge states up to 70+. About 10 EBIT facilities are in operation around the world. These facilities use ion-trapping techniques to enable studies in atomic physics and nanoscale surface science. For most facilities, no data are available on the spatial distribution and dynamical motion of ions inside the trap. The NIST group has used a charged coupled device camera and modeling to determine the thermal distribution within its EBIT and more accurately describe ion behavior within the trap. For this reason, the NIST EBIT is probably the best characterized in the world. As a consequence, the Plasma Radiation Group is in a good position to make quantitative collision measurements of highly charged atomic species. The NIST EBIT is also equipped with a variety of spectrometers that enable measurement of transition wavelengths of highly charged ionic species from the visible to the x-ray region. This capability, coupled with the spectroscopic capability afforded by the new detectors that are being installed, should make the apparatus unique. Furthermore, the panel believes that it is the only EBIT that is coupled to a microscope to allow careful in situ analysis of the effects of high-energy ions impinging on surfaces, which resolves ambiguities in such measurements due to exposure to air.

The group is fitting the GEC Inductively Coupled Plasma (GEC-ICP) plasma source apparatus with a new type of optical-fiber-based tomographic detection system. This will enable three-dimensional imaging of the plasma constituents. This is of potential importance in semiconductor manufacturing, since as the wafer diameters used in semiconductor etching increase, the ability to monitor and control plasma uniformity during the etching process becomes increasingly necessary. There are roughly 30 plasma cells of this type in the country, three of them at NIST.

The group’s ability to perform high-accuracy UV index of refraction measurements has been used to help solve a key materials issue in 157-nm optical lithography. Calcium fluoride, the candidate material for such optical systems, suffers from chromatic aberrations at the 157-nm wavelength that limit its usability. Based on index of refraction measurements made by the group, barium fluoride has been

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

identified as a color-correcting second material that could be combined with calcium fluoride to produce the required material properties at the desired wavelength. The group’s effort on these measurements is unique and noteworthy, particularly because the highly accurate measurements were obtained on outdated equipment.

Quantum Processes. The Quantum Processes Group is one of the few theoretical atomic, molecular, and optical (AMO) physics groups in the United States; as such, it is a national resource and plays a leadership role in the theoretical AMO community in the United States. Its members offer theoretical support for a variety of experiments both at NIST and across the country. They have played a leading role in the understanding of photoassociation spectroscopy and all the molecular aspects of cold atoms. A distinguishing mark of the group is its emphasis on realistic models of the processes it is studying, and for this reason it is often able to confront experimentation in meaningful ways. Over the years it has developed a number of numerical codes and successfully applied them to a wide variety of physical, chemical, and optical phenomena including atomic clocks, quantum degenerate gases, quantum dots, and single-molecule detection. The group now has a significant role in the Physics Laboratory’s new Quantum Information initiative.

Over the past year, the group produced a number of significant advances. Its work on realistic models of the optical properties of complex nanostructures could give the insight needed to impart functionality to potential devices. The group has developed methods for simulating potentially realizable quantum logic gates with neutral atoms. It has successfully explained a number of unusual collisional properties of ultracold and hot cesium atoms using state-of-the-art computational methods and made progress toward similar understanding for rubidium. It has used its expertise in trapping and simulating of nanostructures to identify exciting new types of evanescent atom traps.

Laser Cooling and Trapping. The Laser Cooling and Trapping Group is widely recognized as a world leader in the manipulation and study of cold atomic matter. In the last several years, it produced astounding results on the optical and atom-optical properties of degenerate Bose gases, including the production and propagation of solitons. It has completed a beautiful set of experiments studying the properties of the ultracold plasmas produced by photoionization of ultracold atoms, identifying in a crisp way many of the unique properties of such plasmas. It has made beautiful studies of optical Feshbach resonances in ultracold collisions. It has also begun an important, well-conceived effort in quantum computation using atomic lattices and Bose-Einstein condensates. All the efforts of this group are characterized by state-of-the-art mastery of laser manipulation of atoms and remarkable insights into and understanding of the phenomena so observed.

Atomic Spectroscopy. Two years ago, the Atomic Spectroscopy Group’s efforts in atomic spectroscopy and data compilation were on course for their demise, with moribund funding, loss of personnel, and inability to recruit new staff. At that time the management of the Physics Laboratory presented a 7-year plan to use internal funding to rejuvenate the experimental and theoretical atomic spectroscopy and data compilation core competencies. In its review last year, the panel expressed great satisfaction that the plan was being implemented and that the laboratory had made a very strong commitment to continue the world-class leadership of NIST in these areas. This year it is again satisfied to see this initiative succeeding.

The morale of the group is greatly improved. Researchers are enthusiastically pursuing their work and looking to the future with optimism. Fresh talent has been injected, with several newly hired physicists actively pursing new research projects. The acting group leader has focused the group and is

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

actively mentoring the younger members. An excellent candidate has been identified as a potential new hire who could grow into the position of permanent group leader.

This positive atmosphere is reflected in the results of the group’s work. The group’s Web site, containing compilations of atomic data that have been critically evaluated, has evolved into a tool of major importance to many international scientific and technical communities. In the 1-year period from August 1999 to July 2000, about 1 million hits to this site were recorded. The site is also very user friendly because the group was responsive to feedback from users. The conclusion to be drawn is that NIST’s compiling and documenting of atomic spectroscopic data, while not a glamorous task, is absolutely essential to a broad spectrum of users in the United States and around the world. Its applications support the scientific, technological, and economic health of the nation, and the database is clearly a fulfillment of NIST’s mission and a critical national resource provided uniquely by NIST.

The data compilation group is now rapidly moving in the direction of providing the most commonly used atomic data in convenient e-book form. This is an exciting and forward-looking initiative.

The responsibility for the compilation of fundamental constants has now been merged with that for the upkeep of atomic data. This is a positive move that makes sensible use of resources. The group recently published its first comprehensive updating of the fundamental constants in 13 years. In response to broad community demand, the group has set a goal of updating the compilation every 4 years. This will be challenging since the entire set of constants (other than the gravitational constant, G) must be treated in a fully self-consistent manner. But the pace of modern research requires such a frequent updating for the compilation to maintain its maximum usefulness. The panel applauds the ambitious objective the group has set for itself in this area.

Last year the panel noted enthusiastically the theoretical work carried out in the Atomic Physics Division to develop simple but accurate algorithms for the computation of electron-impact ionization cross-sections of molecules. Results for 70 molecules are now available on the laboratory’s Web site. This work has been successfully extended to ionization cross-sections of atoms and ions in a technically clever way. One can envision applications of such algorithms in any theoretical codes that model the conditions in plasmas, greatly simplifying computations with such codes and making them more accurate.

Quantum Metrology. The Quantum Metrology Group continues its program in x- and gamma-ray spectroscopy. In the past year the group published the proceedings of the International Workshop on High Resolution Gamma-Ray Spectroscopy and Applications in the NIST Journal of Research. The workshop focused on work carried out at the High Flux Reactor of the Institut Laue-Langevin in Grenoble, France, using the NIST ultrahigh-resolution crystal diffraction spectrometer GAMS4. The distinctive features of GAMS4 are its accuracy and its exceptionally high spectroscopic resolving power. This accuracy has been essential to NIST work on the properties of fundamental particles, the determination of fundamental constants, and gamma-ray energy standards. The exceptional resolution is exploited for the determination of nuclear excited state lifetimes between the picosecond and femtosecond levels. In the course of modeling the spectra of these excited states, significant information has emerged on the form of the interatomic potential function in the range 10 eV to 100 eV, a region not accessible by other means.

The group has established the experimental principles for higher-shell x-ray spectroscopy utilizing the EBIT, and acquired initial data. This work is responding to the quantities of data being produced by the Chandra X-ray Observatory. The higher sensitivity and resolution of this observatory is producing data that are impossible to interpret without a better understanding of the processes that occur in hot cosmic plasmas. The Quantum Metrology Group has now recorded detailed spectra from half a dozen relevant highly ionized species and has analyzed these spectra to provide quantitative tests of the models

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

used to interpret astrophysical plasmas. This work will enable the scientific community to get full value from the investment in Chandra, again demonstrating the high value of the EBIT facility.

