May 2006

National Nuclear
Security Administration’s

Lawrence Livermore
National Laboratory

Also in this issue:• Rapid Detection of Animal Diseases• Measuring Temperatures in Extreme Environments• A Small Perturbation with Big Results

Gamma-ray detection is an important technology
for homeland security because it allows security
agencies to search for and detect illicit radioactive
sources. With funding from the Department ofHomeland Security, Livermore scientists are using theirexpertise in radiation detection to improve the nation’s
capabilities in this area. The article beginning on p. 4
describes two Livermore-developed imagers that can
depict gamma rays without mirrors or lenses. The first,
a large-area gamma-ray imager, detected millicuriequantities of a cesium isotope from 85 meters away.
The second imager is a portable system that relies
on Compton scattering to pinpoint the location of a
gamma-ray source. The cover shows one version of
the Compton imager (foreground) and an example
of its results superimposed on a photograph of thesurveyed area.

Cover design: Daniel Moore

About the Cover

About the Review
Lawrence Livermore National Laboratory is operated by the University of California for the Departmentof Energy’s National Nuclear Security Administration. At Livermore, we focus science and technology on
ensuring our nation’s security. We also apply that expertise to solve other important national problems in energy,
bioscience, and the environment. Science & Technology Review is published 10 times a year to communicate, to abroad audience, the Laboratory’s scientific and technological accomplishments in fulfilling its primary missions.
The publication’s goal is to help readers understand these accomplishments and appreciate their value to theindividual citizen, the nation, and the world.
Please address any correspondence (including name and address changes) to S&TR, Mail Stop L-664,
Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551, or telephone (925) 423-3432.
Our e-mail address is str-mail@llnl.gov. S&TR is available on the World Wide Web at www.llnl.gov/str.

© 2006. The Regents of the University of California. All rights reserved. This document has been authored by the Regents of the
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Prepared by LLNL under Contract
No. W-7405-Eng-48

This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the UnitedStates Government nor the University of California nor any of their employees makes any warranty, expressed or implied, orassumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product,or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specificcommercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constituteor imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The
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May 2006
Lawrence
Livermore
National
Laboratory

S&TR Staff
SCIENTIFIC EDITOR
Maurice B. Aufderheide III
MANAGING EDITOR
Ray Marazzi
PUBLICATION EDITOR
Carolin Middleton
WRITERS
Arnie Heller, Ann Parker, Gabriele
Rennie, and Maurina S. Sherman
ART DIRECTOR AND DESIGNER
Daniel Moore

Contents
Features

3 Science and Technology Help the Nation
Counter Terrorism

Commentary by Raymond J. Juzaitis

4 Imagers Provide Eyes to See Gamma Rays
Gamma-ray imagers provide increased radiation
detection capabilities and enhance the nation’s
arsenal for homeland security.

11 Protecting the Nation’s LivestockFoot-and-mouth disease could devastate America’s
livestock; a new assay provides a rapid means todetect it.

PHOTOGRAPHER
George Kitrinos
COMPOSITOR
Louisa Cardoza
PROOFREADER
Pamela MacGregor
S&TR, a Director’s Office publication, is
produced by the Technical Information
Department under the direction of the
Office of Policy, Planning, and Special
Studies.
S&TR is available on the Web
at www.llnl.gov/str.

Research Highlights
18 Measures for Measures
Laboratory physicists combine emissivity andreflectivity to achieve highly accurate temperature
measurements of metal foils.

20 Looping through the Lamb Shift
Livermore scientists measured a small perturbationin the spectra of highly ionized uranium—the firstmeasurement of the two-loop Lamb shift in abound state.

Printed in the United States of America
Available from
National Technical Information Service
U.S. Department of Commerce
5285 Port Royal Road
Springfield, Virginia 22161

UCRL-TR-52000-06-5
Distribution Category UC-99
May 2006

Departments
2 The Laboratory in the News23 Patents and Awards
25 Abstracts

2

The Laboratory in the News

S&TR May 2006

Simulating the future water supply in California
Collaborative research involving Livermore scientists indicatesthat if concentrations of atmospheric carbon dioxide double frompreindustrial levels, the resulting warming may dramaticallychange river flows in California. The simulations show that ina hypothetical El Niño season—a naturally occurring climate
oscillation—state water managers may have to contend withan increased risk of both flooding and water shortages. For thesimulations, researchers assumed that the strength of an El Niño
event, as measured by increased sea-surface temperatures overlong-term averages, would be the same in this warmer future astoday. In California, an El Niño season typically brings more rain,
which increases river flows and flood risk.
California’s water infrastructure is efficient at providing anadequate water supply and minimizing flood risk. The system,
however, works well only in a climate that includes large amountsof mountain snow. Melting snow keeps reservoirs full in the latespring and summer, after rain and snowfall have stopped. Too muchwater falling in the rainy season causes flooding, but too little will
decrease levels in the state’s reservoirs.
If winter temperatures warm because of carbon concentrations,more rain than snow will fall at higher elevations. In areas where
snow does accumulate, it will melt sooner than it does in a normal
year. These changes will result in higher river-flow rates during
winter and lower rates during spring and summer, when flows
normally are from snowmelt. In addition, if river-flow rates are
too high during the winter, water managers will have to reduce
reservoir levels to capture the increased winter flood surges. Thosereleases would further reduce the overall water supply for the entire
year. The collaboration, which was led by professor Edwin Maurer
from Santa Clara University, published its results in the January 27,
2006, issue of Geophysical Research Letters.
Contact: Philip Duffy (925) 422-3722 (duffy2@llnl.gov).

Demonstration checks readiness for biological attack
In January, researchers from Lawrence Livermore and Sandia
national laboratories participated in a two-day demonstration at San
Francisco International Airport to test the response and restoration
protocols that would be undertaken following a biological attack.
This demonstration was part of a three-year collaboration focusedon shortening the time line for restoration after an illicit bioagent
attack. Funded by the Department of Homeland Security, theBio Restoration Demonstration Project included participants fromseveral federal, state, and local agencies.
Livermore and Sandia researchers developed a restoration planwith templates that help airport personnel prepare for a biologicalterrorist attack. Using a mock scenario developed by an interagency
team, participants implemented the plan to demonstrate how afacility could be quickly decontaminated and reopened.

Restoration plans include protocols to acquire samples after
an attack, analyze the results, decontaminate affected areas,
reopen facilities for public use, and if necessary, provide longerterm monitoring. To reduce the cleanup time after an attack, theLivermore–Sandia team also upgraded several technologies,
including a Geographic Information System–based indoor sample
tracking system, a rapid viability test procedure to determine
within days whether anthrax spores are dead or alive, andsampling methodologies to better understand the percentage ofanthrax spores collected in samples. As part of this project, theNational Academy of Sciences is conducting a study to determine
acceptable cleanup levels for anthrax, smallpox, and plague.
Contact: Ellen Raber (925) 422-3985 (raber1@llnl.gov).

Volcanoes curbed rise in sea level
Simulations using 12 new climate models show that the 1883
eruption of the Krakatoa volcano in Indonesia substantiallyreduced ocean warming and sea-level rise during the 20th
century. This study, which included researchers from Lawrence
Livermore, the National Center for Atmospheric Research, theUniversity of Reading in the United Kingdom, and the Hadley
Centre for Climate Prediction and Research, examined the effects
of volcanic eruptions on climate. The models include climateforcing mechanisms such as changes in greenhouse gases, solar
irradiance, and volcanic aerosols. The research team used eachmodel to simulate the climate from 1880 to 2000 and compared thesimulated data with available observations from that period.
Oceans expand and contract with changes in temperature. When
the water is warmer, sea level increases; when cooler, it recedes.
In recent decades, the volume average temperature of oceans(down to 300 meters) worldwide has warmed by about 0.037°C
because of increased atmospheric greenhouse gases. Althoughseemingly small, this increase corresponds to a sea-level rise of
several centimeters and does not include effects from such factors
as melting glaciers.
The team’s results, which were published in the February 9,
2006, issue of Nature, indicate that the sea level would have risenmuch more had the Krakatoa eruption not occurred. Because
volcanic aerosols scatter sunlight, an eruption typically causes theocean surface temperature to cool, an anomaly that is graduallysubducted into deeper layers where it persists for decades.
The research team also studied the 1991 Mount Pinatubo
eruption in the Philippines, which was comparable to Krakatoa
in terms of its size and intensity. Although similar ocean surface
cooling resulted from both eruptions, the heat-content recovery
occurred much more quickly after the Mount Pinatubo eruption.
The observed warming of the upper ocean, which is primarily due
to human influences, more than offsets the volcano’s effects.
Contact: Peter Gleckler (925) 422-7631 (gleckler1@llnl.gov).

