Prospects for an X-Ray FEL Light Source and some Possible Scientific Applications

Free electron lasers are now being designed which will operate at wavelengths down to about 1 A. Due to the physics of the high‐gain, single pass FEL process that these sources will exploit, the radiation produced will have unique properties. In particular: • The FEL peak intensity and peak brightness will be many orders of magnitude higher than can be produced by any other source. • The pulse length will be less than 1 picosecond, orders of magnitude shorter than can be achieved with any other bright source such as a synchrotron. • The FEL radiation will have full transverse coherence and a degeneracy parameter (photons/coherence volume) equal to 109 or more. No other source can produce hard x‐radiation with a degeneracy parameter significantly greater than 1. These properties offer the chance to study chemical, biological, and condensed matter dynamical processes with sub‐picosecond time resolution and angstrom spatial resolution. The high peak power of the FEL radiation (greater than 1014 W/cm2) could ...