Short wavelength FELs

The generation of coherent ultraviolet and shorter wavelength light is presently limited to synchrotron sources. Even though synchrotrons can produce a wide range of wavelengths, the output power in a narrow bandwidth is limited relative to that attainable by free-electron lasers (FELs). The use of FELs for the generation of short wavelength light with high output power is discussed. The progress in the development of brighter electron beams enables the use of much lower energy electron RF linacs to reach short-wavelengths than previously considered possible. The author summarizes the results obtained with synchrotron sources, reviews proposed short-wavelength FEL designs and then presents a new design which is capable of over an order of magnitude higher power in the extreme ultraviolet.<>