The group’s outstanding work on the development of x-ray tools has continued. However, the departure of one contractor forced the termination of the multilayer growth program. This is unfortunate, since the program was internationally recognized as state of the art. Much progress has been made in the development of novel wavelet analysis methods for x-ray reflectivity, which could become a very practical and rapid means of materials analysis in the semiconductor industry. The group is collaborating with NIST researchers in the Materials Science and Engineering Laboratory to produce new x-ray SRMs for this industry, with the Quantum Metrology Group responsible for defining measurement procedures and training. This follows similar cooperation on the new silicon powder SRM, which resulted in samples with a lattice parameter uncertainty of <2 ppm (2σ). The new senior appointment in this group, besides giving strong support to the ongoing work, has brought in additional expertise on the application of novel x-ray methods to protein structure examination. This is highly relevant to the new field of genomics research. This was a position whose creation the panel recommended to the laboratory in earlier reports, and the panel is delighted to see it filled with an able and enthusiastic expert.

The group continued its collaboration with the MEL in a competence project in length metrology. The group has successfully developed the necessary optical interferometry and isolated chamber. All the objectives for this portion of the project have been essentially achieved, with real advances in optical interferometry realized at scales from subnanometer to 5 cm. However, staffing changes at the MEL limited the progress in integrating this system with the remaining components maintained by that laboratory. Those staffing issues now appear resolved, and the panel is hopeful that the ambitious overall project objectives will be met by the time the competence project funding ends later this year.

Program Relevance and Effectiveness

Several of the division’s programs are providing results critical to efforts to successfully implement 157-nm lithography for the manufacture of large-scale integrated circuits. The design of optics for 157-nm processes depends on resolving issues of chromatic aberrations in calcium fluoride, and the division’s index of refraction measurements are invaluable in this effort. These measurements are relevant to the design of optics for both steppers and excimer laser sources for this technology. The division’s capabilities have also enabled the high-accuracy measurement of lasing lines of molecular fluorine near 157 nm in a developmental excimer laser for 157-nm lithography. The division’s ability to explore strain-induced index changes and birefringence in optical materials is also central to the development of the next generation of vacuum ultraviolet semiconductor steppers.

The EBIT promises to be very useful in providing laboratory data for comparison with x-ray astronomical data from the NASA Chandra X-Ray Observatory. Recent efforts to characterize the spatial properties of the plasma within the EBIT, combined with excellent spectroscopic data, should lead to quantitative data on collision processes relevant to astrophysical plasmas. The division’s exploration of use of the EBIT as a source of highly charged ions for surface processing is interesting. The exploratory work is sufficiently mature that a well-defined direction for further work is needed.

While technical progress in instrumenting the GEC-ICP reference cell is impressive, it is not clear to the panel what new scientific questions this device will address. Given that this cell is one of 33 available in the country, the laboratory should consider whether this program is still justified.

The atomic spectroscopy program continues to make very important contributions both to basic

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

research and to commercial applications such as those in the lighting industry. The impact of the Atomic Spectra Database is well illustrated by the number of hits on its Web site.3 As mentioned above, in the 1-year period from August 1999 to July 2000, about 1 million hits to this site were recorded. Over 100,000 of these originated from the U.S. commercial sector, with the semiconductor and computer industries accounting for the heaviest usage. The telecommunications, defense, and aerospace sectors and the chemical and lighting industries also made extensive use of the Web site. The impact of these programs may be limited by funding, however. The current phase of a program on light-source intensity parameterization sponsored by the Electric Power Research Institute is drawing to a close. Given its commercial value to the lighting industry, the panel encourages the division to pursue other industrial funding for this project. The division’s capabilities in Fourier transform spectroscopy are being used to obtain highly accurate spectra of rare earth elements, which have value both to commercial lighting and to astrophysics.

Spectroscopic measurements on singly ionized mercury, which were originally carried out in support of space observations of stellar spectra with the Hubble Space Telescope, are now finding applications in the development of a highly accurate atomic clock based on the trapping of Hg+ ions in a magnetic trap. Spectroscopic data for the lower ionization states of zirconium, originally acquired for stellar astrophysics, are also yielding accurate information about the medium charge states needed in the diagnostics of edge regions of tokamak plasmas.

The Laser Cooling and Trapping Group is by any measure a world leader that is both relevant and effective in its pursuit of this important area of fundamental science. These advances are of course directly applicable to atomic clock technologies. The group’s expertise in optical lattices and Bose-Einstein condensation also places it in a unique position to explore approaches to quantum computation using neutral atoms. The Physics Laboratory initiative in this area, which combines the technical strengths of the Laser Trapping and Cooling Group, the Quantum Processes Group, the Quantum Physics Division, and the Time and Frequency Division, has the ambitious aim of making a 10-qubit register within the next 5 years. This is a high-risk project and no one can know whether the goals set are achievable in this time frame. However, should quantum computing prove possible, its importance to U.S. industry and to national security would be enormous. NIST has assembled one of the most outstanding teams possible in this area, and the panel strongly supports the initiative.

The Quantum Metrology Group has engaged with the semiconductor industry in defining x-ray tools and standards needed for manufacturing needs. It has also built and tested satisfactorily a new x-ray/gamma-ray spectroscope to operate under the arduous conditions that will exist in the National Ignition Facility, currently under construction at the Lawrence Livermore National Laboratory.

Division Resources

Funding sources for the Atomic Physics Division are shown in Table 5.3. As of January 2001, staffing for the Atomic Physics Division included 35 full-time permanent positions, of which 27 were for technical professionals. There were also 13 nonpermanent or supplemental personnel, such as postdoctoral research associates and temporary or part-time workers.

It is clear that a talented permanent staff is the division’s most valuable resource. Flat budgets, combined with mandatory cost-of-living increases for staff salaries, have forced the division to rely

3  

The NIST Atomic Spectra Database (NIST Standard Reference Database #78) is available online at <http://physics.nist.gov/cgi-bin/AtData/main_asd>.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

TABLE 5.3 Sources of Funding for the Atomic Physics Division (in millions of dollars), FY 1998 to FY 2001

Source of Funding

Fiscal Year 1998 (actual)

Fiscal Year 1999 (actual)

Fiscal Year 2000 (actual)

Fiscal Year 2001 (estimated)

NIST-STRS, excluding Competence

5.7

6.7

6.8

6.5

Competence

0.7

0.3

0.3

0.7

ATP

0.2

0.2

0.3

0.3

OA/NFG/CRADA

1.2

0.8

1.1

1.7

Other Reimbursable

0.2

0.2

0.1

0.1

Total

8.0

8.2

8.6

9.3

Full-time permanent staff (total)a

30

32

31

35

NOTE: Sources of funding are as described in the note accompanying Table 5.1.

aThe number of full-time permanent staff is as of January of that fiscal year.

more and more heavily on guest researchers and temporary employees to accomplish its goals. This allows a regular influx of new ideas and is an automatic safeguard against the fossilization of a large permanent staff. However, overreliance on such nonpermanent personnel means that core competencies can be vulnerable (as in the case of the multilayer growth program) and the corporate memory may not be maintained. The morale of the permanent staff remains high. Researchers are clearly excited about the science they can carry out at NIST. However, they expressed concerns about spending increasing amounts of their time raising program funds from outside sources.

Some programs have specific resource issues that the panel wishes to call attention to. The VUV index of refraction program is being carried out on a shoestring, and its success is a tribute to the ingenuity of the researchers involved. Given the importance of this work to the development of 157-nm lithography, NIST should be able to obtain outside funding for it. If the laboratory intends to pursue this direction, it must consider now how to fund the instrumentation needed to support the next step in optical lithography. The EBIT program is another program that is clearly valuable but undermanned relative to the results that could be obtained from it. The panel’s primary concern, however, is the long-term viability of the atomic spectroscopy and data compilation program. The group is clearly being revitalized by the 7 years of internal funding that the Physics Laboratory is committing to it, but to keep the program viable in the long term, the laboratory is calling for it to have external support. Unfortunately, NASA support for this program has disappeared, despite the value of its results to NASA flight programs. Funding from commercial sources is also scant despite their use of data and facilities. The laboratory must make aggressive attempts now to secure funding from sources or the program will again be in crisis in several years time.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

Optical Technology Division

Technical Merit and Appropriateness of Work

The Optical Technology Division states that its mission is to advance knowledge and expertise in targeted areas of optical technology so as to provide the highest-quality services, technical leadership, and measurement infrastructure to promote the U.S. economy and support the public welfare and the national defense. The division is organized into five groups: Optical Temperature and Source, Optical Properties and Infrared Technology, Optical Sensor, Laser Applications, and Spectroscopic Applications. This organization is primarily administrative in nature, as productive interaction among individuals, groups, and other NIST laboratories is an avowed goal of the division management, so the assessment is not organized by group.

