March 22, 2002

LLNL, LBNL collaboration produces improved method for detecting radiation

Five years ago, physicist John Becker thought he’d change career directions.

But instead he had a conversation with some colleagues at Lawrence Berkeley National Laboratory and they started work on something they knew could fine-tune the science of detecting radiation.

The next thing they knew, they had designed and built a mobile, handheld mechanically cooled germanium radiation spectrometer.

The spectrometer not only finds the presence of hard X- and gamma radiation, but also provides information on the species as well. The detector is coupled to a low-power electronics package for control and signal processing.

In the past, in order to attain the high-energy resolution of germanium detectors, the germanium had to be cooled to 90 K in a laboratory setting using liquid nitrogen. However, this new germanium radiation spectrometer is cooled mechanically by a low-power, compact micro cryocooler, eliminating the need for liquid nitrogen, yet maintaining the same precision energy resolution of germanium.

Dubbed Cryo3, the spectrometer, which consists of a hermetically encapsulated germanium detector, utility vacuum housing, micro cooler, and controller, weighs 10 pounds. Cyro3 can operate up to eight hours on two rechargeable lithium ion batteries because of its low power requirements.

Cryo3 properties — precision energy resolution, good sensitivity, lightweight, low-power requirements, and mechanical cooling — mean that gamma-ray radiation spectrometers usually restricted to laboratory use can now be used in the field. Cyro3 can operate continuously unattended for at least six months without ever being turned off.

Cryo3 has clear applications for homeland security and counter terrorism. Researchers say the device would be able to determine the types of radioactive materials no matter where they might be located — at a border crossing, in an airport, or even on a person.

"Cryo3 provides long-term germanium quality spectroscopy in the field with results comparable to laboratory measurements without the need for a liquid nitrogen supply," Becker said."Cryo3 couples the high-energy resolution and efficiency of a laboratory-sized germanium detector with a low-power, lightweight long-lived micro cooler for the first time, enabling a mobile, handheld package."

Other applications for Cryo3 include remote area operation, shipboard operation, portal monitoring, cargo inspection, unobtrusive operations, and general applications where high-resolution gamma-ray spectroscopy is required and large-volume radiation detectors using liquid nitrogen are not feasible.

"Cryo3 offers extremely high-resolution radiation analysis in a portable package," said Lawrence Berkeley engineer Lorenzo Fabris.

The development team consists of John Becker of Livermore and Christopher Cork, Lorenzo Fabris, and Norman Madden of Berkeley. The four-year long development project is funded in part by the U.S. Department of Energy’s Office of Nonproliferation Research and Engineering within the Office of Defense Nuclear Nonproliferation.