Third-generation low-emittance storage-ring light sources based on double- and triple-bend cells and undulator magnets have been in operation around the world for more than two decades. On the horizon is a new generation based on the multi-bend achromat (MBA) lattice concept promising two to three orders of magnitude higher brightness than is available in today's sources. In this paper, the challenges inherent in designing MBA lattices, as well as potential solutions, are described. Topics covered include lattice concepts, scaling of storage-ring performance, brightness optimization, nonlinear dynamics, beam lifetime and injection schemes.

A decade-long effort at the Advanced Photon Source (APS) of Argonne National Laboratory (ANL) on development of superconducting undulators culminated in December 2012 with the installation of the first superconducting undulator "SCU0" into Sector 6 of the APS storage ring. The device was commissioned in January 2013 and has been in user operation since. This paper presents the magnetic and cryogenic design of the SCU0 together with the results of stand-alone cold tests. The initial commissioning and characterization of SCU0 as well as its operating experience in the APS storage ring are described.

A theory of global orbit correction using the technique of singular value decomposition (SVD) of the response matrix and simulation of its application to the Advanced Photon Source (APS) storage ring are presented. The response matrix relates beam motion at the beam position monitor (BPM) locations to changes in corrector magnet strengths. SVD reconfigures the BPMs and correctors into the same number of "transformed" BPMs (t-BPMs) and "transformed correctors (t-correctors), each t-BPM being coupled to at most one tcorrector and vice versa with associated coupling strength which determines the efficiency of orbit correction. The coefficients of these linear transformations can be used to determine which BPMs and correctors are the most effective. Decoupling the weakly coupled pairs will enhance the overall correction efficiency at the expense of accuracy. The orbit errors at decoupled t-BPMs are conserved and the strengths of decoupled t-correctors can be adjusted appropriately to optimize the actual corrector strengths. This method allows for estimating the limitation on orbit correction with given sets of BPMs and correctors, as well as optimizing the corrector strengths without overloading the corrector magnet power supplies.

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Experimental evidence for self-amplified spontaneous emission (SASE) at 530 nm is reported. The measurements were made at the low-energy undulator test line facility at the Advanced Photon Source, Argonne National Laboratory. The experimental setup and details of the experimental results are presented, as well as preliminary analysis. This experiment extends to shorter wavelengths the operational knowledge of a linac-based SASE free-electron laser and explicitly shows the predicted exponential growth in intensity of the optical pulse as a function of length along the undulator.