CERN: Damaged collider to restart at half energy

Physicists have used smaller, room-temperature colliders for decades to study the atom. They once thought protons and neutrons were the smallest components of the atom's nucleus, but the colliders showed that they are made of quarks and gluons and that there are other forces and particles. And they still have other questions about antimatter, dark matter and particle mass they want to answer with CERN's new collider.

They hope the fragments that come off the collisions will show on a tiny scale what happened one-trillionth of a second after the so-called Big Bang, which many scientists theorize was the massive explosion that formed the universe. The theory holds that the universe was rapidly cooling at that stage and matter was changing quickly.

Some skeptics have expressed fears the high-energy collision of protons could imperil the Earth by creating micro black holes — subatomic versions of collapsed stars whose gravity is so strong they can suck in planets and other stars.

CERN and leading physicists dismiss the fears and maintain the project is safe.

The collider's teething problems are typical of complicated accelerators, but it has been especially frustrating to physicists from around the world, who already have been waiting for years to conduct their experiments on the machine.

Physics students are even more upset because they need data from experiments for their theses.

"It's very important to get data for students who are on short time scales," Gillies said. "For career physicists it's an issue but less of one."

Gillies told the AP that CERN management decided at the beginning of the year that it would not try to repair all parts of the collider this year.

"Otherwise, we would never have had a beam before halfway through next year," he said. "So we consciously took the decision that we'll start up at a lower energy and then we'll go in when the experiments have got data to get their teeth into and then we'll do the necessary repairs to get up to 7 TeV then."

Gillies said CERN experts have examined every one of the 1,600 superconducting magnets and each of the 10,000 electrical splices as well as copper protection to carry away any spillover current to prevent damage to the magnets if they heat up as happened on Sept. 19.

They decided some of the splices need to be repaired before the collider goes to full power, but that they can operate safely up to 5 TeV without further repairs now.

That has been set as the highest energy for the collider before its next shutdown for maintenance, probably in November 2010. Then the further repairs will be made so that the energy level can be ramped up.

"We've measured some of the resistance in the copper and it's higher than it should be," said Gillies. "It's very small resistance but it's there."

Another problem with the machine is the superconducting magnets, many of which have to be "retrained" to be able to handle energy up to 7 TeV. Training a magnet is done by applying higher and higher energy to each one until they can safely go up to the design level.

In the examination of the collider over the past year it has been found that some of the magnets have somehow become "detrained," so the process has to be repeated on each of them, Gillies said.

Gillies said he was aware some people have been questioning whether the collider would ever run as planned.

"It'll work," he said.

CERN's director-general, Rolf Heuer, said the collider has been studied very carefully and is much better understood than a year ago.

"We can look forward with confidence and excitement to a good run through the winter and into next year," Heuer said.

At present CERN's member states are Austria, Belgium, Britain, Bulgaria, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden and Switzerland.

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