Performance and operation modes of the Duke FEL storage ring
We present the recent status and performance of the Duke Free Electron Laser (FEL) storage ring. We report a large transverse and energy aperture observed in the storage ring. We describe the consequences of this large aperture on the operation of the storage ring. Several unusual phenomena are reported in this paper, including large amplitude transverse multibunch coherent oscillations (Saturn rings) and beam capture from outside the RF separatrix. We also present the established operation modes for the storage ring, including energy ramping, working point tuning, and different bunch-mode operations to optimize the ring as a synchrotron light source, an FEL, and a gamma-ray source. Finally, we summarize the achieved storage ring parameters since its first operation in November 1994.