  The effects on beam dynamics from long-range and short-range wakefields from
TESLA-type cavities are considered in regard to a proposed FEL oscillator
(FE-LO) operating at 120 nm. This would be driven by the Fermilab Accelerator
Science and Technology (FAST) linac at 300 MeV with a 3-MHz micropulse
repetition rate. Our wakefield studies showed measurable effects on
submacropulse centroid stability and on submicropulse head-tail kicks that can
lead to emittance degradation. In the case of the former, we use MINERVA/OPC to
simulate the ~100-$\mu$m centroid slew effects on the saturated output power
levels of the FELO.
