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Some Official Information and Even Pictures December 5, 2008

Posted by gordonwatts in LHC.

image Robert Aymar is the outgoing Director General of CERN. He gave a recent update of CERN accelerator activities at the ECFA conference. It is a complete update, but there are a few pages in the middle with information on the current state of the LHC. And – lo!!!!! – pictures. Just two. And no ice is visible. I’ve extracted one of the pictures and put in here. That is the link between two magnets – normally the two magnets should be totally lined up.

There are three mitigation strategies that he lists in this talk:

  • Improve the quench detection system. The improved sensors will help better localize problems as well as detect them a bit faster.
  • Add relief valves all around the accelerator. If such a disaster occurs again then these releif valves should prevent the violent pressurization that occurred and caused such a lot of damage (like the moved magnets shown above).
  • Better anchoring of the magnets. So if there is another pressure build up the magnets are less likely to move!

He also mentions two other inter connects similar to the one that failed that have an abnormal resistance – but their resistance is thought to be much less than the interconnect that failed. In ATLAS we’ve been having to evacuate the cavern due to numerous electrical tests of the LHC when they were localizing these. Nanohoms. So small! 🙂

Unfortunately, there is no real mention of schedule in this talk. It is nice to see something that is officially public. This matches the talk I saw on Monday, but, of course, it looks like CERN has made it officially public. It would be nice if they would do the same thing to that other talk too.

What is sad about this is I found this out from a news posting in DZERO, which was linking to a USLHC blog. Why did it come to me that way!? They can do a little better!!



1. Nick - December 5, 2008

Universe Today posted about the same report and showed off this picture of replacement parts. Now I’m curious: you can see one magnet enclosure head-on and it doesn’t look like it’s curved at all. Is the curvature contained within the enclosure or is it just too slight to see? 27 km is a looooong way to go around…

2. Gordon Watts - December 9, 2008

That is a great picture! Make sure to click on that link if you are reading Nick’s comment!

As far as the curvature. I’m not totally sure. First of all, the ring is 27 km around. The dipole magnets are used to bend the beam and are 15m long each (http://public.web.cern.ch/public/en/LHC/HowLHC-en.html). So over the course of that 15m the beam must bend 0.000556 radians. And so if the beam were being deflected as if it were traveling in a straight line as it went over those 15m it would deflect a hair more than 8mm.

That back of the envelope calculation done, I would guess the magnets and the actual beam-pipes do have curvature built in, but the external pipes do not (much cheaper to make that part straight).

BTW, the beam only bends inside the dipoles, otherwise it travels straight. There are plenty of straight sections in the LHC – like the acceleration structures. That means the dipoles must bend the beam more than I’ve calculated above to compenstate for the straight sections.

3. LHC News « Life as a Physicist - July 3, 2009

[…] (electrical connections) in all of the LHC in early August. Those splices are what caused the disaster last September – so it is important that all of them be carefully measured. And once they have […]

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