The activities of the division are diverse, encompassing basic research on light-matter interactions, applications of light scattering as a metrological tool for the characterization of solid surfaces, and repeated and ongoing interactions with scientists and engineers in establishing methodologies and standards for industries relying on optical technologies. The Optical Technology Division also has the institutional responsibility for maintaining two base SI (International System) units: the unit of temperature above 1234.96 K and the unit of luminous intensity, the candela. The division also maintains the national scales for other optical radiation measurements and ensures their relationship to the SI units. These measurement responsibilities include derived photometric and radiometric units, the radiation temperature scale, spectral source and detector scales, and optical properties of materials such as reflectance and transmittance.

The division has targeted research programs to develop optical and spectroscopic tools to gather information on processes in the frequency ranges required to support evolving technologies in the semiconductor, biotechnology, health science, and other industries. The research also aims to solve fundamental problems in the physics, chemistry, and engineering science that underlie these applications.

One component of the research emphasizes unique gas-phase spectroscopic capabilities and analyses. Here, the research seeks to demonstrate new spectroscopic techniques for the measurement of molecular spectra, to provide and analyze such spectroscopic data to determine the fundamental properties of molecular entities of relevance to the scientific and engineering infrastructure, and to collaborate with external researchers in the development and application of spectroscopic techniques. This research program has focused on several themes, chosen for their high external impact or the uniqueness of NIST capabilities in that area. At present one important theme is the use of spectroscopic data and analysis to infer the conformational structure and dynamics of biomolecules. A second scientific theme is techniques to investigate the properties of chiral molecules through an ultrasensitive polarization-resolved cavity ring spectroscopy technique. Applications of gas-phase spectroscopy to atmospheric chemistry and the identification of chemical warfare agents are also under way.

The Optical Technology Division is involved in the development and application of new methods for terahertz spectroscopy. This effort is part of a broader laboratory-wide initiative in terahertz competency. One approach involves continuous wave (cw) terahertz techniques, including photomixing with tunable visible lasers. Another relies on high-performance electron devices. A complementary set of approaches relies on ultrafast pulsed lasers. Ultrafast electromagnetic transients are produced from laser pulses by photoconductivity or optical rectification. The electromagnetic transients are characterized directly in the time domain by sampling techniques using a copy of the ultrafast laser pulse that produced them. Such approaches permit measurements over a broad frequency range and, importantly, allow for characterization of material excitations with short lifetimes. These investigations place NIST

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

at the forefront of a very important and active technical area and build on the division’s traditional strength in infrared spectroscopy, including the novel multichannel detection schemes. Important applications of terahertz spectroscopy capabilities include both gas- and condensed-phase systems.

The Optical Technology Division is carrying out fundamental studies aimed at developing spectroscopic techniques that permit probing material of reduced spatial dimension such as a surface, thin-film, or bulk sample with high spatial resolution. The division is addressing key scientific issues in various disciplines and is very well aligned with other major initiatives in NIST and with areas of external need, such as bio- and nanotechnology, photonics, and electronics. One component of the research program emphasizes precision measurements of surfaces and interfaces. NIST-pioneered broadband, infraredvisible sum-frequency generation provides the power of an interface-specific optical technique with the previously lacking capability for rapid data collection of vibrational spectra. The division team has demonstrated the power of this approach in polymer interfaces and other material systems. While this specific direction is rather new, the precise analysis of optical scattering from surfaces is a fully developed program in the division and unique instrumentation is in place. The program has elucidated fundamental issues and been tightly coupled to materials characterization in the semiconductor industry. The latter feature of the program is exemplified by the publicly available software for scattering analysis on the NIST Web site. Another important research component concerns near-field microscopy and single-molecule detection schemes. This area also has high scientific impact and significant potential for advancing technology. Near-field techniques are capable of probing single molecules and, hence, their local environment and its variability. The division group has also been in the forefront of demonstrating the possibilities of probing biological matter with a custom-designed NSOM.

The division’s Color and Appearance project has been under way for approximately 3.5 years. The division has designed a state-of-the-art colorimeter and compared gloss standards with those of the National Research Council (Canada) and reflectance standards with those of the Physikalisch-Technische Bundesanstalt (Germany). Gloss and haze services are under development. The division’s gloss measurements meet the ASTM D253 and ISO 2813 standards. Evaluation of haze is closely tied to that of gloss, and the division is nearing completion of upgrades that will permit accurate haze evaluation. Work to assemble a reference instrument for measuring the 45°/0° reflected color of a material continues. The Color and Appearance project is a collaborative effort by the division, the Building and Fire Research Laboratory, the Manufacturing Engineering Laboratory, and the Information Technology Laboratory.

Research to develop radiation pyrometry based on absolute detectors will lead to reduced uncertainty in temperature measurement and improved maintenance of the temperature scales. This project bootstraps the metrology of radiation temperature measurement to a higher level of performance. It is a real advance in metrology for radiation temperature, which the panel strongly encourages.

The division’s Facility for Automatic Spectroradiametric Calibrations (FASCAL) provides the basis for spectral irradiance and radiance measurements for U.S. industry, the scientific community, and the military. The upgrade to this facility, FASCAL 2, is nearly complete. FASCAL 2 will improve the quality of calibration and the throughput. Both improvements are of significant benefit to users and are a direct response to long-expressed customer needs. FASCAL 2 will define best-in-the-world for the calibration of spectral irradiance sources. The FASCAL 2 system was designed to enable the transfer of the NIST spectral irradiance detector scale to sources used by NIST customers. In the past year, this chain of realization was actually implemented with the current FASCAL. Very significant reductions in uncertainty are now realized on all calibrations, but particularly in the near infrared. The planned comparison of radiance and irradiance scales to establish the basic equivalence of their methods of realization and to estimate the importance of any experimental bias will further establish the certainty of

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

the NIST realizations. The panel commends the division for having committed personnel, space, instrumentation funds, and other resources to the FASCAL upgrade project.

High-accuracy aperture measurements are being extended to square apertures. Only NIST will have this capability for the foreseeable future. Its importance to all realizations of the optical radiation scale requires that it be treated as a core competency. The requirement for accurately determined apertures becomes more pervasive as the division transfers the maintenance of optical radiation scales to detectors. NIST leadership in the international intercomparison of aperture measurement will improve international agreement on optical radiation scales.

Measurement of retroreflectance, important for the nighttime visibility of highway signage and markers, has been pursued by the division. The division has sought funding from external sources without success. This is unfortunate because of this type of measurement is so important and NIST has a unique ability to improve the metrology of retroreflection. The panel recommends that NIST consider directly funding this activity.

Program Relevance and Effectiveness

The division’s mission statement concisely expresses the need to focus on high-potential and highimpact activities at a level sufficient to maintain and enhance the global position of the United States in science and technology. The mission statement faithfully follows the two themes of the Physics Laboratory’s mission: physics applied to support emerging technologies and physics applied to developing advanced measurement standards. The mission encompasses needs that are changing rapidly, driven by the evolution of new technologies and by the need for improved metrology for existing technologies. This is the impetus for the division’s efforts in basic, long-term theoretical and experimental research.

The division benefits from the inclusive, dynamic strategic planning approach that it initially implemented in 1997. This approach formalizes and documents the division’s values for the direction and choice of its programs. Group and individual plans developed in the framework of the division strategic plan give the division staff, collectively and individually, a clear understanding of the relevance of their contributions to the division mission, the laboratory mission, and ultimately to the mission and vision of NIST. All members of the division understand this vision and communicate it in their technical interactions with colleagues, customers, and collaborators to raise awareness of it and get feedback on it.

The division maintains a liaison with the Council for Optical Radiation Measurements (CORM), which evaluates national needs in optical metrology and provides feedback on the services and standards supplied by the division. The division has also maintained a dialogue with the UV Measurements Focus Group of the industrial association RadTech International North America. The division participates in the focus group’s meetings and advises on its activities. The leadership of focus group is now also involved in CORM.

