New fusion-based neutron source advances education, contraband detection

The University of Tennessee has turned on its own very tiny sun.

This year, the Department of Nuclear Engineering (NE) powered on its first fusion-based neutron source. The Sodern Genie 16 is the newest addition to the NE resource lab in the Zeanah Engineering Complex at UT’s Knoxville campus.

Fusion-based neutron sources can be activated at specific times and the neutrons ‘tuned’ to specific energy levels for precise use cases. Despite their utility, these tools are relatively rare at universities due to their significant shielding needs and certification requirements, which are governed by state-level radiological regulations.

“One of the more difficult parts of achieving this new capability was just having an appropriately shielded facility to house it in,” explained NE Professor Jason Hayward. “It’s not just the generator, it’s having the facility and having gone through the regulatory process to make it safe to use.”

With proper shielding and certifications in place, the Sodern Genie 16 is up, running, and already expanding UT’s NE research capabilities. Hayward and Research Assistant Professor Xianfei Wen are helping kick off the new tool’s career by applying it to improved contraband detection for the US Department of Homeland Security (DHS).

Scaling Up Contraband Detection

In 2021, Hayward and Wen began a five-year, $2.5 million grant from the DHS’s Countering Weapons of Mass Destruction Office. The grant, which is co-led by Associate Professor Qi Cheng of Oklahoma State University (OSU), is part of a federal effort to improve detection of contraband goods in large cargo containers.

“We’re confident enough when we’re talking about smaller packages, like backpacks and small suitcases,” Hayward explained. “But as the container gets larger and larger, our confidence in being able to find contraband goes down and down.”

Larger containers under the project’s purview include shipments processed by the Transportation Security Administration at airports as well as railway cars, full-size trucks, and shipping containers processed by US Customs and Border Protection.

Hayward, Wen, and Cheng are investigating neutron interrogation as a method to increase the probability of contraband detection within these containers while decreasing the rate of false alarms.

Revealing Contraband ‘Signatures’

So far, the team has succeeded in detecting prompt fission neutrons from fissile materials inside large containers.

When neutrons stream toward a non-nuclear material, they pass through without producing fission neutrons. However, when neutrons hit fissile materials like uranium isotope U-235, the resulting fission chain creates new neutrons that can be caught by detectors.

The team’s next goal is to detect gamma emissions stimulated by the neutron beams hitting other types of contraband, such as explosives or illegal drugs.

“When neutrons hit the cargo, they cause the cargo to emit gamma radiation,” Hayward said. “Every element produces a signature form of gamma rays, so reading those rays provides a fingerprint for the elements that are in the cargo.”

Analyzing these gamma rays will allow officers to identify the elemental composition of the cargo. If properly decoded and separated from background noise, a task being aided by NE Assistant Professor Sandra Bogetic, these signatures could even tell officials the specific type of contraband inside.

“We know this works, but it doesn’t work effectively enough to be implemented in practice yet,” said Hayward. “It’s our job to improve the methodology so it can be done quickly and effectively.”

Enhancing Student Experience

NE’s new neutron source is also pushing forward the quality of education for engineering students from the undergraduate to graduate level at both UT and OSU.

“Our students are designing experiments, making nuclear measurements with unique sources like our neutron generators, designing and testing new algorithms to analyze those data—pretty much supporting all the tasks of this project,” Hayward said. “They’re getting training that will prepare them for careers in all sorts of areas like nuclear engineering, applied physics, electrical engineering, and computer science.”

The neutron source’s utility in educating future engineers underscores the importance of having such tools accessible and safe to use within a university.

“It’s really exciting to have these new facilities on campus where we can train students, generate new data, and make contributions to solve this important problem with national security significance,” Hayward said. “The new knowledge and publications we generate in this area can help to improve the state of the art.”