The magnetic end design of pure-permanent magnet Apple-II elliptically polarizing undulators (EPU) is discussed. Constraints on end block dimensions and positions are presented that guarantee steering and displacement free systems in both transverse directions and at all gaps for μ = 1 material. For block material with μ > 1 some beam steering (i.e. integrated dipole) may occur due to the ends; in particular, the integrated dipole strength varies with EPU phase. An optimization process is presented that assumes small perturbations about the μ = 1 solution and minimizes the variation in steering with EPU phase. We present numerical and experimental results that quantify the reduction in integrated dipole variation with phase. © 2006 IEEE.

This paper describes a design study with the objective of optimizing spectral performance of an elliptical wiggler to be installed at the Lawrence Berkeley Laboratory Advanced Light Source (ALS). This device is to produce circularly polarized radiation in the energy range of 50 eV to 10 KeV. A figure of merit, which is a function of flux density and degree of circular polarization, is introduced as the objective function for optimization. An optimum set point for a particular photon energy is characterized by values of peak vertical field, horizontal deflection parameter, and vertical aperture. Optimum performance is evaluated for the nominal ALS operating energy of 1.5 GeV.