Current Events Discussion

The place to discuss the LHC. Commissioning, operation, issues, events ....
Kasuha
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Re: Current Events Discussion

Post by Kasuha » Mon May 17, 2010 2:33 pm

Beam tracks cross in a very narrow angle - design document mentions 285 urad - which means after 22.5 m the beams are still only 6 mm apart.

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PhilG
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Re: Current Events Discussion

Post by PhilG » Mon May 17, 2010 2:35 pm

These are mentioned in some of the LHC documentation so they are real. Search for "displaced collisions" or "parasitic encounters" and see what comes up. Apparently they can also be avoided by increasing the cross-over angle. Some times they are useful which may explain why they were left in the 4x4 scheme last week when they could have been easily avoided without reducing the number of good collisions.

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morgad
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Re: Current Events Discussion

Post by morgad » Thu May 20, 2010 5:27 pm

seen in today's LHCb log
Following days program:
The first physics fill is likely to be with 6 bunches.
The subsequent ones, if all goes well, would be with 12 bunches.
:-)

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LarryS
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Re: Current Events Discussion

Post by LarryS » Thu May 20, 2010 11:13 pm

I suspect that English is not the primary language of some ... which can produce some amusing results:

From LHC Page 1

Comments 20-05-2010 17:43:28

Closing the machine

Access in experiences still possible

till midnight

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PhilG
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Re: Current Events Discussion

Post by PhilG » Fri May 21, 2010 7:08 am

Translations from English to French according to Google:

experiment -> expérience
experimental -> expérimental
experienced -> expérimenté
experience -> expérience

No wonder they are confused

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Bornerdogge
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Re: Current Events Discussion

Post by Bornerdogge » Fri May 21, 2010 9:30 am

^^ And I can affirm French people are not the best for foreign languages... It's not the first time they use strange English on the vistars!

I saw somwhere they could run stable beams with 12 bunches after today's physics fill. Would that mean another 100% increase in luminosity?

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PhilG
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Re: Current Events Discussion

Post by PhilG » Fri May 21, 2010 9:56 am

With 12 bunches you can double the number of crossings per turn from 3 to 6 and still avoid displaced collisions. That is probably what they will do. Actually you can do slightly better and give an extra collision to ATLAS/CMS and still avoid issues. With 15 bunches you can get 8 crossings per turn in each experiment and no displaced collisions.

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PhilG
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Re: Current Events Discussion

Post by PhilG » Fri May 21, 2010 10:21 am

"And I can affirm French people are not the best for foreign languages... "
They are not the worst either...

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Bornerdogge
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Re: Current Events Discussion

Post by Bornerdogge » Fri May 21, 2010 10:58 am

Of course ^^ (I'm a French-speaking Belgian, it's not better here...)

It always baffles me how badly some scientists speak English, although they use it almost everyday...

Kasuha
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Re: Current Events Discussion

Post by Kasuha » Fri May 21, 2010 2:36 pm

Bornerdogge wrote:Of course ^^ (I'm a French-speaking Belgian, it's not better here...)

It always baffles me how badly some scientists speak English, although they use it almost everyday...
Honestly, I am surprised how many english people speak bad english ... no wonder non-english scientists do too.

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Bornerdogge
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Re: Current Events Discussion

Post by Bornerdogge » Fri May 21, 2010 6:27 pm

Kasuha wrote:
Bornerdogge wrote:Of course ^^ (I'm a French-speaking Belgian, it's not better here...)

It always baffles me how badly some scientists speak English, although they use it almost everyday...
Honestly, I am surprised how many english people speak bad english ... no wonder non-english scientists do too.
You could certainly say that for every language :p But let's stop flooding the original subject...

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photino
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Re: Current Events Discussion

Post by photino » Sat May 22, 2010 1:02 am

LHC Operations Status Report - a nice summary of the state of play
http://indico.cern.ch/conferenceDisplay.py?confId=95508

(Apologies if this has been posted already)

pixelmasseuse
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Re: Current Events Discussion

Post by pixelmasseuse » Sat May 22, 2010 3:30 am

Nice indeed... lots of info to digest. I like the delivered luminosity vs. fill # graph on p. 14.

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PhilG
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Re: Current Events Discussion

Post by PhilG » Sat May 22, 2010 7:13 am

That's a nice report. So they will do a run of 13 x 13 with 8 collisions per turn. Then they hope to switch to higher intensity nominal bunches but with beta put back to 5m and starting at 2x2 before stepping up bunch numbers again.

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CharmQuark
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Re: Current Events Discussion

Post by CharmQuark » Sat May 22, 2010 2:50 pm

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

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