Asymmetric figure-8 undulator as multipolarization light source

A novel insertion device called an asymmetric figure-8 undulator is proposed. The electron moves along an asymmetric figure-8 orbit by magnetic fields composed of a normal figure-8 undulator and an additional vertical field. Because cancellation of circularly polarized component is avoided, all harmonics have elliptic polarization. Further calculation shows that when the additional field is small compared to original ones, the 0.5th, 1st and 2nd harmonics are vertically, horizontally and circularly polarized, respectively. Because the power distribution is almost equal to that of a figure-8 undulator, the proposed device has the same advantage that the heat load on optical elements is much lower than that of a conventional linear undulator.