Fast Neutron Technology Used for Explosive Detection
Explosive detection technology has leaped from traditional X-ray and infrared methods to the projection of sub-atomic particles into passenger luggage. This new technology enables the chemical identification of individual items in a bag, according to HiEnergy Incorporated, the company that developed this idea.
“All the current technologies, X-rays, radar, infrared, for detection of explosive materials are chemically blind,” said Bogdan Maglich, chairman and chief scientific officer of HiEnergy Technologies. “They can only determine shapes and densities of objects, leading to false recognition of material that may be physically similar to explosive compounds.”
Comprising two basic components, emitter and receiver, HiEnergy’s SuperSenzor technology accelerates hydrogen atom isotopes to high speeds and forces collisions that release neutrons. The neutrons then are channeled into high-speed streams and aimed at scanned objects, by using by-product gamma radiation. Because neutron can penetrate heavy, dense materials without destroying them, most materials’ chemical makeup can be revealed.
Neutrons are produced by using a high-voltage particle generator that takes two isotopes of hydrogen, deuterium and tritium, and forces them into each other. When the heavy hydrogen atoms hit the tritium atoms, energetic neutrons are released at 14 million electron volts of energy. Along with the neutrons, alpha particles are released at exactly 180 degrees opposite to the neutrons. This setup creates the image and location of an object in a bag.
“The direction of the alpha particles automatically gives us the direction of the neutrons which, in turn, tells us where the neutrons have hit an object,” said Maglich.
SuperSenzor technology uses neutron energies of between 4 and 14 MeV to detect the main elements that comprise most explosives: carbon, hydrogen, nitrogen and oxygen.
With knowledge of MeV values for certain elements like carbon (4.4 MeV), nitrogen (5.1 MeV), and oxygen (6.1 MeV), measurements of gamma radiation are taken and correlated to known elemental energy signatures.
“Unlike with densities, masses or volumes, where the values for a block of cheese or chocolate can be the same as for an amount of Semtex plastic explosive, gamma energy is distinctly different for each element and therefore each substance examined,” noted Maglich. “Once the gamma energy is measured, there can be no doubt as to the composition of a substance.”
SuperSenzor reception of gamma rays is accomplished using a germanium crystal receiver component. As the rays hit the germanium crystals, electrical pulses are given off directly proportional to the energy of each gamma ray.
“Germanium crystals [...] separate the energy of individual gamma rays easily,” said Maglich. “Without this energy separation, you could not determine individual element identities.”
The neutron generator is a cylinder of one meter in length and several centimeters in diameter. The gamma detector is housed in a 12-inch cylinder with a diameter of about four inches. Through a laptop computer, users could plug into the system’s circuit board that will have all the hardware and connections, according to Maglich.
SuperSenzor technology can also be used for checked baggage. Like carry-on bags, checked items are X-rayed before taken to the aircraft. Once loaded into large cargo containers, however, they do not receive any additional screening for explosives.
“Our technology could be used to irradiate entire bundles of suitcases,” Maglich noted. “Since neutrons don’t discriminate between single or multiple bags, a cart-full of luggage could be ‘chemically defined’ as quickly as individual items.”
HiEnergy estimates that SuperSenzor could process as many as 10 cargo containers or 1,000 bags per hour.
Future military applications for fast neutron technology are in anti-mining and bomb defusing operations. The use of metal detectors or ground-penetrating radar to locate landmines often produces a great deal of false feedback due to naturally occurring “clutter” near or around the mines themselves. In many cases, determining live mines from rocky terrain involves the dangerous and time-consuming process of digging up by each anomaly hit.
“With fast neutron technology, landmine location could be as simple as shoot and receive,” said Maglich. “By projecting fast neutrons into the ground and receiving returning gamma rays, an anomaly can be detected with near 100 percent accuracy in less time and with less danger to human life.”
HiEnergy has a current test contract with the U.S. Army’s Night Vision and Electronic Sensors Directorate (NVESD) to use ConfirmationSenzor to detect antitank mines. Operational tests are scheduled for June 2003. The U.S. Navy is also interested in testing ConfirmationSenzor technology (military application of SuperSenzor technology) for use in detecting unexploded ordinance. Operational tests were conducted in January 2003 with official results still pending.