In This Issue...
NIST’s New Compact Atomic Clock Design Uses Cold Atoms to Boost Precision
Physicists at the National Institute of Standards and Technology (NIST) have demonstrated a compact atomic clock design that relies on cold rubidium atoms instead of the usual hot atoms, a switch that promises improved precision and stability.
Described in a new paper,* the heart of the prototype clock (the vacuum chamber containing the atoms) is about the size of a coffee mug, 150 cubic centimeters, set in a small table of lasers and electronics. When improved, miniaturized and integrated with compact lasers and electronics, NIST's new clock design has the potential to be about the same size as NIST's chip scale atomic clock (about the size of a matchbox) while being up to 1,000 times more precise over crucial time spans of a day or more.
By achieving this goal, the cold-atom clock could also match the performance of commercial cesium-beam atomic clocks, common laboratory instruments, but in a smaller package.
"We're trying to push ultraportable clocks to higher performance levels," NIST physicist Elizabeth Donley says. "The aim is to make a clock that does not even need calibration."
NIST pioneered the development of chip-sized atomic clocks in 2004.** Atomic clocks of similar design using atoms in a hot gas were commercialized a few years ago. For the past eight years this NIST research group has concentrated on a spin-off technology, chip-scale atomic magnetometers, but recently refocused on miniature atomic clock designs.
Chip-scale atomic clocks keep time well enough for many applications requiring timing synchronization over short periods, such as GPS receivers. But clock precision tends to drift over time spans beyond a few hours because the atoms are dispersed in high-pressure gases, which alter the atoms' resonant frequency—the clock tick rate—depending on temperature. The new cold-atom clock does not use these gases at all, thus eliminating this source of error. Improvements like this could extend the uses of small, low-power clocks to exacting applications such as synchronizing telecommunications networks.
NIST's cold-atom clock relies on about 1 million rubidium atoms held in a small glass vacuum chamber. The atoms are cooled with lasers and trapped with magnetic fields at very cold, microkelvin temperatures. Two near-infrared lasers excite the atoms symmetrically from above and below. Each laser generates two frequencies of light, which are tuned until the atoms oscillate between two energy states and stop absorbing light. This sets the clock ticking rate at a specific microwave frequency.
By aiming at the atoms from opposite directions simultaneously, the laser arrangement cancels a major source of measurement error—the Doppler shift, or the change in the atoms' apparent resonant frequency as they interact and move with the laser light. The clock also has special quantum features unique to rubidium atoms that boost the signal contrast and make the detection of the clock ticks more precise.
NIST researchers are already working on the next version of the cold-atom clock. In addition to reducing its size, researchers expect to improve its performance by adding magnetic shielding and antireflection coating. The research is funded in part by the Defense Advanced Research Projects Agency.
Edited on Nov. 20, 2013, to clarify the size comparison in the 2nd paragraph.
*F.-X. Esnault, E. Blanshan, E.N. Ivanov, R.E. Scholten, J. Kitching and E.A. Donley. A cold-atom double-lambda CPT clock. Physical Review A 88, 042120. Published Oct. 31, 2013.
**See 2004 NIST news release, "NIST Unveils Chip-Scale Atomic Clock," at www.nist.gov/public_affairs/releases/miniclock.cfm. An early version of this clock recently went on display at the Smithsonian Institution "Time and Navigation" exhibit (http://timeandnavigation.si.edu/).
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Perfect Faults: A Self-Correcting Crystal May Unleash the Next Generation of Advanced Communications
Researchers from the National Institute of Standards and Technology (NIST) have joined with an international team to engineer and measure a potentially important new class of nanostructured materials for microwave and advanced communication devices. Based on NIST's measurements, the new materials—a family of multilayered crystalline sandwiches—might enable a whole new class of compact, high-performance, high-efficiency components for devices such as cellular phones.*
"These materials are an excellent example of what the Materials Genome Initiative refers to as 'materials-by-design'," says NIST physicist James Booth, one of the lead researchers. "Materials science is getting better and better at engineering complex structures at an atomic scale to create materials with previously unheard-of properties."
The new multilayer crystals are so-called "tunable dielectrics," the heart of electronic devices that, for example, enable cell phones to tune to a precise frequency, picking a unique signal out of the welter of possible ones.
Tunable dielectrics that work well in the microwave range and beyond—modern communications applications typically use frequencies around a few gigahertz—have been hard to make, according to NIST materials scientist Nathan Orloff. "People have created tunable microwave dielectrics for decades, but they've always used up way too much power." These new materials work well up to 100 GHz, opening the door for the next generation of devices for advanced communications.
