With the rise of terrorism and the threatened use of a dirty bomb increasing, the need for standoff detection of radioactivity has never been greater. Standoff detection can be conducted at a distance in order to protect people and reduce the potential for damage.

To help with this effort, the Center for Advanced Photonics Research (CAPR) in Temple’s College of Science and Technology has received a $450,000, three-year grant from the Defense Threat Reduction Agency (DTRA) to further develop laser-based technologies created by CAPR for the potential standoff detection of radioactive materials.

“DTRA wants researchers to develop new ways to detect radioactivity in cargo containers, ships, vehicles and airplanes,” said Robert Levis, professor and chair of chemistry and director of CAPR. “They also need a way to do this remotely.”

The technology that Levis and his group will be attempting to validate as a potential remote detector of radioactivity was born out of concepts that emerged from previous research projects to create standoff detection of improvised explosive devices. 

“It’s not an easy project, but it’s a potentially great application for technology that we’ve developed here at Temple,” said Levis.

CAPR researchers discovered that they could detect molecules in the air by using a commercially available laser and a $50 lens to create one of the shortest laser pulses in the world.

“If you take the output of one of these commodity lasers and put the pulse through a 2 meter lens in air, after about 3 meters, you get a really short, few cycle pulse. This pulse duration used to cost up to a $1 million to create,” he said. “But now you can get this short pulse basically for free right out in the air.”

Levis said that any molecules caught in the short pulse start to move in perfect unison, with each type of molecule creating its own pattern or signature. The question is whether radioactive decay in the air creates enough new signature molecules to allow detection, he said.

“When the molecules begin moving as one and you put a weak laser beam through the same volume, you can identify the molecules by their signature movement,” he said. “So we realized we could use this process to perform gas phase spectroscopy to identify the molecules.”

Levis likened this process for identifying the molecules, which his team has been studying for the past four years, to trying to distinguish between the Rockettes doing a dance number and army troops marching across a field without visually seeing them.

“You just listen,” he said. “If they are all moving as one then it’s easy to tell the dance steps from soldiers marching. We ‘listen’ using the lasers.”

Levis said the short pulse could be formed wherever the researchers wanted — 10 meters, 100 meters or even possibly a kilometer away.

“Right now, DTRA views this as fundamental physics research, but if we can validate that our approach works, you could just scan this pulse over or around a cargo container, or a ship out in the harbor, or even a car, to determine whether, there is a potential problem,” he said.