Reducing the Threat of War and Terrorism
| ORNL is developing visualization and measurement technologies that could reduce threats of war and terrorism, such as land mines, unexploded ordnance, biological and chemical warfare agents, and airport explosives. |
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| The peaks in this colorful spectrum are linked to the locations and explosive power of different types of bombs and other unexploded ordnance. The spectrum is derived from data gathered by remote sensors. |
Remote sensing using helicopters or fixed-wing aircraft or small, unmanned, radio-controlled aircraft is being investigated at ORNL as a near-term technology for reducing the threat of war and terrorism. It is also useful for identifying locations of unexploded ordnance (UXO).
“At ORNL a UXO team has been working to develop images and signatures of concealed ordnance at military bases and training sites using remotely collected data,” says David Bell of ORNL’s Computational Physics and Engineering Division, which is working with the Environmental Sciences Division on this project. “Eventually, we will develop a computer program to integrate the data from an array of airborne remote sensors to form an image of a land area. This visualization of the data will enable us to locate buried objects and identify the ones that contain dangerous explosives. In this way, we can achieve ‘footprint reduction,’ determining which land is dangerous and deserves remediation and which area is safe to develop, thus reducing cleanup costs.”
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| A remnant from the era of the war in Vietnam is this still “active” U.S.-made 500-pound bomb located near a family settlement in eastern Cambodia. It is estimated that more than 300,000 tons of such unexploded ordnance are still present in Cambodia. |
Detection of UXO is one of the goals of a Department of Energy and Department of Defense (DOD) program that is funding some of the ORNL work. Other goals are to characterize and develop strategies to defeat or remove UXO safely. DOD wants better technology to supports its demining and cleanup missions. In 1997, Oak Ridge and Sandia national laboratories initiated a multilab DOE effort to develop and test better UXO detection technology; some 14 DOE facilities and numerous university and industrial partners are involved.
“Remote sensing from aerial vehicles is one way to safely detect land mines, unexploded bombs, or other hazardous materials at Department of Defense sites,” says Dick Davis, director of the Defense Programs Office for ORNL. “We are also developing sensors and methods that may be used in future years to detect airport explosives and biological and chemical warfare agents, as well as UXO and land mines, including those made of plastic instead of metal. Besides traditional detection methods, chemical and biological sensors are gaining acceptance.”
One potential remote-sensing method for land mine detection that has been developed at ORNL uses bacteria that emit light while eating explosives. In a recent test, researchers obtained glowing results.
Microbial Minesweepers
On the night of October 20, 1998, in South Carolina, Martin Hunt of ORNL’s Instrumentation and Controls Division searched for experimental land mines with the determination of a tourist wielding a metal detector to find coins buried in beach sand. His tools were unusual: an ultraviolet (UV) mercury lamp and a piece of colored glass the size of a silver dollar. Under the supervision of Bob Burlage of the Environmental Sciences Division, the field had been sprayed with bacteria during the day using an agricultural sprayer (for an actual mine field, a crop duster could be employed). These bacteria were special: Burlage had engineered them to produce the green fluorescent protein (GFP) while they made a meal out of traces of a hidden explosive.
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| Bacteria tagged with the green fluorescent protein give off light. Although each bacterium is approximately one-millionth of a meter long, the fluorescence of the bacteria makes them easily visible under the microscope. |
When it was dark, Hunt shone the UV lamp on various parts of the site while looking through the dark glass, called a notch filter. He saw greenish fluorescent spots at known locations of the test land mines. A team on a cherry picker suspended 15 feet above the mine field also detected the telltale green glow in soil bathed in UV light from a laser-induced fluorescence imaging (LIFI) system. This portable LIFI system, being perfected by Bechtel Nevada for DOE, includes a video camera to collect the emitted light as images that reveal the little green spots, as well as a computer to display and store the image data. These tests of ORNL’s microbial mine detection system were declared a success. The teams showed that one strain of genetically engineered bacteria can signal the presence of hidden explosives, thus offering a potentially cost-effective and safe way of locating antipersonnel mines over a wide area.
