In This Issue...
NIST Sensor Improvement Brings Analysis Method into Mainstream
An advance in sensor design* by researchers at the National Institute of Standards and Technology (NIST) and the University of Waterloo's Institute of Quantum Computing (IQC) could unshackle a powerful, yet high-maintenance technique for exploring materials. The achievement could expand the technique—called neutron interferometry—from a test of quantum mechanics to a tool for industry as well.
Neutron beams can be used in dozens of ways to probe complex molecules and other advanced materials, but few of the analysis techniques require as much care as neutron interferometry. The technique treats neutrons as waves—a feature of quantum mechanics—and measures how the neutron is altered as it passes through a sample material. The results can reveal a variety of details about the magnetic, nuclear and structural properties of the sample. Neutron interferometry is extremely sensitive, but it carries a price: the instruments are so exquisitely sensitive to vibration and temperature that they must be built in a blockhouse the size of a garage, where they can be shielded from seismic activity and maintained at temperatures that are stable to within a few thousandths of a degree Celsius.
The team, working at the NIST Center for Neutron Research (NCNR), found a way to sidestep many of these requirements and render the interferometer much more tolerant of change. The heart of a classic neutron interferometer is a small piece of silicon about the size of a soda can, precisely machined so that three thin walls of silicon jut upwards from its surface. These walls diffract the neutron beam, splitting it in two, sending one part through the sample, and then recombining them. Interference patterns in the output reveal how the neutrons were affected by the sample. The recent innovation is to add an extra wall in a way that increases the overall symmetry of the interferometer.
"By adding a fourth vane to the usual three, we were effectively able to cancel out the effect of many disturbances," says Michael Huber of the NIST research team. "It will allow us to create a device that can be housed in a box the size of a large charcoal grill that sits on the floor."
The advance, Huber says, means the new device can be much closer to the neutron source, delivering more than 10 times as many neutrons on the sample as before and generating data that is far more accurate in a fraction of the time.
"A measurement that might have taken more than a week could be done in a matter of hours now," Huber says. "We can imagine our interferometer becoming more of a 'user facility' that industry and universities can book time on when needed, rather than the esoteric instrument it has been up to this point. This development in neutron interferometry demonstrates that quantum technologies have the potential to emerge from academia to help build practical devices for real-world applications."
Huber adds that the NCNR will still maintain the original blockhouse-style instrument for certain types of interferometry work, but will augment it with the new device, which could start taking measurements when the NCNR resumes neutron production after its expansion project is complete in February 2012.
* D.A. Pushin, M.G. Huber, M. Arif and D.G. Cory. Experimental realization of decoherence-free subspace in neutron interferometry. Physical Review Letters. 107, 150401 (2011), DOI: 10.1103/PhysRevLett.107.150401
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Prototype NIST Device Measures Absolute Optical Power in Fiber at Nanowatt Levels
Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a prototype device capable of absolute measurements of optical power delivered through an optical fiber.
The device is the world's first fiber-coupled cryogenic radiometer that links optical fiber power measurements directly to fundamental electrical units and national standards. It uses a microscopic forest of carbon nanotubes—the world's darkest material—to measure values that are about one-thousandth of the levels typically attained with a cryogenic radiometer lacking direct fiber input capability.* With improvements in temperature control and speed, the device could meet the needs for ultraprecise calibrations at ultralow power in telecommunications, medical devices and other industries.
Optical power and energy are traceable to fundamental electrical units. Radiometers absorb optical energy and convert it to heat. Then the electrical power needed to induce the same temperature increase is measured. Because optical and electrical heating are not exactly equivalent, measurement uncertainties can be relatively large from a metrology point of view.
The demonstration is also a step toward converting radiometry from a classical practice based on electrical units to a quantum practice based on single particles of light (photons).
"We have many customers who request optical power measurements in fiber, mainly for optical communications," project leader John Lehman says. "Also, our single-photon measurements are done in fiber."
The new radiometer is about 70 millimeters (mm) long and incorporates a 1.45-mm-thick optical fiber capped by a light-trapping cavity at one end with the nanotube absorber and a heater. The ultra-dark nanotubes** are grown on a tiny X-shaped piece of micromachined silicon. Light absorption was so high it was difficult to determine measurement uncertainties; Lehman travelled to a special facility at the National Physical Laboratory (the British equivalent of NIST) to make some measurements.
