Simultaneous multiple pass steering at Jefferson Lab

The CEBAF recirculator at Jefferson Lab includes two linear accelerators, each 200 meters in length. Due to varying betatron phase advance for different recirculation passes, misalignment, and other steering effects, orbit correction in the CEBAF linacs presents a complicated problem defying pass-by-pass solutions. Utilization of information from the beam position measurements at all recirculation passes allows us not only to perform multipass steering minimizing beam displacements inside the linacs, but also to determine displacements of linac BPM´s and focusing quadrupoles from an ideal axis. This paper describes a steering algorithm and presents the experience in multi-pass orbit correction