Lawrence Livermore National Laboratory

Commentary by Raymond J. Juzaitis

3

Science and Technology Help the
Nation Counter TerrorismW

ITH the Cold War receding into memory, the U.S. faces ageopolitical environment that is far more complex, lesspredictable, yet every bit as dangerous as before. Although the
U.S. remains a military superpower, traditional models of nuclear
and conventional deterrence do not apply to terrorist groups or
insurgencies. Al Qaeda and other terrorist organizations haverepeatedly stated their desire to acquire and use weapons of mass
destruction (WMD) against the U.S. and its allies and interests.
At Lawrence Livermore, we are dedicated to ensuring andenhancing national security within the global context. In addition
to our historical responsibilities related to maintaining the U.S.
nuclear deterrent, we also strive to reduce the threat posed by the
proliferation or terrorist acquisition of WMD. In particular, we area national leader in the development of technologies, systems, andcapabilities to strengthen the nation’s ability to prevent, detect,interdict, and recover from WMD incidents or terrorist attacks.
Different approaches are needed to counter the various WMD
threats. With the nuclear threat, the goal is to prevent terrorists fromacquiring nuclear materials or, barring that, from reaching theirintended target with their device. The very nature of radioactive
materials makes them detectable at a distance, giving us atechnological approach to locating and interdicting such materials.
The article beginning on p. 4 describes the development of
gamma-ray imagers that can detect weak sources amidst a sea of
background radiation. Our large-area gamma-ray imager offers thecapability to detect millicurie quantities of a radioactive material at
distances approaching 100 meters. A portable system we developed
relies on Compton scattering to pinpoint the location of a gammaray source. Such imaging detectors will significantly improve theability of border agents, customs inspectors, law-enforcement
officers, and incident response personnel to search for, locate, andidentify illicit nuclear material.
A different approach must be taken to address the threat of
biological terrorism. Because the materials and equipment needed
to make biological weapon agents are widespread and have many
legitimate uses, the likelihood of preemptively detecting a biothreat
is very low. Therefore, our efforts are directed at developing
monitoring systems that can detect a bioagent release in time tocontain a disease outbreak. Many of these systems can also be
applied to protect public health and the nation’s agricultural industries.
Additionally, the collaborations and procedures involved in dealing
with a livestock-disease outbreak provide real-world experiencesthat are directly applicable to the response needed to control anaturally occurring or deliberate human-disease outbreak. The article
beginning on p. 11 describes Livermore’s work to develop assays torapidly detect foot-and-mouth disease and differentiate it from otherdiseases with similar symptoms.
The current world situation presents enormous challenges for
U.S. national security. WMD terrorism is a potent, ever-present
danger that we can help mitigate by developing methods forcountering the threats, even as diplomats and others work toaddress the underlying issues that motivate terrorist groups.
Although technology cannot eliminate the WMD terrorism threat, it
is a critical force multiplier that increases the effectiveness of ourcountermeasures.
n Raymond J. Juzaitis is associate director for Nonproliferation, Homeland, andInternational Security.

Lawrence Livermore National Laboratory

S&TR May 2006

4

Imagers Provide Eyes toGamma-ray imagers with improved
detection capabilities help security agencies
search for illicit radioactive sources.

Lawrence Livermore National Laboratory

T

HE ability to detect gamma rays is avital tool for many areas of research.
Gamma-ray detectors allow scientists tostudy celestial phenomena and diagnose
medical diseases, and they have been used
to determine the yield in an undergroundnuclear test. Today, these detectors are an
important tool for homeland security,
helping the nation confront new security
challenges. Government agencies need
detectors for the scenarios in which aterrorist might use radioactive materials to
fashion a destructive device targetedGamma-Ray Imaging 5

S&TR May 2006

See Gamma Rays

against civilians, structures, or national
events. To better detect and prevent
terrorist attacks, the Department ofHomeland Security (DHS) is funding
projects to develop a suite of detection
systems that can search for illicit
radioactive sources in different
environments.
Livermore researchers have been
applying their expertise in radiation
detection for more than 30 years. For
example, detectors designed for use
in treaty inspections can monitor thelocation of nuclear missile warheads in anonintrusive manner. (See S&TR, October
1995, pp. 14–26.) These detectors measure
the gamma rays emitted from the isotopesof nuclear elements contained in weapons.
Over the years, Laboratory researchers
have developed a range of radiation
detection instruments, including detectors
on buoys for customs agents at U.S.
maritime ports (see S&TR, January 2004,
pp. 19–22), cargo interrogation systems(see S&TR, May 2004, pp. 12–15), andhigh-resolution handheld instruments that

Lawrence Livermore National Laboratory

emergency response personnel could use to
search for a clandestine nuclear device (seeS&TR, September 2004, pp. 4–11).
Gamma rays have the highest energy
in the electromagnetic spectrum. They
tend to go straight through matter, rather
than reflect or bend as visible light does.
Mirrors or lenses cannot be used to depict,or image, gamma rays, but their energy
can measured indirectly by observing
how photons interact with a detectormaterial. For many applications, however,researchers need to accurately determine

6 Gamma-Ray Imaging

where gamma rays originate, and doing so
requires imaging technology.
For example, many radiation detectors
have excellent energy resolution andsensitivity to sources within a range ofseveral meters. At greater distances,
however, the source can be lost ina clutter of background gamma-ray
emission from the environment, including
concrete, natural mineral deposits, andsome foods.
Detector developers want to design
instruments that quickly survey large areasat a distance and accurately distinguishillicit from background signals. However,when a detector covers a large area, thesignal from an object in the backgroundcan mimic the signature from a sourceof interest, even though the sources are

S&TR May 2006

widely separated. For example, a concretebuilding 20 meters from the detector
may register the same as an illicit source
located farther away. This similarity
makes the detection of weak signals
impossible unless the characteristics ofthe background are known in advance—
unlikely in searches for clandestineradioactive materials.
Two current projects at Lawrence
Livermore are focused on creating gammaray images without mirrors or lenses. A
multi-institutional collaboration led byLaboratory researchers has developeda large-area gamma-ray imager thatsignificantly increases detection capabilities.
Another Livermore team is designing a
portable system that relies on Compton
scattering to locate gamma-ray sources.

Accurate and Quick Detection
The technology to image gamma rays
was introduced in 1957 by Hal Anger,
an electrical engineer who worked atLawrence Berkeley National Laboratory.
The camera he developed uses gamma
radiation to image metabolic processes
within humans, allowing researchers
to observe, for example, how bloodflows and kidneys function. Biomedical
and nuclear medicine research has
resulted in improved technologies
for gamma-ray imaging. Livermore
scientists have partnered in several ofthese research efforts, such as the small
animal radionuclide imaging system.
(See S&TR, November 2004, pp. 4–11.)
Advancements in nuclear medicine arethus contributing to the development

The Livermore-designed gamma-ray imager can be placed inside a small truck. Two
coded-aperture masks (gray bars shown in the top photo) allow the instrument to image
both sides of a road. In the bottom photo, Klaus Ziock (left) and Lorenzo Fabris (right)
assemble and calibrate the masks and detectors (cylinders shown in the middle).

Lawrence Livermore National Laboratory

S&TR May 2006of gamma-ray imaging systems forhomeland security.
In 2003, Livermore’s Laboratory
Directed Research and Development(LDRD) Program funded a project todemonstrate that imaging techniques
could enhance the search capabilities
over a large area. Led by Laboratory
engineer Lorenzo Fabris, the project
team included researchers from PacificNorthwest and Oak Ridge national
laboratories, the Massachusetts Instituteof Technology, and the University ofCalifornia’s (UC’s) Space Sciences
Laboratory at Berkeley. The collaboration
demonstrated a large-area gammaray imager that can detect millicuriequantities of a cesium isotope located
85 meters away, even while the imager istraveling at 16 kilometers per hour.
With funding from DHS, the teamdeveloped the next-generation prototype
imager in 2005. The instrument, which
is approximately the size of a sofa, candetect gamma-ray energies ranging
from 50 to 3,000 kiloelectronvolts—theenergy range of interest in most national
security applications—and its sensitivity
is much greater than that of nonimaging
instruments. Fabris says, “Because we aremaking an imager that can capture anddistinguish many signals within a large
area, we can design the radiation detector
to be larger.” The prototype instrument,
which costs about $400,000, can bemounted on a small truck and used tosurveil large areas quickly.
Masks Reveal True Signals
In designing this imager, the teamadapted an imaging method originallydeveloped for high-energy astrophysics.
With this method, a coded aperture—alead mask with holes drilled in a special
pattern—is placed in front of a detector
array. As the detector picks up gamma-ray
signals, the photon energy passing throughthe mask casts shadows on the detector
elements, which the imager records. The
detector elements also measure the signal

Gamma-Ray Imaging 7

count and position. As the instrument travels
through an area, it accumulates several
shadow patterns, or “shadowgrams,” andcreates a pixel map of the radiation field of
the surveyed region.
“Each pixel represents an area in thefield of view,” says Fabris. “The pixels are
small enough that, when combined, theygenerate a detailed image of a source ofinterest. With one map of pixels, we cancover distances out to 100 meters.”
The image generated from a codedaperture process is derived from the+variation in gamma-ray signal counts
versus signal position on a detector. In an
ideal situation, only the shadow cast by
the mask would cause these variations.
However, one shortfall of coded-aperture
imagers is that gamma-ray sources
outside an instrument’s field of view
can contribute to the signal count. This
incident radiation may create shadowsthat cause the image to blur.
To compensate for the incident
radiation, the team designed an antimask
whose hole pattern is the inverse of the

+

Mask

=
Antimask

Gamma-ray source

Combining a mask with an antimask whose hole pattern is the inverse of the mask’s pattern effectively
removes background signals outside the surveyed area.

(a)

(b)

(a) In the disk configuration, the Compton imager has orthogonal strips on each side connected to apreamplifier and a digital data-acquisition system to determine the three-dimensional (3D) position foreach gamma-ray interaction. (b) In the cylindrical configuration, the outside contact is divided into pixels
that, when analyzed with a digital signal processor, provide the necessary 3D information.

