Extremely low emittance beam size diagnostics with sub-micrometer resolution using optical transition radiation

Transition radiation (TR) appearing when relativistic uniformly moving charged particle (or bunch of particles) crosses a boundary between two media with different di- electric properties is widely used as a tool for diagnostics of particle beams in modern accelerator facilities. The best resolution which can be achieved using beam profile mon- itors based on TR in optical wave range has a limitation caused by a spatial resolution of an optical system. Using a method based on analyzing a visibility of the TR Point Spread Function one can achieve a sub-micrometer reso- lution. In this report we shall represent the recent exper- imental results of a micron-scale beam size measurement at KEK-ATF2. We shall discuss the hardware status and future plans