A single-disk, "slow" chopper system has been developed at the Penn State University Radiation Science and Engineering Center (RSEC) for the purpose of energy spectrum measurements on thermal neutron beams (E < 1 eV). The primary beam at PSU RSEC was gated with a single-disk neutron chopper, and the distribution in neutron time-of-flight (TOF) across a known distance was recorded. A procedure was defined whereby the recorded TOF distribution was corrected for various experimental conditions and transformed to yield the velocity and energy spectrum of neutrons in the beam. These data were compared to distributions derived from models based on the Maxwell-Boltzmann distribution. This comparison facilitated characterization of the beam and evaluation of the instrument's usefulness and accuracy in spectroscopic measurements.