Lawrence Livermore National Laboratory

8 Gamma-Ray Imaging

S&TR
S&TR April
May 2006

pattern on the mask. Fabris explains, “Themask and the antimask are exposed tothe source at the same time. Backgroundsignals outside the field of view would
be extraneous signals. By subtracting
the measurement taken with one maskfrom the inverse measurement takenwith the antimask, we are left with only
those signals that passed twice throughthe masks—once through the mask
and once through the antimask.” Eachlead mask is 2 meters long and weighs
1,000 kilograms, comprising the bulk of
the instrument’s weight.
Pacific Northwest performed modelingstudies to determine the best detector
configuration. Fabris says, “The mostpractical material for the large-area
gamma-ray detector is cesium iodide. It’s
less sensitive to potential damage induced
by temperature changes than detectormaterials such as sodium iodide, and it
is fairly inexpensive to produce in thelarge sizes necessary for this instrument.”
The cesium iodide is arranged in twoarrays, one for the mask and one forthe antimask. Researchers at the Space
Sciences Laboratory and Oak Ridge

provided navigational data and the image
reconstruction and mapping algorithms.
Physicist Klaus Ziock, who previously
worked on the Livermore team and is now
at Oak Ridge, contributed his expertise on
coded-aperture systems.
The imager provides one-dimensional
images simultaneously from both sides ofa vehicle—a design choice based on its
intended use in suburban or light-urban
areas. The team is also considering a twodimensional (2D) system that could image
both gamma rays and visible light for use
at choke points such as border crossingsand tollbooths. “Ideally,” says Fabris, “wewant to integrate several small imagers that
could track moving targets, for example,
cars changing from one lane to another.
In addition to serving homeland security,
the technology could be used in imagers
designed for medical research, by replacing
the pinhole, or collimator, with codedaperture masks.
Tracking Every Gamma Ray
Livermore’s large-area gamma-ray
detector has demonstrated that imaging
can greatly improve detection sensitivity.

Recent advances in semiconductor detector
manufacture and signal processing areallowing Livermore researchers to increase
detection sensitivity further by designing
gamma-ray imagers with omnidirectional
capability. In another LDRD project, aLivermore team, led by physicist Kai
Vetter, developed a gamma-ray imager
that operates without a collimator orcoded aperture. Instead, it relies on theprinciples of Compton scattering—theeffect that occurs when a high-energy
photon interacts with an electron in amaterial, resulting in a free electron andshifting the photon’s energy and direction.
If the gamma-ray photon still has enoughenergy after the interaction, the scattering
process is repeated until the photon is
stopped by the photoelectric effect, an
atomic process that fully absorbs photons.
(See the box below.)
Livermore’s Compton imager can also
merge images of gamma rays with visual
images. In one experiment, the team
combined a camera and a Compton imager
to demonstrate that the system can visually
identify a gamma-ray source containing an
isotope of sodium.

The Principles behind Compton Scattering
The Compton imager is named after Arthur Holly Compton, who in
1923 observed that the wavelength of high-energy photons, such as x
or gamma rays, increases when the photons interact with electrons in amaterial. This phenomenon is known as the Compton effect. According
to quantum theory, a photon can transfer part of its energy to a looselybound electron when the two collide. Because x- and gamma-ray
photons have high energy, such collisions may transfer so much energy
to an electron that it is ejected from its atom. The scattering of photons
as they pass through and interact with a material is called Compton
scattering. Compton won the Nobel Prize in physics in 1927 for his
work on the scattering of high-energy photons by electrons.
Compton scattering is the principal absorption mechanism for gamma
rays between 100 and 3,000 kiloelectronvolts. Uranium and plutonium
both naturally emit radiation within this energy range. Below this range,
photoelectric absorption is the dominant interaction type.
Compton imaging systems can be designed using various detectormaterials in different configurations. The key to optimizing imaging

efficiency is to induce multiple interactions between the gamma ray
and the detector material so the system can detect the full energyof the incident gamma ray. The gamma-ray interactions must be
separated in space sufficiently so that they can be easily distinguishedfrom each other and their positions can be accurately measured toobtain high angular resolution.
One requirement for Compton imaging is that a gamma
ray must interact with electrons at least twice—once to induce
Compton scattering and once to allow photoelectric absorption—although more than one scatter can occur. For example, a1-megaelectronvolt gamma ray averages three Compton scatteringinteractions before it is finally photoelectrically absorbed by
germanium. When an x- or gamma-ray photon is scattered orabsorbed, high-energy electrons are ejected. The subsequentdeposition of electron energy produces a large number of ionizedatoms. The ionization from Compton scattering or photoelectric
absorption is then recorded by the detectors.

Lawrence Livermore National Laboratory

S&TR May 2006

Because the imager does not require
gamma rays to enter the detector througha mask, it can identify radiation fromall directions. Vetter says, “Compton
scattering occurs whenever photons
in the energy range of about 150 to
5,000 kiloelectronvolts are present. Our
imager takes advantage of this effect.
It calculates the angle of the incident
gamma ray by measuring the positions andenergies of the first two interactions withthe detector.”
Imaging systems based on Compton
scattering were proposed 30 years ago
for astrophysics and nuclear medicine
applications. However, technology
to improve sensitivity and reduce thesystem’s size became available onlyin the past 10 years. Until recently, aCompton imager could not differentiate
photon interactions in the scattering
process because it could not determine
the three-dimensional (3D) position of a
gamma ray with sufficient fidelity. One
technology breakthrough has been the 2D,
segmented semiconductor detectors, which
use materials such as germanium andsilicon to improve energy resolution. The
digital signal-processing equipment that is
now available provides the necessary 3D
position capability.
Designing the Optimal Imager
With funding from DHS, theLivermore team is developing a compact,
portable Compton imager that will detect

Gamma-Ray Imaging 9

and identify sources between 120 to
3,000 kiloelectronvolts and provide
unsurpassed sensitivity. The team hasplanned three generations of the
instrument so design changes can beevaluated at each stage. Monte Carlosimulations showed that the highest
sensitivity could be achieved by
combining high-energy and positionresolution semiconductor detectors tomaximize efficiency. Vetter explains,“For the imager to create an image basedon data from the Compton effect,
incoming gamma rays must interact withthe detector at least twice—once toscatter the photon energy and again toabsorb the photon. A semiconductor witha low atomic number, such as silicon,
induces scattering very well, while one
with a high atomic number, such as
germanium, is effective at absorbing
gamma rays.”
Livermore’s Compton imager uses
four layers of detectors: two silicon
crystals and two germanium crystals,
together measuring about 8 by 8 by
6 cubic centimeters. The detectors are
manufactured at Lawrence Berkeley
National Laboratory and the ResearchCentre Jülich in Germany. With its 3D
position capability and combined detectormaterials, the system can track gammaray interactions to a resolution of
0.5 millimeter.
A detection system based on tracking
gamma rays provides unprecedented

sensitivity not only for Compton imaging
but also for nuclear spectroscopy, which
is used to identify nuclear materials. “The
Compton imager can distinguish gamma
rays that deposit only partial energy inthe detector from those that are fully
absorbed,” says Vetter, “so backgroundsignals can be more easily eliminated.”
The system applies the Compton scatteringformula to the positions of the first andsecond interactions to deduce the angle ofthe incident gamma ray to within a certain
cone-shaped area.
According to Vetter, the ultimate
gamma-ray detector would be one that can
precisely determine the path of an electron
after a gamma ray initially impacts thedetector. Such a system would require aresolution of better than 10 micrometers.
He adds, “If we could measure theelectron’s path, we could determine thedirection of the incident gamma ray
unambiguously, rather than within the areaof a cone.”
The high-resolution silicon andgermanium detectors must remain at low
temperatures to operate, so UC’s Space
Sciences Laboratory built cryostats
cooled by liquid nitrogen for the Compton
imager. The second-generation instrument

22Na source

A Compton imager combined with a camera produced this image, which pinpoints the location of the radioactive source—anisotope of sodium (22Na).

Lawrence Livermore National Laboratory

10 Gamma-Ray Imaging

S&TR May 2006

uses two cryostats—one for the twosilicon detectors and one for the two
germanium detectors. The third and final
Compton imaging system, which the teamplans to complete in 2008, will have one
cryostat for all four detectors.

such as silicon and cadmium–zinc–telluride
so the detector could operate at room
temperature. The overall effort will definea Compton imaging module that is best
suited for homeland security. “Once wecomplete the design of the third-generation
Compton imager,” says Vetter, “scaling tolarger systems would just be a matter ofassembling multiple modules.”The team is using measurements takenwith the first-generation system to calibratesuch parameters as energy, depth, andposition interpolation and is assembling
the second-generation instrument.
Livermore’s imager is the most efficientand sensitive, fully operational Compton
imaging system that has been built. The
only other deployed system is the National
Aeronautics and Space Administration’s
COMPTEL telescope. COMPTEL, built
in 1989 to study gamma-ray sources suchas pulsars and supernova remnants, uses

Future Design Possibilities
One drawback to using liquid nitrogenis that it requires frequent refills and large
dewars, which complicate the instrument’s
operational capabilities. The team will
explore the use of mechanical cooling for
future systems. With mechanical cooling,
the imagers could be used remotely for awider range of applications. The Laboratory
has developed portable radiation detectors,
such as Cryofree/25 and RadScout (licensed
by ORTEC under the name Detective®),which use germanium detectors that aremechanically cooled. The team will also
research the possibility of using materials(a)large-volume sodium iodide detectors,
which provide limited sensitivity.
Ultimately, Livermore’s Compton
imager will provide a spatial resolutionof about 3 by 3 square meters or less at a
distance of 100 meters, with a 500-meterdiameter field of view. Weighing less than
460 kilograms, this portable system willallow security officials to conduct wide-areasurveillance from the ground or in the air.
The goal for researchers designingradiation detection instruments is tomaximize an instrument’s sensitivity indetecting and identifying gamma rays from
illicit sources in the midst of radiationfrom other sources. Livermore’s largearea gamma-ray imager and its Compton
imager add two powerful instruments to
the DHS arsenal of equipment designed tohelp keep the nation safe.
—Gabriele Rennie

Key Words: coded aperture, Compton imager,(b)

gamma-ray imager, large-area gamma-ray
imager, radiation detector.

