Comments on: LHC Magnet Test Failure

By: Edo

Edo — Thu, 12 Apr 2007 21:36:26 +0000

By the way, we do have spares, at least for the most deteriorated magnet. About the other triplets – now know to all have the same shortcoming-, we are looking for an alternative to the replacement of the faulty piece – which would involve removing all triplets, bringing them to the surface and so on…

By: Edo

Edo — Thu, 12 Apr 2007 21:31:14 +0000

More pictures here:
http://8teslas.free.fr/zenphoto/index.php?album=Triplet+incident

By: Doo

Doo — Sat, 07 Apr 2007 03:36:48 +0000

>>>>> Stephen Uitti on Apr 2nd, 2007 at 2:30 pm
>>>>> So, does Fermilab have a couple extra
>>>>>> months to find the Higgs first?

Applauses transforming in ovation.!

By: Sam

Sam — Thu, 05 Apr 2007 17:24:15 +0000

Looks like ‘only the 9′ it says final focus quads – but these would likely carry the most current (shorter focal lengths), probably resulting in a more serious quenching problem, that perhaps was not specificly tested for.

By: JoAnne

JoAnne — Thu, 05 Apr 2007 01:00:03 +0000

I just heard that the experts now have a proposed fix which is under review. Assuming this fix passes the reviews, the remaining magnets of this type can be fixed, in the tunnel without having to be removed. The magnet that blew up obviously has to be replaced. Don’t know if there are spares, or if Fermilab has to build another one, ASAP, from scratch. Nobody knows the impact on the schedule yet.

By: Ellipsis

Ellipsis — Thu, 05 Apr 2007 00:36:58 +0000

Answering my question (#8), via a suggestion from a colleague!:

Amount of stored energy in an LHC quadrupole ~=
7.8 x 10^5 J
(from
http://quench-analysis.web.cern.ch/quench-analysis/phd-fs-html/node12.html
– that is for an arc quad, but final triplet quads are probably of the same order of magnitude)

He heat of vaporization = 82.9 J/mol

.0224 m^3/mol (ideal gas @ STP, as it would quickly heat up to room temp)

=> ~200 m^3 of helium gas!

= a major personnel hazard in the tunnel (oxygen displacement) if released via relief valves in the event of a quench.

By: Sean

Sean — Thu, 05 Apr 2007 00:29:09 +0000

So where did you get that photo, anyway? Did you take it? It's a great shot, and I haven't seen anything as good elsewhere. I notice that Nature borrowed it from us.

By: cyrus biscardi

cyrus biscardi — Wed, 04 Apr 2007 16:47:20 +0000

Looks like a squirm can failure to me

By: Ellipsis

Ellipsis — Tue, 03 Apr 2007 19:55:43 +0000

I overheard (or rather got an e-mail forward) that the support structure for the inner triplets would have to be re-engineered. Would anyone (such as Cherrill, or another magnet engineer) happen to know why one couldn’t just put 10-atmosphere relief valves on the cryo-lines, rather than re-engineering the support?

By: Cherrill, Magnet Engineer

Cherrill, Magnet Engineer — Mon, 02 Apr 2007 23:57:28 +0000

To reply to “njim”‘s quibble:
All quadrupoles in accelerators are used to focus the beam. The millions of particles in a bunch travelling along an evacuated beamline tend to spread out as they repel their same-charged bunch-mates. So, every so-often we put a quadrupole to focus them to reduce their spreading; these “regular” quads do not focus the beam to a very small spot, that is the purpose of the final focus quads.

The “triplet” of quads that suffered the accident at LHC were indeed a set of final focus quads that focus the beam to a very small spotsize at an interaction point where the 2 circulating-in-opposite directions proton beams collide.

These triplets are of a different design from the approximately 400 quads used to focus the LHC beams as they travel around their circular path.

I’m not sure what you meant by “correct the beam”? The term “correct” is usually applied to the function of dipole magnets which steer the particles in the beam so they change direction, and all move in one direction. Whereas a quadrupole affects the particles that are off-center, say left and right, and forces them towards the magnet’s center from both sides, this action we call focusing.

Hope this information will help your future quibbling about accelerator magnets.

By: Stephen Uitti

Stephen Uitti — Mon, 02 Apr 2007 19:30:52 +0000

So, does Fermilab have a couple extra months to find the Higgs first?

By: Mustafa Mond, FCD

Mustafa Mond, FCD — Mon, 02 Apr 2007 00:40:34 +0000

It looks like the duct tape didn’t hold up.

By: Best Of The Day - Asymptotia

Best Of The Day - Asymptotia — Sun, 01 Apr 2007 21:59:36 +0000

[...] On blogs about science, I thought that Resonaances’ post continuing the saga of the (real) construction problems at LHC was really funny. It reports on the resignation of the director general of CERN, and the quote from the new appointee is funny. See that post here (it riffs on an earlier post located here, which also has some good -if alarming- humour). [...]

By: Arun M Thalapillil

Arun M Thalapillil — Sat, 31 Mar 2007 23:15:13 +0000

By: njim

njim — Sat, 31 Mar 2007 22:51:58 +0000

Just to quibble a bit:

“one of the quadrupole magnets, which focus the beams down to tiny size at the collision regions”

I thought most of the quads in an accelerator are used to correct the beam, and that only a few special purposed ones are used for the actual final focus. Of course I could be wrong. (IANAAP)

By: graviton383

graviton383 — Sat, 31 Mar 2007 22:03:14 +0000

I hope there won’t be too much in the way of finger pointing and this problem is solved rapidly. I had heard that the CERN tests ran the magnets in a mode not tested at Fermilab.