Some examples of program relevance and effectiveness follow.

The division’s project on sources of uncertainty in UV radiation measurements is pertinent to the concerns of the UV curing and processing industry. The work pointed out that filters and diffusers can have a significant influence on the reliability of UV radiation measurements. UV curing is a fastgrowing, environment-friendly process for curing inks and coating materials. The industry would benefit from more explicit traceability protocols for both industrial UV measurements and radiometer systems.

The Rapid Thermal Processing (RTP) project is indicative of the division’s responsiveness to critical measurement needs in rapidly developing industries. Driven by industrial demand, the project

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

TABLE 5.4 Sources of Funding for the Optical Technology Division (in millions of dollars), FY 1998 to FY 2001

Source of Funding

Fiscal Year 1998 (actual)

Fiscal Year 1999 (actual)

Fiscal Year 2000 (actual)

Fiscal Year 2001 (estimated)

NIST-STRS, excluding Competence

5.3

5.5

5.4

6.0

Competence

0.6

1.0

0.9

0.6

ATP

1.0

1.0

1.0

1.2

Measurement Services (SRM production)

0.1

0.1

0.0

0.0

OA/NFG/CRADA

3.7

3.8

4.2

4.2

Other Reimbursable

0.5

0.7

0.6

0.5

Total

11.2

12.1

12.1

12.5

Full-time permanent staff (total)a

46

44

46

42

NOTE: Sources of funding are as described in the note accompanying Table 5.1.

aThe number of full-time permanent staff is as of January of that fiscal year.

achieved its goal of measuring the temperature of production silicon wafers to within ±2 °C using a noncontact process control technique. This required the development of improved thermocouples for the evaluation and verification of the radiation thermometry measurement method. The feasibility of this method was demonstrated in the past year. The division hosted the RTP 2000 Conference to disseminate this measurement technology to the semiconductor industry.

A project under way on the noncontact measurement of chips from machine tool operations indicates that the conventional assessment of machine tool operation and the responses to achieve optimization may not in fact lead to the true optimal performance. This has practical application in the optimization of machining rates and the understanding of tool life parameters. This project is producing practical data of use to U.S. industry and of significant economic value.

SRM production is an important service offered by the division. SRMs produced include standard lamps and specular and diffuse reflectance artifacts. The division also has the capability to make gloss measurements in accordance with the ASTM D253 and ISO 2813 standards. The division hopes to shortly add reflective colorimetry and haze measurements to its list of services.

International key intercomparisons are critical to gathering the information needed to advise U.S. industry on metrology issues worldwide, to providing technical guidance on international memoranda of understanding affecting the U.S. economy, and to advancing the skills of the division. The division is involved in six international key intercomparisons: spectral irradiance, spectral responsivity, luminous responsivity, luminous flux, spectral diffuse reflectance, and spectral transmittance. The division is participating in a secondary comparison with selected laboratories on the measurement of aperture areas and is the pilot laboratory for this intercomparison as well as the reflectance and segments of the spectral responsivity intercomparisons.

The effectiveness and relevance of the division’s projects are reflected in the record of publications and presentations. Given the relatively small size of the effort, the results are excellent and their

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

scientific impact is great, reflecting both the quality of the researchers and their aggressive pursuit of new scientific directions, while phasing out well-established directions that have lost their scientific and technological relevance. Such steps are difficult to take and were noted with approval by the panel. A further measure of the effectiveness and relevance of the projects may be the level of support for ongoing projects from other government agencies, industry, and the ATP program. The Optical Technology Division in general and the fundamental spectroscopy areas in particular were able to garner very high levels of such support. In this context, panel members noted that the anticipated reduction in the ATP program may have a significant adverse effect on the budgets of excellent ongoing programs.

Division Resources

Funding sources for the Optical Technology Division are shown in Table 5.4. As of January 2001, staffing for the Optical Technology Division included 42 full-time permanent positions, of which 38 were for technical professionals. There were also 15 nonpermanent or supplemental personnel, such as postdoctoral research associates and temporary or part-time workers.

The division has done an admirable job of maintaining and upgrading its facilities in a time of flat budgets. It would benefit from having its own industrial UV curing equipment for further studies in this area.

Ionizing Radiation Division

Technical Merit

The Ionizing Radiation Division states its mission as providing national leadership in promoting accurate, meaningful, and compatible measurements of ionizing radiations (x rays, gamma rays, electrons, neutrons, energetic charged particles, and radioactivity). The division is organized into three groups: Radioactivity, Neutron Interactions and Dosimetry, and Radiation Interactions and Dosimetry.

Radioactivity. The Radioactivity Group is involved in four areas of scientific and technical activities: (1) standards and methods, (2) metrology in nuclear medicine, (3) metrology and monitoring related to the environment, and (4) quality assurance and traceability programs. The group is largely responsible for establishing and maintaining the primary standards for radioactive counting provided by NIST as a service to the technical and scientific community. It focuses on preparing radioactive standards (SRMs), developing calibration methods, and providing NIST traceability to customers in fields ranging from nuclear medicine and radiopharmaceuticals to environmental monitoring and nuclear power. As a result, it is very customer-oriented.

In the area of standards and methods, the Radioactivity Group disseminates the national standards of radioactivity mainly through the SRM program and through the production and calibration of custom radioactive sources for customers. Other activities include characterization of re-entrant ionization chambers (dose calibrators) as secondary standards for nuclear medicine as well as the evaluation of (and, in some cases, remeasurement of) nuclear decay properties. An example of the latter is a comprehensive review and critical evaluation of the half-life of tritium that was recently completed and published in the Journal of the National Institute of Standards and Technology.

Activities associated with metrology in nuclear medicine include providing measurement and calibration support for the development of standards as well as new and existing radioimmunotherapy agents and devices. Examples include developing methods for standardizing nuclides such as 166Ho and

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

the radiochemical generator system 188W/188Re. Work is ongoing to develop methods for 213Bi and 211At, nuclides that show promise as alpha-emitting radiotheraputic agents. Quantitative destructive assay techniques for pure beta emitters such as 32P, used in coronary stents and as intravascular brachytherapy sources in balloon angioplasty, are also under development. Other notable efforts in this category include bringing online a small hot cell capability to allow the safe preparation of high-level standards requested by the radiopharmaceutical industry and the meticulous determination of factors such as changes in the composition of cocktail solutions used for liquid scintillation that affect the accuracy of assays by this technique.

Metrology efforts associated with personnel and environmental monitoring require the ability to measure radionuclides at very low levels. As a result, much of the work in this area involves careful sample handling and preparation under highly controlled conditions in a clean room facility. To provide closely matched standards to meet user’s needs, the Radioactivity Group engages in developing and characterizing natural matrices such as soils, sediments, biota, and biological systems contaminated with naturally occurring radionuclides from the decay of uranium or thorium or by actinides and fission products from man-made activities. The Radioactivity Group is also developing standard extraction protocols for partitioning radionuclides in sediments and soils to support applications in the geosciences. Additionally, methods for certifying national phantom standards for personnel monitoring and radiobioassay are being pursued.

The Radioactivity Group also supports a number of quality assurance programs for federal, military, and private organizations. This is accomplished by providing standards, establishing and validating traceability programs, performing instrument calibrations, and participating in intercomparison programs. Currently, the customers include the FDA, the Army, the Air Force, DOE and its associated national laboratories, the Nuclear Regulatory Commission, and the nuclear medicine and power industries through the Nuclear Energy Institute.

To enhance its standards, calibration, and traceability efforts, the Radioactivity Group engages in basic and applied research to develop and improve its measurement capabilities. It is imperative that the Radioactivity Group be at the forefront of the radiochemical measurement sciences so it can continue to establish and maintain the nation’s primary standards for radioactive counting.

