ACADEMIA

A new Oak Ridge National Laboratory initiative will consolidate and expand the lab's research and development efforts in radiation detection technologies. The goal of the new Center for Radiation Detection Materials and Systems (CRDMS) is to establish ORNL as the nation's central national laboratory for innovation and development in the field of radiation detection materials and systems. Center Director Lynn Boatner said the program is the latest chapter in a rich ORNL history of radiation detection research that includes development of technologies for national security, non-proliferation, worker safety, medical imaging and other applications. "This center takes what is currently a collection of relatively independent projects and pulls them together into a program with more focus on major goals. It will coordinate and concentrate our efforts by bringing together ORNL physicists, chemists, materials scientists, crystal growers, nuclear engineers, and electrical and electronics engineers," said Boatner, a materials physicist in ORNL's Condensed Matter Sciences Division and an ORNL Corporate Fellow. "There is a lot of expertise here, but we have lacked a cohesive program. Now, in place of individual proposals and relatively small projects, we plan to take on more global challenges." Radiation detection research at ORNL began with reactor and physics instrumentation developed here in the early 1940's. Today, ORNL is a leader in the technology behind radiation detectors that use scintillators - high density crystal, glass, or polymeric materials that give off photons of light when exposed to radiation. The photons are then amplified and converted to electrons which produce an electrical signal that is measured to give a radiation detection reading. Radiation detectors are fabricated from a variety of materials and include electronic materials like germanium and cadmium zinc telluride and scintillators such as lanthanum bromide and lutetium silicate. Materials' properties vary widely: germanium detectors have excellent energy resolution but must operate at cryogenic temperatures, while scintillators operate at room temperature but generally have poor energy resolution. The new center will focus on new crystal growth, fabrication, and characterization methods, continuing an impressive record of scintillator materials development via crystal growth, hot pressing, glass synthesis, sol-gel processes, and other novel methods, Boatner said. Hot pressing uses pressure and heat to mold ceramic powders to form high density bodies with controlled microstructures. In sol-gel chemistry, nanoparticles are formed in a liquid phase, condensed into a gel, and dried at low temperatures. The process allows scientists to change the structure of the material at the nanoscale (billionth-of-a-meter) and create ceramics at near-room temperature. At ORNL, Boatner and colleagues are using a hot press-based process to develop a more versatile, faster way to produce large inorganic scintillators by first synthesizing zinc oxide nanoparticles doped with gallium. Sheng Dai, ORNL Chemical Sciences Division, has used sol-gel processes to form both nanocrystalline and glass scintillators. Boatner said another center priority is to move ORNL technology into the marketplace. Over the years, ORNL scientists have formed companies like ORTEC and TENNELEC for commercial applications of radiation detection technologies. More recently, Zane Bell, ORNL Nuclear Science and Technology Division, has led the development of a new radiation detector material and detector prototype to be licensed to NucSafe, a local radiation detector manufacturer. Bell also is co-developer of the HotSpotter, an inexpensive, handheld gamma-ray spectrometer that uses a cadmium tungstate scintillator. Boatner said the new center will hone technologies to detect illicit nuclear threats such as "dirty bombs," locate stolen nuclear weapons, and verify international agreements to dismantle and convert nuclear warheads into fuel for U.S. nuclear power plants. It also will exploit ORNL's world-class facilities for fabrication and characterization of radiation detector materials, Boatner said. Those facilities include the Environmental Effects Lab, the High Flux Isotope Reactor, the Spallation Neutron Source, the Center for Nanophase Materials Sciences, Leadership Class Computing, and the nation's best facilities for radioisotope preparation and radiation calibration. "ORNL has the most complete set of materials fabrication capabilities in the nation," Boatner said. "We can do almost every known crystal growth technique, and with the capabilities of HFIR and the SNS, ORNL will have the world's finest neutron analysis tools to characterize properties of new scintillator and electronic radiation detection materials including the purity, structure and performance of crystals."