Implementation of horizontal focusing optics at APS

Despite the very small electron beam emittance in third-generation light sources, the horizontal size of the emitted X-ray beam is still determined mainly by the electron beam divergence. Providing a converging electron beam in an undulator straight section can significantly decrease the spot size of the downstream X-rays, which leads to an increase in the photon flux density on the user sample. This converging optics method has been implemented at the Advanced Photon Source in one straight section for evaluation during machine studies. The optimization of the converging optics, the beam dynamics issues arising from the strongly asymmetric lattice optics, as well as the results achieved so far are discussed in the paper