Modern cellphone dielectrics use materials that suffer from misplaced or missing atoms called "defects" within their crystal structure, which interfere with the dielectric properties and lead to power loss. One major feature of the new materials, says Orloff, is that they self-correct, reducing the effect of defects in the part of the crystal where it counts. "We refer to this material as having 'perfect faults'," he says. "When it's being grown, one portion accommodates defects without affecting the good parts of the crystal. It's able to correct itself and create perfect dielectric bricks that result in the rare combination of high tuning and low loss."
The new material has layers of strontium oxide, believed to be responsible for the self-correcting feature, separating a variable number of layers of strontium titanate. Strontium titanate on its own is normally a pretty stable dielectric—not really tunable at all—but another bit of nanostructure wizardry solves that. The sandwich layers are grown as a thin crystalline film on top of a substrate material with a mismatched crystal spacing that produces strain within the strontium titanate structure that makes it a less stable dielectric—but one that can be tuned. "It's like putting a queen-sized sheet on a king-sized bed," says Orloff. "The combination of strain with defect control leads to the unique electronic properties."
One key discovery by the research team was that, in addition to adding strain to the crystal sandwich, adding additional layers of strontium titanate in between the strontium oxide layers increased the room-temperature "tunability" performance of the structure, providing a new mechanism to control the material response. The material they reported on recently in the journal Nature has six layers of strontium titanate between each strontium oxide layer.
The new sandwich material performs so well as a tunable dielectric, over such a broad range of frequencies, that the NIST team led by Booth had to develop a new measurement technique—an array of test structures fabricated on top of the test film—just to measure its electronic characteristics. "We were able to characterize the performance of these materials as a function of frequency running from 10 hertz all the way up to 125 gigahertz. That's the equivalent of measuring wavelengths from kilometers down to microns all with the same experimental set-up," says Orloff, adding, "This material has a much lower loss and a much higher tunability for a given applied field then any material that we have seen."
An international team of researchers contributed to the recent paper, representing, in addition to NIST, Cornell University, the University of Maryland, Pennsylvania State University, the Institute of Physics ASCR (Czech Republic), Universitat Politècnica de Catalunya (Spain), the Kavli Institute at Cornell for Nanoscale Science, Oak Ridge National Laboratory, the Leibniz Institute for Crystal Growth (Germany), The University of Texas at Austin and Temple University.
For additional perspective, see the Cornell University news story, "Tunable antenna could end dropped cell phone calls" at www.news.cornell.edu/stories/2013/10/tunable-antenna-could-end-dropped-cell-phone-calls. For more on the MGI at NIST, see www.nist.gov/mgi/index.cfm.
*C-H Lee, N.D. Orloff, T. Birol, Y. Zhu, V. Goian, E. Rocas, R. Haislmaier, E. Vlahos, J.A. Mundy, L.F. Kourkoutis, Y. Nie, M.D. Biegalski, J. Zhang, M. Bernhagen, N.A. Benedek, Y. Kim, J.D. Brock, R.Uecker, X.X. Xi, V. Gopalan, D. Nuzhnyy, S. Kamba, D.A. Muller, I. Takeuchi, J.C. Booth, C.J. Fennie and D.G. Schlom. Exploiting dimensionality and defect mitigation to create tunable microwave dielectrics. Nature, 502, 532–536, Oct. 24, 2013. doi:10.1038/nature12582.
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NIST Seeks Public Input on Updated Smart Grid Cybersecurity Guidelines
The National Institute of Standards and Technology (NIST) is requesting public comments on the first revision to its guidelines for secure implementation of "smart grid" technology.
The draft document, NIST Interagency Report (IR) 7628 Revision 1: Guidelines for Smart Grid Cybersecurity, is the first update to NISTIR 7628 since its initial publication in September 2010. During the past three years, use of smart grid technology has expanded dramatically, particularly the number of smart energy meters on homes, and technology and laws have progressed as well. These changes prompted NIST to update its document.
"Millions of smart meters are in use around the country now, and as the smart grid is implemented we have gained more knowledge that required minor tweaks to the existing document," says NIST computer scientist Tanya Brewer. "There also have been legislative changes in states such as California and Colorado concerning customer energy usage data, and we have made revisions to the volume on privacy based on the changing regulatory framework."
