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When physicists petitioned the U.S. Department of Energy (DoE) in the early 1980s to build a particle accelerator that would recreate the fiery conditions of the big bang, they picked a name worthy of its magnitude. The Superconducting Super Collider (SSC) located south of Dallas, Tex., would have outshined even the Large Hadron Collider, which after 14 years and $8 billion is about to start shooting particles around its 17-mile (27-kilometer) beam pipe on the Franco-Swiss border.
Slamming protons and antiprotons together at 40 tera-electron volts (40 trillion eV), the SSC would have put out more than enough energy to create the elusive Higgs boson, sometimes called the "God particle," which gives other particles their mass. (The less powerful LHC now has the honor of hunting the Higgs.) But escalating costs prompted Congress to cut the SSC's funding in 1993 before its components were even assembled.
Now, 15 years later, the SSC's sophisticated magnets are finally accelerating protons to high energy, but not for the pursuit of mysterious particles. Trace Life Sciences, based in Denton, Tex., bought the parts in 2003 to make radioisotopes for medical imaging and radiation therapy. If you have ever had a PET scan, the isotopes in your blood might have come from the most spectacular science experiment ever canceled.
The SSC's use in medicine may be unique, but the end comes for all particle accelerators sooner or later. Sooner is the operative word here in the U.S., where flat budgets have made it hard for many aging experiments to continue. Fermi National Accelerator Laboratory in Batavia, Ill., home to the leading Tevatron collider—soon to be eclipsed by the LHC—will shut down its machine in 2010. Last-minute budget cuts by Congress this year forced the Stanford Linear Accelerator Center (SLAC) in California to switch off its PEP-II collider in April ahead of schedule. What will happen to these enormous machines once they go off-line?
Once a particle accelerator is switched on, its fate is sealed as a research tool. The particle collisions that researchers scour for exotic debris also bombard the machine's metal parts with neutrons and other particles that render the metal radioactive. Neutron bombardment can convert iron and cobalt, both found in steel, into the highly radioactive isotopes manganese 54 and cobalt 60.
Given the potential health risks, the DoE does not allow used accelerator components to be put to public use, says Benedict Feinberg, a physicist at Lawrence Berkeley National Laboratory in California. So when an active accelerator retires, its parts typically get put to work on other particle physics experiments. The SSC's case was different: "When the Department of Energy pulled funding for the SSC project, the linac [linear accelerator] had never been assembled and tested," says William Courtney, Trace's director of accelerator operations.
The DoE's moratorium extends to steel reinforcements in concrete radiation-shielding blocks around an accelerator. When Berkeley's Bevatron was decommissioned in 1993, its concrete shielding went to the Relativistic Heavy Ion Collider at Brookhaven National Laboratory in Upton, N.Y. The experiment's large electromagnets, meanwhile, went to other particle research projects. Feinberg says a few steel magnet cores, some copper wiring and shielding blocks remain inside the Bevatron building. Radioactivity levels in these leftover parts and the building itself are now low enough that an April DoE environmental assessment slated the structure safe for demolition.