A director at the Large Hadron Collider in Geneva has told BBC News that some mistakes were made in construction.

日内瓦大型强子对撞机的一位主管称，对撞机的建设过程中出现一些错误需要修复。

The damage that occurred in 2008 took 14 months to repair

Dr Steve Myers said these faults will delay the machine reaching its full potential for two years.

The atom smasher（核粒子加速器） will reach world record power later this month at 7 trillion electron volts¹ (TeV).

But the machine must close at the end of 2011 for up to a year for work to make the tunnel safe for proton（质子） collisions planned at twice that level.

The machine only recently restarted after being out of action for 14 months following an accident in September 2008.

Dr Myers said: "It's something that, with a lot more resources and with a lot more manpower and quality control, possibly could have been avoided but I have difficulty in thinking that this is something that was a design error."

He said: "The standard phrase is that the LHC is its own prototype（原型，标准） . We are pushing technologies towards their limits."

"You don't hear about the thousands or hundreds of thousands of other areas that have gone incredibly well.

"With a machine like the LHC, you only build one and you only build it once."

He said the second problem is not with the most complex technology but involves the copper² sheaths（鞘） around the superconducting（超导的） joints³ in the tunnel.

The copper sheaths are a failsafe（破损安全，失效保护） mechanism⁴ designed to take up the current if one of the magnets（磁铁，磁性） in the Large Hadron Collider warms up - an incident known as a "quench⁵（淬火冷却，断开） ".

The 2008 accident caused one tonne of helium to leak into the tunnel and resulted in a series of "quenches⁶" and a 40m Swiss franc (£24m) repair bill.

Engineers believe the machine is now safe to run at 7TeV but are anxious to avoid another breakdown⁷.

So they have taken the decision to run the machine for 18 to 24 months at half-maximum power before switching it off for a year to carry out improvements to the 27km tunnel.

Dr Myers said the decision was taken jointly⁸ with the physicists⁹ working on the four giant particle detectors¹⁰ on the LHC.

He said they appreciate the chance to test their own equipment while the machine is running at half its maximum power.