NISTIR 7628 remains a three-volume document geared mainly toward cybersecurity specialists. Volume 1 contains mostly technical material for maintaining the security of the grid, including a reference architecture and high-level security requirements. Vol. 2 addresses privacy issues, containing a discussion of potential privacy issues in smart grid compared to other networked systems. Vol. 3 contains analyses and references that support the document's contents.
Brewer says most of the changes are minor additions to existing sections of NISTIR 7628, though there is a newly added section in Vol. 2 regarding privacy. While cybersecurity practitioners will most likely be its primary audience, Brewer says public utility commissioners, vendors and researchers also will find the changes of interest.
The draft version of NISTIR 7628 Revision 1 can be found at http://csrc.nist.gov/publications/PubsDrafts.html#NIST-IR-7628r1. Comments will be accepted until Dec. 24, 2013, and can be submitted to NISTIR.7628.Rev1@nist.gov using the Excel template available at the site. A Federal Register notice announcing the request for comments is available at https://www.federalregister.gov/articles/2013/10/25/2013-25168/request-for-comments-on-draft-nist-interagency-report-nistir-7628-rev-1-guidelines-for-smart-grid.
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Updating Building Energy Codes: How Much Can Your State Save?
How much in energy and cost savings would your state realize if it updated its commercial building energy codes? You can find out in a new on-line publication* from the National Institute of Standards and Technology (NIST). The state-by-state reports were the product of a new building energy efficiency analysis tool developed by NIST.
For each state, benefits and bottom-line impacts of upgrading to later editions of the nation's benchmark energy standard** for commercial buildings are condensed into two-page summaries. Calculated are energy use savings, energy cost savings, life-cycle costs, and energy-related reductions in carbon emissions. For each metric, summaries list total savings to be realized over a 10-year period.
The state-by-state summaries are the latest outputs of NIST economist Joshua Kneifel's analysis of energy usage and other variables for more than 12,500 buildings simulations across 228 U.S. cities. (See States Realize Big Benefits by Keeping Current with Energy Standards for Buildings at www.nist.gov/el/energy-020613.cfm.)
The analysis is based on a new NIST sustainable-buildings database and associated software tools that will debut this winter. Called BIRDS (for Building Industry Reporting and Design for Sustainability), the free, Web-based resource will provide baseline energy-efficiency measurements for prototypical buildings. These measurements will be able to be adjusted to reflect energy-related improvements so that energy, environmental and economics benefits and costs can be calculated.
*J. Kneifel, Benefits and Costs of Energy Standard Adoption in New Commercial Buildings: State-by-State Summaries (NIST Special Publication 1165), Sept. 2013. Downloadable from: http://www.nist.gov/manuscript-publication-search.cfm?pub_id=914711.
**ASHRAE Energy Standard for Buildings Except Low-Rise Residential Buildings (ASHRAE-90.1‑). For more information: https://www.ashrae.org/resources--publications/bookstore/standard-90-1#2007.
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Not Just a Pretty Face: Bodies Provide Important Cues for Recognizing People
Computer recognition of people has focused almost exclusively on faces, but a new study suggests it may be time to take additional information into consideration. A study* published online Sept. 25, 2013 in the journal Psychological Science by researchers at the University of Texas at Dallas and the National Institute of Standards and Technology (NIST) describes a series of experiments that demonstrates there is potentially more valuable information for biometrics-based identity recognition in images of people than the face alone.
"For twenty years, the assumption in the automatic face recognition community has been that all important identity information is in the face," said Jonathon Phillips, an electronics engineer at NIST who is a co-author on the study. "These results should point us toward exploring new ways to improve automatic recognition systems by incorporating information about the body beyond the face."
In a series of experiments, the researchers showed study participants pairs of images of either the same or different people and asked them to determine if the photos matched or not. The images selected for the study were chosen from a database used in the Face Recognition Vendor Test 2006, an international competition of face recognition systems conducted by NIST. The study team selected a subset of the image pairs that automated face recognition systems could not recognize.
The images included a subject's face and upper body. The study found that biometric identification accuracy by humans was essentially random when viewing only the face. Study participants were presented with two additional cases. In the first case, they compared the original images containing the face and upper body; while in the second case, they compared images of the upper body with the face masked. In both cases, human accuracy was the same and above chance. These results showed that participants primarily made decisions based on the upper body.
Even though limited facial information was available, participants reported using facial cues to make identifications. Eye-movement tracking of the study participants, however, told a different story.
