Sharper, smaller, brighter: enhanced optical performance at the X06DA-PXIII beamline after the SLS 2.0 upgrade

The X06DA-PXIII beamline is a crystallography beamline on a superbend magnet at the Swiss Light Source. Since 2008, it has served the scientific community, contributing to 2650 Protein Data Bank structures as of today (i.e. before the SLS shutdown started in autumn 2023). Just before the upgrade of the storage ring, the beamline has been rebuilt with new X-ray optics to exploit the full potential of SLS 2.0. Its new design aims for a unique position in macromolecular crystallography beamlines worldwide: it exploits the excellent electron beam properties of small sizes below 10 µm, uses a toroidal mirror close to the source to harvest a large solid angle of the bending magnet beam, minimizes toroidal aberration with a horizontal 1:2 focusing concept and finally utilizes a high-quality Kirkpatrick-Baez mirror system to focus the beam onto the sample. Herein, we describe the beamline's optical performance during first commissioning and demonstrate how the reduced emittance of the new storage ring improves its focusing capabilities and overall efficiency.