Nuclear physicists working on the large hadron collider have been pleasantly surprised at how the machine has responded after its restart on Friday.

The $10bn atom smasher – located deep below the French-Swiss border – was heavily damaged by a simple electrical fault in September last year.

Some scientists had gone home early on Friday and had to be called back as the project jumped ahead, James Gillies, spokesman for the European Organisation for Nuclear Research, also known as Cern, reported.

At a meeting early yesterday "they basically had to tear up the first few pages of their PowerPoint presentation which had outlined the procedures that they were planning to follow", he said. "That was all wrapped up by midnight. They are going through the paces really very fast."

Cern has taken the restart of the collider step by step to avoid further setbacks as it moves toward new scientific experiments regarding the makeup of matter and the universe. It had hoped by early yesterday to get proton beams in the collider moving in a 27km circular tunnel, but things went so well on Friday evening that it had achieved the operation seven hours earlier.

Praise from scientists around the world was quick. "First beam through the Atlas!" whooped an internet message from Adam Yurkewicz, an American scientist working on the massive Atlas detector on the machine.

"I congratulate the scientists and engineers that have worked to get the LHC back up and running," said Dennis Kovar of the US department of energy, which participates in the project.

"The LHC is a machine unprecedented in size, in complexity, and in the scope of the international collaboration that has built it over the last 15 years," said Kovar.

Cern is using about 2,000 superconducting magnets to improve control of the beams of billions
of protons so they will remain tightly bunched and stay clear of sensitive equipment.

Gillies said the scientists are being very conservative. "They're leaving a lot of time so that the guys who are operating the machine are under no pressure whatsoever to tick off the boxes and move forward," he said.

Officials said Friday evening's progress was an important step on the road toward scientific discoveries at the LHC, which are expected in 2010. "We've still got some way to go before physics can begin, but with this milestone we're well on the way," Cern director general Rolf Heuer said.

With great fanfare, Cern circulated its first beams on 10 September 2008. But the machine was sidetracked nine days later when a badly soldered electrical splice overheated and set off a chain of damage to the magnets and other parts of the collider.

Cern said the improvements since then have made the LHC a far better understood machine than it was a year ago.