  We discuss simulations and experiments on creating micro-bunch beams for
generating narrow band THz radiation at the Fermilab Accelerator Science and
Technology (FAST) facility. The low-energy electron beamline at FAST consists
of a photoinjector-based RF gun, two L-band superconducting accelerating
cavities, a chicane, and a beam dump. The electron bunches are lengthened with
cavity phases set off-crest for better longitudinal separation and then
micro-bunched with a slit-mask installed in the chicane. We carried out the
experiments with 30 MeV electron beams and detected signals of the
micro-bunching using a skew quadrupole magnet in the chicane. In this paper,
the details of micro-bunch beam production, the detection of micro-bunching and
comparison with simulations are described.