In this regard, the Radioactivity Group is investigating the use of resonance ionization mass spectrometry (RIMS) using glow discharge atomization and continuous wave laser excitation to measure long-lived, low-energy beta- and x-ray-emitting radionuclides that are not easily measured using conventional radiometric techniques. Because this technique has the potential for both high selectivity and high efficiency, RIMS could significantly reduce the time required for determining absolute activity by completely bypassing lengthy radiochemical separation procedures. Further, RIMS offers two advantages: several isotopes are measured simultaneously and it is independent of the nuclear decay properties. Consequently, having a viable and robust RIMS capability could also reduce costs. Currently, RIMS is being evaluated for the determination of low levels of 135Cs and/or 137Cs in the presence of stable 133Cs. To date, detection limits of 1 to 2×108 atoms have been demonstrated, and isotopic ratios were found to be in excellent agreement with those measured by the more conventional thermal ionization mass spectrometry (TIMS) method. The results of this work were recently published in the Review of Scientific Instruments.4 Plans for the future includes evaluating RIMS for the detection and measurement of Pu isotopes.

The Radioactivity Group is also working to upgrade and improve its instrumentation in other areas:

4  

Pibida, L., J.M.R.Hutchinson, J.Wen, and L.Karam, “The National Institute of Standards and Technology (NIST) GlowDischarge Resonance Ionization Mass Spectroscopy System,” Review of Scientific Instruments 71(2) (2000).

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

TIMS, large-source radiation imaging using a storage photostimulable phosphor (SSP) imaging plate detection system, gamma-ray spectrometer systems, and calorimetry.

The Radioactivity Group continues to work diligently to automate and bring on line the used, double-focusing TIMS unit. A modest investment in new turbo pumps, power supplies, and electronics offers the promise of an instrument with lower detection limits (~106 atoms), better accuracy and precision, and improved abundance ratio measurement capabilities. These TIMS efforts will take several years.

The SSP system continues to be evaluated as a means for determining and quantifying the distribution of radionuclides over large area surfaces. To date, its usefulness for mapping the location of ultralow levels of radioactivity has been demonstrated but its ability to reliably and accurately quantify activity levels has not yet been proven. Other applications of this technique are being investigated, including measuring radionuclide uptake in teeth as a dosimeter for long-term personnel radiation exposure and as a monitor of the efficiency of bacterial cell labeling with radioisotopes. To keep up with the growing demand for gamma-ray analysis, the data acquisition systems are being converted from UNIX- to Windows-based PCs that are networked. Additionally, commercially available software is being evaluated to determine if the old, no longer well supported UNIX-based custom software can be replaced without any adverse impact.

The Radioactivity Group is attempting to reestablish NIST capabilities as a world leader in radiometric calorimetry. This effort had been hampered to some extent by poor vendor performance. The radiometric calorimeter is a dual-compensated cryogenic calorimeter designed to operate at 8 K and measure the absolute activity of nuclides that decay by pure beta emission and electron capture. There are three stages, each of which is maintained at a constant temperature using a feedback loop that balances power input (via radioactive decay or a current passing through a resistive element) against heat loss and cooling (supplied by a mechanical refrigeration system using a closed-cycle He compressor). As delivered, the calorimeter has never exhibited sufficient sensitivity or baseline stability to allow measurements at the required microwatt power range. Although efforts are ongoing to resolve these problems, a considerable amount of sustained effort and, potentially, a number of design modifications will be needed to complete this effort. At the present time, the performance is at least an order of magnitude away from the design specifications.

As a service-oriented organization, it is essential that the group be abreast of the most suitable measurement techniques for determining isotope radioactivity. Through several years of concentrated effort, the division is ahead of the measurement community with its RIMS capability, but behind the state of the art in calorimetry and with its TIMS equipment. It may take several years for the group to become world-class in these measurement areas.

Neutron Interactions and Dosimetry. The Neutron Interactions and Dosimetry Group benefits greatly from having a world-class facility, the ultracold neutron source at the NIST Center for Neutron Research, to use in its research programs and industry support projects. The group’s activities center on (1) fundamental neutron physics, (2) standard neutron fields and applications, and (3) neutron cross-section standards. The Neutron Interactions and Dosimetry Group provides industrial support for instrument calibration, electric power generation, radiation protection, national defense, radiation therapy, neutron imaging, and magnetic resonance imaging.

The group’s fundamental physics programs involve extensive collaboration with the academic community and DOE national laboratories. Two significant experiments involving weak neutron interactions and neutron lifetime are making substantial progress. The Harvard-led collaboration to measure the beta-decay lifetime of the neutron via ultracold neutron magnetic trapping has made progress with

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

the development of an apparatus with a trapping volume four times greater than that of the previous apparatus. Further improvements in the signal-to-noise ratio are planned using a new 9-Å monochromator. This could lead to a 100-fold reduction in signal-to-noise ratio. Previous work in this area was reported in Nature.5 A separate, NIST-led neutron lifetime experiment utilizes a Penning trap for decay protons. The success of this experiment may rest on a complete understanding and analysis of the complex decay data and the neutron flux. While considerable data were acquired during 2000, their analysis remains to be completed.

The program on developing polarized 3He neutron spin filters continues to sustain NIST’s leadership in this area. Using spectrally narrow diode lasers, a neutron-compatible spin exchange cell was developed that can function at low pressure (1 bar) in contrast to the heretofore higher pressure cells (3.5 bar). This has extended relaxation times to about 400 h, which may be a world record. Such low-pressure cells would allow for quite stable polarization.

The Neutron Interferometry and Optics Facility (NIOF) continues to generate significant industrial interest. Prior work on the characterization of fuel cell membranes has spurred interest in the DOE Office of Transportation Technologies Fuel Cell Program. This could lead to sustained support for the use of neutron tomography in the characterization and development of fuel cell technologies. NIOF is also starting to study the migration of Li ions in batteries. The goal is to resolve long-standing discrepancies between theory and experimental results for these systems.

Phase contrast radiographs of very small objects were developed at the NIOF and reported in Nature.6 Phase-contrast radiography is novel in providing a means of extracting phase information in an image without the use of an interferometer. This technique will be applied to phase-contrast tomography.

The Neutron Interactions and Dosimetry Group’s activities in the area of neutron dosimetry continue to provide much-needed calibrations for industry and government. A significant development was an accelerated test for neutron-induced soft failures in static random access memory (SRAM) and dynamic random access memory (DRAM) computer chips. This work showed that soft neutrons from cosmic rays can induce failures in certain borosilicate glasses used in chip manufacture, which was of major importance to a leading U.S. chip manufacturer.

In the past the group played a leading role in establishing international neutron cross-section standards, but the retirement of a key individual means this effort will now be largely curtailed. However, a recent hire in computational physics has greatly strengthened the group’s computational abilities related to transport phenomena. In fact, recent theoretical work on Compton scattering may lead to new dosimetry capabilities at a microscopic level.

Radiation Interactions and Dosimetry. The Radiation Interactions and Dosimetry Group is also involved in four scientific and technical activities: (1) theoretical dosimetry, (2) industrial dosimetry, (3) medical dosimetry, and (4) protection and accident dosimetry. The group provides NIST-traceable dosimetry to the medical and industrial communities and engages in the development of innovative dosimetry methods and techniques. In support of these uses, the group works on models and codes that assist in the interpretation of dose penetration.

The group’s capabilities in theoretical dosimetry were greatly strengthened by the hiring of a

5  

Huffman, P.R., et al., “Magnetic Trapping of Neutrons,” Nature 403:62–64 (2000).

6  

Allman, B.E., et al., “Quantitative Phase Radiography with Neutrons,” Nature 408:158–159 (2000).

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

research physicist to focus on this area. Substantial theoretical advances have been made in electron scattering cross-section evaluations and in understanding Compton scattering. Such efforts are fundamental to the understanding of the detailed detector response. An appropriate extension of current work on particle interactions would begin to address such interactions with DNA itself. This may be a long-term endeavor that ultimately underlies all bioresponses. Codes and theoretical calculations have been used to aid in the understanding of dose distributions from brachytherapy sources. Fundamental theoretical work is addressing concerns in both the industrial and medical communities.

The group has disseminated notice of the e-calibration service that it is developing to large industrial users of electron beam and gamma processing. NIST will be able to remotely read dosimeters and to evaluate the response of a customer’s instrument via the Internet. This computer-controlled system can then issue temporary certificates of calibration. It relies on the use of electron paramagnetic resonance (EPR) measurements from alanine-based dosimeters. In an extension of this work, the division has developed thin-film, alanine-coated strips and complementary EPR instrumentation. Two major users of low-voltage electron beam processing are now engaged in an evaluation of these alanine-coated, thin-film dosimeters. Acquiring an EPR instrument capable of handling these thin films was crucial to this project. While the division has done considerable work to restore a 1930s accelerator to use in this program, industrial credibility will suffer for want of a state-of-the-art high-current electron beam. Dose rate effects that are significant in some industrial applications cannot be appraised using this very antiquated equipment.

