Wien filter as a spin rotator at low energy

The Wien filter is well known as a common energy analyzer and is also used more and more as a compact variant of a spin rotator at low energy for electrons. The Wien filter is based on homogenous magnetic and electric fields which are perpendicular to each other and transverse to the direction of the electrons. The rotation of the spin vector is caused by the magnetic field. If the force equilibrium condition is fulfilled the beam should not be deflected at the Wien filter. Simulations show that in the fringe fields the electrons get a kick. Therefore full 3D simulations of the electromagnetic fields and beam dynamics simulations are studied in detail at the example of the Wien filter at the new polarized 100 keV electron injector at the S-DALINAC. The results of the simulations with CST Design Environment^tradeand V-Code are presented.