SourceFor further information on the large-area
gamma-ray imager contact Lorenzo Fabris(925) 423-1258 (fabris1@llnl.gov); on theCompton imager contact Kai Vetter(925) 423-8663 (vetter4@llnl.gov).

Incoming gamma rays interact with the detector through Compton scattering. (a) The energies andpositions of the first two interactions define a cone of incident angles. (b) The cones can be projected ontoa plane or sphere (one circle per gamma-ray event) to produce a two-dimensional image of the source.

Lawrence Livermore National Laboratory

S&TR May 2006

11

Protecting the
Nation’s Livestock
A Livermore-developed
assay rapidly detects
foot-and-mouth disease
and look-alike livestock
diseases.

S

INCE 2001, the U.S. has improved
its ability to prevent and respondto terrorist attacks, but the nation’s
agricultural infrastructure could bevulnerable. Although the nation has neverexperienced an attack targeted at
agriculture, such an incident, calledagroterrorism, could have devastatingconsequences.
America’s sheep, cows, pigs, andchickens are particularly vulnerable todiseases that are endemic in other partsof the world but have not appeared inthis country for many decades. If allowed
to gain a foothold in the U.S., a foreign
animal disease (FAD) could spread

Lawrence Livermore National Laboratory

rapidly and be difficult to contain. It could
thus severely affect millions of animals
and the national economy.
Agroterrorism poses a threat because
U.S. farms and feedlots are rarely
guarded and widely dispersed acrossthe country. Should an infection occur,
normal livestock and personnel movement,
including interactions with other herds,
could lead to widespread disseminationof a disease before it is diagnosed. In
addition, the clinical signs of FADs closely
mimic many diseases that regularly occur
in the nation. Homeland security experts
are thus concerned that farmers, local
veterinarians, and others will not be able

S&TR May 2006 13

12 Agricultural Security

to recognize and report a FAD before it
spreads out of control.
A great concern centers on foot-andmouth disease (FMD), a highly contagious
livestock disease that has not been seenin the U.S. since 1929. During the past
decade, however, outbreaks of FMD in
the United Kingdom, Asia, and SouthAmerica have heightened awareness ofthe potential danger. The U.S. clearlyneeds the capability to identify FMD earlyand provide a rapid, large-scale response,
including the diagnostic support forcontrolling the outbreak.
To address this need, a Livermore
team, with support from the Departmentof Homeland Security (DHS) andthe U.S. Department of Agriculture(USDA), has developed a rapid assay thatsimultaneously detects FMD and otherforeign and endemic diseases with similar
symptoms. The assay is being evaluatedby 13 laboratories within the National
Animal Health Laboratory Network(NAHLN) and by the National Veterinary
Services Laboratory (NVSL) at Plum

Island, New York. Once validated andaccepted by the USDA, the Livermore
assay will allow laboratories to quickly
diagnose FMD and diseases that mimic
its symptoms.
“Our goal is to provide federal andstate stakeholders with significantly
improved detection, identification, andresponse capabilities for foreign andendemic agricultural diseases,” says
Ray Lenhoff, a molecular virologist in
Livermore’s Biosciences Directorate. The
FMD assay development team, which isled by Lenhoff, also includes analyticalchemist Ben Hindson and veterinarian
Pam Hullinger of the Laboratory’s Physics
and Advanced Technologies Directorate;
toxicological immunologist Max
Rasmussen, also in Biosciences; and other
Livermore experts in homeland security,
pathogens, and advanced detection
methods. The team is part of the Bioassays
and Signatures Program, which develops
and implements methods to diagnose
agents of bioterrorism. This program
operates within the Laboratory’s Chemical

Foot-and-mouthdisease (FMD) is
endemic in many
parts of the world.
In this map, brown
indicates countries
that reported FMD
occurrences in 2004,
green shows thosewith no reported
occurrences, andpurple denotes
those for which data
are incomplete orunavailable. (Datafrom the World
Organisation for
Animal Health.)

Lawrence Livermore National Laboratory

and Biological National Security Program,
whose mission is to improve the nation’s
capabilities to prevent, prepare for, detect,and respond to terrorist use of chemical or
biowarfare agents.
On the Front Lines
Lawrence Livermore has been on thefront lines of the nation’s biodefense effort
since the mid-1990s. Laboratory-developed
signatures—specific regions of DNA or
RNA that uniquely identify a pathogen—have been used for homeland defense since2001. For example, Livermore assays
are incorporated in DHS environmental
monitoring systems such as BioWatch.
The Laboratory has teamed with stateand federal departments of agriculturein the past. In 2002, Livermore, theCalifornia Animal Health and Food Safety
Laboratory at the University of California
at Davis, and USDA scientists worked
together to contain a natural outbreak insouthern California of exotic Newcastle
disease, an extremely contagious andfatal viral disease affecting all species of

13

S&TR May 2006

birds. At the time of the outbreak, existing
assays required 6 to 12 days to identify thedisease. A key signature isolated by a teamof Livermore researchers allows the virus
to be identified within 4 hours.
In February 2001, during the heightof the FMD outbreak in the United
Kingdom, a Livermore team analyzed
the virus’s tiny genome of 8,000 RNA
bases. The team determined that only one
region of the FMD genome can support asignature-based assay. (See S&TR, April
2004, pp. 4–9.)
FMD: An Enormous Threat
FMD is an extremely contagious viraldisease of pigs and domesticated and wild
ruminants such as cattle, sheep, goats, deer,
and water buffalo. Animals afflicted with
FMD usually do not die, but the disease isdebilitating and animals do not recover. An
infected animal begins to drool, and virusfilled blisters develop in its mouth and at
the junction where skin connects to thehoof wall, making it painful for the animal
to walk. In addition, the virus attacks the
mammary glands, leading to reduced milk
production. The vaccine for FMD only
reduces the severity of symptoms; it does
not prevent infection or completely stoptransmission of the disease. Humans do
not get sick, but they can act as carriersof the virus.
FMD is endemic in many nations andremains the most important barrier toworld trade in live animals and animal
products. In 2000 and 2001, a Pan-Asianstrain caused outbreaks in Korea, Japan,
Russia, Mongolia, South Africa, the United
Kingdom, France, and the Netherlands.
Economic losses from an agroterrorist
incident, especially one caused by anextremely contagious disease such as
FMD, could be enormous. (See the box on
p. 16.) The potential costs include testing
thousands (perhaps millions) of animals,
destroying and disposing of infectedanimals, quarantining uninfected premises,and disinfecting and repopulating farms. In
addition, such an outbreak would jeopardize

Agricultural Security 13

the business continuity of the domestic
livestock industries, including many jobs
in agriculture, food processing andproduction, domestic and export markets.
“Early detection is critical to limiting thescope of an outbreak,” says Hullinger. One
estimate is that the U.S. would lose up to$3 million in direct costs for every hour’sdelay in diagnosing FMD.
Currently, a veterinarian or farmer
who suspects a case of FMD contacts the
USDA or a state agricultural department,
which sends a veterinarian who has been

trained by the USDA to diagnose FADs.
This diagnostician questions the farmer,
examines the animals, and if warranted,
sends specimens to the Plum Island
laboratory for definitive analysis.
Plum Island averages about 300 FAD
investigations a year. Many of the tests
it uses, such as those to isolate the FMD
virus, are time-consuming and laboratory
intensive. During an FMD outbreak,the demand for analytic services would
almost certainly far exceed the capacity
at NVSL. “In such cases, the NAHLN

NVSL

(a)

Livermore’s assay for foot-andmouth disease is being evaluatedby 13 National Animal Health
Laboratory Network laboratories(blue stars) and the National
Veterinary Services Laboratory(NVSL) at Plum Island, New York
(red star). Without a fast andaccurate assay, an outbreak could
rapidly overwhelm NVSL’s diagnostic
capabilities.

(b)

When this shorthorn heifer in the United Kingdom became afflicted with foot-and-mouth disease,(a) she began to drool, and (b) virus-filled blisters developed in her mouth and at the junction where
skin connects with the hoof walls.

