Charles L. Britton Jr. and Alan L. Wintenberg, both of ORNL's Instrumentation and Controls Division, have designed a radiation-resistant chip for storing information resulting from particle collisions measured in a high-energy physics experiment planned for DOE's recently closed Superconducting Super Collider (SSC) project. The researchers are now looking toward designing radiation-resistant circuits for robots that may someday be used to clean up contaminated tanks at DOE waste sites.
The researchers have also designed a less expensive chip not hardened against radiation, for use in collider physics experiments at other accelerators. "Chips like this," Britton said, "could be used for storing television signals long enough to process them into improved TV images. By processing the stored signals in a few millionths of a second, TV pictures could be made clearer, sharper, and steadier."
The radiation-hardened chip was made by a special process for manufacturing complementary metal oxide semiconductor chips. Harris Semiconductor Inc. of Melbourne, Fla., developed this process to meet military needs. Britton and his colleagues developed circuits using computer-aided design and drafting tools and sent the designs to Harris by electronic mail. Harris then manufactured about 200 chips to meet ORNL's specifications.
To determine each chip's resistance to radiation damage, the ORNL researchers have subjected them to gamma radiation from a cobalt-60 source this year at Argonne National Laboratory. "These chips are supposed to be able to withstand as much as 10 million rads of radiation," Britton said. "By contrast, ordinary chips would be destroyed by about 20,000 to 30,000 rads.
DOE asked ORNL to develop radiation-hardened chips to store information resulting from high-energy physics experiments to be conducted in the Superconducting Super Collider, which has since been cancelled.
"The chips had to be hardened against radiation because of the highly energetic gamma rays and neutrons that would have been produced from proton collisions and other particle interactions," Britton said.
Radiation-hardened memory chips now will not be needed for the SSC, but they may be used for experiments involving U.S. scientists at a somewhat smaller collider to be constructed in Switzerland.
The ORNL researchers are working with ORBIT Semiconductor to produce chips that have similar circuit designs but are not radiation-hardened. These chips, which can be made for a much lower cost than the radiation-hardened ones, will be used in several upcoming experiments involving ORNL physicists. Several applications are planned for the PHENIX experiment at the Relativistic Heavy Ion Collider Center under construction at Brookhaven National Laboratory in New York and an existing accelerator at the European Center for Particle Physics (CERN) in Geneva, Switzerland.
Glenn Young, Frank Plasil, and others in ORNL's Physics Division have worked on these experiments since 1986. "In the past," Britton says, "they have used conventional electronics developed at ORNL for these experiments. But for these new experiments they will use custom chips from ORNL for the first time."
The funding for developing radiation-hardened analog memory chips for the SSC came from DOE through the SSC Laboratory in Dallas, Texas. DOE's Office of Energy Research also supports development of the other chips for the Brookhaven and CERN accelerator experiments.
ORNL, one of DOE's multiprogram research laboratories, is managed by Martin Marietta Energy Systems Inc., which also manages the Oak Ridge K-25 Site and the Oak Ridge Y-12 Plant.