Current Events Discussion

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jmayes
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Re: Current Events Discussion

Post by jmayes » Fri Jul 30, 2010 12:23 am

Woopie!!!
:clap: :angry-screaming: :dance: :clap: :dance:

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CharmQuark
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Re: Current Events Discussion

Post by CharmQuark » Fri Jul 30, 2010 12:49 am

Way to go guys!!!!!!!!!!!!!!!!!! :clap: :dance: :thumbup:
Anyone who doesn't take truth seriously in small matters cannot be trusted with large ones either by Albert Einstein.

ferar
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Re: Current Events Discussion

Post by ferar » Fri Jul 30, 2010 2:55 am

Hi, I see that about 20% of the beam is lost (It started at 2.5E12 and now it is ~2.0E12). Is this caused by collisions? Is it safe to loss this amount of particles?
Thanks
Fernando.

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PhilG
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Re: Current Events Discussion

Post by PhilG » Fri Jul 30, 2010 6:52 am

A few protons are lost due to collisions with molecules of the imperfect vacuum in the tube, but most are being lost on the collimators as the beam spreads out. So long as the loss rate is not too high that is perfectly safe. The collimators are designed to take the loss and protect more delicate components.

oldboson
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Re: Current Events Discussion

Post by oldboson » Fri Jul 30, 2010 9:49 pm

I can see nearly 2,5 10e30cm-2s-1 lumi, is this a new record?
oldboson

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DCWhitworth
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Re: Current Events Discussion

Post by DCWhitworth » Fri Jul 30, 2010 10:13 pm

It was around about that level yesterday too.
DC

The LHC - One ring to rule them all !

tomey36
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Re: Current Events Discussion

Post by tomey36 » Sat Jul 31, 2010 2:54 am

does any one know when live collisions will be veiwable again?

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morgad
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Re: Current Events Discussion

Post by morgad » Mon Aug 02, 2010 8:35 am

Interesting comment in LHCb log book:
Message ID: 16934 Entry time: 02-Aug 04:32
Author: Conor Fitzpatrick

Additional amazingness can be seen in the AB & OP logbook- they are seeing the effect of the tides on the beam
energy.
Dave

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Bornerdogge
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Re: Current Events Discussion

Post by Bornerdogge » Wed Aug 04, 2010 6:32 pm

tomey36 wrote:does any one know when live collisions will be veiwable again?
Nearly every day, just have a look at the "coordination" page on the vistars...

By the way, new record today, they've just broken the 3e30 barrier! :clap:

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CharmQuark
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Re: Current Events Discussion

Post by CharmQuark » Wed Aug 04, 2010 6:43 pm

Nice work guys :thumbup: :clap:
Anyone who doesn't take truth seriously in small matters cannot be trusted with large ones either by Albert Einstein.

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Bornerdogge
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Re: Current Events Discussion

Post by Bornerdogge » Fri Aug 06, 2010 9:28 am

Does anybody know why they witness such a drop in instantaneous luminosity (50% in a few hours), where the beam intensity stays nearly constant?

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DCWhitworth
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Re: Current Events Discussion

Post by DCWhitworth » Fri Aug 06, 2010 9:36 am

Bornerdogge wrote:Does anybody know why they witness such a drop in instantaneous luminosity (50% in a few hours), where the beam intensity stays nearly constant?
I was wondering that too, I guess the bunches start to spread out over time so making collisions less likely and hence luminosity lower.
DC

The LHC - One ring to rule them all !

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photino
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Re: Current Events Discussion

Post by photino » Fri Aug 06, 2010 10:28 am

Does anybody know why they witness such a drop in instantaneous luminosity (50% in a few hours), where the beam intensity stays nearly constant?
Also luminosity is proportional to (intensity)^2, so you would expect it to drop faster.

Harbles
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Re: Current Events Discussion

Post by Harbles » Fri Aug 06, 2010 10:38 pm

I observe a rapid decline at the same time as tune and orbit feedback are turned off at declaration of stable beams. Comments from the enlightened?
And every collision (or grazing contact) kills some protons, plus losses at the collimators and beam gas events cut down the available participants. It seems they start with an instantaneous luminosity of almost 3 units and let it decay down to about 1 unit after 14 hours or so then dump and do a refill.

So 4 am Friday till 7 pm physics, reset 7pm till 1:42 AM sat 1:42 stable beams again.
Almost routine. :mrgreen: :clap:

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Tau
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Re: Current Events Discussion

Post by Tau » Sat Aug 07, 2010 3:30 pm

It is just a guess, but it could be that some protons are "better" at colliding than others.
If that is the case, the "good" ones would be the ones to go first, so that the quality of the beam quickly deteriorates, and that luminosity drops as a result.
- Tau

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