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FCC-ee optics tuning WG
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Europe/Zurich
6/R-012 - conference room (CERN)
FCC-ee optics tuning WG meeting
Alexey, Magnet updates including magnets and tapering
Recap of the agreed approach for the location of correctors (H corr in bend, V corr in quads, quad corr in quads, skew quad in sexts). The standalone HV orbit corrector will also be studied as it is needed for the IRs.
150mT of skew quad in sextupoles is possible with 10% margin (tt bar operation). It induces a dipole component of b1 between 8 and 20 units and a4 50-90 units. FQ is the same in the two options studied. Optimizations to decrease dipolar component could be explored but it is not easy and would imply different configurations in SD and SF. This dipolar component will introduce the need to correct orbit when skew quad (or sext) is trimmed. FQ needs to be recomputed at Z strength for simulations.
Alexey is happy with this design as it allows to separate the 2 apertures of the sextupolar. He requested a clear definition of focusing and defocusing sextupole. For him field should be positive on the H plane for a focusing sextupole. Pantaelo argues that the 2 apertures should have the same field (rogelio illustrated it visualizing an offset of the 2 sextupole apertures in H, that generate the same quad polarity from feeddown). To be checked off-line.
For the quadrupole 40 mTm of vertical corrector (at tt bar) of gives 91 units of a3 (to be included in simulations, Kevin). Probably this will be OK once we assume correction with dedicated a3 correctors that are needed for the dipoles (to be checked in simulations of a3 corrections, Wietse). We need the a3 at Z (action, Alexey).
The separate corrector will be a window frame magnet.
Christian, News on BBA
The pending issues were the failing seeds and the outlyers in GHC. These outlyers could be reduced by changing the location of the orbit corrector slightly.
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