Choose timezone
Your profile timezone:
FCC-ee tuning meeting
→
Europe/Zurich
zoom
zoom
CEPC optics tuning, Speaker: Yiwei Wang (IHEP)
A general presentation of the CEPC lattice is given. They have found that having 4 SF sextupole pairs in a row followed by 4 SD sextupole paris in a row Q'' is lower. This should be tested in FCC-ee.
Optics correction strategy is similar to FCC-ee, starting without sextupoles for the orbit correction. Dispersion free steering (DFS) is applied. LOCO is used to generate an effective model and corrects beta-beating and dispersion. Sextupoles are mounted on movers and thanks to this the sextupole misalignments are assumed to have misalignment to 10um (instead of 100um). Rogelio comments that this technology might need to be demonstrated. Oide-san asks what happens if instead of 10um, 100um is used, but they have not tried this as optics did not converge. Closed orbit is corrected to below 50um rms. Dispersion is corrected 2.7mm rms. beta-beating is ~10% rms after correction without IR quad strength errors. No girders are assumed, neither BPM errors. Sextupoles have no strength error.
Emittance and DA is satisfactory after tuning, including radiation and tapering.
Simone asks about the need of first turn orbit threading, tune and chromaticity corrections. Yes, these 3 issues are corrected. Dispersion is corrected twice, with DFS and LOCO, presented plots are after all corrections? It seems so. It might be helpful to have the first round of DFS for FCC-ee.
Rogelio asked if the CEPC would have time to simulate FCC-ee lattice. They said that after their TDR (end of this year) they will have time. Let's continue to stay in touch trough these meetings (Yiwei is added to the invitation list).
##################################################################
FCC-ee IR matching and tuning knobs, Speaker: Leon Van Riesen-Haupt (EPFL - Ecole Polytechnique Federale Lausanne (CH))
Optic Matching strategies have been successfully developed to avoid errors from code language translation or slicing sequence (down to 3 slices!). Attention is put to functionality of sections. This can also be extended to be included in tuning techniques.
Various knobs have been generated:
-Tune: QI magnets in RF section (9 quads). Does not disturb critical phase advances as it is far from IP. No beta-beating generated (below 0.5%). Linear dependencies are shown (with small parabolic aberrations) versus knob settings. Range of [-0.1,0.1].
-Horizontal waist shift knob: QA and QB quads in Disp free region, after IR sextupole section. Allows for changes of 10cm in H waist, with small perturbation in V waist. Quadratic knob improves this perturbation.
-Vertical waist shift knob was not easy to be generated. Oide-san mentioned to use QC1 (closest quad to IP).
Rogelio asked Oide about the dispersion knobs he generated. He said he used offsets in sextupoles. Most important knobs will
Dmitry says that most critical distortion could be betas at IP and at crab sextupoles. Leon will take a look.
##########################################3
Progress with FCC-ee tuning with the ESRF algorith, Speaker: Simone Liuzzo (ESRF)
Simone has used commissioning optics from Leon (with larger beta*). Computation of response matrix takes 19h. Assigned misalignments are 10um. Correction runs obtaining good on-momentum DA for 10 seeds. However off-momentum DA is very low also for ideal lattice. This could be due to the particular chromaticity correction applied.
Tessa commented that all arc sextupoles were used in her simulations to change chromaticity.
Oide-san comments that response matrix calculation takes 19h. Analytical calculations could speed this up and Andrea Franchi prepared a good batch of these equations. Tessa and Esmaeil (in ELEGANT) had a similar problem and would benefit from this.
There is a project to write python functions to optics corrections. Simone will inform us about the project in the future.
Next meeting: Thursday in one week with a report from Tessa.
There are minutes attached to this event.
Show them.