Both industrial and medical users rely on the Radiation Interactions and Dosimetry Group for calibrations to a national reference 60Co beam. It is crucial that this beam be cross-calibrated with an older, weaker 60Co source that had been used as a reference. All industrial and radiotherapy calibrations (there are more than 5000 installations nationally) are linked to this 60Co reference beam. It is therefore imperative that the source calibration be transferred from the old to the new source in a timely and comprehensive manner. The group should consider this a high priority and complete work on it during this calendar year.

To keep up with the needs of the medical community, NIST needs to move quickly to water-based dosimetry from its current air kerma system. This should first be carried out with the new 60Co source using water calorimetry. The next step should be to establish the water-based calibration on a modern high x-ray beam. In this regard, the existing Medical/Industrial Radiation Facility accelerator falls short of providing the quality and similarity to conventional radiotherapy electron linac needed for this calibration. A state-of-the-art 6- to 8-MeV linac is needed if NIST is to play a leadership role in this area.

With respect to low-energy photon calibrations, some concern emerged over the divergence of air kerma measurements from calibrations performed using the wide-angle free-air chambers and the well counters. While these discrepancies seem to have been resolved, it would benefit the medical community that relies upon these source calibrations to have a comprehensive report on them. A workshop in this area for involving brachytherapy seed manufacturers and the Accredited Dosimetry Calibration Laboratories might also be considered.

The Radiation Interactions and Dosimetry Group is engaged in commendable programs involving mammography proficiency testing, improved international dose traceability for mammography testing, and comparisons of mammography quality. These involve collaborations with international organizations, such as the International Atomic Energy Agency (IAEA) and the World Heath Organization, and with national laboratories in the United Kingdom and Germany.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×
Program Relevance and Effectiveness

The division maintains a significant presence in national standards organizations, such as the American Society for Testing and Materials, the American National Standards Institute, and the Institute of Electrical and Electronics Engineers. It is also active in the international standards community through bodies such as the International Commission on Radiation Units and Measurements, the International Electrotechnical Commission, and the International Committee for Radionuclide Metrology. Division personnel are members of key professional associations, such as the American Association of Physicists in Medicine and the Health Physics Society, and of national bodies such as the National Council on Radiation Protection and Measurements and the Council on Ionizing Radiation Measurements and Standards (CIRMS). The division has been attentive to national needs as spelled out by CIRMS, an independent, nonprofit coordinating council that draws its constituents from industry, academia, and government. It is through these organizations and its direct contact with the scientific and industrial communities that the division demonstrates leadership in establishing appropriate standards and in identifying critical measurement issues in its fields of expertise.

The division’s SRM program provides industry, government agencies, and the scientific community with well-characterized materials certified for radiochemical and/or isotopic composition. These SRMs are used to calibrate measuring instruments, to evaluate methods and systems, and to produce scientific data that can be readily referenced to a common base that is traceable to national standards. To ensure that the division is in touch with the needs of the communities it serves, members participate in a number of user organizations, such as the Nuclear Energy Institute (NEI), and in measurement assurance programs for radioactivity measurement traceability. Through NEI, the division provides traceability services in two areas: (1) for suppliers of radiochemical and radiopharmaceuticals, dose calibrators, and nuclear pharmacy services and (2) to the nuclear power industry for utilities, source suppliers, and services laboratories. For the radiopharmaceutical industry, which comprises about 10 participating companies or organizations, the division provides 10 different SRMs on a one-per-month schedule. With the exception of 99mTc, the SRMs are provided each month in two activity levels, high (tens to hundreds of millicuries) and low (tens to hundreds of microcuries). During the other 2 months of the year, NEI member organizations interact with the division to address traceability issues related to new diagnostic or therapeutic techniques under development involving radionuclides not yet available as SRMs or to resolve measurement problems they might be experiencing with existing products.

A similar but low-activity-level SRM program is also administered to support environmental and bioassay analyses. Interactions with organizations such as CIRMS, the National Voluntary Laboratory Accreditation Program, and the DOE’s National Analytical Management Program provide the division with guidance on the radioisotopes that require measurements. Division staff often take leadership roles with such organizations and sponsor workshops to address methods and procedures for detecting, measuring, and analyzing radioactive materials found in a wide variety of environmental and biological matrices. This division also completed the fourth year of the NIST Radiochemistry Intercomparison Program to provide measurement traceability for low-level environmental measurements in accordance with the acceptance criteria as defined in ANSI-N42.22, “Traceability of Radioactive Sources to NIST and Associated Instruments Quality Control.”

The division also enjoys excellent industrial and academic collaboration predicated on having a world-class facility, the ultracold neutron (UCN) source, and on the outstanding nondestructive analytical capabilities of the NIOF. These tools have enabled the division to engage in projects on the cutting edge of small-scale power generation: analysis of fuel cell membranes and investigations into ion transport in Li batteries. The division also has excellent rapport with the nuclear power industry.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

The Neutron Interactions and Dosimetry Group does an outstanding job of balancing industrial concerns with fundamental research. However, the fundamental research projects are complex, and a more complete perspective, as provided by an overview of these projects, milestones passed, and milestones expected, would be helpful.

More frequent updates are needed to keep the medical and industrial communities abreast of developments and issues involving calibrations and dosimetry determinations. For example, concerns about variances in air kerma calibrations could be put to rest by more frequent updates on results for the user community. Quarterly updating of relevant information, perhaps on the NIST Web site, would be useful.

The panel commends the division for its response to the suggestion that it engage in issues involving nuclear waste and waste disposal. In April 2000, in collaboration with CIRMS, the division hosted the workshop “Radiation Measurements in Support of Nuclear Material and International Security.” How the outcome of this workshop fits into the division’s agenda remains to be determined. In 2000, the division hosted seven such workshops in conjunction with CIRMS covering a broad spectrum of division and CIRMS interests.

Division Resources

Funding sources for the Ionizing Radiation Division are shown in Table 5.5. As of January 2001, staffing for the Ionizing Radiation Division included 38 full-time permanent positions, of which 34 were for technical professionals. There were also 3 nonpermanent or supplemental personnel, such as postdoctoral research associates and temporary or part-time workers.

Division staff have demonstrated a notable esprit de corps. This may be attributable to improvements in facilities—for example, better lighting and fresh paint—to an invigorated scientific mission, and to solid divisional leadership. The division had 45 refereed articles published in a variety of journals in the past year, a figure that speaks to the quality of the staff.

TABLE 5.5 Sources of Funding for the Ionizing Radiation Division (in millions of dollars), FY 1998 to FY 2001

Source of Funding

Fiscal Year 1998 (actual)

Fiscal Year 1999 (actual)

Fiscal Year 2000 (actual)

Fiscal Year 2001 (estimated)

NIST-STRS, excluding Competence

4.3

4.5

4.3

4.3

ATP

0.2

0.2

0.2

0.1

Measurement Services (SRM production)

0.1

0.1

0.1

0.1

OA/NFG/CRADA

1.5

1.6

1.5

2.0

Other Reimbursable

0.8

0.9

1.2

1.1

Total

6.9

7.3

7.3

7.6

Full-time permanent staff (total)a

35

36

33

38

NOTE: Sources of funding are as described in the note accompanying Table 5.1.

aThe number of full-time permanent staff is as of January of that fiscal year.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

However, the division’s group leaders are at times overextended, taking on project responsibilities in addition to their managerial functions such as the training of new personnel and maintaining a division presence at international and national measurement forums. A strategic hire to enhance computational capabilities in the Radiation Interactions and Dosimetry Group is unfortunately offset by the loss of a key person in nuclear data in the Neutron Interactions and Dosimetry Group.

The division’s essentially flat budget (taking into consideration cost-of-living increases, it is, in effect, declining 2 to 5 percent every year) will eventually erode the division’s ability to pursue its mission and damage the above noted esprit de corps. Of particular concern are crucial areas in which division projects are dependent on cofunding from other federal departments or agencies, including the traceability program to bring agencies into compliance with ANSI N42.22 and commitments to develop a regulatory guide for the Nuclear Regulatory Commission.