Lawrence Livermore National Laboratory

14 Agricultural Security

S&TR May 2006

labs could provide regional and scalable
diagnostic support under the directionof the USDA,” says Hindson. “Theavailability of a validated, rapid testfor detecting and identifying FMD anddifferentiating it from other diseases that
present similar clinical signs would beinvaluable.”
A Tool for Homeland Security
The Livermore animal assay
research, which began in early 2005, isfunded by DHS’s Agricultural Assays
and Agricultural Security Domestic
Demonstration and Application Program.
DHS is charged with coordinating U.S.
efforts to protect against agroterrorism,
while the USDA is responsible forresponding to major outbreaks of disease
involving agriculture.
Within the USDA, the Animal and
Plant Health Inspection Service (APHIS)
is responsible for protecting animals
and plants from agricultural pests anddiseases, including the introduction of
FADs, and for coordinating the responseto an agricultural disease outbreak. NVSL,
which is part of APHIS, coordinates thestate and university veterinary diagnostic
laboratories belonging to NAHLN.
In developing signatures for bacterial
and viral pathogens, Livermore scientists
use the KPATH technique, which was(a)developed by Laboratory computerscientist Tom Slezak. KPATH compares
the genome of a target pathogen to theexisting library of microbial genomes,
searching for areas that are unique to thetarget organism. The DNA or RNA regions
selected are present in every strain of thepathogen and absent in all other organisms
sequenced to date. The assay development
team also takes advantage of advances in
rapid polymerase chain reaction (PCR).
This technique makes multiple copies ofa particular RNA or DNA segment from asample so that enough exists to be detected
and identified.
Multiplexing Speeds the Process“Traditionally, the USDA labs lookfor one disease at a time,” says Lenhoff.
Separate tests are made for each disease,using a variety of laboratory techniques. If
the reading is negative for FMD, the test
does not identify the disease agent that ispresent. To speed diagnosis, the Livermore
team developed a multiplexed assay—one
that simultaneously tests a single sample
for all similar diseases, both endemic andforeign. Thus, a negative reading for FMD
will likely be accompanied by a positive
response identifying a similar disease.
“With our technology, laboratories will
be able to screen for many diseases at
one time,” says Lenhoff. “In this way, our(b)To test theLaboratory’s
multiplexed assay,(a) analytical chemist
Ben Hindson
collected samples
at a dairy farm near
Davis, California, and(b) veterinarian Pam
Hullinger collected
them at the animal
science facilitiesof the University ofCalifornia at Davis.

Lawrence Livermore National Laboratory

assay provides more confidence in thenegative FMD diagnosis.”
Multiplexing reduces labor andthe costs of reagents. Compared withtraditional diagnostic tests, the Livermore
assay significantly increases speed andconvenience of testing. The assay screensfor both DNA and RNA viruses at thesame time and detects the seven major
subtypes of FMD. The test looks for
17 target signatures, including 2 that detect
all 7 serotypes, or strains, of FMD. In all,the 17 signatures represent 7 diseases.
Three of these are the foreign diseases
FMD, vesicular exanthema of swine,and swine vesicular disease. Four are theendemic diseases bovine viral diarrhea,
bluetongue, bovine herpes-1 (also known
as infectious bovine rhinotracheitis), andbovine parapox virus complex (bovine
papular stomatitis, contagious ecthyma,
and pseudocowpox). The panel also
incorporates five internal controls toincrease confidence in the results.
The assay uses multiplex analysis
technology developed by Bio-Rad
Laboratories, a bead-based liquid array
technology by Luminex Corporation, andcomponents supplied by other companies.
The assay first extracts nucleic acids fromthe sample and purifies them. RNA fromRNA viruses is then converted to DNA,and all DNA is amplified.

S&TR May 2006

Agricultural Security 15

Luminex polystyrene beads areindividually tagged with a sequence of
nucleotides that complement the signaturesof interest. The beads are embedded with
precise ratios of two fluorescent dyes,
each with a unique spectral address.
Each microbead is then interrogated bya flow cytometer. A laser excites thedye molecules inside a microbead toindicate the kind of microbead—that is,
the pathogen—it is screening. Anothertype of laser excites fluorescently labeledmolecules bound to each microbead’s
surface during the assay, which indicate
how much of the pathogen is present
in the sample. The flow cytometer canread up to 400 beads per second andsimultaneously test for 100 different
pathogens in a single sample.

says Hindson, who oversaw training andequipment installation.
During the follow-on evaluation thisyear, NAHLN laboratories will analyze
clinical diagnostic samples they receivefrom the field using their standard assays
and Livermore’s multiplexed assay. Results

Extensive Performance Evaluation
The Livermore assay is undergoing
thorough testing, which consists of an
NAHLN interlaboratory comparison andfollow-on evaluation. During October andNovember 2005, 13 NAHLN laboratories
and NVSL were equipped with thenecessary tools for performing the assay,
including a specialized flow cytometer (BioRad Bio-Plex Workstation), small disposable
items such pipette tips and plastic ware, andreagents. The equipment became the propertyof the participating laboratories. Livermore
personnel worked with Bio-Rad field service
engineers and application specialists to
conduct training at each NAHLN laboratory.
The Livermore training team, which included
Rasmussen, Christina Sanders, Jaqui Lee,James Thissen, and Celena Carrillo, gave
instructions on operating the workstation,
performing the assays, and analyzing andinterpreting data.
Each laboratory then analyzed nearly
200 clinical samples “spiked” with known
domestic viruses that mimic FMD. The
samples were sent from Livermore in aviral transport medium that preserves thevirus. “All of the laboratories ran the sametests on the new equipment using ourassays and reported the results back to us,”

DNA

from the two analyses will then be compared.
“The labs have reference tests that are notnecessarily based on PCR,” says Hindson,
who is also coordinating the interlaboratorycomparison. “The tests could be basedon immunology, fluorescent staining, orscanning electron microscopy. Comparing

RNA
DNA
Bovine viraldiarrhea (1)Bovine herpes-1 (2)Endemic animal diseases

Bovine parapox
virus complex (3)RNA
Foreign animal diseases
Bluetongue (2)RNA

Swine vesiculardisease (4)RNA
RNA
Vesicular exanthemaof swine (3)Foot-and-mouthdisease (2)The Livermore assay tests for three foreign animal diseases (green border) and four endemic diseases(blue border). Electron micrographs of each virus are shown. Numbers in parentheses denote thenumber of signatures the assay uses to detect each disease.

Lawrence Livermore National Laboratory

16 Agricultural Security

S&TR May 2006

results from the two methods will help
us characterize the performance of ourassay and establish an even greater level ofconfidence in its results. It also allows us toevaluate the assay’s performance in the handsof the end users.”

A scientist at Indiana Animal Disease Diagnostic
Laboratory at Purdue University learns to use theLivermore multiplexed assay.

High Throughput Using Robots
The team has also developed a highthroughput, semi-automated systemthat uses two robotic workstations.
Together, the workstations can analyze
1,000 samples in a 10-hour shift with
two laboratory technicians. “If there
is a disease outbreak, we need a highthroughput capability to process a large
number of samples,” says Lenhoff.
Two NAHLN laboratories are testing therobotic system in a seven-day exercise thisspring to simulate an outbreak scenario.

The demonstrations include field sample
collection and identification, sample
receipt, sample processing, data analysis,
and a mechanism for reporting results.
The high-throughput system integrates
the USDA’s electronic sample identification
technology with the laboratories’
information management systems. “Wewant to demonstrate to state and federal
authorities and laboratory personnel an
integrated system that can function end
to end during the response to a FAD
outbreak, from collecting and processing
samples through reporting the results,”
Hindson says. The portable system can be
deployed to any location. The team is also
developing a laboratory mounted inside atruck, which could provide mobile regional
diagnostic support in the early phases of an
outbreak response.

Calculating the Cost of Foot-and-Mouth Disease
The foot-and-mouth disease (FMD) virus consists of a single
strand of RNA packed inside a tough protein coat. The hardy virus
can live 28 days in cool soil and up to 180 days in a slurry of cow
dung. It can be spread directly from animal to animal, or it can betransported indirectly by a person or vehicle traveling from one farmto another—for example, with mud containing the virus caked onboots or tires. Livermore’s Pam Hullinger, a foreign animal diseasediagnostician and veterinary epidemiologist, notes that FMD is socontagious, an animal can become infected after contact with as few
as 10 virus particles.
Although the U.S. has not had an FMD outbreak since 1929, it isendemic in many parts of the world. In 2000 and 2001, a Pan-Asianstrain caused outbreaks in Korea, Japan, Russia, Mongolia, South
Africa, the United Kingdom, France, and the Netherlands. Economic
losses from an agroterrorist incident, especially one caused by anextremely contagious disease such as FMD, could be enormous.
The 2001 outbreak of FMD in the United Kingdom is estimatedto have caused about $5 billion in losses to the food and agriculture
sector and even greater losses in tourism. Up to 10-million sheep,
pigs, and cows were slaughtered, and for several months, the nation
was banned from exporting livestock and animal products that could
potentially transmit the virus.
Hullinger answered the call for expert veterinarians during
the 2001 epidemic and saw many animals slaughtered. “There isno substitute for first-hand experience in gaining respect for thedevastation that a foreign animal disease can inflict on a nation,”

she says. Many veterinarians were asked to decide whether a flock or
herd was infected based solely on clinical signs observed during an
initial visit without the aid of testing or laboratory support.
“We now know that many uninfected animals were destroyed
because we lacked rapid diagnostics for FMD,” says Hullinger. “I
saw thousands of animals killed in Britain, and thousands of farmers
lost their livelihoods. I don’t want to see that happen here.”

Up to 10-million sheep, pigs, and cows were slaughtered during the 2001
outbreak of foot-and-mouth disease in the United Kingdom.

