Towards an International Linear Collider: Experiments at ATF2

Abstract

For linear colliders, realizing extremely small and stable beam is essentially important. At ILC (International Linear Collider), designed vertical beam size and required position stability at the interaction point is nanometer level. In ATF (Accelerator Test Facility) at KEK, study of the final focus system has been performed using small emittance beams extracted from the damping ring. The project is called ATF2. The ATF2 beam line is designed as a prototype of the final focus system of ILC, with basically the same optics, similar beam energy spread, natural chromaticity and tolerances of magnetic field errors. Its design, construction and operation have been performed as an international collaboration. We have demonstrated the local chromatic correction method, which will be used for ILC, and observed the vertical beam size about 55 nm. Test and demonstration of intrapulse orbit feedback has been successfully performed in the middle of the ATF2 beam line. For demonstration of nm level stable beam, high resolution beam position monitors were installed around the focal point. Here, we report our achievement, status and future plans.