Dear colleagues,

SwissFEL produced first light ten years ago in the Aramis hard-X-ray line, and four years later in the Athos soft-X-ray line. Although it is still a young and growing facility, it is time to look to the future. We have worked closely with the Swiss and international photon-science community to identify the developing trends and demands in ultrafast X-ray sciences. Based on the discussions, we have developed an upgrade pathway called SwissFELplus. 

The achievements of SwissFEL have been enabled by state-of-the-art accelerator, undulator and endstation systems that have far exceeded their initial design parameters. SwissFELplus will further develop SwissFEL towards a fully coherent X-ray laser source with extended pulse control and higher X-ray energies. The upgrades are motivated by the evolving demands of the science community for enhanced and tailored control over the X-ray pulse characteristics — including full temporal coherence, duration, spectral content and polarization state — and, in the long term, for more capacity. The proposed improvements are fundamentally important for SwissFEL to maintain its competitive edge in a highly dynamic global research environment, and they will enable unique research opportunities for our user community.

We invite you to read our Conceptual Design Report and share your feedback with us. We are looking forward to hearing from you.

Christoph Bostedt 
on behalf of SwissFEL in the PSI Center for Photon Science

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

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When people fracture their hip in a fall, it is typically in the femoral neck, the narrow section of bone directly below the hip joint. This often happens with advanced age, when the bone has lost density. Usually, the femoral neck fractures from the top side, where it is generally much more porous than on the underside. However, this correlation is not always present: sometimes a femoral neck fractures even though it is not porous. X-ray analyses at SLS and at MAX IV in Lund have now revealed the possible cause: an altered nanostructure of the bone. The studies suggest that fractures of the femoral neck are not simply due to insufficient bone density. Also significant is the bone's nanostructure: the arrangement of the collagen fibres and mineral platelets that make up bones — which the researchers were able to visualize thanks to small-angle X-ray scattering tensor tomography (SAXS-TT), a method that has been developed at PSI over the past ten years and tested for the analysis of various materials, including bone.

T. Tänzer et al., Advanced Materials 38, e73848 (2026)
DOI: 10.1002/adma.73848

Rendering a drug effective or ineffective in a flash at the appropriate location — this is the focus of research in photopharmacology. The goal is to develop drugs that can be switched on and off with light of a specific wavelength. Orally administered medications could then be selectively activated by irradiating only a specific part of the body with light; the medication would remain ineffective in the rest of the body, thus reducing side effects. An international team of researchers working at SwissFEL and at the Linac Coherent Light Source (LCLS) has now observed how the photoswitchable beta-blocker photoazolol-1 interacts with its corresponding biological receptor at the molecular level. Most importantly, they observed in detail how the light-switched molecule settles into a new shape within the receptor within seconds, changing its effectiveness in the body in the process. The insights obtained by the team could now serve as a structural roadmap for designing ligands with improved optical control of receptor function.

R. Stipp et al., Angewandte Chemie International Edition 65, e17995 (2026)
DOI: 10.1002/anie.202517995

Additive manufacturing is considered a promising technology for producing components for future fusion reactors. Metal 3D printing makes it possible to create complex structures for key components such as breeding blankets or divertors. These materials must withstand extreme conditions: high temperatures, strong mechanical stresses and intense radiation. Crucial to their ability to do so is the material microstructure, which develops during the printing process. Advanced X-ray and neutron experiments at SINQ and SLS, and at DESY in Hamburg, now provide new insights into the formation process of such microstructures. The studies reveal two distinct unwanted phases that appear during 3D printing — retained austenite within the steel itself, and an iron–tungsten intermetallic phase at interfaces between tungsten and steel — but the research also shows how the printing process can be tuned to limit both. The findings thereby add to a deeper understanding of how stresses can develop in components and how the design of materials for future fusion reactors can be optimized.

N. Garrivier et al., Additive Manufacturing 115, 105055 (2026)
DOI: 10.1016/j.addma.2025.105055

N. Garrivier et al., Materials & Design 266, 116057 (2026)
DOI: 10.1016/j.matdes.2026.116057

Layered nickel oxides have joined the ranks of unconventional superconductors with the discovery of superconductivity in Ruddlesden–Popper nickelates under pressure. A question that remained open is how the magnetic and density-wave order seen at ambient conditions gives way to superconductivity. To gain insight, a PSI-led team studied the trilayer nickelate Pr₄Ni₃O₁₀ using muon-spin rotation and relaxation techniques at SμS. Measurements from ambient pressure up to 2.2 GPa established a sequence of three magnetic transitions on cooling: a sharp, weakly first-order onset of spin-density-wave order near 158 K, a subtler change around 90–100 K, and a low-temperature transition near 25–27 K linked to ordering of the praseodymium sublattice. Applied pressure steadily suppresses the temperature and ordered nickel moment of the high-temperature transition, establishing a magnetic phase diagram that forms a quantitative microscopic baseline from which superconductivity is expected to emerge under further compression.

