Figure-8 undulator as an insertion device with linear polarization and low on-axis power density

A new type undulator for linearly polarized radiation, figure-8 undulator, is proposed. It has the advantage that the on-axis power density is much lower than that of an ordinary planar undulator. Electrons inside the proposed device move along the trajectory which looks like a figure-8 when projected on the plane perpendicular to the beam axis. The spectral performance and the power density are calculated and compared to those of an ordinary planar undulator.