CIRMS has expressed concerns about division staffing. It believes that growing demands in the medical applications and emerging issues such as food irradiation will require increased NIST efforts in these areas. It also recommends increasing the level of effort for occupational radiation protection.

The division derives some revenues from its SRMs, calibration and traceability services. This income is prone to vary from year to year and should not be counted upon for planning purposes. This customer-based source of revenue is at best able to support two to three staff professionals.

The panel has noted in previous reviews the need for the division to develop a capital plan. To date the panel has not seen such a plan. Four specific items that the panel suggests the division considered in such a plan are (1) a state-of-the-art TIMS that would put the Radioactivity Group ahead of the current state of measurements in terms of resolution and sensitivity; (2) an upgrade in neutron imaging capabilities to improve resolution down to 10 μ and significantly reduce the time to generate an image (as use of neutron imaging increases, the time factors involved in image generation must be addressed); (3) a state-of-the-art, high-current, low-voltage laboratory electron beam accelerator (a number of leading industrial firms recently obtained an innovative high-current, low-voltage self-contained solid state and computer-controlled laboratory unit for less than $150,000); and (4) a 6- to 8-MeV medical linac that will have sufficient beam intensity to also serve as a bremsstrahlung source and be used for standards and reference purposes.

Time and Frequency Division

Technical Merit

The Time and Frequency Division states its mission is to support U.S. industry and science through provision of measurement services and research in time and frequency and related technology. The division is organized into six technical groups: Time and Frequency Services, Network Synchronization, Atomic Standards, Ion Storage, Phase Noise Measurements, and Optical Frequency Measurements. There are strong connections and interactions between the groups, so this assessment is not organized by group.

The Time and Frequency Division is experiencing extraordinary success and productivity. Long-range research is flourishing. Research results obtained over the last 20 years are bearing fruit in improved techniques, including the connection of optical and microwave frequencies and the use of trapped ions for significantly improved stability of frequency standards, and real improvements in standards and services are being realized. Morale in the division is high. Staff members have a real sense of advancing the state of the art, enjoying the fruits of many years’ worth of discovery and development, and of exploiting recently developed techniques and opportunities.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

As planned, the NIST cesium fountain frequency standard, NIST-F1, has replaced the cesium beam standard, NIST-7, as the nation’s primary frequency standard. The current evaluation of NIST-F1 indicates a frequency uncertainty of 1.7×10–15, a threefold improvement over the performance of NIST-7. NIST-F1’s frequency agrees, within stated uncertainties, with a number of international standards, including two other fountain standards. Agreement with NIST-7 is also within the uncertainties. A report on the evaluation has been submitted to Metrología and three formal evaluations have been submitted to the International Bureau of Weights and Measures (BIPM), as is required for NIST-F1 to be included in the determination of Coordinated Universal Time (UTC). The present performance of NIST-F1 certainly ranks it among the best cesium standards in the world, and it perhaps is the best.

The Time and Frequency Division continues to further refine and improve NIST-F1. The team is trying to implement transverse cooling of the cesium in the fountain standard. This is important in reducing the uncertainty in the density shift, presently the largest uncertainty in the measurement. In addition, the uncertainty in the gravitational shift of NIST-F1 at its current location has been further reduced, to 2×10–17.

The Time and Frequency Division has developed a special time scale, AT1E, for comparing primary frequency standards. AT1E involves the use of five hydrogen masers with cavity autotuning, which, in combination with frequency comparison data attained through satellite-based methods, provides for absolute comparisons of the frequencies of NIST standards against those of other countries without the need for simultaneous operation of those standards. This has allowed quick measurements aimed at refining the atom density frequency shift in NIST-F1 and intercomparisons between NIST’s UTC and other countries’ time scales.

The division continues to improve the stability of the NIST UTC time scale with respect to the UTC disseminated by BIPM. Improvements in comparison of time scales have been achieved by the application of two-way time transfer and carrier phase common-view techniques. AT 1E has enabled comparing frequency standards at very high precision over extended periods of time. Division staff also added a new comparison and measurement system at 100 MHz to enable better measurements of local high-performance frequency standards.

The Time and Frequency Division continues its development of an optical frequency standard based on the locking of an ultrastable laser to an ultraviolet transition in a single Hg+ ion. The Q (ratio of the transition frequency to the line width) achieved in this system exceeds 1014, four orders of magnitude larger than that achieved for the microwave transitions currently used in frequency standards. This standard has the potential to reach an accuracy of 1×10–18, well beyond that of the best microwave frequency standards and even beyond other optical standards. This work is defining the state of the art. Substantial developments in the measurement of the Hg+ frequency using frequency combs, as described below, are also essential for the characterization and eventual use of this and other optical frequency standards.

Substantial progress has also been made on a calcium optical frequency standard. This standard, based on a narrow resonance in calcium atoms that are laser cooled and trapped in a magneto-optical trap, has very good short-term stability (currently 4×10–15 at one second), as well as other attractive characteristics (low sensitivity to external fields, cooling, trapping, and probing done with diode lasers). The standard serves as a useful companion to the mercury ion standard; however, owing to its lower Q (by two orders of magnitude), it does not appear to be a serious competitor for use as the eventual primary standard.

In the past year, the division moved quickly to capitalize on German developments in frequency comb generation and measurement techniques. In collaboration with German colleagues, the division has demonstrated an optical frequency comb produced by injecting femtosecond pulses from a mode-

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

locked laser into a microstructure fiber. After emerging from the fiber, the periodically spaced, phase-coherent modes span an octave of frequency. The modes of the comb are phase-locked to a reference, such as a hydrogen maser. The frequency of every line in the comb is then known with the precision of the frequency of the reference. Such a system allows any frequency in the spectral range of the comb to be measured with the uncertainty of a primary frequency standard. One of the significant applications of the femtosecond comb to measurements of atomic frequencies was measuring the 282-nm transition of a single Hg+ ion relative to the optical transition in calcium. The uncertainty in the measured Hg+ frequency is 1000 times lower than that in previous results and is limited by the uncertainty of the calcium frequency. Just recently, the frequency comb was used to measure the absolute frequencies of the Hg+ and Ca optical-clock transitions with unprecedented precision. Such a connection between microwave and optical frequencies has been a long-sought goal of the frequency-measurement community. This connection allows a system to benefit from both the high Q of an optical transition and the cycle-counting capabilities that exist at lower frequencies, and thereby from the translation of the high performance of optical standards to microwave frequencies. In a demonstration of the generation of a microwave output from an optical standard, a line in the comb was locked to the Hg+ optical frequency standard. The stability of the resulting microwave output exceeded that of the best quartz oscillators. Given these new techniques, the path is clear for optical standards to replace microwave standards such as the cesium fountain clock.

The division’s continuing work on correlated states of trapped ions plays a major role in the Physics Laboratory’s quantum computing initiative and is relevant to reducing noise in trapped-ion frequency standards. In the past year, the division published news of the first successful quantum entanglement of four particles, performed using beryllium ions. This achievement was heralded widely and is setting the pace for the division’s competitors. The division recently demonstrated operation of a decoherence-free quantum memory. An experiment with a pair of ions showed a clear violation of Bell’s inequality while avoiding a problem with detection efficiencies present in previous experiments using other systems.

The Time and Frequency Division is continuing its work on a small gas-cell frequency standard using coherent population trapping. The gas cell is irradiated with 852-nm light from a vertical-cavity surface-emitting laser, which is frequency modulated at 4.596-GHz, half the hyperfine frequency of cesium. This gives two coherent laser emission frequencies corresponding to the frequencies of transitions from the ground state hyperfine levels to an excited state. When the frequency difference is equal to the hyperfine level separation, there is reduced absorption by the atoms, leading to an increase in the transmitted light through (or a reduction in the fluorescent light from) the gas cell. An 85-Hz line width at 4.596 GHz has been obtained. The narrow line is used to stabilize the frequency of the 4.596-GHz modulation. Since there is no microwave excitation of the gas cell, no microwave cavity is needed and the device can be made very small, perhaps 2000 mm3. Power consumption is also expected to be low, perhaps 100 mW. The performance of such a standard should be similar to that of rubidium gas-cell devices. In view of its potentially small size, low power, and moderately good performance, this gas-cell standard could have many military and commercial applications, particularly in telecommunications.

