Damage to the world's largest particle accelerator will take much of the winter to repair, the European Organisation for Nuclear Research (Cern) has said.
The problems, caused by a single bad electrical connection, will be fixed over the winter and the Large Hadron Collider (LHC) will be back in operation next spring, Cern spokesman James Gillies said on Friday.
But damage to insulation and other parts around 29 of the magnets will most likely require that they be brought to the surface for repair.
The failure of the LHC, just days after it was launched, was caused by an electrical arc that punctured an enclosure holding the liquid helium used to keep the collider cold, said a Cern statement.
Around six tons of helium leaked out as a result, three times as much as originally thought.
The remaining 114 tons of liquid helium in the collider was unaffected by the leak, said Gillies.
He added that Cern had enough spares to make any needed replacements of the equipment, but that the repairs would take the whole winter.
It takes one month to warm the LHC gradually to room temperature from its operating temperature at near absolute zero, colder than outer space. Once the repairs are made, it will take another month to re-cool it.
The cost of fixing the $10 billion (SFr11.34 billion) machine is not yet known.