R. Khasanov et al., Superconductor Science and Technology 39, 085020 (2026)
DOI: 10.1088/1361-6668/ae90f7

So-called mirror-sector models predict parity-conjugate partners of ordinary particles and have been discussed as a possible connection to dark matter. In a dedicated storage experiment with ultracold neutrons (UCN) at the PSI UCN source, a PSI-centred collaboration searched for neutron to mirror-neutron (n–n′) oscillations in the remaining parameter space associated with previously reported anomaly regions at 2.5σ, 3σ and 5.2σ significance. Magnetic fields between 5 and 109 µT were scanned to probe possible resonance conditions. The analysis combined UCN count asymmetries for opposite field polarities with detailed magnetic-field mapping and simulations of the accumulated oscillation probability along the neutron trajectories. No anomalous neutron losses were observed. The new limits on the oscillation time τ exclude the previously claimed anomaly regions at the 95% confidence level for 99.98% of the possible mirror-magnetic-field B′ directions.

N. J. Ayres et al., Physical Review Letters 137, 051802 (2026)
DOI: 10.1103/2qck-n6mb

The PSI Particle Physics Summer School

From 23 to 28 August, the 27th PSI Particle Physics Summer School took place in Morschach. The school is a biennial opportunity for young physicists to be introduced to advanced key concepts of particle physics. The topic of this year's school was “Precision on the Edge” and it featured lectures about precision collider physics, QCD and parton showers, muon physics, precision low-energy physics and effective field theory as well as an introduction to AI and machine learning. The evening lecture covered exciting ongoing research on multi-messenger astrophysics and gravitational waves. A special feature of the Particle Physics Summer School is the mix of experimentalists and theorists, with ample time for discussions and exchange of ideas and experiences. Not least, the school serves as an opportunity for the young scientists to network and get a wider view of the rich field of particle physics.

34th International Workshop on Vertex Detectors

The 34th International Workshop on Vertex Detectors (VERTEX) was held in Stoos from 20 to 24 July, jointly organized by PSI, the University of Zurich and ETH Zurich. The annual workshop provides an international forum for reviewing recent developments, ongoing activities and future directions in silicon-based vertex detectors. This year’s edition attracted more than 90 participants, with strong representation from Swiss research institutions active in the field of silicon detectors. Thanks to the support of the Swiss National Science Foundation (SNSF), fellowships for 10 early-career researchers were established, so that they could attend the workshop and present their research. The scientific programme provided a comprehensive overview of the current state of vertex and tracking detector research and highlighted exciting directions for future developments in high-energy physics, future colliders and applications beyond particle physics.

ISIS-PSI Muon Collaboration Meeting

On 21 July, 11 members of the ISIS Muon Group and 12 of the PSI Laboratory for Muon Spin Spectroscopy met at PSI for a collaboration meeting, during which the status of both muon facilities was presented, followed by extensive discussions on future opportunities for collaboration. Several areas for closer cooperation were identified, including data-analysis software for positive and negative muons, use of web-based platforms such as AiiDAlab for DFT and other applications, particle-tracking detectors and sample environment, as well as outreach activities such as e-learning tools, training schools and initiatives to increase the visibility of the muon community. It was agreed that this form of collaboration through annual face-to-face meetings will be continued, so that mutual synergies can be put to greater use in future.   

CHRISP — Handover of the MIDAS development to the next generation

For more than 30 years, the Maximum Integrated Data Acquisition System (MIDAS) has supported particle-physics experiments around the world. Born from a collaboration between Stefan Ritt at PSI and Pierre-André Amaudruz at TRIUMF in the mid-1990s, MIDAS has continuously evolved, embracing new technologies and methods. Today it is used by major experiments at PSI, TRIUMF and beyond, including the Fermilab g-2 experiment. As the original developers approach retirement, it is time to prepare MIDAS for its next chapter. This August, PSI’s Thomas Rudzki and Stefan Ritt visited TRIUMF to meet the younger generation of MIDAS developers. Together, the team discussed the future of the repository, new documentation and long-term support. Just as important was strengthening the personal connections that have kept this collaboration alive for decades. Thomas Rudzki will take over long-term MIDAS support on the PSI side, working closely with the new generation at TRIUMF, ensuring that MIDAS remains in good hands for many years to come. 

