We present an experimental and theoretical study of symmetric Xe 54+ +Xe collisions at 50, 30, and 15 MeV/u, corresponding to strong perturbations with vK /vp = 1.20, 1.55, and 2.20, respectively (vK : classical K-shell orbital velocity, vp: projectile velocity), as well as Xe 53+ + Xe collisions at 15 MeV/u. For each of these systems, x-ray spectra were measured under a forward angle of 35 • with respect to the projectile beam. Target satellite and hypersatellite radiation, Kα s 2,1 and Kα hs 2,1 , respectively, were analyzed and used to derive cross section ratios for double-to-single target K-shell vacancy production. We compare our experimental results to relativistic time-dependent two-center calculations.