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Atom collider successfully restarts

GENEVA — Scientists switched on the world's largest atom smasher Friday night for the first time since the $10 billion machine suffered a spectacular failure more than a year ago.

It took a year of repairs before beams of protons circulated late Friday in the Large Hadron Collider for the first time since it was heavily damaged by a simple electrical fault.

Circulation of the beams was a significant leap forward. The European Organization for Nuclear Research, known as CERN, has taken the restart of the collider step by step to avoid further setbacks as it moves toward new scientific experiments — probably starting in January — regarding the makeup of matter and the universe.

Progress on restarting the machine, on the border between Switzerland and France, went faster than expected Friday evening and the first beam circulated in a clockwise direction around the machine about 10 p.m., said James Gillies, spokesman for CERN.

"Some of the scientists had gone home and had to be called back in," Gillies told the Associated Press.

This is an important milestone on the road toward scientific discoveries at the LHC, which are expected in 2010, he said.

About two hours later, the scientists circulated another beam in the opposite direction, which was the initial goal in getting the machine going again and moving it toward collisions of protons, CERN said. The LHC also will be used later for colliding lead ions — basically the nucleus of the element that is about 160 times as heavy as a single proton. That should reveal still more scientific secrets.

"It's great to see beam circulating in the LHC again," said CERN director general Rolf Heuer. "We've still got some way to go before physics can begin, but with this milestone we're well on the way."

With great fanfare, CERN circulated its first beams Sept. 10, 2008. But the machine was sidetracked nine days later when a badly soldered electrical splice overheated and set off a chain of damage to massive superconducting magnets and other parts of the collider, in a 17-mile circular tunnel under the Swiss-French border.

CERN spent $40 million on repairs and improvements on the machine to avoid a repetition.

"The LHC is a far better understood machine than it was a year ago," said Steve Myers, CERN's director for accelerators. "We've learned from our experience and engineered the technology that allows us to move on. That's how progress is made."

The LHC is expected soon to be running with more energy than the world's current most powerful accelerator, the Tevatron at Fermilab near Chicago. It is supposed to keep ramping up to seven times the energy of Fermilab in coming years.

This will allow the collisions between protons on the machine to give insights into dark matter and what gives mass to other particles, and to show what matter was in the microseconds of rapid cooling after the Big Bang that many scientists theorize marked the creation of the universe billions of years ago.

The two parallel tubes the size of fire hoses send billions of protons whizzing around the collider in opposite directions at nearly the speed of light. In rooms the size of cathedrals 300 feet below the ground, the magnets force them into huge detectors to record what happens.

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