  Particle accelerators as photon sources are advanced tools in studying the
structure and dynamical properties of matter. The present workhorses of these
sources are storage ring-based synchrotron radiation facilities and linear
accelerator-based free-electron lasers, delivering light with high repetition
rate and high peak brilliance (power), respectively. The steady-state
microbunching (SSMB) mechanism was proposed to bridge the gap of these two
kinds of sources to generate high-average-power, high-repetition-rate coherent
radiation in an electron storage ring. Such a novel light source promises new
possibilities for accelerator photon science and industry applications, for
example in ultra-high-energy-resolution angle-resolved photoemission
spectroscopy and extreme ultraviolet lithography. The six orders of magnitude
extrapolation of the electron bunch length in an SSMB storage ring compared to
that of a conventional ring provides tremendous opportunities for accelerator
physics research.
  This dissertation is devoted to the theoretical and experimental
investigations of SSMB, with important results achieved. The work presented can
be summarized as: first, how to realize SSMB; second, what radiation
characteristics can we obtain from the formed SSMB; and third, experimentally
demonstrate the working mechanism of SSMB in a real machine.
