ATF2 for Final Focus Test Beam for Future Linear Colliders

Abstract In future linear colliders, extremely small beam size is required at collision point for high luminosity. For example, it is of order of nanometer in ILC( International Linear Collider ). ATF2 is a project at ATF(Accelerator Test Facility) in KEK which demonstrates performance of final focus system experimentally. ATF2 beam line is a prototype of ILC final focus system where the local chromaticity correction scheme is adopted. The optics is basically the same and the natural chromaticity, too. Thus the tolerance of magnet alignment and field error is similar for both of the beam lines. We report here observation of small beam size of about 45nm there. We also report plan for smaller beam size with higher beam intensity.