L. Nahon et al., OPHELIE - A VARIABLE-POLARIZATION ELECTROMAGNETIC UNDULATOR OPTIMIZEDFOR A VUV BEAMLINE AT SUPER-ACO, Journal of synchrotron radiation, 5, 1998, pp. 428-430
A planar/helical crossed overlapped undulator, called OPHELIE, is pres
ented, composed of two identical ten-period (each 25 cm long) crossed
undulators whose magnetic fields are produced by electromagnets. Such
a design is quite simple, with only one mechanical translational motio
n, and versatile. After the presentation of the general concept of the
crossed undulator and of its actual magnetic design, the expected per
formances in terms of flux and polarization capabilities are described
. It appears that any state of polarization can be produced, at least
on the first harmonic, with a large total polarization rate and a pote
ntially high polarization switching frequency.