Steady-State Micro-Bunching based on Transverse-Longitudinal Coupling

In this paper, three specific scenarios of a novel accelerator light source mechanism called steady-state micro-bunching (SSMB) have been studied, i.e., longitudinal weak focusing, longitudinal strong focusing and generalized longitudinal strong focusing (GLSF). At present, GLSF is the most promising among them in realizing high-power short-wavelength coherent radiation with a mild requirement on the modulation laser power. Its essence is to exploit the ultrasmall natural vertical emittance of an electron beam in a planar storage ring for efficient microbunching formation, like a partial transverse-longitudinal emittance exchange at the optical laser wavelength range. Based on indepth investigation of related beam physics, a solution of a GLSF SSMB storage ring which can deliver 1 kW-average-power EUV light is presented. The work in this paper, such as the generalized Courant-Snyder formalism, the analysis of theoretical minimum emittances, transverse-longitudinal coupling dynamics, and the derivation of bunching factor and modulation strengths for laser-induced microbunching schemes, is expected to be useful not only for the development of SSMB but also for future accelerator light sources in general that demand increasingly precise electron beam phase space manipulations.