Large Hadron Collider Is Set to Halt for Upgrades

Maintenance, improvement work and data analysis will keep scientists busy as the European collider's planned closure begins

By Geoff Brumfiel and Nature magazine

CERN's visitor center in Geneva will remain open during LS1. Image: Flickr/Ricardo Hurtubia

With the discovery of the Higgs boson or something very like it under its belt, the world?s most powerful particle collider is ready to take a well-earned rest. The Large Hadron Collider (LHC) will shut down on 11?February ahead of around two years of upgrade work.

The break, known as LS1 for ?long stop one?, is needed to correct several flaws in the original design of the collider, which is located underground at CERN, Europe?s particle-physics laboratory near Geneva in Switzerland. The fixes will allow the collider to almost double the energy at which it smashes protons together.

But there will be no long holiday for the thousands of physicists who depend on the LHC for their data. A bruising schedule of maintenance, upgrades and forward planning will keep the scientists who work on the collider?s detectors busy (see ?Down time??). Meanwhile, graduate students and postdocs will be poring over the past three years? worth of data, refining their measurements of the Higgs-like particle discovered last summer and searching for any unusual signals. ?It?s absolutely not time off,? says Dave Charlton, the deputy spokesman for ATLAS, the largest detector at the LHC.

Image: Courtesy of Nature magazine

The LHC?s spectacular run got off to a shaky start in 2008. Shortly after operators fired it up, a single bad electrical connection caused coolant to vaporize, triggering an explosion that damaged an entire sector of the machine (see Nature 455, 436?437; 2008). Repairs took more than a year, and a subsequent review revealed potentially dangerous flaws in the original design, according to Steve Myers, CERN?s director for accelerators. The worst lay in a system of copper bars designed to draw current away from delicate superconducting cables in the event of an emergency shutdown or failure. The way in which the bars had been installed made them vulnerable to failure, Myers says.

To protect the machine from further disaster, the accelerator team made the decision to run the collider at half power until all 10,000 copper connections could be repaired and additional safety measures put in place. These repairs will begin almost immediately after the LHC switches off and will involve hundreds of people working double shifts, Myers says. The goal is to restart the collider at its full design energy of 14?teraelectronvolts by December 2014, but the complex schedule will be extraordinarily tight. ?There?s no margin,? he says.

Cathedrals of science
Meanwhile, crews responsible for the underground detectors will take advantage of their first full access to the machines in more than three years. ?The experiments at the LHC are a lot like satellites?, says Paolo Guibellino, the spokesman for ALICE, a detector that collects data on collisions of heavy ions such as lead and gold.

The innards of the instruments ? the largest of which is 46 meters long and 25 meters wide, half the size of Notre Dame cathedral in Paris ? have been largely inaccessible since the LHC began running in 2009. Now, hard-hat-wearing scientists responsible for the machinery will pull them open to conduct repairs and upgrades. ALICE, for example, will get a new set of instruments designed to track electrons and photons flying from collisions.

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