Dear colleagues,

On 21 August, we celebrated the inauguration of SLS 2.0, a major upgrade that places Switzerland among the few countries worldwide with one of the most advanced national synchrotron light sources. The project highlights the long lead times required for large-scale research infrastructures: first ideas took shape soon after the completion of the original SLS, inspired in part by developments at MAX IV in Sweden. Only many years of consistent planning and reliable funding have now turned this vision into reality.

Looking ahead, Switzerland — like many other countries — is facing tighter financial conditions. The federal budget is affecting the ETH Domain as well, including PSI. Growth will slow while costs continue to rise. The reasons are familiar: the Covid pandemic, the energy crisis, the war in Ukraine and broader geopolitical tensions have all left their mark on public finances. In this situation, it is understandable that governments are carefully reviewing their priorities.

What remains crucial, however, is continuity. Interruptions to research and innovation funding are very difficult to make up later, as infrastructures, knowledge and talent depend on sustained support. This is a global challenge: research institutions everywhere are under pressure, and delays today can mean lost opportunities for years to come.

For PSI the conclusion is clear: funding in large-scale facilities is not simply expenditure, it is a long-term investment. The successful inauguration of SLS 2.0 reminds us that even in challenging times, Switzerland maintains world-class infrastructures. This must remain our guiding principle for the years ahead.

Thierry Strässle
Chief of Staff PSI

An overview of all proposal submission deadlines of the PSI facilities can be found here.

In the twilight of the Jurassic period, a giant ruled the seas: Temnodontosaurus, an ichthyosaur more than ten metres long, with eyes the size of footballs. New analysis of fossil structures now suggests that this marine predator may have had highly specialized adaptations for quieter swimming — enabling it to advance without producing eddies or noise before attacking its prey. These are the findings of an international team led by researchers from Lund University. They have analysed, for the first time, the soft-tissue structures of an exceptionally well-preserved Temnodontosaurus forefin. Key insights into the delicate sample were obtained by synchrotron radiation X-ray tomographic microscopy (SRXTM), acquired at the TOMCAT beamline of SLS. Using this technique, the team visualized the three-dimensional structure of the calcified cartilage in detail, providing crucial guidance for understanding its mechanical function. Their data suggest an evolutionary adaptation to suppress noise when swimming, comparable to the serrated flight feathers of an owl, a contemporary species with the capability to glide while producing barely any sound.  

J. Lindgren et al., Nature 644, 976 (2025)
DOI: 10.1038/s41586-025-09271-w

Magnetic frustration occurs when competing interactions prevent a material from reaching a simple magnetic arrangement, potentially giving rise to exotic quantum states. While well-studied in magnetic insulators, frustrated metals present additional challenges due to the complex role of conducting electrons. An international team led by PSI researchers and colleagues at the Max Planck Institute for Chemical Physics of Solids in Dresden has now used the intermetallic compound HoInCu₄ as a model system to show that a theoretical treatment with Hamiltonians neglecting the charge degree of freedom can still be appropriate to describe frustrated metals — provided that they have a low electronic density at the Fermi surface. In experiments on three SINQ instruments (ZEBRA, DMC and CAMEA), they determined that the material exhibits antiferromagnetic interactions close to a critical ratio that places it near a magnetic phase boundary. Despite classical theory predicting well-defined magnetic excitations, the team observed overdamped fluctuations that arise from quantum effects. These quantum fluctuations account for the strongly reduced magnetic moment observed in the ordered state, showing how quantum mechanics can influence magnetism in frustrated metallic systems.

X. Boraley et al., Physical Review Letters 135, 046702 (2025)
DOI: 10.1103/38ds-xjl3

Quantum spin liquids represent exotic states of matter where magnetic moments remain disordered even at absolute zero temperature. In honeycomb lattices, such states can emerge from competing Heisenberg and Kitaev magnetic interactions, but achieving the right balance between these interactions has proven extremely challenging. An international team of researchers has now demonstrated that hydrostatic pressure can successfully tune this delicate balance in the spin-1/2 honeycomb lattice of Ag₃LiRh₂O₆. Combining muon spin relaxation data obtained at SμS with magnetization and X-ray measurements, they observed that pressure suppresses the antiferromagnetic ordering temperature while modifying bond angles in a way that changes the Kitaev-to-Heisenberg ratio. Remarkably, unlike other candidate Kitaev materials that undergo structural dimerization at low pressures, Ag₃LiRh₂O₆ remains stable up to 5 GPa. This provides a welcome opportunity to explore the quantum critical regime between magnetically ordered and spin liquid phases through pressure tuning alone.

