Campus Currents

Tracking Nasty Neutrons A deep-space gamma-ray telescope can help find dirty bombs by David Sims '81

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UNH astrophysicist James Ryan knows how to detect radioactive emissions from across the vast sweep of the Milky Way. So several years ago, as he watched National Guardsmen struggle to track down the source of a "dirty bomb" during a mock terrorism drill, the proverbial light bulb began to glow warmly in his head.

For the Compton Gamma Ray Observatory, a NASA mission that ran from 1991 to 2000, Ryan and colleagues from UNH's Space Science Center helped build and operate a gamma-ray imaging telescope. But to help track down radioactive emissions on Earth, Ryan has turned his telescope 180 degrees, so to speak, to fabricate a prototype portable gamma-ray and neutron detector that will be aimed at shipping containers and buildings in search of contraband radioactive materials.

Illustration by Wesley Bedrosian

"Basically, what people have to do now is go into a building or a container and fish around in hopes of finding the source," Ryan says. "But the expertise that has been acquired over many years in the space program can now be brought to bear on this problem of locating nuclear bomb-making material from a safe distance."

UNH's high-energy detection research began in the mid-1950s when professor Jack Lockwood "launched" a neutron detector by driving it up to the summit of Mount Washington. But even now it is exceedingly difficult work.

"They're slippery little devils," Ryan says of the high-energy subatomic particles. "A neutron has no electric charge, so it just flies right on by. You have only a one-in-10-thousand chance to actually detect it." But because the portable neutron spectroscope can reconstruct the velocity, direction and radioactive signature of neutrons by using a bank of parallel detectors, an outer space NASA mission will have a down-to-Earth application for the nation's security.