A possible FEL based on LEP superconducting cavities

After the LEP shut-down, 2.7 GV of superconducting cavities at the frequency of 352 MHz will become available for other uses. For instance, they can be used to drive a Free Electron Laser (FEL) in the VUV and soft X-rays spectral region. Some preliminary calculations show the feasibility of such a device. In particular some GW of peak power can be obtained in the "water window" part of the spectrum, for a 1.5 GeV beam and using state-of-the-art technology for the wiggler and the injector. Technological limits and possible extension are also briefly discussed.