VUV-wiggler scheme with non-sinusoidal magnetic field profile for high energy storage rings

A planar undulator scheme with a non-sinusoidal magnetic field profile along the undulator axis is proposed. The advantage of this scheme is in the fact that it has lower on-axis power density as compared to that of an ordinary planar undulator, because the maximum longitudinal velocity of the electron beam does not coincide with the maxima of the magnetic fields. The spectral performance and the power density are calculated and compared to those of an undulator with a sinusoidal magnetic field.