The Extraction Lambertson Septum Magnet of the SNS

In the Spallation Neutron Source, after multiple injections to an accumulator ring, a final extraction delivers the full proton beam to the target, achieved by a series of kickers and a thin septum magnet. Here we discuss the lattice geometry, beam dynamics and optics, and the vacuum, electromagnetic and mechanical design aspects of the Extraction Lambertson Septum Magnet (ELS). Relevant datum are established. Vector calculus is solved for pitch and roll angles, which are shown schematically in magnet sections.