<title>Present time-structure properties of storage-ring-based x-ray sources</title>

Abstract

For storage ring based synchrotron radiation sources which deliver high flux coherent X-ray pulses at a high repetition rate, the figure of merit is the brilliance. Third generation synchrotron radiation sources provide a brilliance in the 1020 range, in the usual units, for 10 keV photon beams. Such a performance approaches the ultimate limit imposed by the diffraction limit of synchrotron radiation emission. A gain of up to 6 orders of magnitude, with respect to the brilliance of second generation sources, was obtained by reducing transverse electron beam emittances and by optimizing undulator radiation. The horizontal emittance was dramatically decreased by reducing the dispersion function in the bending magnets. As a consequence, the dispersion of the electron revolution time around the ring, as a function of energy, was reduced. Under this quasi-isochronous condition, electron bunch lengths were naturally shortened and reached the few tens of ps range. The quasi-isochronous tuning of storage rings was further tested on third generation rings to evaluate the possibilities of reaching the subpicosecond range and improving the present peak brilliance of 1023. Unfortunately, the nature of the electromagnetic environment, with which the electron bunch interacts, makes the bunch lengthen with increasing current. Best predictions of peak brilliance performances achievable on storage rings will leave them far behind linac driven FEL sources if the principle of Self Amplified Spontaneous Emission works as predicted.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.