[Infowarrior] - Bird messes up the LHC

[Richard Forno]

Original URL: http://www.theregister.co.uk/2009/11/05/lhc_bread_bomb_dump_incident/

Large Hadron Collider scuttled by birdy baguette-bomber
Bread on the busbars could have seen 'dump caverns' used

By Lewis Page

Posted in Physics, 5th November 2009 13:23 GMT

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 doughnut.

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 metres 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 CERN 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  
barrelling 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 (http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/beam.htm 
). 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 last  
September.

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 the  
LHC. In these large artificial caves, each beam would power into a  
"dump core (http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/components/beam-dump.htm 
)", 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 metres of solid granite lie  
between the cavern and the surface. 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 (http://hcc.web.cern.ch/hcc/cryo_main/cryo_main.php?region=Sector81 
) to their proper 1.9 K. ®