  This paper presents expected THz radiation spectra emitted by micro-bunched
electron beams produced using a slit-mask placed within a magnetic chicane in
the FAST (Fermilab Accelerator Science and Technology) electron injector at
Fermilab. Our purpose is to generate tunable narrow-band THz radiation with a
simple scheme in a conventional photo-injector. Using the slit-mask in the
chicane, we create a longitudinally micro-bunched beam after the chicane by
transversely slicing an energy chirped electron bunch at a location with
horizontal dispersion. In this paper, we discuss the theory related to the
micro-bunched beam structure, the beam optics, the simulation results of the
micro-bunched beam and the bunching factors. Energy radiated at THz frequencies
from two sources: coherent transition radiation and from a wiggler is
calculated and compared. We also discuss the results of a simple method to
observe the micro-bunching on a transverse screen monitor using a skew
quadrupole placed in the chicane.
