Scientific opportunities for FEL amplifier based VUV and X-ray research

It has become increasingly clear to a wide cross section of the synchrotron radiation research community that FELs will be the cornerstone of fourth generation radiation sources. Through the coherent generation of radiation, they provide as much as 12 orders of magnitude increase in peak power over the third generation storage ring machines of today. Facilities have been proposed which will extend the operating wavelength of these devices well beyond the reach of existing solid state laser technology. In addition, it appears possible to generate pulses of unprecedented brevity, down to a few femtoseconds, with mJ pulse energies. The combination of these attributes has stimulated considerable interest in short wavelength FELs for experiments in chemical, surface and solid state physics, biology and materials science. This paper provides a brief overview of how the features of these FELs relate to the experimental opportunities.