"Eye movements revealed a highly efficient and adaptive strategy for finding the most useful identity information in any given image of a person," said the study's lead author Alice O'Toole of the University of Texas. The eye-movement results suggest that the participants were unaware of how important the body was in their decisions.
The results of this research indicate that automatic face recognition systems could improve their accuracy by incorporating the body into their decision process.
For more information on the Face Recognition Vendor Test, visit www.nist.gov/itl/iad/ig/frvt-home.cfm.
*A. Rice, P.J. Phillips, V. Natu, X. An, A.J. O'Toole. Unaware person recognition from the body when face identification fails. Psychological Science, Sept. 25, 2013. doi: 10.1177/0956797613492986. A PDF file of the article is available to reporters on request.
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New Spectrometry Standard for Handheld Chemical Detectors Aids First Responders
When it comes to detectors for dangerous chemicals, toxins or nefarious germs, smaller and faster is better. But size and speed must still allow for accuracy, especially when measurements by different instruments must give the same result.
The recent publication of a new standard—a culmination of years of research at the National Institute of Standards and Technology (NIST)—provides confidence that results from handheld chemical detectors can be compared, apples-to-apples.
Such detectors are used by emergency responders to check for the presence of explosives or toxic chemicals that threaten public safety. Quality control managers in the pharmaceutical industry use them to verify the identity of chemicals going into their production lines.
The new standard, published recently by ASTM International, is intended as a guide to correct the output from different handheld Raman spectrometers, so that different instruments produce the same result for the same sample.
Raman spectrometers identify chemicals by shining laser light on a sample and detecting the very small changes in the wavelength of that light as it is re-emitted from the sample. However, spectrometers from different manufacturers can produce signals with different peak intensities. These differences can be confusing, particularly if first responders from different agencies use different instruments and get differing results on an unknown sample in the field.
"Our goal is that people get the same answer for the same sample on any machine," says NIST chemist Steven Choquette.
His team developed a series of NIST Standard Reference Materials (SRMs) that are used to correct Raman systems with differing excitation lasers. These standards enable the correction of the differences in peak intensities reported for the same sample by different Raman spectrometers. They then continued to work with spectrometer manufacturers to develop an industry consensus standard to enable comparisons among Raman spectrometers. Their work was funded by the NIST Law Enforcement Standards Office (OLES) and the Department of Homeland Security.
The newly published industry consensus standard, Standard Guide for Relative Intensity Correction of Raman Spectrometers (designated as E2911-13), is available from ASTM International at www.astm.org/Standards/E2911.htm. For more on OLES, visit www.nist.gov/oles. For more on the NIST reference materials for fluorescence and Raman spectroscopy, visit www.nist.gov/mml/bbd/bioassay/fluorescence_raman_intensity_standards.cfm.
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NIST Fellow Ron Ross Honored With Inaugural McNulty Information Security Leadership Award
National Institute for Standards a Technology (NIST) Fellow Ron Ross has been awarded the inaugural Lynn F. McNulty Tribute U.S. Government Information Security Leadership Award. The (ISC)2* U.S. Government Advisory Board for Cyber Security (GABCS) announced the award on Oct. 29, 2013, in recognition of Ross’s “key role in establishing cybersecurity requirements for federal agencies for decades.”
Ross leads the Federal Information Security Management Act (FISMA) implementation project and is the principal architect of the NIST Risk Management Framework. A former director of the National Information Assurance Partnership, Ross also currently leads the interagency program synchronizing U.S. government cybersecurity standards and guidelines.
The award was established last year after the death of (ISC)2 Fellow and IT security evangelist Lynn F. McNulty, CISSP.* McNulty was considered by those in the community as the "pioneer" of government information security. The Tribute Award recognizes a member of the U.S. federal information security community who upholds McNulty's legacy as a visionary and innovator through outstanding service and commitment.
Ross worked with McNulty during the 1990s when McNulty was NIST’s Associate Director of Computer Security.
"Ron's insight and leadership in producing a library of guidance publications over the past decade has greatly contributed to the advancement of information security in government and around the world," said Peter Gouldmann, CISSP, director of information risk programs, Office of Information Assurance, U.S. Department of State, and member, (ISC)2 GABCS. “His highly collaborative approach, incorporating government and industry, has resulted in products that are being adopted and adapted for use on national security systems, transcending the unclassified and classified systems landscape.”
(ISC)2 is a not-for-profit information security professional body specializing in information security education and certifications, including the Certified Information Systems Security Professional (CISSP).
*(ISC)2 and Certified Information Systems Security Professional (CISSP) are registered marks.
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