  Here we present designs for a static septum magnet with two adjacent
apertures where ideally one aperture has a uniform dipole field and the other
zero field. Two designs are considered. One is a true septum magnet with a thin
layer of coils and materials separating the dipole field region from the null
field region. During the beam switching process, the intense electron beam will
spray across this material septum leading to concerns on beam control, vacuum
quality, radiation damage, etc. due to the lost particles. Therefore, another
configuration without a material septum is also considered. With this
configuration it is more difficult to achieve high field quality near the
transition region. Shaped shims are designed to limit the degradation of beam
quality (emittance growth). This approach is closely related to a previous
septum magnet design with two oppositely oriented dipole field regions
presented by the authors [1]. Simulations are performed to obtain the magnetic
field profile in both designs. A PIC simulation is used to transport a beam
slice consisting of several thousand particles through the magnet to estimate
emittance growth in the magnet due to field non-uniformity.