Experiments and calculations indicate the new radiometer can measure a power level of 10 nanowatts with an uncertainty of 0.1 percent. By comparison, typical measurements of optical power delivered through fiber have an uncertainty of 3 percent or more at similar power levels. More importantly, these commercial devices rely on a series of calibrations to establish traceability to national standards.
NIST aims to develop an absolute quantum standard for optical power and energy based on single photons. The effort includes development of sources and detectors spanning a wide range of optical power measurements, from single photon counts to trillions of photons. Single photons are already used in quantum communications systems, which offer novel capabilities such as detecting extremely weak optical signals and providing quantum guarantees on security.
* D. Livigni, N. Tomlin, C.L. Cromer and J.H. Lehman. Fiber-coupled cryogenic radiometer with carbon nanotube absorber. Paper presented at 11th International Conference on New Developments and Applications in Optical Radiometry (NEWRAD 2011), Maui, Hawaii, Sept. 19-23, 2011.
D.J. Livigni, N.A. Tomlin, C.L. Cromer and J.H. Lehman. Optical fiber-coupled cryogenic radiometer with carbon nanotube absorber. Metrologia. Forthcoming.
** See the 2010 NIST Tech Beat article, "Extreme Darkness: Carbon Nanotube Forest Covers NIST's Ultra-dark Detector" at http://www.nist.gov/pml/div686/dark_081710.cfm.
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NIST Releases First Certified Reference Material for Single-Wall Carbon Nanotubes
The National Institute of Standards and Technology (NIST) has issued the world’s first reference material for single-wall carbon nanotube soot. Distantly related to the soot in your fireplace or in a candle flame, nanotube-laden soot is the primary industrial source of single-wall carbon nanotubes, perhaps the archetype of all nanoscale materials. The new NIST material offers companies and researchers a badly needed source of uniform and well-characterized carbon nanotube soot for material comparisons, as well as chemical and toxicity analysis.
With walls of carbon only one atom thick and looking like a sheet of chicken wire curled into a cylinder, single-wall carbon nanotubes are one of several families of pure carbon materials that, because of their nanoscale size, have special properties. “Single-wall carbon nanotubes,” says NIST chemical engineer Jeffery Fagan, “have exquisite optical, mechanical, thermal and electronic properties, and because of their small width but long lengths—think of something like a long piece of hair but 10,000 times thinner—full development of these materials should enable lighter, stronger materials, as well as improve many technologies from sensors to electronics and batteries.”
Unfortunately, nanotubes are difficult to produce without significant impurities or in large quantities. Single-wall nanotubes, in particular, have been notorious for their relatively low quality and batch-to-batch variability. They typically are produced in complex processes using small particles of metal catalysts that promote the growth of the nanotubes. The resulting material—often a powder not unlike the soot you would find in your fireplace—has frequently contained large amounts of impurities, such as other forms of carbon, and sometimes significant levels of catalysts.
“One of the issues that this reference material addresses is that there's no homogeneous lot that people can buy to do comparative measurements,” says Fagan. “Even batch-to-batch, raw carbon nanotube powder samples have varied so much that there is no interlaboratory consistency. And that's particularly a problem for comparisons such as toxicity measurements. If you bought carbon nanotubes, you were pretty much guaranteed that your sample could be so different from anyone else's samples that either your measurements could be specific to some flaw of your material, or that others might not be able to reproduce what you were doing.”
To address these issues, a multidisciplinary research team at NIST has worked to develop the metrology necessary for quantitative single-wall carbon nanotube measurements through a three-prong approach: basic measurement and separation science, documentary protocols and standards through international standards organizations, and now certified reference materials.
