Author: Jaouen, N.
Paper Title Page
Optimization of APPLE-II Quasiperiodic Undulators at SOLEIL and Spectral Peformances  
  • F. Briquez, M.-E. Couprie, N. Jaouen, O. Marcouillé, M. Valléau
    SOLEIL, Gif-sur-Yvette, France
  The introduction of a slight aperiodicity in an undulator enables to generate irrational harmonics, for the distinction between a one or two photon process. In the case of an APPLE-II undulator generating various types of polarizations, the aperiodicity is generally introduced by shifting vertically some magnets on arrays. The optimization of the system is not fully satisfying since different optima of magnet displacements are found for the various polarization modes, as reported in examples from SOLEIL undulators. Besides, the intensity of the first harmonics is slightly reduced. In addition, a residual photon signal appears between pseudo-harmonics. Measured spectra from built APPLE-II undulators at SOLEIL are compared to calculated ones from magnetic measurements, and confirm these observed trends, and in particular the residual structure between the pseudo-harmonics. An analytic approach is given and consequences for scientific applications are also driven.