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Dashboard tune plots seem... out of tune?
Posted: Sun May 29, 2016 11:53 pm
by Xezlec
Watching the LHC dashboard lately, I notice that the "tune" plots usually show the dots right on the lines. I thought the lines represented resonances they aren't supposed to hit. So why are they parked on them most of the time? Anyone know?
Re: Dashboard tune plots seem... out of tune?
Posted: Wed Jun 01, 2016 12:41 am
by Xezlec
I think this may have had something to do with it (page 7):
https://indico.cern.ch/event/506413/con ... 016_EB.pdf
Re: Dashboard tune plots seem... out of tune?
Posted: Thu Jun 02, 2016 11:23 am
by mfb
The red line is not as problematic as the other lines (it just means horizontal and vertical tune are the same). If it hits one of the other lines, I don't think they can keep the beam.
Re: Dashboard tune plots seem... out of tune?
Posted: Sun Jun 05, 2016 12:27 pm
by Xezlec
mfb wrote:The red line is not as problematic as the other lines (it just means horizontal and vertical tune are the same).
Really? I can't find it now, but I thought I read somewhere that the red line represented a "more subtle type of resonance", though whatever I was reading didn't elaborate beyond that.
Re: Dashboard tune plots seem... out of tune?
Posted: Mon Jun 13, 2016 10:01 am
by Tau
mfb wrote:The red line is not as problematic as the other lines (it just means horizontal and vertical tune are the same). If it hits one of the other lines, I don't think they can keep the beam.
It is not as hard as you think. The red line indicates where horizontal and vertical tunes are the same. That means that if there is any coupling between the oscillations in the two directions (which is unavoidable), the oscillations in the two directions may influence each other, so that resonances in one direction may cause trouble in the direction.
So that line is also better not be crossed.