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FCC-ee optics tuning WG meeting
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CERN
CERN
FCC-ee optics tuning WG meeting
E. Musa presents updates on tuning simulations, assuming no BBA (100 µm - 200 µm) with ballistic optics. No drastic change is observed for larger misalignments. For the baseline lattice with improved optics corrections, DFS, RDT correction etc. a good DA is obtained. C. Carli notices that there is always one bad seed, and E. Musa answers that this is always the same one.
C. Carli suggests to simulate the full commissioning strategy with steps in-between.
S. Jagabathuni presents updates on tuning studies using AT. The FF doublets should be aligned to 10 µm. 30 µm alignment seems to be the tolerance for crab sextupoles. All other elements are misalingned by 100 µm. In total 75% of the seeds succeed. Applying IP knobs DA is not reduced further.
C. Goffing presents on BBA updates for the FCC-ee and measurements at KARA. For FCC-ee using a quadrupole modulation lower than 1% seems beneficial. Using more quadrupoles simultaneously does not decrease the BBA performance. Parallel BBA for quadrupoles is performed successfully at KARA and yields similar values compared to individual BBA. Parallel sextupole BBA at KARA is reproducible vertical, but has large fluctuations horizontally.
J. Keintzel suggests to increase misalignments to 200 µm.
B. Dalena presents updates on emittance tuning for the high energy booster using cpymad. 80 out of 100 seeds succeed. The others are lost when correcting phase advance, dispersion and tune. The target emittance is reached after the tuning procedure for these seeds. There is one outlier out of the 80 seeds which remains to be investigated. It will be tried to improve the number of successful seeds by trying e.g. sextupole ramping. S. Jagabathuni comments that without sextupoles the MA could be too low. B. Dalena answers that for now this does not seem to be a problem, but will be investigated.
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