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Message 16654 - Posted: 1 Apr 2007, 13:49:53 UTC
Last modified: 1 Apr 2007, 13:50:03 UTC

On Tuesday, March 27, there was a serious failure in a high-pressure test at CERN of a Fermilab-built “inner-triplet” series of three quadrupole magnets in the tunnel of the Large Hadron Collider. The magnets focus the particle beams prior to collision at each of four interaction points around the accelerator.

Safety precautions were followed during the test, and no one was injured.


This was the first paragraph from the "Fermilab Statement on LHC Magnet Test Failure"

Are there any additional information available from the project team?

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Henry Nebrensky

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Message 16659 - Posted: 2 Apr 2007, 15:34:00 UTC - in response to Message 16654.  

On Tuesday, March 27, there was a serious failure in a high-pressure test at CERN of a Fermilab-built ?inner-triplet? series of three quadrupole magnets in the tunnel of the Large Hadron Collider. The magnets focus the particle beams prior to collision at each of four interaction points around the accelerator.

Safety precautions were followed during the test, and no one was injured.


This was the first paragraph from the "Fermilab Statement on LHC Magnet Test Failure"

Are there any additional information available from the project team?


Everybody seems to be rather tight-lipped about it, although Fermilab have promised an update for tomorrow (Tuesday).

Even if the damaged magnet set is repairable, I reckon there's likely to be a significant delay in getting the LHC running, while that one's pulled out, fixed and replaced.

If they have to redesign/rebuild all of them... :(

Henry
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Message 16660 - Posted: 3 Apr 2007, 5:25:54 UTC - in response to Message 16659.  
Last modified: 3 Apr 2007, 5:27:15 UTC




If they have to redesign/rebuild all of them... :(

Henry



According to the article, those magnets are used in only 4 spots on the ring.
The worst case is they would have to replace a handful of these assemblies.
Best case is that they can solve the problem by putting a reinforcement onto the part.

I'm not the LHC Alex. Just a number cruncher like everyone else here.
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Message 16661 - Posted: 3 Apr 2007, 18:48:04 UTC

Here's the official update by fermilab on this issue.

Last paragraphs:
Review of engineering design documentation reveals that the longitudinal force generated by asymmetric loading was not included in the engineering design or identified as an issue in the four design reviews that were carried out.

The goal at CERN and Fermilab is now to redesign and repair the inner triplet magnets and, if necessary, the DFBX without affecting the LHC start-up schedule. Teams at CERN and Fermilab have identified potential repairs that could be carried out expeditiously without removing undamaged triplet magnets from the tunnel. All three of the pressure-tested triplet magnets at Point 5, plus the associated DFBX, will be removed from the tunnel for inspection and, if necessary, repair.

CERN will manage the redesign and repair effort and has scheduled a review for April 24-25 to validate the selected method. Fermilab will take part in the review.

Repair of the triplet magnets would begin after validation by the reviewers. The immediate goal is to have a repaired triplet in another sector of the accelerator ready to participate in a pressure test scheduled for June 1.

The effort between Fermilab and CERN is being closely coordinated. Fermilab personnel are on site at CERN. Fermilab physicists, engineers and technicians will continue to provide whatever assistance CERN requests, both at Fermilab and at CERN.

In addition to addressing the current problem, Fermilab has begun examining all aspects of US-supplied components to identify any other potential vulnerabilities.

Fermilab will appoint an external review committee to analyze how this problem occurred and determine root causes and lessons learned.

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Message 16663 - Posted: 4 Apr 2007, 6:15:41 UTC

BBC story covers the same ground.


Wave upon wave of demented avengers march cheerfully out of obscurity into the dream.

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Henry Nebrensky

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Message 16667 - Posted: 4 Apr 2007, 20:07:05 UTC - in response to Message 16660.  
Last modified: 4 Apr 2007, 20:08:07 UTC

N.B. this is a personal opinion - I'm not connected with the LHC !


If they have to redesign/rebuild all of them... :(


According to the article, those magnets are used in only 4 spots on the ring.
The worst case is they would have to replace a handful of these assemblies.
Best case is that they can solve the problem by putting a reinforcement onto the part.


Well, 8 sets (one each side of the 4 experiment interaction points).

But it's not just these magnets - the obvious worry is that if the engineering review processes missed out some expected behaviour for these components, what about all the others? Potentially the operational safety procedures (HAZOP, etc) might need reviewing, too.

Even if this only means burrowing through heaps of paperwork and doesn't mean any other mechanical modifications, it's going to eat up a lot of someone's time - that might be why CERN have left Fermilab to do the public announcements, they're worrying about other things!

Henry
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Message 16669 - Posted: 5 Apr 2007, 7:32:34 UTC - in response to Message 16667.  

N.B. this is a personal opinion - I'm not connected with the LHC !



I'm not connected with LHC either.
I'm just speculating out here in text form.

It might be valuable to see what the sixtrack simulator says the force of the magnet on the particle beam is compared to the design spec.
Typically, someone will build to a device to a factory acceptance test.
And the Factory acceptance test will be designed to an initial estimate of what a product 'should' do .
The original design of things like magnets were done prior to the 2004-2006 boinc experiment.

Can they assume that the force will be mass times (change in velocity) divided by (change in time)? or do they have to take into account relativity?


I'm not the LHC Alex. Just a number cruncher like everyone else here.
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Henry Nebrensky

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Message 16670 - Posted: 5 Apr 2007, 17:32:53 UTC - in response to Message 16669.  

N.B. this is a personal opinion - I'm not connected with the LHC !

I'm not connected with LHC either.

It might be valuable to see what the sixtrack simulator says the force of the magnet on the particle beam is compared to the design spec.


I think that would largely be irrelevant!

