Sneak has decided to return to the subject of CERN's Large Hadron Collider, now that the follow up report about what went wrong on 19 September 2008 has been released. The report goes into a fair amount of technical detail about the incident, but the upshot is - it was a very large 'quench', known in the trade as a 'catastrophic quench', where helium expands explosively due to the previously superconducting wires becoming non-superconducting wires, heating up and boiling off the helium.

How explosive was this one? Well it ripped up magnets weighing 10 tons from the floor, when a couple of tons of helium made a bid for freedom. Overall it looks like six tons of helium escaped - which could fill an awful lot of those toy balloons kids love so much.

Currently repairs are underway - as seen in this amusing video clip. Look out for the man with a 'universal adjuster' - or hammer as they're known in the trade - just doing some precision engineering on the experiment estimated to cost as high as €6bn - or £6bn if Sterling keeps falling as rapidly as it has been recently.

Sneak's last post on LHC in July did actually bring up the possibility that a quench could happen, but pointed out that, "LHC has quench detection and protection schemes", to stop this from happening. Sneak presumes the CERN boffins will be working fit to bust to make sure this never happens again, although whether they'll be successful is a moot point given the fact that the time between the temperature rising from almost zero to in excess of 500K (over 200C) looks to be on the order of half a second.

Remember Brian Clough's classic quote that, "It only takes a second to score a goal"? Well, it only takes half a second for a catastrophic quench to cause an estimated $21m of damage.

Anybody who has an unquenchable desire to delve deeper into practicalities of quench avoidance systems can download a PowerPoint from the UK's Cockcroft Insititute site in which Martin Wilson can take you through quenches (slides 12-39) in fairly hefty physics and maths detail.

CERN is doing the annual shutdown of LHC - due to last until May next year - but the best estimate of when LHC will be up and running again is June 2009, and Sneak wishes CERN all the best.