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nanotimes News in Brief
12-04 :: April/May 2012
Radiation Detection // Novel Radiation Surveillance Technology
© Based on Material by Gatech R
esearchers at the Georgia Tech Research Institute (GTRI) have developed the Nano-
photonic Composite Scintillation Detector, a prototype that combines rare-earth elements and other materials at the nanoscale for improved sensiti- vity, accuracy and robustness. A scintillation detector commonly employs a single crystal of sodium iodide or a similar material, while a solid-state detector is based on semiconducting materials such as germani- um. Both technologies are able to detect gamma rays and subatomic particles emitted by nuclear material. 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.
“Each reaction to a gamma ray takes a very short time – a fraction of a microsecond,” co-principal investigator Brent Wagner said. “By looking at the number and the intensity of the pulses, along with other factors, we can make informed judgments about the type of radioactive material we‘re dealing with.” But both approaches have drawbacks. A scin- tillation detector requires a large crystal grown from sodium iodide or other materials. Such crystals are typically fragile, cumbersome, difficult to produce and extremely vulnerable to humidity. A germanium- based solid-state detector offers better identification of different kinds of nuclear materials. But high-
purity single-crystal germanium is difficult to make in a large volume; the result is less-sensitive devices with reduced ability to detect radiation at a distance. Moreover, germanium must be kept extremely cold – 200 degrees below zero Celsius (-328° F) – to function properly, which poses problems for use in the field. To address these problems, the GTRI team has been investigating a wide variety of alternative materials and methodologies. After selecting the scin- tillation approach over solid-state, the researchers developed a composite material – comprised of nanoparticles of rare-earth elements, halides and oxides – capable of creating light.
Image: Pictured here are examples of scintillators produ- ced from molten glass by the researchers. © Gary Meek