A glimpse into the invisible

The PSI is Switzerland's largest research centre for the natural and engineering sciences, and is home to one of Europe's most advanced research facilities: the Swiss Light Source (SLS). It produces extremely bright X-ray light, enabling researchers to examine matter in great detail. After more than 20 years in operation, the SLS has now been comprehensively upgraded, opening a new chapter for science and industry.

The SLS is a synchrotron light source that accelerates electrons to near-light speeds. In the process, it generates extremely intense X-ray light, which researchers can use at dedicated beamlines to visualise materials, biological samples, and technical components at the atomic and molecular levels. Since its commissioning in 2001, the SLS has been a cornerstone of Switzerland's research infrastructure. To date, more than 22,500 experiments have been conducted and over 10,000 protein structures have been decoded. The experiments have contributed to several Nobel Prizes. Researchers coming to Switzerland from all over the world go to Villigen because no other Swiss laboratory can provide data to match that of the SLS.

Synchrotron light is millions of times brighter than conventional laboratory X-ray sources. Its brightness and coherence enable structures measuring just a few nanometres to be revealed, three-dimensional images to be produced without destroying samples, and chemical states to be determined with great precision. For biology and medicine, this means that the structure of proteins, cells, and tissues becomes visible. This could help improve our understanding of neurodegenerative diseases such as Alzheimer's.

After more than two decades, the PSI has comprehensively modernised its largest research facility. The SLS 2.0 project cost around CHF 129 million and was officially inaugurated in August 2025. As part of the work, the 288-metre-long storage ring was completely redesigned to fit perfectly into the existing building. Five hundred copper vacuum chambers and a thousand high-precision magnets have replaced the old components. At the same time, energy efficiency has been boosted, aided by a new solar roof. The upgrade has made it possible to generate a beam of light that is up to a thousand times brighter than before.

This significant improvement in performance makes previously impossible experiments feasible. High-resolution 3D imaging of tissue and cells is crucial for developing new drugs and therapies. Researchers explain how experiments that once took days can now be completed in minutes. In materials science, the tiniest structures in semiconductors, batteries, and catalysts can be examined in unprecedented detail. Even delicate cultural artefacts, such as paintings or archaeological finds, can now be analysed more gently than ever before.