The new NIST product, Standard Reference Material (SRM) 2483, “Single-Wall Carbon Nanotubes (Raw Soot),” will directly address the issue of comparability. It is possibly the world's single largest supply of homogeneous, chemically analyzed, carbon nanotube soot where the uniformity of the samples from unit to unit is assured. Each unit of SRM 2483, a glass vial containing 250 milligrams of soot, is certified by NIST for the mass fraction values of several common contaminants: barium, cerium, chlorine, cobalt, dysprosium, europium, gadolinium, lanthanum, molybdenum and samarium. Reference values (values believed to be accurate, but not rising to the level of confidence that NIST certifies) are provided for an additional seven elements.
NIST also provides additional reference data useful for nanotube analysis, including thermal gravimetric and Raman data, as well as informational values for ultraviolet-visible-near-infrared absorbance spectra, near-infrared fluorescence spectra, Raman scattering spectra and scanning electron microscopy images. With these sets of information, purchasers of the material should be able to compare their results against the NIST values and against those from suppliers or after processing, ensuring a consistent point of comparison.
Single units of SRM 2483, “Single-Wall Carbon Nanotubes (Raw Soot),” are available from the NIST Standard Reference Materials Program at www.nist.gov/srm/. See https://www-s.nist.gov/srmors/view_detail.cfm?srm=2483 for details.
Standard Reference Materials are among the most widely distributed and used products from NIST. The agency prepares, analyzes and distributes more than a thousand different materials that are used throughout the world to check the accuracy of instruments and test procedures used in manufacturing, clinical chemistry, environmental monitoring, electronics, criminal forensics and dozens of other fields.
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Atoms Dressed with Light Show New Interactions, Could Reveal Way to Observe Enigmatic Particle
Physicists at the National Institute of Standards and Technology (NIST) have found a way to manipulate atoms’ internal states with lasers that dramatically influences their interactions in specific ways. Such light-tweaked atoms can be used as proxies to study important phenomena that would be difficult or impossible to study in other contexts. Their most recent work, appearing in Science,* demonstrates a new class of interactions thought to be important to the physics of superconductors that could be used for quantum computation.
For more details, see the JQI news announcement, “The Impact of Quantum Matter” at http://jqi.umd.edu/news/291-the-impact-of-quantum-matter.html.
* R.A. Williams, L.J. LeBlanc, K. Jiménez-García, M.C. Beeler, A.R. Perry, W.D. Phillips, I.B. Spielman. Synthetic Partial Waves in Ultracold Atomic Collisions . Science Express, 8 December 2011.
“Changes made to the document reflect changes in the state of the art,” explains NIST computer security expert Tim Polk, Cryptographic Technology Group manager at NIST. “There are new techniques and tools available to government agencies, and this provides them more flexibility in choosing the best authentication methods for their individual needs, without sacrificing security.”
When SP 800-63 was first released, its authors assumed that most agencies would handle the business of figuring out if users were who they claimed to be in-house. But since that time, an industry has grown around providing authentication services, and it is often in the best interest of agencies to take advantage of commercial systems or those of other government entities. And while passwords are still the leading mechanism for authenticating user identity, a growing number of systems rely on cryptographic keys or physical tokens.
The revision broadens the discussion of technologies available to agencies and gives a more detailed discussion of these technologies. The guideline applies whether agencies choose to handle authentication directly or leverage services provided by other parties, including commercial companies.
Government agencies have the option of using the services of companies that have had their authentication systems certified through the Federal Chief Information Officer Council’s Trust Framework Provider Adoption Process (TFPAP). This program assesses credentialing processes against federal requirements, including those established in 800-63. To ensure consistency and avoid redundant analysis, NIST strongly encourages agencies to leverage the TFPAP process.
SP 800-63-1 is the official implementation guidance for the Office of Management and Budget (OMB) Memorandum 04-04, “E-Authentication Guidance for Federal Agencies.*” Polk stresses that the revised NIST guideline may inform but is not intended to restrict or constrain the development or use of standards for implementation of the National Strategy for Trusted Identities in Cyberspace (NSTIC). NIST SP 800-63-1 is specifically designated as a guideline for use by federal agencies for electronic authentication. NSTIC, in contrast, has a broader charge: the creation of an Identity Ecosystem, “an online environment where individuals and organizations will be able to trust each other because they follow agreed upon standards to obtain and authenticate their digital identities.”
