RESONANT CONDITIONS FOR A STORAGE-RING SHORT-WAVELENGTH FEL WITH POWER EXCEEDING RENIERI LIMIT

In this paper we discuss the possibility of operating a storage ring F EL with resonant conditions providing for preservation of electron bea m structure on an optical wave scale. We suggest tuning the storage ri ng betatron and synchrotron tunes on one of the high (Nth) order reson ances to compensate dynamic diffusion of optical phase. This mode of o peration does not require isochronicity of the ring lattice. In these conditions optical phase will be restored after N turns around the rin g and stochastic conditions used in the derivation of Renieri limit ar e no longer applicable. We discuss the influence of high order terms i n electron motion, RF frequency stability, and synchrotron radiation e ffects on preservation of optical phase.