Advances in physical design of diffraction-limited storage ring

A new generation of ring-based light source, called diffraction-limited storage ring (DLSR), has attracted increasing attention from accelerator scientists worldwide. This article introduces the progress in the physical design and optimization of DLSR at home and abroad in the past few years. In the linear optics design multi-bend achromats with compact layout are usually adopted, so as to achieve ultralow emittance within a reasonable circumference. In the nonlinear optimization, phase manipulation technique, theoretical and numerical optimization methods are usually used to minimize the strong nonlinearities caused by the chromatic sextupoles. Associated with the small acceptance of a DLSR, off-axis injection with pulsed multipoles and on-axis injection with fast kickers are considered. Collective effects, especially the intrabeam scattering and the Touschek effects, become significant as emittance decreases, requiring methods of bunch lengthening and transverse feedback to ensure the stability of the particle motion.