New type of cavity for a Raman free-electron laser

A new type of cavity, a distributed feedback cavity from periodically rippled walls is developed. The Raman free electron laser (400 KeV/800 A) with the new cavity is studied. The spectral measurements using a microwave grating spectrometer are presented. The frequency selection, narrowed spectral bandwidth with central wavelength at 8 mm, and output power enhancement show that oscillation happened.