P. Sakrikar et al., Nature Communications 16, 4712 (2025)
DOI: 10.1038/s41467-025-59897-7

Some materials exhibit fascinating quantum properties that could lead to transformative technologies. However, in thermal equilibrium these properties often remain hidden. One approach to access them is to use ultrashort pulses of light to alter the microscopic structure of and the electronic interactions in the material. The challenge is that these light-induced states typically persist for only a few picoseconds, making it difficult to harness them for practical applications. In rare cases, light-induced states can last considerably longer, but our understanding of these phenomena is limited, and there is no general framework for designing long-lived excited states. An important contribution comes now from a team led by Harvard scientists. Together with colleagues from PSI, they used the Athos beamline at SwissFEL to manipulate the symmetry of electronic states in the model cuprate ladder Sr₁₄Cu₂₄O₄₁. They demonstrated that tailored optical excitation can induce a metastable non-equilibrium electronic state, driven by a transfer of holes from chain-like charge reservoirs into the ladders. This charge redistribution is symmetry-forbidden at equilibrium and, intriguingly, persists for tens of nanoseconds.

H. Padma et al., Nature Materials online publication (2025)
DOI: 10.1038/s41563-025-02254-2

The Young-Koppel (YK) model describes the interaction of slow neutrons with diatomic gases such as H₂ and ²H₂ (D₂), taking into account the spin correlation effects as well as the rotation and vibration of the molecules. A unique signature for distinguishing the YK model from the monoatomic approximation is its temperature dependence. A team led by PSI researchers now reports on the first experimental results of ultracold neutron (UCN) scattering over a wide temperature range. Their findings support the YK model for gaseous D₂, revealing a significant difference in the temperature dependence compared to a low-energy low-temperature approximation (LETA). They interpret this analysis of the D₂ gas data as a strong validation of a temperature-dependent term in the YK model, beyond the T ^½ scaling. The total cross section of UCNs in H₂ gas was also measured and analysed applying the YK model — though over a more limited temperature range — confirming the theoretical prediction. This study represents an important confirmation of the YK theory and has implications for the understanding of deuterium-based ultracold neutron sources.

G. Bison et al., Physical Review C 112, 014007 (2025)
DOI: 10.1103/1r5v-6h9p

The new Swiss Light Source is inaugurated

On 21 August, PSI inaugurated its newly upgraded Swiss Light Source (SLS). Around 150 guests from politics, business and science were present to celebrate the achievement, including Federal Councillor Guy Parmelin and Martina Bircher, a member of the cantonal government and Head of the Department of Education, Culture and Sport of the Canton of Aargau. The new SLS is one of the most ambitious science infrastructure projects in Switzerland — one that will enable experiments that were previously unthinkable. “The SLS was at its inception and is now after its comprehensive upgrade a national infrastructure built for the common good,” said PSI Director Christian Rüegg. “It is a tool for Swiss researchers and industry, and for our international guests to answer questions that matter for the future of people and the planet.” A remarkable engineering feat was the installation of the new machine within the old building, saving many tens of millions of francs. Central to this is the new 288-metre-circumference storage ring. With all its custom-made components from magnet systems to vacuum chambers, the ring was meticulously designed to fit within the existing building. The light that it produces will be up to 1,000 times more intense than before, yet the upgraded facility uses 33% less electricity, thanks to state-of-the-art engineering choices that make the operation more efficient and to a new solar-panelled roof.  

WOPM2025 at PSI

The 2025 edition of the Workshop on Optically-Pumped Magnetometers (WOPM2025) took place at PSI from 6 to 8 August. High-precision magnetometers are key components in the n2EDM apparatus, which is used to search for the neutron electric dipole moment at PSI’s ultracold neutron (UCN) facility. The UCN Physics group has therefore long operated a dedicated magnetometry laboratory, and this sustained commitment led to the group hosting this year’s WOPM. The event began with a full day of Summer School lectures, followed by scientific sessions attended by 145 researchers from institutions worldwide. Participants discussed the latest advances and challenges in high-precision magnetometry, with particular focus on sensors based on spin-polarized atomic vapours such as caesium, rubidium and helium. While these technologies are central to precision fundamental physics experiments, they are also finding growing applications in medical diagnostics and are approaching readiness for industrial deployment. 

