by Lewis Page
November 5, 2009
A bird dropping a piece of bread onto outdoor machinery has been
blamed for a technical fault at the Large Hadron Collider (LHC)
this week which saw significant overheating in sections of the
mighty particle-punisher's subterranean 27-km supercooled magnetic
According to scientists at the project, had the LHC been operational
- it is scheduled to recommence beaming later this month - the snag
would have caused it to fail safe and shut down automatically.
This would put the mighty machine out of
action for a few days while it was restarted, but there would be no
repeat of the catastrophic damage suffered last September. On that
occasion, an electrical connection in the circuit itself failed
violently, causing a massive liquid-helium leak and knock-on damage
along hundreds of meters of magnets.
Reg readers alerted us yesterday to the temperature rises in the
LHC's Sector 81, which began in the early hours of Tuesday morning:
most of the collider's operational data can be viewed on the web for
all to see. Initial enquiries to CERN press staff led to assurances
that the rises were the result of routine tests.
However Dr Mike Lamont, who works at the CERN control centre
and describes himself as "LHC Machine Coordinator and General
Dogsbody" later confirmed that there had indeed been a problem.
Lamont, briefing reporters at the
control room yesterday, told the Reg that machinery on the surface -
the LHC accelerator circuit itself is buried deep beneath the
Franco-Swiss border outside Geneva - had suffered a fault caused by
"a bit of baguette on the busbars", thought perhaps to have been
dropped by a bird.
As a result, temperatures in part of the LHC's circuit climbed to
almost 8 Kelvin - significantly higher than the normal operating
temperature of 1.9, and close to the temperature at which the LHC's
niobium-titanium magnets are likely to "quench", or cease
superconducting and become ordinary "warm" magnets - by no means up
to the task imposed on them.
Dr Tadeusz Kurtyka, a
engineer, told the Reg that this can happen unpredictably at
temperatures above 9.6 K.
An uncontrolled quench would be bad news with the LHC in operation,
possibly leading to serious damage of the sort which crippled the
machine last September.
At the moment there are no beams of
hadrons barreling around the huge magnetic doughnut at close to
light speed, but when there are, each of the two beams has as much
energy in it as an aircraft carrier underway. If the LHC suddenly
lost its ability to keep the beam circling around its vacuum pipe,
all that energy would have to go somewhere - with results on
the same scale as being rammed by an aircraft carrier.
About to get hit by an aircraft carrier? You need a Dump
But there's no cause for concern, according to Lamont. The LHC's
monitoring and safety systems have always been capable of coping
with an incident of this sort, and have been hugely upgraded since
Had this week's feathered baguette-packing saboteur struck in coming
months, with a brace of beams roaring round the LHC's magnetic
motorway, the climbing temperatures would have been noted and the
beams diverted - rather in the fashion that a runaway truck or train
can be - into "dump caverns" lying a little off the main track of
In these large artificial caves, each
beam would power into a "dump core", a massive 7m-long graphite
block encased in steel, water cooled and then further wrapped in 750
tonnes of concrete and iron shielding. The dump core would become
extremely hot and quite radioactive, but it has massive shielding
and scores of meters of solid granite lie between the cavern and the
Nobody up top, except the control room
staff, would even notice.
This whole process would be over in a trice, well before the
birdy bread-bomber's shenanigans could warm the main track up to
anywhere near quench temperature. Should the magnets then quench, no
carrier-wreck catastrophe would result.
According to Lamont, provided the underlying fault didn't take too
long to rectify, the LHC could be up and beaming again "within, say,
three days" following such an incident.
We asked if more such incidents would occur, once the Collider is up
and running for real from later this month.
"It's inevitable," the
particle-wrangling doc told the Reg. "This thing is so
complicated and so big, it's bound to have problems sometimes."
Meanwhile, it would seem that this
particular snag has been solved, as the Sector 81 temperatures are
now headed back down to their proper 1.9 K.