Large Hadron Collider to restart in fall after 1-year hiatus

The world's largest particle accelerator is scheduled to gradually start up again in November after being shut down for more than a year.

Won't reach full energy for more than a year

The world's largest particle accelerator is scheduled to gradually start up again in November after being shut down for more than a year.

The Large Hadron Collider, which straddles the Franco-Swiss border on the outskirts of Geneva, will initially run at 3.5 tera-electron volts (TeV), or 3.5 million-million electron volts —half of its official maximum energy per beam — reported the European Organization for Nuclear Research (which goes by the French acronym CERN) Thursday.

The accelerator, which is designed to smash subatomic particles into each other at high speeds in order to break them down and allow the discovery of smaller, more fundamental particles, isn't scheduled to run at full energy for at least another year.

"We've selected 3.5 TeV to start because it allows the LHC operators to gain experience of running the machine safely while opening up a new discovery region for the experiments," said the group's director general, Rolf Heuer, in a statement.

The $9-billion project was shut down on Sept. 19, 2008, after just nine days of operation. The meltdown of a small electrical connection had caused the release of a large amount of liquid helium into the 27-kilometre long tunnel, near the Franco-Swiss border. Its restart date has been delayed several times since then.

The problems have been traced to abnormally high resistances found in the accelerator's high-current superconducting electrical connections. Those were repaired, and testing showed no further problems, CERN reported this week.

"This means no more repairs are necessary for safe running this year and the next," the news release said.

Heuer said the machine is now "a much better understood machine than it was a year ago." CERN expects to run the collider at 3.5 TeV for several weeks until a "significant data sample" has been collected, then gradually increase the energy to 5 TeV per beam. It expects to run a test with lead ions at the end of 2010 before shutting the machine down again in an effort to get it ready to move towards its maximum power.