The Time and Frequency Division continues high-quality work on phase and amplitude noise measurements and standards and on electronics for the primary frequency standards. It has made several copies of a flexible microwave synthesizer for frequency standards that it developed. These have low phase noise and very high phase stability with ambient temperature changes. High efficiency and low noise power supply design is critical in these units. It is particularly noteworthy that these standards are made completely from commercially available parts. Phase and amplitude noise measurement capability has been extended to 110 GHz. The phase noise measurement technique for microwave

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

pulse amplifiers has been further improved. This technique uses the cross correlation method and provides tens of decibels improvement over previously available measurements.

As a first step toward assessing the performance of frequency standards delivered over optical fibers, a 3.5-km fiber link between NIST Boulder and the University of Colorado was established in the past year. Network lines were assigned, and the first experiments in transmission of a frequency standard over these lines were encouraging. Light of 1.3-μ wavelength, modulated at 2.36 GHz and locked to a hydrogen maser, was launched into the fiber, and its stability was measured after one round-trip through the link. The observed stability is better than 10–12 τ–1/2, limited by the noise floor of the measurement system.

Program Relevance and Effectiveness

In addition to producing outstanding work on basic science and technology and the related development of enhanced primary standards, the Time and Frequency Division carries out development work and provides services that are directly relevant to a large number of customers.

At the time the panel met, the division’s network time service was receiving 40 million hits per day compared with 25 million a year previously. New servers are being installed to meet the increasing demand, which will bring the total of servers to 14. The division is in discussion with commercial firms that have expressed interest in taking over this authenticated time service and hopes to transition its activity to the private sector. The division also has a new Web site, time.gov. This site, intended for the nontechnical user, provides official United States time with an uncertainty of less than 1 second and is traceable to both the U.S. Naval Observatory and NIST. In October 2000, the site received 3.7 million hits.

Many of the Time and Frequency Division’s results on phase and amplitude noise measurement capability and microwave frequency synthesizers for frequency standards have direct and important applications in industry. The division even provides systems for measurements of phase noise in pulsed radar amplifiers. It also performs many calibrations for industry, receiving about $2000 per month for its services.

The division is also working on issues of timing for code division multiple access cell phone technology. In case the Global Positioning System’s (GPS’s) reference signal is lost, these cells must be able to maintain accurate time (holdover) to within 3 μs for 24 hours. Better estimates than those produced by the current smart clock technique of the raw oscillator noise and drift performance are desired, and wavelet analysis is being considered for this purpose.

The Frequency Measurement Service has been enhanced in terms of both measurement uncertainty and flexibility. Uncertainty has been reduced to 2×10–13 for 24-hour averaging, and the system can measure any frequency from 1 Hz to 120 MHz in 1-Hz increments.

The upgrade of NIST frequency broadcast station WWVB is complete. While the station now radiates 35 to 40 kW rather than the 50 kW originally planned, the simultaneous use of both available antennas improves the received signals by about 5 dB within the continental United States. The division has now turned its attention to replacing the high-frequency antennas for station WWVH in Kauai. The 30-year-old antennas have been corroded by the saltwater environment and are being replaced with fiberglass whip antennas designed for marine environments.

The Time and Frequency Division is in the process of surveying customers about its time and frequency services, an exercise it carries out approximately every 10 years. The survey will soon be posted on the Internet and published in professional journals. Based on past experience, approximately

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

5000 responses are anticipated. The results of the survey will be used to make decisions about the broadcast and Internet time services and their formats. The primary customers for these services are in the transportation, telecommunications, and financial industries.

The division is currently working with four industry customers who are current or potential providers of time signals. These companies are considering taking over some part of the distribution of time signals in the United States and Japan, where NIST is currently setting itself up to provide time services.

Reports on the progress with the small gas cell standard have provoked interest in an ultraminiature standard—a clock on a chip. A meeting will be held soon with government and industry participants to consider the possibility of developing such a device for use in GPS receivers for telecommunications and military purposes. As noted above, the low-power, small gas-cell Cs standard should have many applications, both military and commercial, particularly in telecommunications.

With its 54 publications of good to extremely high quality in the last year and its impact and substantial participation at conferences and workshops, the Time and Frequency Division’s dissemination of results to the primary scientific community has been excellent. This community includes academic scientists and scientists and engineers working in industry.

Division Resources

Funding sources for the Time and Frequency Division are shown in Table 5.6. As of January 2001, staffing for the Time and Frequency Division included 39 full-time permanent positions, of which 34 were for technical professionals. There were also 6 nonpermanent or supplemental personnel, such as postdoctoral research associates and temporary or part-time workers.

The division continues to attract and retain high-quality personnel. One of its strengths is its management system, in which group leaders are primarily scientific and technical leaders rather than administrators. Leadership is distributed, with group leaders involved in major decisions. The division experienced a 20 percent staff turnover in the last 3 years, with half of the departures due to retirements.

TABLE 5.6 Sources of Funding for the Time and Frequency Division (in millions of dollars), FY 1998 to FY 2001

Source of Funding

Fiscal Year 1998 (actual)

Fiscal Year 1999 (actual)

Fiscal Year 2000 (actual)

Fiscal Year 2001 (estimated)

NIST-STRS, excluding Competence

5.9

6.0

6.0

5.9

Competence

0.3

0.0

0.1

0.4

ATP

0.0

0.1

0.1

0.2

OA/NFG/CRADA

1.9

2.6

2.5

3.3

Other Reimbursable

0.7

0.6

0.9

1.0

Total

8.8

9.3

9.6

10.8

Full-time permanent staff (total)a

38

40

39

39

NOTE: Sources of funding are as described in the note accompanying Table 5.1.

aThe number of full-time permanent staff is as of January of that fiscal year.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
×

It is currently staffed at a level sufficient to continue good progress on all ongoing scientific and technical projects. While the division is reasonably well supported, division staff have enough outstanding ideas to keep a significantly larger staff very productively engaged. The division has done a very good job of managing its resources and, because of the high quality of its work, has been able to bring in enough funding from other agencies. However, with level budgets and increasing overhead and other costs, division leadership may need to reduce total staff levels in the future.

The quality and quantity of laboratory space has been a problem for the division. Construction of new laboratory space for the ion storage group is under way. This is a much-needed step forward. Other laboratory improvements presumably must wait for the major infrastructure and renovation projects being considered for all of the labs in Boulder.

MAJOR OBSERVATIONS

  • The ongoing programs in the Physics Laboratory are of extraordinarily high technical merit. The laboratory is an indispensable national asset in terms of the technical capability that it maintains for the nation.

  • While many programs in the Physics Laboratory are clearly reaching their customers in industry and the scientific community, others did not have a clear focus. Clearly articulated overall strategic goals for the Physics Laboratory would improve the alignment of individual programs with the laboratory mission and improve communication of the value and effectiveness of programs to NIST stakeholders.

  • The laboratory’s planned emphasis on nanotechnology is based on a strong existing competency and addresses an area of clear future importance. Clearer program goals would improve stakeholder support of this program.

  • The laboratory’s initiative in quantum computing is a model of vision, organization, and technical excellence. It is based on a strong existing competency in an area in which the laboratory leads the world. Despite the long-term, high-risk nature of the project, the Physics Laboratory has very specific goals that bode well for program success.

  • The panel is concerned that gradually declining real budgets will impact the laboratory’s ability to renew staff skills by replacement hiring. Such a scenario would devastate the technical quality of the laboratory’s work over the long term.

Suggested Citation:"5. Physics Laboratory." National Research Council. 2001. An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001. Washington, DC: The National Academies Press. doi: 10.17226/10204.
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An Assessment of the National Institute of Standards and Technology Measurement and Standards Laboratories: Fiscal Year 2001 Get This Book
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This volume represents the 42nd annual assessment by the National Research Council (NRC) of the technical quality and relevance of the programs of the Measurement and Standards Laboratories of the National Institute of Standards and Technology (NIST). This report provides judgments regarding the overall state of the NIST Measurement and Standards Laboratories (MSL),and offers findings to further increase the merit and impact of NIST MSL programs. It also offers in-depth reviews of each of the seven laboratories of the MSL, with findings aimed at their specific programmatic areas.

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