LHC High L pp run ends for 2023

In summary, the LHC bellows failed, causing a small leak in one of the cryogenic sectors. The sector has since been replaced and the run plan for the rest of the year is low luminosity special pp running and heavy ions.
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TL;DR Summary
Due to bellows failure, the high luminosity pp running at the LHC has ended for 2023.
A bellows failed at the LHC near IP8 (LHCb). It has been replaced and the sector is cooling. Beam is expected on or near September 11. There will not be enough time to return to high luminosity pp running, so the run plan for the rest of the year is low luminosity special pp running and heavy ions, which I believe will be PbPb.
 
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What is a 'bellows' in this context?
 
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  • #3
Expansion joints between superconducting magnets.
 
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  • #4
Drakkith said:
What is a 'bellows' in this context?
The sound of scientists annoyed by the interruption of their data.
 
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  • #5
Like some kind of expensive Rube Goldberg machine, this was ultimately caused by a tree falling over some 50 km away.

Here's an official write-up (albeit no mention of the tree):
https://home.cern/news/news/acceler...-inner-triplet-magnet-causes-small-leak-major

Here is the damaged bellows before being replaced. There was a crack in a weld only 1.6 mm in length. It is just about visible in the centre of the zoomed-in picture.

leak_found2.jpgleak_found3.jpg
 
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  • #7
Drakkith said:
What is a 'bellows' i
The nosy doctor in I Dream of Jeannie.
 
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  • #8
This incident highlights area where, while I wouldn't call them weak spots exactly, places where if we had to do it over we might try and improve.

One is that there are only 8 cryogenic sectors (the Tevatron, 4x smaller had 6) so amy cryo problem is a big cryo problem.

Another is that the vacuum quality requires running beam through the machine for a while to "clear out the crud". This is probably not helped by the first point.

It;s a great machine, and it's done a lot of science, don't get me wrong - but like all one of a kind devices, we know more about what would have worked better after we've used it.
 
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  • #9
The news this summer from the LHC has not been good. On July 17 a tree fell on two high-voltage power lines, causing beams to dump, magnets to quench, and damage (a helium leak) to occur in the cryogenics for an inner triplet magnet. See here for more details. Fixing this required warming up a sector of the ring, with the later cooldown a slow process. According to this status report today at the EPS-HEP2023 conference in Hamburg, there will be an ion run in October, but the proton run is now over for the year, with integrated luminosity only 31.4 inverse fb (target for the year was 75).

From Not Even Wrong.
 
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  • #11
Great, so there will be Pb-Pb collisions this year as planned :-))))!!!!
 
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The answer to that is "maybe". Additional Pb-Pb running beyond what is scheduled is competing with low beam current proton runs, e.g. van der Meer scans and the like. The run plan they are coming up with now may be altered later in the year as we know more.
 
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