IT WOULD be easy to hate this place. It is decrepit and grey, and feels overwhelmingly like a neglected university campus.The fact that the March sky is the colour of damp concrete and releasing sleet that barely falls does not help. During my long tramp across the sprawling particle physics lab near Geneva, it seems to slap into my face like a cold, wet mop. Then there’s the buildings are numbered. There is no discernible system. Once they’d found building 217, finding the Higgs boson must have been a walk in the park.
I could get excited by the fact that somewhere beneath my feet is the Large Hadron Collider – except that there are no particle beams whizzing around its gigantic tunnel. No data is being gathered in preparation for an announcement that will thrill the world. CERN has no magic today: it’s just grim. Until, that is, I meet its people.
You could be forgiven for thinking CERN’s work is done. After all, the Higgs boson has been found, and the machine that nabbed it has been sitting idle since mid-February. But the place is still buzzing. In a million minutes’ time, come February 2015, the LHC will start up again, revamped and raring to go. Last year, running at an energy of 7 tera-electronvolts, it saw the Higgs boson. When it restarts, it will be capable of more than 13 TeV.
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Or at least that’s the plan. “There’s a lot to do before then,” says Mike Lamont. He has a slightly distracted air, as if he is seeing the world about 20 minutes into the future. Maybe that’s why he walks and drives between the various CERN facilities so fast: clearly, his body is forever trying to catch up with his mind. For Lamont, 2015 is coming soon – very soon. He is responsible for making sure the beams of particles go around the upgraded accelerators just as they are meant to. That means making all the beam-bending magnets work perfectly, which means, essentially, that his work is now back where it was in 2008.
Before the LHC turned on, nobody knew whether the machine would work as it was supposed to. No one was more elated than Lamont when it managed to circulate a beam of protons. And no one was more crushed when, eight days later, a bad soldering joint caused a short circuit that ripped apart scores of his precious magnets in the 27-kilometre-round tunnel. “We’re now making sure that can’t happen again,” Lamont says.
In the vast hangar that is building 180 (half a kilometre north-west of building 181 and even farther from building 179), he shows me some of the safeguards being put in place. One is a set of springy copper talons that stretch between segments of the magnets and ensure that electrical connections remain intact even when all the components are at the operating temperature of -271 °C.
Before the machine turns back on, Lamont will have overseen the opening up of all of the 1695 devices that surround the magnets and keep them cool. Once they are open, his technicians will repair upwards of 1000 of the 10,170 electrical joints. They will also swap 19 of the magnets for ones in better condition, and install extra pressure-relief valves. If something should go wrong, and an electrical arc vaporises the superfluid helium that cools the magnets, they want all that expanding gas to escape before it does the same kind of damage as last time.
And that’s only the damage-limitation work. They still have to show that the upgraded magnet systems work. That’s what’s being tested right now in enormous rigs that cool the magnets and monitor the fields they produce. The hard part is getting the field shapes exactly right, so that they guide and focus the particle beams on target. “It’s a bit of a dark art,” Lamont says.
Lamont is not the only one under time pressure. “When they made the decision to delay the shutdown so they could take another week’s data, some people round here got very anxious,” says Steve Goldfarb, who works on , one of the LHC’s four huge underground detectors. That’s why the experimenters got to work as soon as it was safe to enter the LHC tunnel, after the proton beams switched off in February.
Every day a dozen or so people swarm over and inside ATLAS, repairing it and preparing it for 2015. “After all this time, there are things that don’t work as well as they used to: when you have 100 million active components, there are things that break,” Goldfarb says. Technological advances mean that it is now worth replacing some components with improved versions. And then there’s upgrading ATLAS to give it new capabilities. “We’ve put in an extra layer of tracking that will allow us to identify different types of particles.”
When Goldfarb uses “we”, it’s a very collective term. “Most of us aren’t going down there and working on the detector,” he says of the 3000-strong team of scientists.
Border restrictions
Despite the sense of urgency, those that do go into the tunnel keep reasonable hours – for now, at least. At this point in the long shutdown, there’s no point in working people to exhaustion: tired physicists are apt to make mistakes. Haste can be a dangerous thing, according to Stéphane Wiand, who heads one of CERN’s fire crews. With the pressure on for everything to be ready for the restart, people might be tempted to cut corners with safety. “We know that everybody will work in a bit of a hurry because the planning time is short,” Wiand says.
The clock is ticking wherever you are at CERN. Maria Borge, for example, has to tear down and rebuild a couple of buildings within the next few months. Borge is the director of a facility called , which produces beams of radioactive ions for probing the properties of atoms, construction materials and biological tissue. As well as undertaking the building projects, the ISOLDE team is upgrading its accelerator. Borge has a different problem to the LHC; hers is not the largest accelerator in the world, but it is probably the only one constrained by an international border.
The easiest way to upgrade the accelerator would have been to make it longer. Unfortunately, because of where it sits on the CERN site, that would mean the accelerator crossing from France into Switzerland, and that’s not an option: none of CERN’s buildings above ground are allowed to straddle the international frontier.
Different rules apply to the LHC because it sits 100 metres below the surface. “I think it’s so that, if war breaks out between France and Switzerland, they can both patrol their side of the border,” Borge says.
