Researchers develop sensitive radiation surveillance method

Researchers have devised a new approach to illicit radioactivity surveillance using a nano-photonic composite scintillation detector.

The team at the Georgia Institute of Technology claim their prototype, which combines rare-earth elements and other materials at the nanoscale, improves sensitivity, accuracy and robustness.

Scintillation detectors and solid-state detectors are two common types of technology for radiation surveillance. A scintillation detector uses a single crystal of sodium iodide or a similar material, while a solid-state detector is based on semiconducting materials such as germanium.

When gamma rays or particles strike a scintillation detector, they create light flashes that are converted to electrical pulses to help identify the radiation at hand. In a solid-state detector, incoming gamma rays or particles register directly as electrical pulses.

However, both require the growth of large, pure crystals that are difficult to produce and sensitive to things such as humidity. The researchers thus experimented with composite material powders that can be much easier to make and handle.

However, a scintillator crystal must be transparent to convert incoming energy from gamma rays to flashes of light, and when a material such as crystal or glass is ground into smaller pieces its transparency tends to disappear.

To overcome this issue, the team reduced the particles to the nanoscale. When a nanopowder reaches particle sizes of 20nm or less, scattering effects fade because the particles are now significantly smaller than the wavelength of incoming gamma rays.

The researchers found that, by heating gadolinium, cerium, silica and alumina and then cooling them from a molten mix to a solid monolith, they could successfully distribute the gadolinium and cerium in silica-based glasses. As the material cools, gadolinium and cerium precipitate out of the aluminosilicate solution and are distributed throughout the glass in a uniform manner. The resulting composite gives dependable readings when exposed to incoming gamma rays.

‘We’re optimistic that we’ve identified a productive methodology for creating a material that could be effective in the field,’ said Brent Wagner of Georgia Tech in a statement. ‘We’re continuing to work on issues involving purity, uniformity and scaling, with the aim of producing a material that can be successfully tested and deployed.’