Optics for Insertion-Device Beam Lines,
NAVAL WEAPONS CENTER CHINA LAKE CA
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This paper presents an overview of optical, thermal, and mechanical problems encountered with optical elements in beams of synchrotron radiation SR emitted by electron sidewinders such as wigglers, undulators, and free electron lasers FELs. Perhaps the most challenging problem is the management of the high power densities from wigglers without degradation of the optical quality of the beam. Another challenging problem is the reduction of near specular scattering by surface microroughness on the mirrors. Near specular scattering becomes more important as the degree of coherence and collimation to be maintained increases from bend magnet SR to undulator and FEL radiation. It is emphasized that the surface autocovariance length of the mirror is the determiner of the angular distribution of scattering, and that very long autocovariance lengths are required for highly coherent SR beams.