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a couple of questions

Posted: Fri Dec 11, 2009 2:00 am
by seedyjay
There are two or three questions I am having difficulty finding the answers for. Firstly, I have heard the path traveled by the beams described as a spiral, which makes perfect sense, but are they spirals even when kept in a holding pattern for longevity testing? Also, can the beams be held that way indefinitely (I have read that 4 then 10 and now 25 hours was the longest they have been sustained) in theory? Finally, where can I get a LHC blueprint so I can build one of my own?.......just kidding about the blueprint :D

Re: a couple of questions

Posted: Fri Dec 11, 2009 7:55 am
by dh2va
I am no beam physicist, but afaik you can in first order assume a circular reference orbit.

(LHC is no circle but more an octagon.. long straight sections LSS and dipole arcs ARC)

Ok, assume now a protons runs on this reference orbit. It gets disturbed by some external force (kick it!). The guide systems will try to push it back and eventually over-do it which creates some wobbling around the reference orbit. The beam 'rings' just like a bell.

The trick is now to stay away from these beam 'tunes' as when such a tune gets excited ('resonance disaster') part of the beams will eventually hit the collimators and be lost (reduced lifetime). This can be achieved by properly setting the feedback terms for the orbit corrections.

This external force is not even necessary as any imperfection from injection will show up as a tiny wobble already.

All in all, high respect for the beams division. It used to be black magic and maybe still is sometimes.. :D

Re: a couple of questions

Posted: Sat Dec 12, 2009 12:30 am
by seedyjay
Thanks for taking the time to give me this information. Hopefully, somebody will be able to expand on it some. At the very least I know a little bit more than before reading it.

Re: a couple of questions

Posted: Sun Dec 13, 2009 1:14 pm
by josch222
seedyjay wrote: (...) Finally, where can I get a LHC blueprint so I can build one of my own?.......just kidding about the blueprint :D
Why kidding?
There are a lot of blueprints on the web, not only at CERN sites.
Here is an example from a local university:
http://www1b.physik.rwth-aachen.de/~cms ... r/Modules/
Good luck for your DIY collider ;-)

Joerg.

Re: a couple of questions

Posted: Sun Dec 13, 2009 2:37 pm
by seedyjay
josch222 wrote:
seedyjay wrote: (...) Finally, where can I get a LHC blueprint so I can build one of my own?.......just kidding about the blueprint :D
Why kidding?
There are a lot of blueprints on the web, not only at CERN sites.
Here is an example from a local university:
http://www1b.physik.rwth-aachen.de/~cms ... r/Modules/
Good luck for your DIY collider ;-)

Joerg.
Thanks. But since my net worth is probably closer to that of a sharecropper than Bill Gates or Warren Buffet, I will be putting off construction for some time yet. :P

Re: a couple of questions

Posted: Mon Dec 14, 2009 4:29 pm
by DCWhitworth
seedyjay wrote:Thanks for taking the time to give me this information. Hopefully, somebody will be able to expand on it some. At the very least I know a little bit more than before reading it.
Take a look at this great thread. Info from pcatom in chat that Chris has posted to the forum.

http://lhcportal.com/Forum/viewtopic.php?f=4&t=219

Re: a couple of questions

Posted: Tue Dec 15, 2009 7:32 am
by seedyjay
Thanks for the link D C, well worth reading.