  In the case of single-digit picosecond bunch length, synchrotron light
sources produce intense coherent radiation up to the THz range. The reduction
of the bunch length by lowering the momentum compaction factor (low-$\alpha$)
gives rise to the micro-bunching instability, which is on one hand a crucial
roadblock in the X-ray range during to the resulting effective bunch
lengthening but on the other hand also an opportunity for the generation of
intense THz radiation if it can be controlled appropriately. In the KIT storage
ring KARA (Karlsruhe Research Accelerator), two parallel plates with periodic
rectangular corrugations are planned to be installed in an electron storage
ring. These plates create an additional longitudinal impedance based on their
geometry, which can affect the beam dynamics. The resulting impedance
manipulation will be used to study and control the longitudinal electron beam
dynamics and the emitted coherent synchrotron radiation (CSR). This paper
presents the results of systematic studies in simulation of the impact of
additional corrugated plate impedances on the longitudinal beam dynamics using
the example of the KARA storage ring. If the periodicity of the wake function
of the corrugated plates matches the size of the substructures in the
longitudinal bunch profile, the instability threshold can be effectively
manipulated. This extends intense THz radiation to different beam current
regimes.
