Optical configurations with variable β* at different IP locations in ATF2

Abstract

During ATF2 commissioning, it will be important to focus the beam to a proper waist at IP locations both upstream and downstream of the nominal one, where different beam size monitors will be placed with typical resolutions larger than that of the Shintake monitor at the nominal IP. In this note, a method to obtain optical configurations with variable β* at these different IP locations is described, enabling to match the measurement resolutions of these monitors with the linear beam size at the waist, while attempting to retain the overall features of the local chromaticity correction in the final focus optics. During commissioning, it is expected that one will gradually reduce β* after measurements at these different locations