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 Post subject: Blast! Were we blasted?
 Post Posted: Thu Jul 26, 2012 4:39 am 
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Joined: Sat Apr 28, 2012 5:48 am
Posts: 16
Location: Kenosha, WI
I noticed an alarming spike on the Vistar luminosity screen.

LHCb seeing 13000 ub.s^-1 instantaneous luminosity ! (Target luminosity 400 ub.s^-1)
After they dumped fill 2875 (15+hr, 172/pb) they switched polarity on LHCb and loaded a light fill for IP optimization.
(I have a luminosity page screen grab jpg to insert here, but no web page to publish it on.) ;-)

The only chronologically relevent comment in ELOG:

25-Jul 12:35 LHC Comments optimising IP8 after polarity change

There was an access interval shortly thereafter, austensibly for previously requested muon detector repair. (muon trips and voltage monitor error seen earlier)
Are these detectors so indestructible that a 3250% over-illumination is inconsequencial or were there some consequences that were not reported in the public logbook?


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 Post Posted: Wed Oct 07, 2015 3:57 pm 
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Joined: Sat Oct 03, 2015 7:58 pm
Posts: 148
I know this thread is old, but the question is without answer: A collision rate that would correspond to this luminosity would immediately saturate many triggers, draw much more power, probably clog the pipelines due to the "challenging" event reconstruction and hopefully lead to various safety mechanisms stopping data-taking and the detector as a whole. If the detector is shut down, the collision rate is unproblematic. Sure, you accumulate radiation damage a bit faster, but 100 times the design rate multiplied by a few seconds is irrelevant.

This luminosity was not real, however (ATLAS and CMS would have loved it!). Just a software glitch somewhere that lead to a faulty report. We have another massive one (at 16 times design luminosity) in this year's statistics, this time from ATLAS. CMS has a smaller one as well, at ~80% design luminosity.


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