SLS — Virtual tissue staining in 3D

Since its inception in the 19th century, pathology — the study of disease processes — has essentially been based on the time-consuming examination of thin tissue sections that are stained and then viewed under a microscope. By contrast, X-ray-based methods offer the advantage of "virtual sectioning" while retaining the full three-dimensional volumetric representation of the tissue. However, micro-computed tomography (µCT) has traditionally been limited by its greyscale nature. Now an international team led by PSI researchers has managed to overcome this limitation. Combining phase-contrast µCT with a deep neural network, they generated virtual histological stains of tissue samples. They applied their strategy to identify 3D collagen-based remodelling of pulmonary arteries in patients with pulmonary hypertension — establishing how the method could support non-destructive 3D pathology in future.

SwissFEL — Liquid-jet capabilities for ultrafast chemistry at Alvra

The Alvra endstation on Aramis, the hard-X-ray branch of SwissFEL, was designed to probe ultrafast structural and electronic dynamics in chemical and biological systems. A new paper now describes the recirculating liquid-jet system used at Alvra to deliver solutions, nanoparticle suspensions and other liquid samples for time-resolved X-ray experiments. Cylindrical jets from 15 to 200 µm and flat-sheet jets, both thin (up to 30 µm) and thick (from 100 µm), cover a wide range of samples, while a fully closed recirculation loop keeps oxygen- and water-sensitive samples free from air exposure. Typical experiments consume only 20–30 ml of sample, delivered at flow rates of 0.5–3.0 ml/min. Combined with Alvra's tender-X-ray emission spectrometer — currently unique among X-ray free-electron laser endstations worldwide — and its sub-35 fs time resolution, this sample-delivery system enables ultrafast chemical dynamics to be studied across a broad range of liquid-phase samples. The paper presents a variety of experimental results from the first years of SwissFEL commissioning and user operation — from capturing transient structural intermediates and following ultrafast chemical reactions to resolving subtle electronic changes in complex samples.

SINQ & SLS — A world-first lens brings neutrons into sharper focus

Neutrons, unlike X-rays, can penetrate deeply into many metals whilst remaining highly sensitive to light elements such as hydrogen and lithium. This makes neutrons a powerful imaging modality, but the same weak interaction with matter also makes them notoriously difficult to deflect or focus — a fact that has limited the development of advanced imaging techniques. Drawing on an earlier breakthrough in X-ray optics achieved at PSI, the development in 2022 of an achromatic X-ray lens for synchrotron and X-ray free-electron laser facilities, a team of researchers has now combined this know-how with neutron-imaging expertise at SINQ. The result is the world’s first achromatic lens for neutron imaging. The lens overcomes a longstanding obstacle in the field: focusing neutrons of different wavelengths well enough to form a sharp, magnified image, thereby enabling the use of efficient detection systems without loss of spatial resolution — and establishing a path towards high-resolution neutron microscopy. 

SμS — New world-record low-energy muon rate

During the last accelerator shutdown, the final quadrupole triplet in the μE4 beamline at SμS was replaced by a normal-conducting solenoid. The goal was to achieve better focusing of the surface muon beam onto the muon moderator target. The result: a new world-record event rate for low-energy muons (LEM) of up to 3,500/s was measured at a proton beam current of 2.2 mA. This corresponds to an increase of around 40%, which is consistent with the beam-transport simulations and enables LEM experiments to be carried out significantly faster and with higher sensitivity than previously possible. A key factor in this success was the minimization of the magnetic stray fields of the solenoids. This was achieved by mounting the main coils inside an optimized iron housing and fitting additional compensation coils to the outer surfaces of that housing.

When extreme weather disrupts beamtime

This summer, Europe and Switzerland experienced recurring heatwaves. At PSI, the temperature of the Aare rose to levels that made it necessary, at times, to shut down the proton accelerator. This directly affected scheduled beamtimes at SINQ and SμS. Although operating the facilities safely and responsibly must always take priority, such interruptions inevitably have significant consequences for the user community.

For users, cancelled beamtime represents much more than the loss of experimental hours. Samples may have been prepared for a narrow measurement window, travel and accommodation already arranged, and research teams assembled from several institutions. The consequences can be particularly serious for doctoral students and early-career researchers working within limited project timeframes.

On behalf of JUSAP, I would therefore like to express our sincere appreciation to the PSI User Office, PSI management, accelerator teams, instrument scientists and technical staff for their efforts to keep affected users informed and, wherever possible, to reschedule their experiments. Finding replacement slots within already highly subscribed experimental programmes is far from simple, and these efforts demonstrate a strong commitment to protecting users’ scientific projects.

This summer’s experience also encourages us to think about the resilience of large-scale research facilities in the face of increasingly frequent extreme-weather events. Timely and transparent communication, clear principles for rescheduling and particular attention to time-critical experiments and early-career researchers will remain essential.

JUSAP invites affected users to share their experiences with us — including what worked well and what could be improved. Such feedback will help us represent the community effectively and contribute constructively to future contingency planning.

As the autumn experimental period continues, we wish all PSI users and staff successful beamtimes and productive collaborations.

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