Lawrence Livermore National Laboratory

S&TR May 2006(a)

Agricultural Security 17

(b)

(c)

(a) A specialized flow cytometer, the Bio-Rad Bio-Plex Workstation, analyzes DNA using bead-based liquid array technology by Luminex Corporation. (b, c) To
speed diagnosis during a disease outbreak, Livermore researchers designed robotic equipment to replace most manual operations.

Looking Ahead
Later this year, APHIS will examine
the results of this extensive evaluation anddetermine whether the multiplexed assay
will be permanently adopted nationwide.
In the meantime, the Livermore teammeets regularly with USDA officials tobetter understand their needs. Although
the assay was developed with a focus onagroterrorism, it could also help federal
and state agencies perform routine
agricultural disease surveillance. If a FAD
were suspected based on a surveillance
screening, then a disease investigation
could be initiated quickly and samples sent
to Plum Island to confirm the diagnosis.
Because the Luminex bead technology
can screen for 100 different signatures at
a time, the Livermore assay has room to
expand. The team plans to add diseases tothe original assay and develop new assays.
One possibility is a multiplexed panel
focused on diagnosing bovine fetal abortion,
which can be caused by both viruses andbacteria. “We also want to develop speciesspecific assays for pigs, cows, and sheep,”says Lenhoff. Plans are already under way
to develop assays for poultry.
Livermore chemist Julie Perkins is
working with the National Center for

Foreign Animal Diseases in Canada todevelop multiplexed assays that would
determine both the type of FMD andwhether animals vaccinated for FMD
have also been infected by the virus.
“Having a diagnostic tool available
to rapidly and reliably determine if
vaccinated animals have subsequently
become infected is critical to the decisionmaking process involved in FMD vaccine
use in the face of an outbreak,” says
Hullinger.
Hullinger is also part of a Livermore
effort to model FMD and other FADs soexperts can evaluate different response
scenarios to an outbreak. “We’retrying to give decision makers a better
understanding of the effects of various
disease control options,” she says.
“The labs are really excited,” says
Hindson. “They can see a lot of value inthe technology. For many applications,
our multiplex technology can significantly
improve their diagnostic capabilities.”
The Livermore team is just beginningto develop improved detection methods
for animal diseases. National security andAmerica’s agricultural industries are theclear winners.
—Arnie Heller

Lawrence Livermore National Laboratory

Key Words: agroterrorism, bioassay, footand-mouth disease (FMD), foreign animal
disease (FAD), homeland security, National
Animal Health Laboratory Network (NAHLN),
National Veterinary Services Laboratory(NVSL), U.S. Department of Agriculture(USDA).

For further information contact Ray Lenhoff(925) 424-4034 (lenhoff2@llnl.gov).

Research Highlights

S&TR May 2006

Measures for
Measures0.6
Calculated emissivity

18

D

URING many physics-related experiments—especially those thatinvolve the extreme pressures and temperatures of high-explosive
detonations—scientists and engineers need to directly measure thetemperature of a material’s surface and, at the same time, its density
or pressure. Investigators commonly use the infrared radiation
emitted from a material’s surface to infer its temperature. However,
the accuracy of this approach is limited because the emitted radiation
depends not only on a material’s surface temperature but also on aproperty known as emissivity.
Emissivity is the ratio of the power radiated by a perfect emitter,called a blackbody, to the power radiated by the material inquestion. A blackbody is assigned an emissivity value of 1, and amaterial that does not radiate at all has an emissivity of 0. The
values for all other materials fall between 0 and 1.
The emissivity of a radiating material depends on the type ofmaterial being studied, its surface conditions, and such properties as
its roughness and color. A black surface radiates more than a shiny
surface at the same temperature. Highly reflective materials havevery low emissivities. For example, aluminum foil has an emissivityof about 0.03, one-thirtieth that of a blackbody.
Previous methods that use emissivity to determine
temperature do not have the accuracy needed for many of today’s
applications. Rather than measure emissivity directly for eachexperiment, some researchers use data collected from pastexperiments in calculations that convert emitted power totemperature. However, this technique can result in errors ranging
from 10 to 20 percent.
Livermore scientists need more accurate surface temperature
measurements for their stockpile stewardship work. Such data help
them better understand material properties at the microstructurallevel and how these properties change during a high-explosives
shock. A highly accurate thermometry method for extreme
temperatures will allow researchers to refine calculations of amaterial’s equation of state.
Reducing the Error
To improve the accuracy of thermometry readings, Livermore
physicists Peter Poulsen and Stanley Ault use the fact thatemissivity and reflectivity must add up to one. The method they
developed incorporates nearly simultaneous measurements ofemitted and reflected radiation. With these measurements, they cancompute the surface temperature and determine how emissivity
varies with wavelength. For example, they can measure a metal’s

0.5
0.4
0.3
0.2
0.1
0

0

1.5

2.0
2.5
3.0
3.5
Wavelength, micrometers

4.0

4.5

The emissivity of a surface as a function of wavelength must be determinedto achieve highly precise surface temperature measurements.

surface temperature with an error of less than 1 percent. “Wedeveloped this method to measure the temperature of shockedsurfaces,” says Poulsen. “Our readings are completed very
quickly—in less than a millionth of a second.”
Conventional infrared measurements do not take into account thatemissivity is normally a function of the wavelength of the emitted
radiation. “Characterizing the emissivity with a single number
independent of the wavelength is not sufficient,” says Poulsen. Most
metals have an emissivity that decreases significantly withincreasing wavelength, so that more emission takes place at shorter
wavelengths. Scientists may, thus, interpret the observed radiation
spectrum as resulting from a higher temperature.
Putting Theory into Practice
The Livermore approach uses a multichannel spectrometer andan external light source to measure, almost simultaneously, theemitted and reflected powers over a range of wavelengths. The
experimental apparatus developed by Poulsen and Ault to test themethod incorporates a pulse-heated molybdenum foil. Car batteries
provide the current for heating the foil. An inert gas replaces the air
within the device to prevent oxidation of the foil. A window that istransparent to light in the infrared range of wavelengths provides
optical access to the foil for the detectors that measure the emitted
and reflected radiation.
In the experiments, batteries heat the metal foil until it reaches thedesired temperature, as determined by a thermocouple connected to
the foil’s surface. Samples of the radiation (light) emitted by theheated foil pass through six fiber-optic cables and are recorded for
200 nanoseconds by the detectors of a multichannel spectrometer.
An external pulse of full-spectrum light is then directed from the endof a fiber-optic cable to the metal’s surface. The spectrometer’s six
detectors also record this reflected light and provide the results as thesum of emitted and reflected light. The entire process takes only a
few hundred nanoseconds. Each channel measures the signal over a
known range of wavelengths. The external light source is located atLawrence Livermore National Laboratory

S&TR May 2006

the same point in space as the detectors and illuminates the same
area viewed by the detectors.
One detector serves as a reference channel, so that data and thegoverning relations from the remaining channels can be normalized
to those from the reference channel. This process removes any
dependency on the absolute magnitudes of the signals. Then foreach nonreference channel, the normalized emitted-signal data are
combined with the reflected-signal data to generate a curve that
determines temperature as a function of assumed emissivity in thereference channel.
In an ideal experiment, the curves would intersect at one point,
giving the temperature of the metal’s surface as well as emissivity
in the reference channel. However, because slight inaccuracies
occur in setting up and performing experiments, the curvesintersect at different points within a small area of deviation.
Poulsen and Ault use this area of deviation to estimate thetemperature and the uncertainty in the measurement. To validate
their method, they compared the results obtained with thetemperature recorded by the thermocouple. Poulsen notes,
however, that the spectrum method can be used alone inapplications that require noncontact measurement techniques.
A Boon for Process Control
The accuracy of the spectrum method will allow Livermore
physicists to acquire high-fidelity equation-of-state data on weapons

Fiber-optic
bundleLithium fluoride
window
Pulse-heatedmolybdenum foil
Electrical cables
for foil heat current
Chamber filledwith inert gas

Absolute emissivity for normalization channel

High-Precision Thermometry 19

1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
800

1,000
1,200
Temperature, kelvins

1,400

The intersectionof the four curves
determines
the measured
temperature and its
error. In this example,
the temperature is
1,113 ± 1.8 kelvins.
Emissivity in thereference channel
is 0.490 ± 0.003.
The thermocouple
recording provided
a temperature of
1,110.4 kelvins.

materials undergoing high-explosives shocks. More applications
abound in both research and industry. “This method will be beneficial
in the field of process control,” says Poulsen. “In the fabrication ofsteel, aluminum, plastics, or even silicon wafers, processes always
depend on temperature.” In fact, because materials can change
phase as temperature changes, temperature often must be tracked
dynamically during fabrication processes.
The ability to constantly monitor temperatures in jet-turbine
engines is also of great interest to the aircraft industry. High-precision
dynamic thermometry can help determine the optimum runningtemperature for jet engines. These high-performance engines runvery hot—in fact, they are more efficient at higher temperatures.
However, temperatures that are too extreme may cause safety andreliability problems. According to Poulsen, the spectrum method
could be used to develop systems that constantly monitor andcontrol the temperature of jet engines.
Because of its accuracy, the spectrum method can also be applied
to determine when to replace parts. “Rather than routinely replacing
parts when an average threshold for service has been reached,considerable resources could be saved by monitoring components andreplacing them when their useful life is reaching the end,” says
Poulsen. “We developed this instrumentation for the Laboratory’s
shock experiments, but it can be useful across many fields, fromdefense to industry, because of its ability to improve safety andresource management.”—Maurina S. Sherman
Key Words: emissivity, high-precision thermometry, infrared spectrometry,
relative reflectivity method, spectrum method.

