Longitudinal damping time measures the time to damp a longitudinal plane (energy offset - longitudinal coordinate along the bunch) oscillation of a particle. For a centered orbit and a FODO lattice it is 2 as fast as the damping of transverse oscillations. The damping time scales with beam energy as 1/E3. The transverse damping times are given in the FCC-ee parameter table.
What is the longitudinal damping time?