SLS — Ready for users: successful limited call for proposals

Following the long shutdown in 2024 for the SLS 2.0 upgrade, and the subsequent successful start-up of the machine at the beginning of 2025, the first beamlines again have light at their endstations. After a commissioning and pilot user phase, five SLS beamlines are now ready for regular user operation. A limited call for proposals for ADDAMS, Debye, PolLux, PXIII and superXAS beamlines was published in July, for beamtime between 17 November and 19 December 2025. A total of 58 proposals were submitted, requesting 510 shifts (each shift corresponds to 8 hours of beam time), which is much more than we can offer. The proposals are currently under evaluation, and we very much look forward to welcoming the first regular users back to the beamlines in November 2025 to gain experience with the upgraded SLS 2.0. 

In parallel, we are working to bring the other Phase-I beamlines (cSAXS, I-TOMCAT, ISS, PXI, PXII, SIM and S-TOMCAT) into operation by the end of the year, before a longer shutdown in the first and second quarters of 2026 for the installation of the second phase of beamlines and new sources, such as superbends and new insertion devices.

SINQ: 2D and 3D neutron imaging for battery research

A comprehensive study establishes neutron imaging in 2D and 3D as a versatile tool for investigating sodium-ion batteries, a potential alternative to lithium-ion batteries. The international team used neutron tomography and radiography at the IMAT beamline at ISIS and the BOA beamline at SINQ to visualize electrolyte degradation and sodium-metal accumulation on the electrodes of these batteries. Unlike X-ray imaging, which is limited by the low attenuation of sodium, neutron imaging offers sufficient contrast to observe these critical degradation processes in 3D. The team successfully linked distinct plating patterns with different electrolyte compositions, further establishing neutron imaging as a powerful tool for battery research. The technique offers spatial resolution down to tens of micrometres and the capability to provide semi-quantitative analysis of electrolyte degradation without the need for destructive testing.

SμS: Coherent control of muonium states

Coherent control of quantum systems is an important tool in fundamental research and emerging quantum technologies. A team of PSI scientists has now extended such control to the spin states of muonium, a hydrogen-like system consisting of a muon and an electron. They implemented methods based on microwave pulses at the GPS instrument of SμS, which enabled them to observe coherent quantum behaviour of muonium states formed inside SiO₂ and Si, namely Rabi oscillations and Ramsey fringes. In SiO₂, muonium coherence times were intrinsically long compared to the lifetime of a muon. By contrast, shorter coherence times were encountered in Si, but these were successfully prolonged by dynamical decoupling from the magnetic environment. This ability to coherently control muonium states with high precision opens up new avenues for studying their behaviour in matter and for performing high-precision spectroscopy to test fundamental theories such as quantum electrodynamics.

SwissFEL: World record attosecond measurement

As scientists and engineers push X-ray free electron lasers into the attosecond regime, more precise diagnostic tools are needed. SwissFEL researchers have now demonstrated the ability to characterize pulses as short as 300 attoseconds, setting a new world record for time resolution using electron-beam streaking. The team used PolariX — a type of radiofrequency deflector device developed by PSI in collaboration with CERN and DESY — to measure FEL power profiles on the soft X-ray beamline Athos. They resolved root mean square pulse durations as short as 300 attoseconds, thus meeting the ambitious requirements of attosecond science. These experiments establish the power of combining the variable polarization feature of PolariX with the capability of achieving attosecond temporal resolution. This should create new possibilities for multidimensional beam phase-space characterization at unprecedented resolution. 

CHRISP: A compact frozen-spin trap for the search for the electric dipole moment of the muon

A European collaboration has published a concept paper outlining an innovative experiment to probe physics beyond the Standard Model at PSI’s High-Intensity Proton Accelerator (HIPA). The project outlines how researchers will use a novel ‘frozen-spin’ technique — applied for the first time in a compact magnetic solenoid connected to the muon beamline at PSI — to explore one of Nature’s unsolved puzzles: the potential electric dipole moment (EDM) of the muon. This novel approach exploits the high effective electric field, E ≈165 MV/m, experienced in the rest frame of the muon with a momentum of about 23 MeV/c when passing through a solenoidal magnetic field of 2.5 T. By studying muons, the team seeks to detect an EDM, which would signal new physics beyond our current theories. With over four million muons delivered per second, the experiment aims to achieve unprecedented sensitivity in the coming years, with the potential to reach a record precision on the order of 10^-23 e cm within the next decade.

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