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

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:

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.