Shintake Monitor Nanometer Beam Size Measurement and Beam Tuning

A novel final focus system design featuring the Local Chromaticity Correction scheme has beenproposed for ILC. This is to be verified at ATF2, a test facility for ILC, through focusing an e-beam down to the design vertical beam size ("σy") of 37 nm. Shintake Beam Size Monitor ("IPBSM"),installed at the virtual interaction point of ATF2, is the only existing device capable of measuring σy below 100 nm, making it indispensable for achieving the goals of ATF2 and a strong candidate for R&D at future linear colliders. This is attributed to its ingenious technique of scanning the phase oflaser interference fringes relative to the e-beam. Beam sizes are derived from the resulting Compton signal modulation measured by a downstream detector. Having been upgraded in a variety of ways since its first debut at FFTB, Shintake Monitor is capable of measuring a wide range of σy from 25 nm to 6 μm with better than 10% resolution. This paper describes the system's design, role in beam tuning, and various hardware upgrades to further improve its performance.