Powering the Large Hadron Collider

When the LHC starts up tomorrow, it will draw twice the power of nearby Geneva

9 September 2008—The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN), set to start up tomorrow, is the largest physics experiment in history, and it’s probably the most power hungry. Spanning the border between Switzerland and France, the 27-kilometer accelerator ring with its accompaniment of radiation-hardened integrated circuits, feeder accelerators, computers, and supercooled superconducting magnets will, according to varying estimates, draw between 220 and 300 megawatts of electricity—enough to power the city of Geneva twice over. Keeping the power flowing reliably takes a good bit of ingenuity, as a sudden loss of power could mean serious damage to the machine and months of lost work.

Once all of these accelerators are fully operational in 2009, CERN’s estimated annual electricity consumption could approach 1000 gigawatt-hours, IEEE Spectrum learned on a visit to the lab in July. The massive LHC will account for about 60 percent; less than 15 percent of the total will go to mundane functions like keeping the lights on; and the other accelerators in the complex will account for the rest. A big part of the consumption is the hundreds of enormous superconducting magnets, though they draw much less power than equivalent conventional magnets would. The superconductors must be cryogenically cooled to temperatures between 1.8 and 4.5 kelvins (colder than outer space). If the temperature creeps even a fraction of a kelvin above that, the magnets stop working and lose control of the beam. An uncontrolled beam can melt 500 kilograms of copper in an instant, causing serious damage and halting the experiment for months. So it is crucial to keep power flowing into CERN at all times.

But CERN does not generate any of its own power, so how does it ensure an unbroken supply of electricity?

The LHC’s location enables a unique power procurement system: power comes in from both France and Switzerland. CERN has an agreement with French supplier Électricité de France (EDF) that guarantees a source of reliable, affordable electricity, with one caveat: for 22 days a year during the winter, power costs become prohibitive. (During that time, all the experiments at CERN are shut down.) The contract stipulates that the accelerators will operate mainly from spring to fall, when the public strain on the electrical grid is low. The agreement also means that CERN must reduce its electricity consumption on demand or pay a whopping fine.

But what if EDF’s system fails? Because the results of a power outage would be so disastrous, CERN also has a number of backup plans. For one, the laboratory has a system that can seamlessly switch to the Swiss power grid. In the event of a catastrophic failure that knocks out both the Swiss and French grids due to, for example, a natural disaster, CERN has several massive diesel generators designed to power submarines, which are poised to roar to life at the first hint of an emergency.

”We can’t keep the machine and experiments running on diesel,” says CERN physicist Rüdiger Schmidt, ”but we can supply enough emergency power to safely shut them down.”

Figuring out how to control the laboratory’s grid with the LHC at full power was a challenge because this state-of-the-art experiment rests on a good deal of 1970s-era infrastructure—including four smaller accelerators that feed into the LHC.

For most of CERN’s existence, management of experiments was decentralized, with local control rooms presiding over their respective accelerators. But the sensitivity of the LHC, combined with its dependence on older infrastructure, caused CERN officials to reconsider this system. In early 2006, the CERN Control Centre (CCC) was built on the French side and reigns sovereign over all operations.

”This way, you can immediately see if there is a problem in any of the accelerators” or any of the electrical supplies or cryogenics equipment, says Bettina Mikulec, an engineer for one of the feeder accelerators who also worked on the construction of one of the major LHC experiments. And in fact, on the hot July day of the IEEE Spectrum visit, a problem with one of the older accelerators upstream of the LHC had shut off all power to the accelerators downstream, including the LHC itself.

The CCC looks almost like an Ikea office showroom—all glass and blond wood and polished metal. Sliding glass doors part quietly into a large, modern room with windows that stretch all the way up to the high ceiling. The room is divided into four workstations, circular islands inside which technicians gaze at their respective panoply of screens. Two islands control the various older accelerators that feed into the LHC, and one is dedicated to the big accelerator itself. In the fourth quadrant is an island devoted exclusively to the maintenance of the CERN infrastructure. Unlike the other stations, which control experiments with significant downtime in the winter, that fourth station is manned 24 hours a day, seven days a week, 365 days a year. There, engineers are able to divert, start, and stop power to any of the accelerators, or any other part of CERN.

On the day of our visit, one screen at the station showed an influx of 87 MW of electricity. By tomorrow that amount will seem just a trickle, as the power ramps up to 220–300 MW.