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FCC-ee tuning meeting
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FCC-ee tuning meeting
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FCC-ee magnetic field quality, Jeremie Bauche
Dipole, quadrupole and sextupole magnetic designs are presented along with FQ expectations and tapering schemes. The quadrupole design presents significant limitations due to coupling between the two apertures. Alternatives designs are being explored. Dipole and quadrupole prototypes have been built and measured. Field quality is quite poor for both types of magnets. Dipoles feature a b3 between 15 and 30 units @10mm. Quadrupoles feature large b1 (center shift) and b3. Mitigations could be to use lattice sextupoles for b3 components, dipoles to compensate qudarupole b1 components, and quads to compensate b2 of dipoles. These strategies should be studied by optics to assess correctable range of errors. Further magnetic designs and simulations will be pursued to improve field quality as much as possible.
Sextupoles are found too pushed and maybe length should be increased. Combined sextupole and dipole or skew quadrupole has demonstrated to yield very complex operation, e.g. in ESRF as commented by Simon White. This can pose a severe challenge since already the ideal lattice features important limitations in current tuning studies. It should be studied if dedicated space is available for orbit correctors, skew quadrupoles and BPMs (Leon started to look into this).
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FCC-ee lattice repository, Michael Hofer
A very well structured and informative lattice repository has been placed on-line. Users are asked to navigate it and provide feedback. In principle it is open to user contributions in many different aspects (macros, lattices, solenoid, etc.).
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FCC-ee optics tuning progress, Tessa
Including for the first time linear chromaticitiy correction in the tuning process results in a large increase of both equilibrium emittances. This is due to the orbit at sextupoles and implies that iterative corrections of coupling and chromaticity are needed lengthening the full tuning process. Initial chromaticies were in the order ~15 units.
An effective realistic lattice can be achieved by introducing only 10% of the errors used so far and apply tuning, followed by rotating quads to increase vertical emittance. So far lattices are produced for ttbar. Felix is interested for lower energies too (Z). Tessa replies that this can be done but it is time consuming. To discuss off-line how this can be efficiently achieved.
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