Bahrdt, J.; Sasaki, S.: CHALLENGES OF QUASIPERIODIC APPLE UNDULATORS. In: Proceedings of IPAC 2012, New Orleans, Louisiana, USA. , 2012, p. 705-707

Abstract:
In many synchrotron radiation facilities APPLE undulators have become workhorses for the production of variably polarized light. In helical mode higher harmonics are not produced. In the linear modes (horizontal, vertical, inclined) higher harmonics may contaminate the first harmonic and spoil the quality of experimental data. Planar undulators employing a quasiperiodic magnetic structure have been built and are successfully operated at several facilities. The implementation of a quasiperiodic lattice in an APPLE undulator is more complicated since the device is operated in various polarization modes. A detailed analysis of the magnetic and spectral performance of a quasiperiodic APPLE is presented. http://accelconf.web.cern.ch/AccelConf/IPAC2012/papers/moppp064.pdf