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FCC-ee optics tuning WG
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354/1-016 (CERN)
FCC-ee optics tuning WG meeting
Actions:
- Simulate failure of correctors and BPMs
- Repository for tuning result seeds --> To be followed up to have one repository for tuning and tuned lattices (S. Jagabathuni, J. Salvesen, J. Keintzel, K. Skoufaris, etc), meeting next week
- Max BPM to quadrupole alignment --> more studies to be done
- Including long-range misalignments: --> Values provided by Jürgen and Vincent in ~mid September
- Tuning simulations with larger H errors after BBA and split errors between arc and IR: news next tuning meeting
- a4 correction to be studied:
- Split arc and IR BPM resolution
- BPM resolution for RDTs measurements: news next tuning meeting
- IP dispersion impact: updates today
Tapering and H corrector discussion: Current working hypothesis H corrected in 1/3 dipoles (for tuning and tapering), other 2 dipoles tapering. 1 taper circuit per arc for dipoles.
Exercise on 2 vs 3 dipoles presented in ATDC meeting: Decision to remain with 3 dipoles.
M. Le Garrec reproduced in SuperKEKB HER beta, phase, sextupole, octupole RDTS and amplitude detuning by adding 0.4% gradient in one quadrupole in the abort section (on the opposite site of the IR) between 1 strong sextupole pair. It should be communicated to Y. Ohnishi et al. The model does not include the cancel coil error.
Jacqueline presents estimates of Dy tolernace for energy calibration. With new tools she reproduces LEP numbers. For FCC-ee she finds that 2um D*y would require 1.6nm offset control at the IP. The 2um value is what Tirsi pessimistically concluded in his last presentation.Third order Dy has about a factor 10 weaker tolerance. It is not dominating but should be monitored. Energy of collisions at different IPs for the corrected machine could reach 5 keV offsets from seeds provided by Satya to Jorg. This should be chenced for latest error tables. Corrections are possible with orbit bumps and RF triming, to be checked.
Vaihabi collects all the tolerances on IP parameters she studied so far. Higgs and tt show a factor tighter Dy tolerance than Z and W. HIgher order Dys are more relaxed in general. Chromatic coupling tolerances are also provided.
Pantaleo recalls that at IP BPM resolution should not be 0.1um but ~1nm. We should discuss this with BI. ESRF has demonstrated this.
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