For precise beam energy measurements at 45 and 80 GeV
the use of resonant depolarization
has been suggested for FCC e+e-.
The principle behind resonant depolarization is that a
vertically polarized beam excited through an oscillating horizontal magnetic field
gets depolarized when the excitation frequency is in a given relationship with the beam
The studies of the possibility of self-polarized leptons have been
pursued for the current 45 and 80 GeV optics.
In this talk results of simulations in presence of quadrupole misalignments and
beam position monitors (BPMs) errors are presented.