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Does anybody know, what is the role of collimators in LHC? I have found some documents about the construction of the collimators and about the placement into the tunnel, but I cannot find anything about their role in the accelerator.

Thanks in advance for any info

Jakub

The collimators scrape away particles that have gone slightly off track in order to prevent damages to the beam pipe and the magnets (a small fraction of the beam hitting a magnet might for example cause a quench http://lhc-collimation-project.web.cern ... uction.htm).
The collimators are even resistant enough to protect the machine in the case that the kicker magnets to the beam dumps fail. During the operation of the LHC the collimators are going to become quite radioactive!

For cool movies of collimators in action and sounds of particles hitting them, see
http://lhc-collimation-project.web.cern ... movies.htm

Now I understand why they chose the term squeezing.
Looks really as if they try to squeez the beam mecanically.
And I thought that squeezing in the LHC would be done by magnets.

They wouldn't have much of the beam left soon if they were squeezing it just with collimator jaws. They act more like sandpaper, making the beam less 'hairy'.
Plus, squeezing is a special process aimed at having the beam as narrow as possible in the collision area which means it will defocus again behind it (something like if you focus sunlight with magnifying glass).

I see 2 different term in the scheduel:
1. collimator setup
2. collimation setup test

is there a difference or is the 2nd only a check if it is still OK?