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Scientists lining up to study new elements at revamped facility
OAK RIDGE, Tenn.,
July 10, 1995
Hundreds of researchers from all over the world are awaiting their chance to unravel some of the mysteries of the universe using the Holifield Radioactive Ion Beam Facility (HRIBF) at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL).
The Holifield facility, expected to be operational in the summer of 1996, will enable physicists to create and accelerate radioactive nuclei that do not occur naturally on earth. The nucleus is the positively charged central portion of an atom. By studying products of these exotic nuclei colliding with various targets, scientists hope to learn more about how stars generate energy and perhaps why they ultimately explode. With this facility, astrophysicists and nuclear structure researchers may also learn more about the elemental history of the universe and gain answers to questions they have pondered for decades.
Construction began last year to convert the lab's Holifield Heavy Ion Research Facility into the HRIBF. The project, which began with a proposal submitted to DOE in 1991, involves reconfiguring two accelerators from the old facility and connecting them to the $3 million Daresbury Recoil Separator and the new recoil mass spectrometer. The Daresbury Recoil separator, a huge instrument, was donated to ORNL by the Daresbury Nuclear Structure Facility in England. More than half of the money for the recoil mass spectrometer was provided by the state of Tennessee and a group of southeastern universities.
Scientists will use the Daresbury Recoil Separator to separate and measure products of fusion reactions from radioactive beam particles. Light ion beams from an accelerator produce isotopes that don't exist on earth. These isotopes, which are produced in a nuclear reaction, are then accelerated in the 25-million-volt tandem electrostatic accelerator. The process of accelerating, or firing, heavy radioactive particles at hydrogen targets simulates what happens as stars explode. During this process, light elements, such as carbon and oxygen, are converted to heavier elements, generating a tremendous amount of energy. Such explosions, called novae or supernovae by astronomers, also scatter heavy elements into space, where they can form other bodies, such as our planet Earth.
When the HRIBF is completed, scientists hope to explain some of the events, such as exploding stars, seen recently through the increasingly sophisticated astronomical instruments, such as the Hubble Space Telescope and those at the Compton Gamma Ray Observatory.
An important milestone in the project was reached in November, when the Radioactive Ion Beam (RIB) injector platform produced its first stable beam in the electron beam plasma, target-ion source. This even showed equipment on the high-voltage platform was operational and that work could begin on the next phase of the project, said Jerry Garrett, scientific director of the Holifield facility. The next phase of the conversion involves connecting the beam transport line of the RIB injector to the tandem electrostatic accelerator. This portion of the project is expected to be complete this summer, Garrett said.
"By the end of summer, we hope to have the first accelerated radioactive ion beams from the facility," Garrett said. With these new beams of radioactive ions, scientists will be able to produce and study 150 to 200 new "nuclear species." About 285 exist in nature.
"The driving force is the physics," said ORNL physicist Ron Auble, adding that the HRIBF will be an important tool for expanding research. "The physics community is interested in studying beams we're planning to produce," said Auble, who described the research as "exciting new physics" that provides researchers with great opportunities.
Scientists are expected to come from several universities, including the University of Tennessee, Georgia Tech, Louisiana State University, Mississippi State University, the University of North Carolina, Vanderbilt University, Yale University, England's universities of Liverpool and Surrey, the University of Giesson in Germany and Edinburgh in Scotland, Garrett said. Thirty percent of the researchers expected to conduct experiments at the new facility are from outside the U.S.
Japanese and Italian researchers are also studying all aspects of the facility, which represents a major technological feat in itself, said Alan Tatum, an engineer in ORNL's Physics Division. From an engineering perspective, one major challenge involved designing the radioactive beam facility within the existing building. It wasn't practical to move the two massive accelerators, so ORNL engineers had to work with that constraint. Other hurdles included developing an ion source and designing beam line transport systems, a remote handling system for the radioactive source, and the necessary vacuum control, electromagnetics and electrostatic systems. Critical alignment to ensure the beam follows a prescribed course is also vitally important and poses further engineering challenges.
In addition, the HRIBF requires a high-voltage (300,000 volts) platform, which provided an array of engineering challenges of its own. The platform, needed for the ion source and isotope and mass separators, rests atop insulated footings, about four feet above the floor. Platform edges are rounded to prevent the tremendous amounts of electricity from arcing to the concrete walls.
Engineers also had to design the facility so that electronic equipment would be protected from radiation generated when the HRIBF is operating. Electronics are quickly damaged by radiation, Tatum said.
The cost of the project is $2.6 million, which ORNL researchers describe as modest considering the expected benefits. Funding was provided by DOE's Nuclear Science Division, Garrett said.
You can learn more about this research and many other exciting projects by visiting ORNL on Oct. 21, 1995, during its Community Day event. Many of our facilities will be open to the public that day. For additional information, call ORNL Public Affairs, 865-574-4160.
ORNL, one of DOE's multiprogram research laboratories, is managed by Lockheed Martin Energy Systems, which also manages the Oak Ridge K-25 Site and the Oak Ridge Y-12 Plant.