LHC magnet failure

John Conway at Cosmic Variance has a post which I thought corrected my misunderstanding of 'quench'.

This was apparently due to a “quench” in which the magnet goes rapidly from the superconducting to the normal conducting state, which then means that the tremendous electric current in the magnet suddenly starts heating it up, causing huge internal mechanical stresses.

But on reading further I find my initial guess may be on the right lines after all:

While a beam of particles by itself creates very little heat, beam particles straying from the core of the beam will heat up surrounding material. It takes just a small number of beam particles hitting a magnet in one spot to raise the magnet’s temperature above a critical point, causing it to suddenly change from superconducting to “normal” conducting. This change, called a quench, releases the stored energy of the magnet and its neighbors; it can heat a small part of the magnet from -271 to 700°C (-456 to 1300°F) in less than one second.

But yesterday's press release from CERN definitely says there was no beam circulating.

Geneva, 20 September 2008. During commissioning (without beam) of the final LHC sector (sector 34) at high current for operation at 5 TeV, an incident occurred at mid-day on Friday 19 September resulting in a large helium leak into the tunnel. (emphasis mine)

I'm still confused! Grow into these trousers... >>

A setback for the LHC

After it's much applauded launch the LHC has hit a glitch and been shut down. A CERN press release today said:

Preliminary investigations indicate that the most likely cause of the problem was a faulty electrical connection between two magnets, which probably melted at high current leading to mechanical failure...

A full investigation is underway, but it is already clear that the sector will have to be warmed up for repairs to take place. This implies a minimum of two months down time for LHC operation. For the same fault, not uncommon in a normally conducting machine, the repair time would be a matter of days.

This doesn't seem to be a major or unexpected setback. As they say, if this were at normal temperatures the repair would take only a few days, but because of the extreme cold needed for the superconducting magnets the cycle of warming things up, making the repair and re-cooling the system could take weeks.

The main loss is time, sadly, and a few tons of liquid helium^*.
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UPDATE:
The BBC calls the incident 'a quench' which to me implies that the particle beam has hit the wall of the tube. However the CERN report above says there was no beam circulating at the time. Hmmm, I'm waiting to find out.
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* Listen here for a 7min podcast on the discovery, uses and rarity of helium on Earth. From Chemistry in it's Element. Grow into these trousers... >>

Has the LHC destroyed the world yet?

A thorough and in-depth analysis of the current situation can be found here.
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Note: if you are interested, look at the page source code. It's cool Javascript.
Hat tip to Shores of the Dirac Sea.
Grow into these trousers... >>

Guess what? The Earth is still here.

First beam. Grow into these trousers... >>

Big Bang Week on Radio 4

Pull up your trousers here, here and here (lol).


Interest in the switch-on of the LHC is growing apace. Good ol' Radio 4 has some fun videos on their site and is running a day full of linked broadcasts tomorrow. There's a history of CERN too, I'm listening to part2 live on radio right now, but you'll be able to get them both from the BBC for the next few days.

BBC news has a page of video presentations explaining the layout of the LHC and the different detectors. (Flash based)

Also the Quirks & Quarks podcast has a special feature on the LHC.

No doubt there will be TV coverage too but I've already got a backlog. Grow into these trousers... >>

Brian Cox hits back at doom mongers

"Anyone who thinks the LHC will destroy the world is a t---."

Full article at the Telegraph. Grow into these trousers... >>

More on the LHC

Following up on yesterday's post, here are a couple of old BBC Horizon broadcasts (~50min each).

The Six Billion Dollar Experiment


What on Earth is wrong with gravity?

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via Online Documentaries 4 U Grow into these trousers... >>

Our understanding of the structure of matter is about to change

We've all heard the hype, the world is about to end! OMFG!!


The Large Hadron Collider, or LHC, at CERN is about to be fired up. First beam as they euphemistically call it...

On Wednesday, after about 15 years of work, a science team numbering many thousands (to say nothing of the engineers, technicians, electricians, plumbers, cleaners, tea-ladies and PhD students) will throw a switch and turn on the biggest scientific experiment ever undertaken.

This project is huge with a capital HU!

Phil Plait, the Bad Astronomer was lucky enough to visit the LHC earlier this year. He wrote:

"It’s difficult to convey just how astonishing this all is. The scale of it is simply awesome. Standing off to the side, taking in the size and complexity of CMS and ATLAS, I was filled with a sense of pride. People built this! Every single cable (and there were miles of cable!), every rivet, every bolt, every iron block and metal plate, everything, was dreamed up, designed, redesigned, built, and assembled."

More from Phil later, but what exactly will this thing do?
I'll let the charismatic Prof. Brian Cox explain:



This is impressive science, a massive construction to try to observe the smallest and most fleeting glimpses of an underlying structure to what we see and feel in the world around us.

Here's Phil Plait again with his own video from LHC:




And listen to Phil and Brian in conversation on a CERN podcast
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Oh, and the stories of microscopic black holes eating the Earth - BULLSHIT - see Hawking Radiation. The folks at LHC will know if they have created a black hole by its pattern of decay!
Grow into these trousers... >>