The Large Hadron Collider will soon be ready for use, but after last year's systems failure a different approach will be taken to firing it up next time, writes DICK AHLSTROM
THE TEAM preparing for the restart of the world’s biggest atom-smasher has decided that when it comes to energy, less is more. They plan to take a “conservative” approach when firing up the repaired Large Hadron Collider in mid-November.
The Large Hadron Collider (LHC), based at Cern, the European organisation for nuclear research, started up on September 10th last year, but within nine days a serious systems failure forced it to shut down.
It has taken more than a year and €26 million to repair the damage, but this remarkable machine, built at a cost of €4 billion, will soon be ready for service, says Belfast man Steve Myers. As Cern’s director of accelerators and technology his role has earned him the nickname “the lord of the rings”.
The LHC is a 27km-long ring around which hydrogen nuclei are sent spinning at close to the speed of light. It carries two beams, circulating in opposite directions, which can be crossed to create atomic collisions of incredible power.
The particles are tiny, but collisions release enormous energy given their speed. Temperatures at the point of collision reach into the millions of degrees. The LHC will allow scientists to recreate conditions as they were a tiny fraction of a second after the Big Bang that created the universe we see today.
None of this is possible without a way to keep the beams moving fast and in a controlled direction and this is achieved using 1,600 huge superconducting electromagnets positioned along the ring.
These are not your typical magnets. Each contains 10,000 tonnes of iron, more than was needed to build the Eiffel Tower. They are also chilled to an astounding minus 271.3 degrees using liquid helium.
Unfortunately, some of these failed causing the shutdown of the LHC barely a week after starting up. It was a decidedly high-profile failure, given the international public interest in what the LHC might discover and the intensive coverage afforded it by the world’s media.
“The whole business from last September, the repair of 53 magnets and the reconditioning of spares, the total cost has been 40 million Swiss francs (€26million),” says Myers.
While the shutdown was a blow, it has not been without some gains, he believes. “We understand the LHC much better, we have discovered lots of things,” he says. “It may have been a benefit in disguise. Now I think there can’t be any more surprises, so we should start off with a beam by mid-November.”
The final system tests were signed off at the end of July and Cern has announced a conservative start-up plan, which will keep beam energies low, at least in the beginning.
Physicists measure energy in “electron volts”, which in the case of colliders reaches into the millions and billions of electron volts. The highest collider energies yet achieved, by Fermilab in the US, stand at one million million electron volts, or one Teraelectron volt (1 TeV).
The LHC is designed to achieve routine energies as high as 14 TeV, about the energy of two speeding locomotives colliding head-on. But planners, including Myers overseeing the restart, are going to start start low and then slowly build up energy levels to 3.5 TeV per beam line or a combined 7 TeV. “It is a little bit of caution,” Myers acknowledges.
“We decided the priority was to get some data,” says Cern’s spokesman James Gillies. “The 3.5 TeV is very conservative, but it will allow the experimenters to get their hands on some data.”
The team also made another important decision – to run the LHC without interruption through the coming winter, Myers adds. “The schedule at the moment calls for us to run from this November through to October next year.” The practice with the LHC’s predecessor, the Large Electron–Positron Collider, had always been to shut down during the winter months.
This allowed for maintenance, but it also meant that the collider was not drawing down more costly electricity during the coldest time of the year.
The mood at Cern is certainly improved from last September, Myers adds. “People have been working flat out for three years to get the machine going and people are feeling confident about [the start up]. We are all looking forward to it.”