Collider 'needs warning system'

By Pallab Ghosh Science correspondent, BBC News

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LHC project leader Professor Lyn Evans shows how the super-conducting magnet was damaged

An official investigation into the accident at the Large Hadron Collider has recommended that an early warning system be installed.

This system would detect the early stages of a helium leak, following an incident that has shut down the LHC until June 2009.

The collider is built to smash protons together at huge speeds, recreating conditions moments after the Big Bang.

Scientists hope it will shed light on fundamental questions in physics.

Basically, they have been pulled off their feet and the interconnects have been broken Lyn Evans, Cern

The report identified the uncontrolled release of one tonne of helium gas as the cause of damage to 53 superconducting magnets.

Better gas pressure release valves could avoid a repeat of the accident on 19 September, it says.

The investigation carried out for the European Organization for Nuclear Research (Cern), confirmed that the cause of the accident was an electrical fault in one of the connectors linking one of the 1200 superconducting magnets that accelerate sub-atomic particles around the LHC.

The fault triggered the release of helium gas within one of the magnets.

Sudden release

It has emerged that valves that should have released the gas pressure couldn't cope with the sudden build up of helium. That led to an uncontrolled release which knocked one of the magnets forward, pushing it on to the magnet in front, dislodging it.

Guide to the Large Hadron Collider and how it works

"Basically, they have been pulled off their feet and the interconnects have been broken," said LHC project leader Professor Lyn Evans.

Prof Evans said the incident happened at the very end of the LHC's commissioning process.

"We are extremely disappointed, especially as we had already commissioned seven of the eight sections of the LHC up to full energy," he said.

"This was the last sector to be commissioned and this was really the very last electrical circuit. I must say it felt like a real kick in the teeth."

The report also confirmed the damage would cost