Studies on the asymmetric magnet pole undulators

A new class of asymmetric planar undulators, in which the upper and lower pure-permanent-magnet arrays have different period lengths, is proposed and studied. Through optimizing the period lengths, the amplitudes of magnetic fields and the phase shift between the two magnet arrays, the asymmetric undulators are capable of generating different types of magnetic fields. Various undulator radiations characterized by different features can be achieved, such as suppressing the high harmonic radiation or generating the partially circularly polarized radiation in the off-axis orbit and reducing the on-axis heat load. The undulator designs and the corresponding radiation characteristics are numerically studied and analyzed with some practical considerations to verify the potential applications of the asymmetric undulators.