Current Events Discussion

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

Post by Glacialis » Tue Apr 20, 2010 8:22 pm

I really should look at the presentations more. Thanks Kasuha!

Ver Greeneyes
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Re: Current Events Discussion

Post by Ver Greeneyes » Tue Apr 20, 2010 9:12 pm

With squeezing tests going well, it seems they decided to do something a bit more adventurous: introducing the squooze! :)
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Harbles
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Re: Current Events Discussion

Post by Harbles » Tue Apr 20, 2010 10:23 pm

Even with Squoozed beams the LHC_Config screen still shows 10-11m betas.
Hopefully once commissioning is done in early May all the vistars will work correctly.

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mrgumby
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Re: Current Events Discussion

Post by mrgumby » Wed Apr 21, 2010 5:42 am

yeah...the squoozedness is one thing we can't follow live :cry:

Kasuha
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Re: Current Events Discussion

Post by Kasuha » Wed Apr 21, 2010 3:20 pm

I finally had time to read today's presentation ... and they definitely have things to polish on the squeeze process. But overall it's a great success that they finally did it :thumbup:

tomey36
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Re: Current Events Discussion

Post by tomey36 » Thu Apr 22, 2010 7:48 pm

how much of the beam comissioning they are doing now will need to be repeated when they run at 7Tev? will all of the work they are doing now, need to be done at the higher energy, or can they skip some steps beacuse they already did them at 3.5 Tev? i basically want to know if we will be waiting the same amount of time for high intesity collisons at 7Tev, as we are now for high intensity collisions at 3.5Tev.

Kasuha
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Re: Current Events Discussion

Post by Kasuha » Thu Apr 22, 2010 8:32 pm

They could reuse what they do now at 450 GeV (injection, orbit, start of ramp etc) and some general principles they found at 3.5 TeV but they'll need to go through all high energy tuning carefully again as at higher energy the beam behaves differently.
In fact they'll need to re-commision 450 GeV too but it should be easier as there will not be substantial changes to it after the upgrade.

JNW
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Re: Current Events Discussion

Post by JNW » Fri Apr 23, 2010 3:37 am

tomey36 wrote:how much of the beam comissioning they are doing now will need to be repeated when they run at 7Tev?
They will have a much better understanding of the machine by the time they go to 7TeV. And many of the problems that they've solved will stay solved. So re-commissioning at 7TeV should go significantly faster.

However, the LHC will undergo a full thermal cycle, so it will be a slightly different shape. They will have to redo a lot of beam studies at both 450GeV and 7TeV.

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mrgumby
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Re: Current Events Discussion

Post by mrgumby » Fri Apr 23, 2010 7:05 am

I hope they will be at least as careful at 7TeV per beam......at those energy levels it could be messy if something goes wrong... :scared-yipes:

Kasuha
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Re: Current Events Discussion

Post by Kasuha » Fri Apr 23, 2010 7:28 am

7 TeV beam at current intensity is as dangerous as 3.5 TeV beam at twice the current intensity (protons per bunch, bunches per beam) - which they are going to start trying soon.
Special reactions they are expecting to occur at 7 TeV do not happen at collisions with stationary targets which is the case of accidents, see the discussion about beam dump.
And they have much bigger reserve in increasing the beam intensity than in increasing the energy.

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mrgumby
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Re: Current Events Discussion

Post by mrgumby » Fri Apr 23, 2010 7:40 am

Kasuha

I think you misunderstood me.

I'm not predicting doom.

I'm just saying that I expect the operators to continue being careful.......thats all...

Kasuha
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Re: Current Events Discussion

Post by Kasuha » Fri Apr 23, 2010 8:14 am

Nono I don't think you're predicting doom. It's just that by going to 7 TeV from 3.5 TeV, the beam will become "just" twice as energetic. While by going from 1e10 protons per bunch to 1e11 protons per bunch it will become 10 times more energetic. And by coming from 2 bunches to "just" 43 bunches it will become 20 times more energetic.
But regarding potential damage in case of accident, it's really hard to estimate as it highly depends on what case of accident it is. In general case twice as energetic beam is not twice as dangerous. At certain intensity it will simply drill a hole through anything that stands in its way and the rest of energy will dissipate in the ground surrounding the ring. The only thing that will become gradually more dangerous and which they will need to continually improve are beam losses during beam manipulation (injection, ramp, squeeze, ...). But they need to address this with any beam energy increase.

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mrgumby
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Re: Current Events Discussion

Post by mrgumby » Fri Apr 23, 2010 8:23 am

I see what happened...I think.....

I should have said "I hope they will be at least as careful at full power".

I understand that there is a lot more to it than the TeV level.

I don't have the physics vocabulary to always express myself clearly.

:oops:

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mrgumby
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Re: Current Events Discussion

Post by mrgumby » Fri Apr 23, 2010 9:10 am

just watching the op log during squeeze tests.

it started out saying "first squeeze step sent, @23"

then "squeeze step @ 280"

and on till the last one

"squeezing to 1285 [END]"

I assume that 1285 = 2m. but does anyone know what these numbers actually represent?

Its obviously something that goes up as the squeeze progresses.....Luminosity?

???????

Kasuha
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Re: Current Events Discussion

Post by Kasuha » Fri Apr 23, 2010 9:15 am

I believe they are steps in the squeeze program sequence.

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