About PNNL
Contact: Greg Koller, (509) 372-4864
Release date: June 12, 2001
PNNL engineer Randy Hansen tests the Timed Neutron Detector. The system's inventor, Richard A. Craig, garnered a $100,000 fellowship from the Christopher Columbus Foundation as part of the 2001 Discover Magazine Innovation Awards.
(Image available to download from PictureThis.)
Physics enables detector to find plastic, metal landmines
Contrast is the key to all systems designed to locate landmines. A new, award-winning system developed at the Department of Energy's Pacific Northwest National Laboratory focuses on the contrast between hydrogen in the ground and in landmines. The Timed Neutron Detector created at PNNL recognizes the presence of hydrogen in the casings and explosive materials of plastic or metal landmines.
For his work on the detector, PNNL physicist Richard Craig received a $100,000 fellowship from the Christopher Columbus Foundation in June 2001. The foundation each year honors a scientist who is trying to improve the world through scientific endeavors and chooses the recipient from entries to the annual Discover Magazine Innovation Awards.
While other landmine detection systems also can locate plastic and metal mines, the Timed Neutron Detector goes a step beyond. It is portable, comparatively inexpensive and easy to operate.
"We wanted to develop a system that would be feasible for use in countries that have the greatest need for this capability," said Craig, a physicist and principal investigator. "Simplicity has been our goal since the beginning, and our system is elegantly simple."
Gruesome images of landmine victims motivated Craig and the team with which he worked. Each year, landmines claim 24,000 new victims, of which nearly 10,000 die, according to the Landmine Survivors' Network. The United Nations' Landmine Database estimates that at present rates it would take 1,100 years to clear the world's 110 million landmines hidden in the soils of nearly 70 countries.
Rosalyn Queen Alonso, Christopher Columbus Foundation chair, commended Craig's team for this development. "This device can be produced for use by Third World countries at a relatively low cost, yet the savings in human life and suffering could be priceless," she said. "If landmines are neutralized, these countries and their people could begin to rebuild their lives and restore their agriculture."
A neutron source (top round image) emits neutrons in all directions while slowed neutrons are returned to the detector box.
(Image available to download from Photo Library.)
With practicality a goal, the team developed a system that would detect hydrogen because it is a common element of all landmines. Hydrogen exists in the explosive material of metal landmines as well as the casings of plastic mines.
While the Timed Neutron Detector resembles a metal detector, unseen are the neutrons from Californium-252 that shoot out of the detector into the soil. As neutrons leave the detector, a time-tagging radiation source obtained from DOE's Oak Ridge National Laboratory records each neutron's exit and return.
Then, neutrons return after either interacting with the soil or with hydrogen found in landmines. Neutrons that interact with soil will return to the detector at nearly the same speed at which they left. The detector ignores those neutrons.
Instead, the detector focuses on neutrons that interact with hydrogen. The neutron's speed slows down when it interacts with hydrogen because it has about the same mass as a hydrogen nucleus.
"It's like playing billiards in a way," Craig said. "When a cue ball strikes another ball of the same mass, the second ball will 'take' part of that energy and move. So the cue ball loses energy and slows down. In the same way, neutrons that collide with hydrogen will slow down because they are about the same mass. We simply detect those slowed neutrons."
Craig and his team plan to use the foundation's award to further refine the Timed Neutron Detector. They expect to test it at a mock landmine field later this year.
Battelle, which operates PNNL for DOE, funded development of this technology.
