For several years, physicists have been wanting to build an atom smasher larger than anything in existence or under construction. As originally conceived, it would be a ring between 60 and 100 miles in circumference, a big jump up from the current record-holder, a four-mile ring at the Fermi National Accelerator Laboratory near Chicago, better known as Fermilab. It would also dwarf the 16-mile ring being built in Switzerland.

The Energy Department, which funds such facilities, has not approved the project -- the Superconducting Super Collider, which would cost about $4 billion -- but a blue-ribbon panel of scientists took a major planning step last week by announcing selection of a design for the magnets that would steer the beam of subatomic particles around the circle.

The options ranged from relatively weak magnets that would work only in a larger ring to stronger magnets that could bend the particle beam more sharply, allowing use of a smaller ring. The panel opted for the stronger magnets, which means the ring need be only 60 miles around.

Many states are vying for the smasher site, which would bring not only billions in spending but the prestige of playing host to physicists in their ultimate quest: to learn what the world is made of at the most fundamental level.