The Swiss Light Source (SLS) has been operational now for over 18 years. In this period, it has spearheaded much groundbreaking research in biomedicine, engineering and the natural sciences, thanks in large part to the excellent performance of the underpinning electron accelerator and storage-ring complex. In addition, it has led the world in industrial exploitation, particularly by the pharmaceutical sector, and spawned numerous new companies, including one of the most successful Swiss-technology spinoffs, Dectris. For much of this time, the SLS was a benchmark in regard to how closely its performance matched the theoretical limits defined by its machine parameters. However, with the advent of the next generation of quasicontinuous short-wavelength light sources, called diffraction-limited storage-rings, that yield an emittance and brightness improved by up to two orders of magnitude, it has become imperative to upgrade the SLS (called SLS-2.0) in like manner.
The SLS 2.0 upgrade requires a comprehensive rebuild of the storage ring and magnet lattice, resulting in an improvement in emittance and associated increase in brightness by a factor of forty compared to the existing performance in the most commonly used hard x-ray regime. A phased program of upgrades of the beamlines will begin in parallel to optimize exploitation of the ring. This will start in the same funding period, so that Switzerland can continue to lead in the SLS research most immediately and positively impacted by the enhanced brightness offered by the upgrade, such as ptychography (scanning lensless imaging), macromolecular crystallography, and full-field tomography. All of these fields are expected to undergo sea-changes in scope and quality, because ring brightness improvements will be multiplied by photonic instrument advances, to yield data-rate increases of up to four orders of magnitude. In this manner SLS 2.0 will maintain the competitive edge of PSI, the ETH Domain, and Switzerland for the next two decades in the most multidisciplinary and sought-after category of large-research facilities.