Micro-gamma ray detector developed

By Control Engineering Staff April 3, 2006

Detroit, MI —Scientists at the U.S. Department of Commerce’s National Institute of Standards and Technology (NIST) have designed and demonstrated what’s claimed to be the world’s most accurate gamma ray detector. Eventually it’s expected to be useful in verifying inventories of nuclear materials and detecting radioactive contamination in the environment.

The tiny prototype detector, described at the American Physical Society national meeting in Baltimore, can pinpoint gamma ray emission signatures of specific atoms with 10 times the precision of the best conventional sensors used to examine stockpiles of nuclear materials. NIST’s tests, performed with different forms of plutonium at Los Alamos National Laboratory, also show that the prototype greatly clarifies the complex X-ray and gamma-ray emissions profile of plutonium.

Emissions from radioactive materials such as uranium or plutonium provide unique signatures that, if accurately measured, can indicate the age and enrichment of the material and sometimes its intended purpose or origin.

The 1-square-mm prototype collects only a small amount of radiation, but NIST and Los Alamos researchers are collaborating to make a 100-sensor array that could be deployed in the field, perhaps mounted on a cart or in a vehicle.

“The system isn’t planned as a primary detection tool,” says NIST physicist Joel Ullom. “Rather, it is intended for detailed analysis of material flagged by other detectors that have larger collection areas but less measurement accuracy.” An array could be used by inspectors to determine, for example, whether plutonium is of a dangerous variety, whether nuclear fuel was made for energy reactors or weapons, or whether what appears to be radium—found naturally in the environment—is actually explosive uranium.

“People at Los Alamos are very excited about this work,” says Michael Rabin, a former NIST postdoctoral candidate who now leads a collaborating team at Los Alamos. Los Alamos National Laboratory operates and improves the capability to handle nuclear materials and sends scientists to participate in United Nations nuclear inspection teams.

Richard Phelps , senior editor, Control Engineering