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FCC-ee optics tuning WG meeting
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FCC-ee optics tuning WG meeting
News, Jacqueline
Progress with the IPAC 2025 paper
SuperKEKB measurements, Onishi-san
HER TbT measuremements with kicked stored bunch (single bunch medium intensity) at beta*=1mm do not show decoherence as expected from simulations. This can originate from impedance.
With detuning optics beta*y=81mm measurements are easier at larger kicks.
The cancel coil error in HER explains part of the measured survival ratio in the H plane. In the V plane impedance seems to play a big role. Measurements and simulations could be compared at low bunch current and also at large betay*. Forced oscillaitons could be used with bunch-by-bunch feedback system.
Measurements also done with RF phase modulation (in BPMs via Dx). Acceptance difficult to infer from these measurements.
Injection efficiency strongly depends on beta*_x.
Vertical amplitude detuning different than model in LER.Source could be impedance. Measurements should be done with low intensity and open collimators if possible.
HER amplitude detuning also disagrees. Cancel coil error explains part of the discrepancy.
Large vertical emittance in operation is suspected to originate from x-y coupling at the IP but data analysis does not show that. Further analysis might be needed. Data could be made available.
For sharing data together with SAD models some colleagues have access. Maybe missing information is a data log with information on the configuration of the measurements. Similar discussions happened in the beam-beam forum. Jacqueline proposes to extract data identified by Onishi-san. Takashi Mori suggests Belle II support, however they would not know to identify useful data.
IP coupling could be corrected with QCS skew quadrupole coils.
Ideas for measurements, Jacqueline
A collection of potential measurements for future runs is presented. Ideally, visitors will attend SuperKEKB operation. Mael also suggeted vibration mesaurements to be defined.
Multiple tolerances, Abid and Kyriacos
Multipole tolerances computed for lattice version GHC 24.3 taking into account injection efficiency. Values confirmed in general the tight values obtained for the circulating beam. More refined values will be presented later. Concern that the dipole multipole tolerances do not reduce for larger orders. Maybe even larger orders should be considered.
Tuning simualations with girder displacements, Satya
Recap of the eeFACT presentation on IP tuning is given. DA is similar in the new simulations, however vertical emittance has increased is significantly. Removing IR errors improves significantly the vertical emittance to a comparable value as obtained by Elaf (although 10% seeds failed in the initial thread, not seen by Elaf). It seems that the FD errors are driving this emittance increase.
Even 1-2 um urad errors in FD increase vertical emittance. Maybe dedicated skew quadrupole corrector should be added to the FD to increase the tolerance.
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