Design Concept of an Electromagnetic Undulator to Produce Arbitrarily Polarized Light

An undulator magnet design is described consisting of four electromagnet arrays to produce arbitrarily polarized photon beams including a linear inclined mode. Polarization changes are effected by a current switch rather than mechanical longitudinal translations. The capability of choosing a variety of current excitations in each double coil of the structure can produce any desired polarization mode. This concept exhibits an advantage over mechanical designs especially for superconducting design versions of this undulator. In this paper, we will discuss the magnet structure concept, the current distribution in each double coil and magnetic field features for various polarizing modes. In addition, the concept of current switching will be discussed, which allows to reduce the number of individual current sources from eight to one.