To accurately determine the temperature on a metal’s surface during a highexplosives shock, Livermore physicists developed an experimental device tomeasure the emitted and reflected radiation. Fiber-optic cables connected todetectors of a multichannel spectrometer record the data.

For further information contact Peter Poulsen (925) 422-6692(poulsen1@llnl.gov) or Stan Ault (925) 423-4624 (ault3@llnl.gov).

Lawrence Livermore National Laboratory

20

Research Highlights

S&TR May 2006

Looping through theLamb ShiftS

OMETIMES in science, a small measurement can have big
ramifications. For a team of Livermore scientists, such was
the case when they measured a small shift in the spectrum of
extremely ionized atoms of uranium.
The measurement involves the Lamb shift, a subtle change
in the energy of an electron orbiting an atom’s nucleus. The
precision of the Livermore result was 10 times greater thanthat of existing measurements, making it the best measurement
to date of a complicated correction to the simplest quantum
description of how atoms behave. The measurement introduces
a new realm in the search for deviations between the theoryof quantum electrodynamics (QED), which is an extension ofquantum mechanics, and the real world. Such deviations, if
discovered, would have far-reaching consequences, indicating that
QED is not a fundamental theory of nature.

A Test of QED
The Lamb shift has nothing to do with sheep and everything
to do with quantum theory, which deals with the world of thevery small—atoms, electrons, neutrons, photons, and so on.
According to quantum theory, energy is emitted and absorbed
in tiny, discrete amounts, or quanta. When an electron changes
from one energy level to another, it emits or absorbs a photon oflight. This light can be observed through spectroscopy, and its
frequency is directly proportional to the difference between thetwo energy levels.
Most of the Lamb shift can be explained by two basic QED
phenomena: self-energy and polarized vacuum. The self-energy
effect occurs when electrons subjected to electric and magnetic
fields spontaneously and randomly emit photons and, within an
incredibly short time span, reabsorb them. Through a techniquecalled renormalization, QED theory provides a means todetermine the energy of this electron self-interaction as asmall, finite correction to the energy that binds the electron
to the nucleus.
The polarized vacuum effect involves pairs of “virtual
particles,” one with a positive charge and one with a negative
charge. Such pairs are created spontaneously from a vacuum inthe presence of a positive or negative field and then are polarized,
or aligned, by the field’s charge. For example, say that a virtualelectron–positron pair occurs in the presence of a positively
charged ion. The virtual electrons, drawn to the positive charge,

SuperEBIT, Livermore’s electron-beam ion trap, can create and trap highly
charged ions.

tend to align closer to the ion’s nucleus than virtual positrons,
which are repelled by the positive charge. Thus, an electron thatorbits an ion travels with fickle companions—swarms of virtualphotons and electron–positron pairs—randomly winking in and outof existence.
The Lamb shift is a tiny difference in the energy of an ion’s
electron between two quantum states that are otherwise identical
except for the shape of the electron’s orbit around the nucleus.
Because of this dissimilarity in the electron’s orbit in the twostates, the electron interacts slightly differently with virtual
particles—photons, positrons, and electrons—that appear anddisappear in quantum fluctuations. The resulting energy difference,called the Lamb shift, can be measured when the electron jumps
from one energy level to another.
Theory also predicts that even smaller, higher-order contributions
to the Lamb shift exist. For the second-order Lamb shift, virtual

Lawrence Livermore National Laboratory

S&TR May 2006

Two-Loop Lamb Shift 21

photons and electron–positron pairs interact with themselves andeach other to generate two loops. (See the figure below.)“For instance,” says Livermore physicist Peter Beiersdorfer,“a photon could be emitted, and, before it is reabsorbed, anotherphoton could be emitted or an electron–positron pair created. In aanother instance, an electron–positron pair could be created, andthe virtual electron from that pair could emit a photon, which isquickly absorbed.” In all, 10 second-order interactions are possible.
(See the background image on p. 22.) Measuring the higher-ordercorrection to the spectrum with sufficient precision would validate
the model.
Uranium Ion Takes the Field
Previous experiments measured QED effects on hydrogen,which has a single electron but a very weak field. However,Beiersdorfer’s team, which was funded by the Laboratory Directed
Research and Development Program, decided to study the uranium
atom, which has 92 electrons. “The stronger the electric andmagnetic fields experienced by the electron, the stronger or more
visible the interactions should be,” says Beiersdorfer. “The electricfield of a uranium ion is a million times stronger than that ofhydrogen, which makes QED effects that much more pronounced.”
Another advantage is that scientists know more about thesize of the uranium atom’s nucleus than they do about that of thehydrogen atom. Knowing the size of the nucleus is important inmaking a precise measurement, particularly when it is extended
to many decimal places. A problem with hydrogen is the highdegree of uncertainty in the size of its nucleus, the proton. Three
measurements for the proton’s radius are often quoted, but theerror bars of the three do not overlap, thus forming a comparatively

(a)

(b)

large band of uncertainty. “The precision in QED measurementsof hydrogen has hit a wall,” says Beiersdorfer, “because themeasurements now outstrip the precision with which the hydrogen
nucleus is known.”
To measure highly charged uranium, the Livermore team used
SuperEBIT, an electron-beam ion trap developed by Laboratory
scientists. (See S&TR, November 2000, pp. 19–21; June 2002,
pp. 20–24.) SuperEBIT uses a tightly focused and energy-tunable
electron beam to create and trap highly charged ions. This beam,
which has a current density of up to 5,000 amperes per squarecentimeter, passes through a series of three drift tubes to create
ions of the element being studied. These positively charged ionsare confined radially because they are attracted to the center of theelectron beam. Voltages applied at each end of the drift-tube series
trap the ions axially. When the beam’s electrons collide with an ion,they strip electrons off the ion until the energy required to remove
the next electron is higher than the beam’s energy. Once created, thehighly charged ions are held while the scientists record the spectra.
SuperEBIT is the only ion source that can create such highly
charged ions at rest. Other sources produce highly charged ions;however, because they use accelerators, these sources increase an
ion’s velocity to extremely high energies.
For the Lamb shift experiments, the team stripped off 89 of the
92 electrons in each uranium atom, leaving uranium ions with only
three electrons bound to each nucleus. High-resolution spectrometersdeveloped at Livermore then recorded the light emitted by theelectrons of these lithiumlike uranium atoms. Spectra were recorded
for about two months to collect enough data for analysis. “The countrate for this event is quite low, something like four to five counts perhour,” says Beiersdorfer, “and the signal is very faint.”
(c)

(d)

Feynman diagrams, which are used to illustrate quantum theory, show contributions to the Lamb shift. Double lines represent bound electrons, wavy lines
represent virtual photons, and double circles represent virtual electron–positron pairs. When an electron is subjected to electric and magnetic fields, it can(a) emit and reabsorb a virtual photon or (b) emit and reabsorb a virtual electron–positron pair. These interactions involve a single loop of virtual particles and are
the first-order contribution to the Lamb shift. More complex interactions are possible, in which two or more loops of virtual particles are generated. Examples of a
two-loop contribution to the Lamb shift are shown in (c) and (d). In (c), an electron emits one photon and then, soon after, another, so that the two overlap in time.
In (d), when a virtual electron–positron pair is emitted, the virtual electron emits a photon that is reabsorbed.

Lawrence Livermore National Laboratory

S&TR May 2006

22 Two-Loop Lamb Shift

Shedding Light on QED
The team measured the contribution of both the one- andtwo-loop Lamb shifts to the observed spectrum and improved theexisting experimental precision by nearly an order of magnitude. In
doing so, the team surpassed the precision achieved by researchersat the Heavy Ion Research Institute in Germany.
“These were the first measurements of the two-loop Lamb
shift in a strongly bound system,” says Beiersdorfer. The results,
which were chosen as a 2005 highlight by the American PhysicalSociety’s News Bulletin, are stimulating new calculations in
QED theory. Laboratory physicists K. T. Cheng and Mau Chen,in collaboration with Jonathan Sapirstein from Notre Dame
University, are making calculations, which they will compare
to the experimental results. Livermore physicist Elmar Träbert,
together with Beiersdorfer, is leading a study to measurehighly stripped bismuth. Bismuth’s electric field is weaker thanuranium’s, but its nuclear magnetic field is very strong. Träbert’s
study, which includes Livermore physicists Hui Chen, Greg

Brown, and Daniel Thorn, will examine the processes that createsuch strong magnetic fields inside the nucleus.
“In QED experiments such as these, we are looking for one of
two outcomes,” says Beiersdorfer. “If the measurements support
theoretical calculations, they reaffirm that the theory fits reality.
If the measurements and calculations do not agree, scientists are
faced with a mystery to solve, because the discrepancies show usthat we have more to learn.”—Ann Parker
Key Words: electron-beam ion trap, ions, polarized vacuum, quantum
electrodynamics (QED), quantum fluctuations, quantum mechanics, selfenergy, spectroscopy, SuperEBIT, two-loop Lamb shift, uranium, virtual
particles, virtual photons.

For further information contact Peter Beiersdorfer (925) 423-3985(beiersdorfer1@llnl.gov).

Lawrence Livermore National Laboratory

Patents and Awards

Each month in this space, we report on the patents issued toand/or the awards received by Laboratory employees. Our
goal is to showcase the distinguished scientific and technicalachievements of our employees as well as to indicate thescale and scope of the work done at the Laboratory.

