Intensity dependent effects at ATF2, KEK

The Accelerator Test Facility 2 (ATF2) at KEK is a prototype for the Final Focus Systems of the future e+e- linear colliders, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC). In this paper both simulation and experimental results are presented with special emphasis on intensity-dependent effects. The importance of these effects is shown using the PLACET code and realistic ATF2 machine simulations (including beam jitter, misalignment, wakefield, Beam Based Alignment (BBA) correction). The latest experimental results are also presented, in particular the impact of the beam intensity on the beam size at the IP.