SwissFEL

SwissFEL, or the Swiss Free-Electron Laser, is a X-ray free-electron laser facility operated by the Paul Scherrer Institute (PSI) in Villigen, Switzerland. It provides ultrafast, high-brightness X-ray pulses for experiments in chemistry, biology, physics, and materials science. SwissFEL is designed to deliver intense, coherent X-rays with femtosecond duration to enable time-resolved studies at the atomic scale and to support a broad international user community.

The facility employs a superconducting linear accelerator to accelerate electron bunches, which then traverse undulators to produce X-ray radiation via the self-amplified spontaneous emission mechanism. SwissFEL comprises two independent beamlines, Aramis and Athos, that cover complementary ranges within the X-ray spectrum and offer different coherence and photon-energy characteristics. The pulses are typically femtoseconds long and can be delivered at high repetition rates, enabling fast pump–probe experiments.

Researchers from universities and industry worldwide access SwissFEL through a user program that funds experiments, instrumentation, and data analysis support. Experiments span time-resolved spectroscopy, crystallography, diffraction, imaging, and spectroscopy of ultra-fast processes. The facility hosts a variety of end stations, detectors, and sample-delivery systems, along with software tools for data collection and analysis.

Construction and commissioning of SwissFEL began in the early 2000s, with first light and user operations in the mid to late 2010s. It remains a flagship European X-ray facility, complementing other synchrotron and FEL sources and contributing to Switzerland’s research and industrial innovation efforts.