Beam halo collimation studies and measurements at the Accelerator Test Facility ATF2

A beam halo collimator was installed at the Accelerator Test Facility ATF2 in the spring of 2016. The main objective of the collimator is the reduction of background photons that limit the performance of key diagnostic devices around the Interaction Point, especially the Shintake Monitor, used for measuring the nanometer level vertical beam sizes, and the vertical and horizontal Diamond Sensors, used for transverse beam halo measurements. In this paper we present the simulations performed to optimize the efficiency of the collimator as well as the wakefield study performed in order to optimize the geometry and material of the collimator jaws. Finally, measurements of the cleaning efficiency and of the collimator induced wakefields impact on the orbit, performed during the Spring and Fall 2016 runs, are presented and compared with simulations.