None of the accounts I've checked (Fermilab/BBC/NewScientist) actually explains the failure too well (and I'm trying to go home now, but):

Liquid Helium keeps the magnets cold (~2K) and so superconducting, which means they have "zero" resistance and can carry huge electrical currents. If, for some reason e.g. slightly too warm, they "quench": they stop being superconducting. This means that i) they do have a resistance, and ii) they (instantaneously) are still carrying some huge current. Ohmic heating then heats them up very fast, and this can cause the liquid Helium to boil.

My understanding (ICBW!) is that the test involved deliberately quenching one of the magnets in the triplet, thus putting "hot" Helium gas (at 20 atm) round one quad vs. liquid Helium around the next across any support structures separating them, IYSWIM.

Typically, someone will build to a device to a factory acceptance test.
And the Factory acceptance test will be designed to an initial estimate of what a product 'should' do.


No, the Factory acceptance test will be designed to what the spec./design/contract state unambiguously.

The problem here is that clearly there is a mismatch between what the designers have built the equipment to do, and what the operators expect it to do, and as I've suggested below that mismatch may have consequences beyond getting (or not) some protons round the ring under ideal conditions...

Henry
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Message 16671 - Posted: 6 Apr 2007, 2:05:15 UTC - in response to Message 16670.  

Well, in that case, they could work around the problem by adding a pressure relief valve to their plumbing to reduce pressure load.

As long as they don't fix it with plastic and duct tape....

I'm not the LHC Alex. Just a number cruncher like everyone else here.
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Henry Nebrensky

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Message 16718 - Posted: 15 Apr 2007, 21:11:49 UTC - in response to Message 16671.  
Last modified: 15 Apr 2007, 21:20:33 UTC

Well, in that case, they could work around the problem by adding a pressure relief valve to their plumbing to reduce pressure load.


3 possible reasons why that's a bad idea:
- You end up spraying Helium into a confined space (tunnel) giving an asphysiation risk
- Spraying very cold Helium all round electrical equipment is a bad idea
- Helium's in short supply and getting darn expensive

As I implied before, the whole LHC is _very_ complex, and the specific magnet flaw is only part of the problem exposed here...

Henry

(and why do we have to have this idiot BBCode thing that can't manage simple lists?)
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Ariel
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Message 16780 - Posted: 30 Apr 2007, 9:30:14 UTC - in response to Message 16723.  
Last modified: 30 Apr 2007, 9:36:50 UTC

You mean lists like:

    *you would pipe helium escaping a relief valve away from the confined space
    *then no danger with electrical equipment
    *ok, who's hoarding all the helium?


Ooo, nice.... I like. Here are the reasons I like Dagorath's post:

    *Look at me! I know how to use BBCode lists
    *I'm a big smart ass
    *Dagorath is a way-bigger smart ass
    *Helium can make you talk like a munchkin!



Sweet.




Ariel: Certified "Too Cute for LHC" Cruncher!


. . . . . . . . . . . . -- Consider the lilies.
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Message 16795 - Posted: 1 May 2007, 17:11:25 UTC

Ariel
HG's Most Fearless Cruncher award he had to work real hard to win. Looks better on his signature without Ariel typed on it.

Pizza@Home - Rays Place - Rays place Forums
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Message 16804 - Posted: 3 May 2007, 5:51:38 UTC - in response to Message 16795.  
Last modified: 3 May 2007, 6:11:56 UTC

HG's Most Fearless Cruncher award he had to work real hard to win...

"...he had to work real hard to win" ? "Looks better on his signature" ? ---I thought HomeGnome was a she. Boy am I embarrassed.

By the way, Ray, how does one go about winning a "Certified" award like yours and HG's? I've wondered this for a long time! I would like to run for "Certified Big Mouth" or something. Any info would be much appreciated.



_______

"Three quarks for Muster Mark!"
. . . . . . . - James Joyce, Finnegans Wake . . . .

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Message 16820 - Posted: 5 May 2007, 23:14:33 UTC - in response to Message 16804.  
Last modified: 5 May 2007, 23:17:39 UTC

HG's Most Fearless Cruncher award he had to work real hard to win...
"...he had to work real hard to win" ? "Looks better on his signature" ? ---I thought HomeGnome was a she. Boy am I embarrassed.

I think that HomeGnome is gender confused.

And yes, Ray, I say that without fear.
Word to your Motherboard!





Ariel: Certified "Too Cute for LHC" Cruncher!


. . . . . . . . . . . . -- Consider the lilies.
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Message 16981 - Posted: 5 Jun 2007, 4:59:21 UTC - in response to Message 16661.  

Repair of the triplet magnets would begin after validation by the reviewers. The immediate goal is to have a repaired triplet in another sector of the accelerator ready to participate in a pressure test scheduled for June 1.


Does anyone know if the scheduled June 1 pressure test took place and what happened ?

-- David




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Message 16983 - Posted: 5 Jun 2007, 12:17:03 UTC - in response to Message 16981.  

Does anyone know if the scheduled June 1 pressure test took place and what happened ?


For anybody that doesn't know, Fermilab are keeping an archive of magnet news items.

I can't see a specific date given for the pressure test itself though.

Henry
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Message 16985 - Posted: 5 Jun 2007, 15:44:23 UTC - in response to Message 16820.  

"...he had to work real hard to win" ? "Looks better on his signature" ? ---I thought HomeGnome was a she. Boy am I embarrassed.

I think that HomeGnome is gender confused.


The woman in the avatar wasn't me, but it was someone else.
I think.
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David Ball

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Message 16992 - Posted: 6 Jun 2007, 5:45:15 UTC - in response to Message 16983.  

For anybody that doesn't know, Fermilab are keeping an archive of magnet news items.


Thanks Henry!

That's a good link for info.

-- David
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