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FCC-ee optics tuning WG
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Europe/Zurich
FCC-ee optics tuning WG meeting
J. Keintzel introduces Tatiana Benilan as new summer intern.
P. Yang presents error analysis for STCF. The most sensitive alignments are from the final focus quadrupoles (30 um). It is found challenging from alignment.
The same misalignments lead to 8.4% beta beating at the IP. No girders are foreseen. H/V correctors next to focusing/defocusing quads. At sextupoles H/V correctors. Skew quadrupoles at sextupoles or near some quads. 25% of SV values are used. 1000 seeds are used. 40% of those seeds are threaded through the first turn without correction. After tuning X/Y orbit is about 50 um rms, with corrector strengths less then 35 urad. IP knob for X/Y are generated and applied, reducing the orbit to 5.5/1.2 um.
Then beta, dispersion and coupling is corrected. Beta beating rms is below 1%, but at the IP vertically it is sometimes up to 50%. Then IP knobs for beta are generated. IP beta are simulated being measured using K-mod (paper F. Calier et al). With that a max of 2.2 % betay* beat are found over the seeds.
Afterwards a local bump is applied for final correction of the orbit at the IP, of course, assuming these BPMs work reliably. This corrects vibrations leading to orbit jitter.
It is studied if sextupole movers are needed. At HEPS light source about 5um are achieved. If movers are used, corrections should be done without sextupoles.
R. Tomas asks about field error studies in elements. P. Yang comments these studies could be done in the future.
C. Goffing presents thoughts on BBA for 3 different BPM locations. H/V correctors are next to the dipole/quadrupole. Only 10 mm distance between BPM and element are assumed. For quadrupole BBA the BPM should be located as close as possible to the quadrupole, similar for the sextupole.
P. Raimondi suggests misalingments of 16 um to all sextupoles to see the effect on the optics.
P. Raimondi adds that at ESRF, corrections must be done every 1-2 months, suspected to stem from orbit through the sextupoles.
R. Tomas summarizes that the 3 positions give approximately the same results.
K. Lasocha comments that the wakes will be studied in the future.
J. Keintzel presents the impact of orbit corrections on the spin tune shift for KARA. A beam test is foreseen to take place from 29 to 30 June.
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