To operate at a higher power without upsetting higher powers, ISOLDE’s design team has come up with a set of magnets that are supercooled to create fields powerful enough to accelerate the particles to the required energy before they reach Switzerland. “At ISOLDE we do politically motivated innovation,” Borge says with a grin.
That innovation has to be ready well before the LHC starts up again. Borge already has researchers pencilled in to smash the new high-powered beams into their various targets next year. And that, in turn, means that Detlef Küchler, over in building 9 (next door to buildings 628 and 101) has even less time to get ready.
Küchler’s job is to supply all the various things that CERN researchers want to smash together. He is the starting point for every single accelerator experiment, the guy that provides the radioactive ions and protons that might end up as away or as for detailed experiments on antimatter. Whatever you might read in the papers, CERN is not just about the LHC – a network of a half-dozen accelerators take Küchler’s particles.
Many of the experiments at the ends of these accelerators are scheduled to be up and running again just as soon as Küchler can get them going. He is facing what he admits is a “huge work schedule” to make sure the various upgrades to the sources are ready. “Two years?” he scoffs. “We restart at the beginning of next year.”
As if there weren’t enough things to worry about with this shutdown, Küchler and his team are already thinking about the next shutdown in several years’ time. When CERN halts its experiments again in 2017, they will replace the source of protons for the LHC with one that provides even more protons.
At least they know what they’ll be doing the next time the accelerators turn off. Ten kilometres north and 100 metres beneath the ground under Cessy in France (the village where Tim Berners-Lee lived when he invented the World Wide Web), researchers are gazing into crystals desperately trying to see the future of their detector. It’s not fortune telling, just a case of seeing how well another of the LHC’s giant experiments is faring – the .
Every time the CMS detector’s lead tungstate crystals are hit by particles, they emit light, which is collected and analysed to reveal what kind of particles are flying around. But these events also affect the crystal structure, reducing the amount of light the crystals will put out the next time a particle hits them. In the past two years they have received only 5 per cent of the radiation they are due to receive in their lifetime, but it’s important to figure out now whether they are becoming too dark too quickly. “You have to think about the time it takes to build things,” says Dave Barney, who leads the team that relies on the crystals. “We may need to build a new detector, and if you don’t start thinking about that now, it won’t be ready by the time you need it.”
Barney’s detector is relatively low-maintenance compared to other parts of CMS. That doesn’t mean his team can relax and put their feet up, though. CMS splits open fairly easily into 11 separate pieces, but researchers on other projects will need to pull some of those pieces apart, potentially breaking Barney’s detector. “It can become a nightmare of epic proportions,” Barney says.
Kicks from computing
In the meantime, there is plenty of CMS computing to work on: upgrading algorithms and processors, and the custom-designed electronics that decide whether or not it is worth hanging on to the data coming out of the detector. It’s the kind of task that CERN’s head of IT, Frédéric Hemmer, has to keep an eye on during the shutdown. The demands on his team haven’t diminished since the accelerators were turned off and the data stopped flowing from the detectors. The requests that they somehow do their work without altering anything keep on coming. “When the machines are running, they tell us we can’t modify anything,” Hemmer says. “Now that the machine has stopped, they tell us not to change anything because they need everything running as they go inside.”
Hemmer has to ignore some of the pleas: his team has work to do, too. All around the 27 kilometres of the LHC ring, for instance, technicians are installing Wi-Fi to improve in-tunnel communications between researchers. They also have to replace 500 network switches during the shutdown. “You can’t do that when the machine is running because the control system depends on them.” Others are preparing new data centres that will store the results of the LHC’s next experimental run – at the same time keeping all the previous data available for the experimental teams to analyse. Theorists, meanwhile, want ever more computing power because they are busy simulating what they expect from the machines when they turn back on. “Computing is essential to the discoveries now,” Hemmer says. “We get quite a kick out of that.”
Some time in the next few months, Hemmer’s team will also upgrade the wall-mounted electronics and servers in , and that prospect is giving the room’s occupants a new headache. What will they do with all the empty bottles of champagne arranged along the cupboard tops? Every significant CERN event, every achievement of every experimental team, is fully celebrated, with the successful teams responsible for buying the booze. With all the success here over the last few years, that adds up to a lot of bottles.
“What will they to do with all the empty bottles of champagne arranged along the cupboard tops?”
Today, though, the control room is quiet apart from the noise from construction of the new visitor centre next door. “It’s a bit sad to see the place so empty,” says Mirko Pojer. Lamont doesn’t agree. “It means there’s less going on for me to worry about.”
Lamont and Pojer were both here when the magnets blew up. It was a horrible moment, Lamont recalls. But it is very much in the past. Since then, CERN has become almost legendary, a place that attracts around 100,000 visitors a year. Almost everyone on the planet knows about the LHC, and the boson its researchers found last year. In fact, the only CERN staff that could justifiably take it easy during the shutdown are the press officers. Renilde Vanden Broeck has stopped telling people where she works when she goes away on holiday. “People just mob me – they want to know everything about the place,” she says. Clearly, her work here is done. For everyone else, though, it’s only just begun.
This article appeared in print under the headline “Million minute makeover”
