The influence of a periodic landscape of pinning sites on the vortex dynamics in Pb thin films is explored by ac-susceptibility measurements. For different amplitudes h of the ac-drive, the ac-susceptibility x=x+ix exhibits a complex field dependence associated with different dynamic regimes. At very low ac-drives where both, multiquanta vortices trapped by the antidots and interstitial vortices oscillate inside the pinning potential (intra-valley motion), a small kink in x(H) together with a very low dissipation is observed. At intermediate ac-excitations such that vortices in the antidots remain pinned whereas interstices are driven out of the pinning well, a more pronounced kink in the screening coinciding with the onset of dissipation (x(H) ~ 0) indicates the entrance of interstitial vortices. Eventually, at high enough amplitudes all vortices are set in motion and the penetration of interstitial vortices appears as a sudden reduction of the shielding power. We show that these distinctive features allow us to clearly identify the maximum number of flux quanta per hole regardless the vortex dynamic regime.
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