Insertion Devices & Brilliance
Synchrotron storage rings optimized for insertion devices (photo below) are called "third-generation" light sources. Some, like the Advanced Light Source in California and the SuperACO in France, provide radiation in the ultraviolet/soft x-ray part of the spectrum. The 7-GeV APS and its sister facilities, the 6-GeV European Synchrotron Radiation Facility in France, and the Super Photon Ring 8-GeV (SPring-8) in Japan, can produce a range of x-rays up to those of the hard (highly penetrating) variety because of higher machine energies.
Third-generation storage rings maximize those x-ray beam qualities, flux and brilliance, that are needed for frontier experimentation. Flux and brilliance are benchmarks of x-ray beam quality. Both are based on a measure of the number of photons per second in a narrow energy bandwidth and in a unit of solid angle in the horizontal and vertical directions. Flux is the number of photons per second passing through a defined area, and is the appropriate measure for experiments that use the entire, unfocused x-ray beam. Brilliance is a measure of the intensity and directionality of an x-ray beam. It determines the smallest spot onto which an x-ray beam can be focused.