From the Third to the Fourth Generation of Synchrotron Radiation Light Sources

Abstract
Originally, the third generation of synchrotron radiation light sources aimed at reaching a target average brilliance from undulators in the 10¹⁸ range. The very first of these Light Sources were successfully commissioned three years ago, and some of them, including the ESRF, had largely surpassed the target within a few years. They have shown themselves to be fantastic tools and outstanding experimental results have already been produced. An excellent scientific case can be drawn for both higher brilliance (more coherence or even diffraction limited beams) and shorter pulses. The upgrades of existing 3rd generation Light Sources plus the new ring based light sources to come as well as the new linac driven PEL ones, must push performances along these lines. With regards to the average brilliance, the 10²² range could be accessible. The ESRF should reach 10²¹ with the completion of the forthcoming upgrade. As for the time structure, the sub-pico second seems to be out of the range of circular Light Sources. The linac PEL is claimed to be more appropriate and if the 5 year R&D programme underway is successful, we could even imagine producing intense 100 fs pulses with such Light Sources. The presentation will elaborate on the latest status of these developments.