Patents
Rapid Process for Producing Transparent, Monolithic Porous GlassPaul R. Coronado
U.S. Patent 6,998,102 B2
February 14, 2006

A process for making transparent porous glass monoliths from gels.
The glass is produced much faster and in much larger sizes than present
technology for making porous glass. The process reduces the cost of
making large porous glass monoliths because (1) the process does not
require solvent exchange nor additives to the gel to increase the drying
rates, (2) only moderate temperatures and pressures are used so relatively
inexpensive equipment is needed, and (3) net-shape glass monoliths canbe used. The process depends on the use of temperature to control thepartial pressure of the gel solvent in a closed vessel, resulting in controlledshrinking during drying.
System and Method for Characterizing Voiced Excitations of Speech
and Acoustic Signals, Removing Acoustic Noise from Speech, andSynthesizing Speech
Greg C. Burnett, John F. Holzrichter, Lawrence C. Ng
U.S. Patent 6,999,924 B2
February 14, 2006

The present invention is a system and method for characterizing human(or animate) voiced excitation functions and acoustic signals, forremoving unwanted acoustic noise that often occurs when a speaker uses a
microphone in common environments, and for synthesizing personalized
or modified human (or other animate) speech on command from acontroller. A low-power electromagnetic (EM) sensor is used to detect
the motions of windpipe tissues in the glottal region of the human speechsystem before, during, and after speech is produced by a user. Fromthese tissue motion measurements, a voiced excitation function can bederived. Furthermore, the excitation function provides speech production
information to enhance noise removal from human speech, and it enables
accurate transfer functions of speech to be obtained. Previously stored
excitation and transfer functions can be used for synthesizing personalized
or modified human speech. Configurations of EM sensor and acoustic
microphone systems are described to enhance noise cancellation and toenable multiple articulator measurements.
Conductive Inks for Metallization in Integrated Polymer Microsystems
James Courtney Davidson, Peter A. Krulevitch, Mariam N. Maghribi,
William J. Benett, Julie K. Hamilton, Armando R. Tovar
U.S. Patent 7,005,179 B2
February 28, 2006

focused light. In one embodiment, the grating has rulings immersed into a
germanium surface.
Parallel Object-Oriented Decision Tree System
Chandrika Kamath, Erick Cantu-Paz
U.S. Patent 7,007,035 B2
February 28, 2006

This data-mining decision tree system uncovers patterns, associations,anomalies, and other statistically significant structures in data by reading
and displaying data files and extracting relevant features for each of
the objects. The system recognizes patterns among the objects based on
object features by using a decision tree that reads the data, sorts the data
if necessary, determines the best manner to split the data into subsets
according to some criterion, and splits the data.
Boattail Plates with Non-Rectangular Geometries for Reducing
Aerodynamic Base Drag of a Bluff Body in Ground Effect
Jason M. Ortega, Kambiz Sabari
U.S. Patent 7,008,004 B2March 7, 2006

An apparatus for reducing the aerodynamic base drag of a bluff bodyhaving a leading end, a trailing end, a top surface, opposing left and rightside surfaces, and a base surface at the trailing end substantially normal
to a longitudinal centerline of the bluff body. The based surface is joinedto (1) the left-side surface at a left trailing edge, (2) the right-side surface
at a right trailing edge, and (3) the top surface at a top trailing edge.
The apparatus includes left and right vertical boattail plates, which areorthogonally attached to the base surface of the bluff body and inwardly
offset from the left and right trailing edges, respectively. This producesleft and right vertical channels that generate, in a flow stream substantiallyparallel to the longitudinal centerline, respective left and right verticallyaligned vortical structures. The left and right vertical boattail plates eachhave a plate width defined by a rear edge of the plate spaced from thebase surface. Each plate also has a peak plate width at a location between
top and bottom ends of the plate corresponding to a peak vortex of therespective vertically aligned vortical structures.
Optical Probe with Reference Fiber
Luiz B. Da Silva, Charles L. Chase
U.S. Patent 7,013,173 B2March 14, 2006

A system of metallization in an integrated polymer microsystem. A
flexible polymer substrate is provided, and conductive ink is applied to thesubstrate. In one embodiment, the flexible polymer substrate is silicone. In
another, it is poly(dimethylsiloxane).

This system for characterizing tissue includes steps for generating anemission signal, generating a reference signal, directing the emission
signal to and from the tissue, directing the reference signal relative to theemission signal, and using the reference signal to compensate the emission
signal. In one embodiment, compensation is provided for fluctuations inlight delivery to the tip of the probe due to cable motion.

Compact Catadioptric Imaging Spectrometer Utilizing Immersed
Gratings
Scott A. Lerner
U.S. Patent 7,006,217 B2
February 28, 2006

Imaging Spectrometer Utilizing Immersed Gratings with Accessible
Entrance Slit
Michael P. Chrisp, Scott A. Lerner
U.S. Patent 7,016,037 B2March 21, 2006

This imaging spectrometer has an entrance slit for directing light, a lensthat receives the light and reflects it, a grating that defracts the light backonto a lens that focuses the light, and a detector array that receives theThis compact imaging spectrometer includes an entrance slit, acatadioptric lens with a mirrored surface, a grating, and a detector array.
The entrance slit directs light to the mirrored surface of the catadioptric

Lawrence Livermore National Laboratory

23

24 Patents and Awards

S&TR May 2006

lens. The mirrored surface then reflects the light back through the lens to
the grating. The grating receives the light from the catadioptric lens anddiffracts it to the lens away from the mirrored surface. The lens transmits
the light and focuses it onto the detector array.

Speaker Verification System Using Acoustic Data and
Non-Acoustic Data
Todd J. Gable, Lawrence C. Ng, John F. Holzrichter, Greg C. Burnett
U.S. Patent 7,016,833 B2March 21, 2006

Near-Infrared Spectroscopic Tissue Imaging for Medical Applications
Stavros Demos, Michael C. Staggs
U.S. Patent 7,016,717 B2March 21, 2006

A method and system for speech characterization. One embodiment
includes a method for speaker verification that collects data from aspeaker, wherein the data comprise acoustic and nonacoustic data. The
data are used to generate a template that includes a first set of “template”
parameters. The method further includes receiving a real-time identity
claim from a claimant and using acoustic and nonacoustic data fromthe identity claim to generate a second set of parameters. The first setof parameters is compared to the second set to determine whether theclaimant is the speaker. The two sets have at least one purely nonacoustic
parameter, including a nonacoustic glottal shape parameter derived fromaveraging multiple glottal cycle waveforms.

Near-infrared imaging using elastic light scattering and tissue
autofluorescence are explored for medical applications. The approach
involves imaging using cross-polarized elastic light scattering and tissue
autofluorescence in the near infrared coupled with image processing andinterimage operations to differentiate human tissue components.

Lawrence Livermore National LaboratoryM o n t hSecurity officials are anticipating possible scenarios in whicha terrorist might use radioactive materials to fashion destructive
devices. To help mitigate this threat, the Department of Homeland
Security is funding two Livermore projects to develop gamma-ray
imagers that significantly increase detection capabilities. The largearea gamma-ray imager, which was developed in a collaboration
led by Laboratory researchers, can detect millicurie quantities ofa cesium isotope from a distance of 85 meters while traveling at
16 kilometers per hour. Livermore researchers are also designing
imagers that rely on Compton scattering to determine a gammaray source. This imager is the most efficient and sensitive, fully
operational Compton imaging system to be built to date. The
portable instrument will allow security officials to conduct widearea surveillance from the ground or in the air.
Contacts:
Lorenzo Fabris (925) 423-1258 (fabris1@llnl.gov) or Kai Vetter(925) 423-8663 (vetter4@llnl.gov).

Protecting the Nation’s Livestock
America’s livestock are vulnerable to diseases that are endemic
in other parts of the world but have not appeared in this country
for many decades. If allowed to gain a foothold in the U.S., these
foreign animal diseases could spread rapidly and be difficult tocontain. Much concern centers on foot-and-mouth disease (FMD),
a highly contagious livestock disease that has not been seen in
the U.S. since 1929. The nation needs the capability to identify
FMD early, so it can provide a timely and effective response tocontrol an outbreak. To address this need, a Livermore team, withsupport from the Department of Homeland Security and the U.S.
Department of Agriculture (USDA), has developed a rapid assaythat simultaneously detects FMD as well as several foreign andendemic diseases that mimic the symptoms of FMD. The assay is
being evaluated by the USDA’s National Animal Health Laboratory
Network and the National Veterinary Services Laboratory at Plum
Island, New York. If validated and accepted by the USDA, theLivermore assay will allow state and federal laboratories to quickly
diagnose FMD and livestock diseases with similar symptoms.
Contact:
Ray Lenhoff (925) 424-4034 (lenhoff2@llnl.gov).

A fellowship program provides
Ph.D. candidates with science andengineering expertise and worldclass facilities to complete theirdissertations.

Also in June
• Livermore researchers play an active role in
the National Science Foundation’s Center for
Adaptive Optics, located at the University ofCalifornia at Santa Cruz.
• Genetically engineered viruses provide thebase for “growing” tiny gold nanowires.
• Livermore scientists couple climate andcarbon-cycle models to predict the effects ofglobal warming.

U.S. Government Printing Office: 2006/570-077-10018

N e x tImagers Provide Eyes to See Gamma Rays

Training the
Next Generation

C o m i n g

Abstracts

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