Burlage and Hunt were participating in a test around the prepared land mines constructed at the National Explosives Waste Technology and Evaluation Center in Edgefield, South Carolina. In their field test, they did not know the locations of the actual land mines containing trinitrotoluene (TNT). The mines were not fused, so they could not explode.
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| Bob Burlage examines specially engineered bacteria in a petri dish. These bacteria fluoresce when exposed to TNT compounds such as those that may leak from buried land mines. |
“Land mines leak small amounts of TNT over time, leaving a chemical trace for bacteria on the soil surface,” Burlage says. “When the bacteria of one of our strains of Pseudomonas putida encounter the TNT, they will scavenge the compound as a food source, activating the genes that produce proteins needed to digest the TNT. Because we attached the GFP gene obtained from jellyfish to these activated genes and included a regulatory gene that recognizes TNT, the GFP gene will also be turned on. It will produce the protein that emits extremely bright fluorescence when exposed to ultraviolet light.”
Burlage is encouraged by the results of these tests conducted for the Defense Threat Reduction Agency. He thinks it would be possible to detect land mines remotely from rolling towers or helicopters by looking for glowing microbes on soil illuminated with UV light. Says he: “No one yet has told me it can’t be done.” Perhaps ORNL will get the green light to develop a bacteria-based remote-sensing method for land mine detection.
Chemical Sensors
One of the early devices used to sniff for chemicals in the environment was built at ORNL. In the late 1980s, Marc Wise, leader of the Instrumentation Group in ORNL’s Chemical and Analytical Sciences Division, and his associates developed ORNL’s first direct-sampling ion trap mass spectrometer (DSITMS). Over the years, thanks to advances in ion traps, electronics, and computers, this device was improved upon and reduced in size for environmental measurements on site. Wise also added a unique modular sampling system. The result was an instrument that can rapidly sample and analyze pollutants from air, water, and soil. It tells researchers at the site within a few minutes the identity and concentration of pollutants present. This versatile instrument, which has been approved for use by the U.S. government, enables analysis of environmental samples in 10% of the time and at 20% of the cost of traditional laboratory analysis.
Multithreat analyzer. For the past three years, with support from DOE’s Office of Nonproliferation and National Security, ORNL researchers have been developing a fully self-contained, battery-powered DSITMS for use in detecting threat chemicals. It will be the size of a briefcase instead of a desk.
“Our multithreat analyzer is intended to be carried by a worker to any site that is difficult to reach with a vehicle or wherever portable monitoring is required,” Wise says. “It might be needed to search for drugs in cargo containers or hidden explosives in an airplane cabin or mine field.”
How will it work? If vapor molecules of TNT are present, for example, they are sucked through a long tube into the ion trap analyzer cell. There they are converted to ions that are trapped in the cell’s electric field when a radiofrequency (rf) signal of 100 volts is applied. As the rf voltage is ramped up to as high as 7500 volts, ions of increasingly higher mass escape the trap. These ions are counted. By applying the rf voltage known to eject TNT and checking for a signal, it is possible to determine whether the explosive is present.
Warfare agent detector. An advanced DSITMS is the heart of a new chemical biological mass spectrometer (CBMS) being developed for the U.S. Army at ORNL. The CBMS will more accurately detect chemical and biological warfare agents and warn soldiers to wear protective gear or to avoid contaminated areas. An improved technology is needed: During the Persian Gulf War, Army detectors could not easily distinguish among vapors from diesel fuel, pesticides, rocket and gun propellants, industrial chemicals, and chemical warfare agents. Many false alarms were sounded.
Concerned that soldiers could be exposed to biological warfare agents (e.g., anthrax spores), as well as chemical agents (e.g., nerve agent VX) during hostilities and terrorist incidents, the U.S. Army Soldier and Biological Chemical Command began funding development of the first-generation CBMS in Germany. In 1996 it asked ORNL to lead the development of the second-generation one because of our mass spectrometer expertise.
