Dynamics of a storage-ring FEL oscillator with the inclusion of the microwave instability

We present an analysis of the dynamical behavior of a storage-ring FEL oscillator with the inclusion of the microwave longitudinal instability. We prove that the FEL interaction provides a damping mechanism for this type of instability and we discuss the relevant physical interpretation. We also show that the numerical model, exploited to include the microwave instability effects, reproduces the relevant phenomenology and yields a dynamical basis for the Boussard criterion.