Yellow, purple and metallic crystals used in the detection of radiation levels are developed from research in WSU’s Center for Materials Research (CMR).
Border crossing control, nuclear weapons dismantling, airport baggage scanning and medical imaging, start with crystal research headed by Director of the CMR Kelvin Lynn. The department grows fluorescent yttrium aluminum garnet (YAG) and cadmium zinc telluride (CdZnTe).
Drew Haven, a graduate research student in the CMR who works with the YAG crystals, said they study growth methods in the attempt to remove microscopic defects.
“We basically try to eliminate defects within the crystal structure to improve light output and therefore resolution,” Haven said. “(The defects) are never going to be gone entirely, but the goal is to limit or negate the issues.”
Depending on the light output of a material, YAG crystal detectors can determine the energy level of the radiation and consequently what the radiating object might be, Haven said. In the lab, they study the effects of altering variables like the doping substance in the crystal solutions, the atmosphere elements in the Czochralski furnace and the chamber temperature, he said.
“These crystals are much more perfect than anything you would actually find in nature,” Haven said. “Most garnets or rubies that are grown are not a particularly good quality, but that is what makes them perfect for gemstones.”
Jeremy Kingma, a graduate research student in the CMR, said the program at WSU is one of few in the country and is gaining recognition because the crystal growing industry is in high demand. He said the graduate students and Lynn each write grants for funding as part of the program.
“Writing grants is a lot of work, but it is good to go through the process and learn how to do it,” Kingma said. “With the newer growth methods I am researching, we are just trying to perfect the process so we can show funding agencies we are capable of growing this particular type of crystal.”
The crystal growth method Kingma researches may not produce a crystal as robust as the crystal produced by Haven’s Czochralski furnace method, but may be able to detect neutrons in radiation, Kingma said.
Santosh Swain, a graduate research student in the CMR, said the different crystals have different applications, making each important in certain circumstances. YAG crystals can provide better resolution in medical imagery, while CdZnTe crystals can detect infrared radiation, he said.
“They can get bigger crystals, so if the radiation energy is highly energetic and needs a thicker material to pass through and stop it, then theirs is the option,” Swain said. “(CdZnTe) has a lower stopping power, but can be used in compact and handheld detectors.”
Amlan Datta, a graduate research student the CMR, said CdZnTe research is in demand because it is useful to organizations like the Department of Homeland Security. He said he hopes to continue research in the growing industry.
“I joined Dr. Lynn’s group because I heard the group is working well when it comes to detecting radiation,” Datta said. “The demand of this material is very high and attractive.”