How To Fix a Broken Collider: the LHC's Restart Checklist

Work Order LHC engineers install new superconducting magnets to bend protons around the 17-mile collider. Courtesy Cern

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Before scientists can put the Large Hadron Collider back to work this month solving the mysteries of particle physics, the LHC’s engineers face critical repairs to the $5-billion device. First up: Fix the 53 superconducting magnets trashed in September 2008 when a power cable broke, causing the magnets to warm above their –458˚F operating temperature and lose conductivity, or “quench.” Then pipes for helium coolant melted, further damaging the magnets. Here, the other key upgrades and a few of the thousand chores still to go:

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1. Drill eight-inch relief valves into half of the 1,232 dipole magnets that steer the proton beam around the track, to allow for a controlled pressure release in case of another leak.
2. Install a new quench-protection system, which is 1,000 times as sensitive as its predecessor and shuts off the accelerator if it detects an abnormal voltage increase—an indicator of a heat spike.
3. Search for and eliminate electrical faults between the magnets—especially where the cables join—which could increase electrical resistance, causing the cables to overheat and melt.
4. Cool the entire 17-mile track back down to –458˚F with liquid helium. (Engineers brought the sections up to room temperature so they could work inside the tunnel.)
5. Ramp up the current in the magnets from a couple hundred amps to 6,000 over a few weeks. During this time, test the quench-protection system by intentionally overheating the magnets.
6. Perform the final machine check, covering some 10,000 items, such as the systems that inject the proton beam into the collider and extract it within 1/5,000 of a second if a magnet fails.