Small stuff is big deal for radiation detection New technology uses nanopowder to improve design of scintillation detectors
By Doug Page
University researchers have found a way to address deficiencies in common scintillation radiation detection technology. A team at Georgia Tech Research Institute is using novel materials and nanotechnology to improve the sensitivity, accuracy and robustness of radiation detection.
Standard scintillation detection technology is proficient at detecting gamma rays and subatomic particles emitted by nuclear material, but it requires large, difficult-to-produce crystals grown from sodium iodide or other materials. In addition, the crystals are fragile, bulky and vulnerable to humidity.
The Georgia Tech approach uses a nanopowder glass material composed of rare-earth element halides and oxides. The researchers say nanopowder is much reasier to make than crystals, and you don’t have to worry about trying to produce a single large crystal that has zero imperfections.
"Our glass detector has the advantage of simple preparation, stability and does not need to be enclosed or otherwise protected," said Bernd Kahn, of Georgia Tech’s Electro-Optical Systems Lab.
Kahn told Homeland1 that the Georgia Tech detector can be used as a hand- or vehicle-carried radiation monitor to survey areas and people or as a fixed monitor to scan passing vehicles or people.
Regular scintillator crystals must be transparent to light, which provides its ability to detect radiation. A perfect crystal uniformly converts incoming energy from gamma rays to flashes of light. A photo-multiplier then amplifies these flashes of light so they can be accurately measured to provide information about radioactivity.
However, according to the researchers, when a transparent material, such as crystal or glass, is ground into smaller pieces, its transparency disappears. As a result, a mixture of particles in a transparent glass would scatter the luminescence created by incoming gamma rays. That scattered light can't be photo-multiplied in a uniform manner, badly skewing the resulting readings.
To overcome this issue, the Georgia Tech team reduced the particles to the nanoscale. When a nanopowder reaches particle sizes of 20 nanometers or less, scattering effects fade, because the particles are now significantly smaller than the wavelength of incoming gamma rays.
Right now, Kahn said, they are trying to "improve the energy response, or light yield, and energy resolution by improving the glass-making process."
They would also like to scale the detector in larger and smaller dimensions, but support under a DHS Domestic Nuclear Defense Office and National Science Foundation grant has expired.
"We are seeking further sponsorship," Kahn said.