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OMC Celebration Meeting
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Europe/Zurich
6/R-012 - conference room (CERN)
Description
2016: 1% rms beta-beating, C- of 0.0002 and lot more to celebrate
Present: OMC team, K. Oide, K Ohmi, S. Fartoukh
David, Gone with the noise
Octupoles did not change the coupling, it was just noisier signal due to the increased decoherence. This has been verified with simulations. Noise increases the measured average coupling for one BPM method. For 2 BPM method average goes down due to the phase noise that tends to scatter the vectors -> Better error bar might be needed.
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Andreas, Systematic error was, phase I
Analytic estimates or systematic errors works. This is faster than Montecarlo even excluding the pre-CCC simulations. Next is for alfa.
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Andy, Lord of the ring and the return of the AC dipole
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Lukas, (De)tuned ring and a look into the crystal ball
Tune change along the ESRF has been measured and reproduced in simulations. Oide san mentioned that this is not possible! A new python implementation of interpolating FFT was developed by Jaime in about 10 lines of code.
The new FFT does not feature this problem! Should be related to the SUSSIX algorithm.
Oide san suggested a fit.
The new code has no penalty in time.
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Jaime, Monty Python and the holy GUI
New feature in the GUI, 2-beam matching with possibility to modify parameters for both beams.
Stephane asked for posibility to match on- and off- momentum lattices at the same time. Yes, this is possible.
A tolerance on the beta function measurement uncertainty is 1%.
Large correction cancelling each other appear in Q2A/B. Stephane mentioned that this might imply that this trim might be needed.
Felix remarked that K-modulation beta uncertainty is expected to be larger than 1%. So is for beta from amplitude.
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Ana, IndiAna jones and the last calibration
Beta from amplitude is severely affected by few bad BPMs, it is fundamental to identify them.
rms of ~4% of beating in amp wrt
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Luis, beta-beat correction of beam-beam
Using Q4 and Q5 or even sextupoles we can compensate beta-beating from the HO and long rage BB.
Stephane, changes on crossing angle from Q4/5 trims; Non-colliding bunches? IP8 colliding/non-colliding bunches?
MD foreseen at injection energy.
Oide san mentioned that tails will not see the beta-beating. Operational scenarios have to be considered.
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Felix, stR DTrek; b4 the enterprise; Short terminator: judgment DA
RDTs have been successfully observed in TbT data at 40cm. It is a promissing method to set non-linear corrections.
AC dipole DA under study, shows first consistent measurements with octupoles.
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Tobias, Dr. OMC or How we stopped worrying and started loving the Amplitude dependent closest tune approach
The tunes would not approach as expected by the linear DQmin. This was observed in measurement and reproduced in simulations. The prediction that this effect disappears with using MOF/MOD opposite polarites was confirmed in a recent MD.
This effect is not seen at all with AC dipole!
Felix, how do you expect the AC dipole to affect? We know the direct detuning terms are affected by the AC dipole.
Stephane, maybe refined analyses are needed.
Elias, this should affect the footprint and what was needed in some first simulations was not following the proposed analytical formula. Rogelio, yes, we need a more complete theory!
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Ewen, IR non-linear corrections and DA with coupling (in galic!!!)
4mm offset in B1 MCSX! This affects non-linearities and crossing angle settings.
In the crossing angle scan the effect of uncorrected orbit was non-negligible. To be analyzed.
MKA B1 H-to-V swap!!
Simulations predict dependence of DA on coupling. Clear observation in last experiment confirms this.
Amplitude detuning depends on coupling from PTC and seen in experiment.
Stephane comments on the substantial appearance of higher order amplitude detuning.
a4 + b4 also generates amplitude dependent closest tune approach.
Elias, now we have 40 amps in the octupoles. Instabilities still being observed, how far can we go in oct amps?
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