NIST SP 800-63-1, Electronic Authentication Guideline, is available at www.nist.gov/manuscript-publication-search.cfm?pub_id=910006. For more NIST computer security publications, see http://csrc.nist.gov/publications/PubsSPs.html.
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The National Institute of Standards and Technology (NIST) is now accepting applications for the 2012 Summer Undergraduate Research Fellowships (SURF) programs at its Gaithersburg, Md., and Boulder, Colo., campuses. The programs provide research opportunities for undergraduate students to work with internationally known NIST scientists and gain exposure to cutting-edge research.
The SURF programs are supported by the National Science Foundation, and each summer, more than 100 students spend about 11 weeks at one of the NIST sites, meeting peers and gaining valuable hands-on research experience. In 2012, NIST expects it will host approximately 78 students at Gaithersburg and about 18 at Boulder.
The fellowship programs are open to colleges and universities located in the U.S. and its territories with degree-granting programs in computer science, mathematics, materials science, chemistry, biology, engineering, and/or physics. Applications are submitted by the schools, not the students, so students wishing to participate need to contact their college or university to let them know they wish to participate.
Nominated undergraduate students must be U.S. citizens or permanent residents with a technical major. New applicants must be enrolled to continue their undergraduate education for fall 2011, but previous SURF participants who will graduate in spring 2011 are also eligible. Participants receive stipends and housing and travel allotments (as needed). The programs are expected to run between May and August, with some accommodations possible for alternate school schedules.
At the Gaithersburg campus, students can work in the areas of nanoscale science, engineering, computer science, mathematics, materials science, chemistry, biology, neutron research and/or physics. In Boulder, SURF students can participate in research in computer science, mathematics, materials science, chemistry, biology, engineering and/or physics.
Applications should be submitted through the Grants.gov (www.grants.gov) Website under either Federal Funding Opportunity code 2012-NIST-SURF-G-01 (Gaithersburg site) or 2012-NIST-SURF-B-01 (Boulder site). Applications must be received no later than 5 p.m. EST, Feb. 15, 2012, for Gaithersburg, and 5 p.m. MST for Boulder.
For more information on the SURF Gaithersburg program, visit: http://www.nist.gov/surfgaithersburg/ or see the Gaithersburg announcement and application at Grants.gov:
For more information on the SURF Boulder program, visit: http://www.nist.gov/surfboulder/index.cfmor see the Boulder announcement and application at: http://www07.grants.gov/search/search.do?&mode=VIEW&oppId=134213.
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The National Institute of Standards and Technology (NIST) has announced that it is accepting proposals for funding for a broad range of potential research projects and related activities that support the institute’s measurement science and engineering programs. The combined announcement for the NIST Measurement Science and Engineering (MSE) Research Grant Programs, issued on Dec. 7, 2011, describes nine separate research and development funding programs of the research agency.
Potential R&D topics under the programs span the breadth of NIST’s interests. The nine MSE programs include:
In fiscal year 2011, the combined MSE grant programs funded a total of 86 new projects with a total of more than $15.6 million. The funding generally goes to support scientific or engineering research, but may also support conferences, workshops or other technical research meetings that are relevant to NIST’s work.
Proposals for these grant programs are accepted on a rolling basis, without fixed deadlines. Proposals to the Fire Research Grant Program received after 5 p.m. Eastern time on January 30, 2012, may be considered for funding under this solicitation in either the current or next fiscal year, subject to the availability of funds. For the other eight programs, proposals received after 5 p.m. Eastern time on June 1, 2012, may be considered for funding under this solicitation in either the current or next fiscal year, subject to the availability of funds.
Details of scope, anticipated award sizes, requirements and the proposal submission and review process vary with the individual grant programs. The full documentation for this solicitation is available as an Announcement of Federal Funding Opportunity (FFO) at the Grants.gov Web site www.grants.gov under Funding Opportunity Number 2012-NIST-MSE-01 and/or Catalog of Federal Domestic Assistance (CFDA) Number 11.609 (Measurement and Engineering Research and Standards). See http://www07.grants.gov/search/search.do?&mode=VIEW&oppId=133134. The FFO is also is available at www.nist.gov/director/ocfo/grants/grants.cfm.
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