LHC beta* 3.5 meters

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CharmQuark
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Re: LHC Beta* 2 meters

Post by CharmQuark » Wed Jun 09, 2010 11:59 pm

Nice post Orion :D :thumbup:
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mrgumby
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Re: LHC Beta* 2 meters

Post by mrgumby » Thu Jun 10, 2010 8:09 am

A picture is worth a 1000 words....well done

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CharmQuark
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Re: LHC beta* 3.5 metres

Post by CharmQuark » Thu Jun 17, 2010 5:06 pm

You are more than welcome ;)
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chriwi
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Re: LHC beta* 3.5 metres

Post by chriwi » Fri Jun 18, 2010 10:27 am

But it also shows that the beta doesn't necessarily say anything about the real concentration of protons at the colissionpoint rather about the angle they collide in.
But I still belive that there is some relationship which makes beta something like a good guess for the proton-densety at the collisionpoint, but it also depends on the overall aperture of the rest of the beam. (I hope I used the right words)
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Tau
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Re: LHC beta* 3.5 metres

Post by Tau » Fri Jun 18, 2010 11:30 am

Yes, if you halve beta*, you double the luminance.
- Tau

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chriwi
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Re: LHC beta* 3.5 metres

Post by chriwi » Fri Jun 18, 2010 1:47 pm

Do you have the math for that?
At least it is not trivial.
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Re: LHC beta* 3.5 metres

Post by Kasuha » Fri Jun 18, 2010 3:31 pm

Tau wrote:Yes, if you halve beta*, you double the luminance.
This is only true if you apply some more constraints, such as that the cross-section of the beam stays the same at both ends of the cavity in the middle of which is the focus point.
Otherwise I can imagine scenarios involving changes to beta* without any effect on luminance.

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Tau
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Re: LHC beta* 3.5 metres

Post by Tau » Mon Jun 21, 2010 9:24 pm

Indeed, I assume emittance stays the same, and the beams stay nicely focused exactly on each other. It is all in "accelerators for pedestrians", but I admit I have a hard time reading it.
The basic idea is that the particles in the beam do not all have the same sideways (transverse, they say) speed. When steering the beam, you have the choice between steering them very accurately to a point (so that the speeds differ by a lot), or a more "relaxed" steering where the speeds are more equal, but the beam is wider.
A wide beam with almost equal speeds has high beta*, where a narrow beam with lots of speeds difference (variance, they say) has a low beta*.
- Tau

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