EuCARD-2 XPOL workshop on “Polarization Issues in Future High Energy Circular Colliders”

This XPOL workshop will review schemes to produce and use polarized beams in future high-energy storage rings, with a focus on the FCC-ee. Two candidate schemes considered for precise beam energy calibration at the FCC-ee include resonant depolarization of self-polarized pilot bunches as well as the injection and spin precession of a pre-polarized beam. Self polarization using the Sokolov-Ternov effect was successfully realized at LEP and HERA. The  injection of polarized bunches may require Siberian snakes in the lepton booster ring. The lepton ERL of the FCC-he will definitely require a intense sources of polarized electrons, and possibly positrons. The possibility of obtaining polarized hadron beams in the FCC-hh may also be discussed, e.g. extrapolating from RHIC experience. Higher precision polarimetry is of interest for all  operation modes with polarized beams.