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Comment: Re:They did have stable beams (Score 1) 149

by chtephan (#31545560) Attached to: LHC Hits an Energy of 3.5TeV

From the CMS e-commentary ."..the beams were extremely stable
during this period and had a very long lifetime."

Yes, but only for about two minutes, then they were dumped because the protection system was acting up. That's a major PITA when running such machines. The protection system is overly sensitive and needs to be carefully tuned to safely detect "safe" conditions and only report minor deviations. Since it has never been run at that energy with beam it it, there are still a few things to sort out, which needs a bit of time (and a certain amount of trial and error). Well, better safe than sorry.

And, by the way. The beams were stable is not what is meant by the term "stable beams". The latter usually refers to the state when they are actually declared stable by LHC operations. When they are declared stable, the experiments can safely turn on their detectors since LHC then guarantees that no beam will go awry and shoot particles into sensitive parts while they are on high voltage. When LHC declares stable beams, this usually means that they are well measured, well positioned and brought to collisions. The "stable" referred to in the blog just means that they were staying in the LHC and not getting into troublesome resonances and scratching collimators and such. (which is a good thing, since beam optics depend on the beam energy, which means LHC was able to keep things under control while ramping, which by the way they did in an amazing short amount of total ramp attempts, which IIRC you can count on one hand)

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