Dynamics in an adiabatic free electron laser

Theoretical work in progress indicates that an FEL (free-electron laser) with a recirculating beam of electrons might be a practical device, as long as the wiggler parameters change slowly during trapping and detrapping of the beam, so that excessive beam heating does not occur. This could greatly increase the efficiency of a short-wavelength FEL operated in the Compton regime. Standard tapered wigglers are adiabatic for the trapped particles, but these particles are significantly heated each time they enter and exit the wiggler