Scientists have found a new method of using X-rays to detect hidden nuclear materials. The new development could soon see use in airports and border security to help combat illegal smuggling of radioactive materials and nuclear terrorism.
The technique was developed by University of Texas in Austin (UT) nuclear engineer Andrew Gilbert and other researchers at the Pacific Northwest National Laboratory (PNNL) where the research was conducted.
Gilbert says that they wanted to use already existing technology similar to the X-ray machines used in airports. By improving upon existing technologies, the researchers hoped to be able to create a new technique that could differentiate between nuclear materials like Plutonium and dense metals such as iron or lead.
"We first had to develop a computational model for how X-rays move through materials and how they are detected so that we could predict what an image will look like once the radiation passed through an object," said Mark Deinert, another researcher from the UT. "With that in hand, we applied an 'inverse algorithm,' varying the composition of the object until the predicted image matched the measured one. We also gave our algorithm additional details about density and other factors -a process called 'regularization'- to adaptively enhance its ability to discriminate materials." Deinert is also one of the authors of the paper on the subject published in the Journal of Applied Physics.
Normal airport x-ray machines can only provide block images of scanned objects. However, most bags and suitcases are composed of numerous layers containing a wide variety of materials. Current X-ray machines produce images by counting the number of X-ray photons that penetrate and pass through certain materials. However, this type of technique is limited in the machine, and its operators won't be able to tell the difference between a container full of iron or lead and another container full of plutonium.
The new technique developed by Gilbert and his colleagues uses spectral radiography that takes into consideration the slight differences in the energy levels of photons after passing through different types of objects and materials. By keeping an eye out for specific energy ranges known to be produced when scanning dangerous materials such as plutonium, scientists can now detect potentially hazardous materials using the new technique.
The researchers demonstrated the feasibility of the technique by simulating x-rays passing through different layers made out of plutonium, cotton and steel. The scientists took into account various characteristics of the materials to differentiate between them. The scientists are now exploring their options in order to attempt to recreate their results on a larger scale.