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| Wayne Griest checks the analyzer and associated electronics in a testbed for evaluating systems of the chemical-biological mass spectrometer. This instrument is being developed at ORNL to detect biological and chemical warfare agents. |
“The Army wants the next-series instrument to be smaller, lighter, faster, less expensive, more sensitive, more easily maintainable, and able to detect and distinguish among a wider variety of airborne chemicals and microorganisms, as well as chemicals on the ground,” says Wayne Griest, manager of the CBMS Program at ORNL. “The new CBMS should be more accurate than the detectors used today in determining if warfare agents are present.”
Innovative technologies have been developed by five ORNL divisions and three contractors to collect and heat airborne particles, handle data, and control the mass spectrometer. In 1999 three initial units of the six-module CBMS will be built at ORNL. They will be tested on site on minute concentrations of warfare agents in federally approved facilities. Orbital Sciences Corporation will develop an economically producible instrument for military use by 2000.
The final product will improve protection of U.S. troops. It should not sound any false alarms, but it is hoped there will be no need for real ones.
Microcantilever Sensors
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| Thomas Thundat picks up a platinum-coated cantilever chip (like the one magnified on the screen) that was designed at ORNL and fabricated at the Massachusetts Institute of Technology. |
In 1991 Thomas Thundat of LSD was using an atomic-force microscope to examine the effect of humidity on DNA. The humidity degraded the performance of the microscope’s cantilever, which is used to map the atomic mountains and valleys of surfaces, just as a phonograph stylus traces grooves in a vinyl record. It occurred to Thundat that this microscopic springboard had the potential to be a sensor. Thanks to new micromachining techniques, his group was able to obtain silicon chips as small as rice grains from which barely visible cantilevers project. Each sensor chip is rugged and extremely sensitive yet costs little and uses little power. The cantilever technology has been licensed for several fields of application to Graviton, Inc., in San Diego.
Thundat and his colleagues showed that a cantilever bends or changes its natural vibration in a measurable way if it is coated with a material that attracts another material from the air. For example, a cantilever coated with a gelatin absorbs water, causing it to bend and measure humidity. Cantilevers can also be used to measure changes in temperature, sound wave velocities, and fluid pressures and flow rates.
“Cantilevers can store electrical charge or resist the flow of electricity,” Thundat says. “When a cantilever bends or changes in its vibration, this ability is altered in a way that can be measured electrically. Also, by steadily bouncing a laser diode light off the cantilever, we can tell when it bends or wiggles by measuring changes in the angle of light deflection in an optical position-sensitive detector.”
Thanks to funding from the Federal Aviation Administration (FAA), Thundat and his colleagues are developing a matchbox-size device to detect explosives in airport luggage and land mines. The device will contain cantilevers coated with platinum or a transition metal. If TNT is present when a cantilever is heated to 570°C and held at that temperature for 0.1 sec, the TNT will react with the coating, causing a mini-explosion (autocombustion). The cantilever’s resulting characteristic wiggle can be teased out of the background noise using a wavelet analysis algorithm.
It is believed that dogs can detect explosives in airline passenger baggage and land mines by sniffing easily vaporized organic chemicals, such as acetone and toluene, at part-per-billion levels. So the Treasury Department’s Alcoholism, Tobacco and Firearms agency is looking for a device that emulates a dog’s nose and that could be part of a walking cane to detect the presence of an explosive. One contender is ORNL’s calorimetric microspectrometer (CalSpec), which received an R&D 100 Award in 1998. Another candidate technology is ORNL’s “nose on a chip” device, which contains a series of cantilevers individually coated to pick up a different specific organic compound (see the Incredible Shrinking Labs article for details). A computer will determine if the detected compounds spell out the signature of an explosive.
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| Bruce Warmack (left) and Chuck Britton examine an ORNL chip they designed with Thomas Thundat and others; this “nose on a chip” contains 640 microcantilevers. |
Efforts are under way to obtain industrial partners to help test, miniaturize, and manufacture these ORNL technologies. Meanwhile, there are plans to evaluate the cantilever sensors, DSITMS, and other ORNL technologies at the testbed for evaluation of security- related equipment at the McGhee-Tyson Airport in Knoxville. This testbed is sponsored by FAA’s National Safe Skies Alliance and is managed by the National Transportation Research Center, headed by ORNL’s Bob Honea. It is hoped that all of ORNL’s technologies will pass with flying colors.
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