Dear colleagues,

As the summer period has arrived, many of us are balancing beamtime, conferences, proposal deadlines, manuscript writing, student supervision and — hopefully — some well-deserved holidays. It is also a good moment to look ahead. For the PSI user community, the coming months and years will be shaped by important facility developments, new scientific opportunities and practical questions that matter directly to users.

For many of us, PSI is much more than the place where we carry out a scheduled experiment. It is a scientific environment built on trust, long-term collaborations, technical expertise and the intense shared experience of beamtime — from preparing proposals and samples to solving problems at the instrument, analysing data and training the next generation of users.

This is why the role of JUSAP is important. As the Joint Users Association at PSI, JUSAP represents the user community across the PSI large-scale facilities and provides a direct link between users, the User Office, facility management and PSI management. Our role is to ensure that the experience, needs and concerns of users remain visible in discussions about access, infrastructure, communication and future developments.

Now is a particularly exciting and important period for the PSI user community. With SLS 2.0, users are beginning to return to a substantially upgraded synchrotron, opening new scientific possibilities while also bringing practical questions as beamlines resume operation. Looking further ahead, the IMPACT/HIMB upgrade will strongly shape the future of muon and proton-based research at PSI and will require careful planning from both the facility and user communities.

In this context, good communication is essential. Planning an experiment does not stop at scientific ideas; it also involves access modes, scheduling, sample logistics, accommodation, local support, data treatment, and continuity for students and early-career researchers. JUSAP therefore encourages all users — experienced users, new users, students, postdocs, academic users and industrial users — to share feedback, suggestions and concerns with the JUSAP panel members. Practical issues are not secondary issues: they often determine whether beamtime is efficient, inclusive and scientifically successful.

On behalf of JUSAP, I would like to thank the PSI User Office, instrument and beamline scientists, technical teams and PSI management for their continued dialogue with the user community. I wish all PSI users and staff a productive summer period, with successful experiments, smooth planning and some time to recharge. JUSAP looks forward to continuing to support the exchange between the user community and PSI.

Yasmine Sassa on behalf of the JUSAP Committee

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

Van der Waals materials exhibit a variety of states that can be switched with low power at low temperatures — making them strong candidates for the cryogenic memory required for the classical control electronics of solid-state quantum computers. Scientists from PSI and the Jožef Stefan Institute in Slovenia have now peered inside the layered van der Waals material 1T-TaS₂ to better understand its switching properties. Using spatially resolved X-ray diffraction at the microXAS beamline of SLS, the team tracked how atomic layers of the crystal reorganize during device operation. They found that electrical switching of 1T-TaS₂ differs fundamentally from the filamentary process of conventional memories. Rather than forming localized conductive paths, a metallic ‘hidden’ state appears as an extended, well-ordered region that spans a significant volume of the device. This region penetrates deeply into the material and even extends beneath the metal electrodes, showing that switching is a bulk, collective process involving many atomic layers. By reconstructing the stacking of the van der Waals layers before and after switching, the team showed that electrical pulses change how the layers are arranged on top of each other. This structural rearrangement stabilizes the metallic state and explains its non-volatile character at low temperatures — thereby advancing our understanding of how electrical switching in ultrathin cryogenic memory devices works.

C. Burri et al., Nature Communications 16, 10296 (2025)
DOI: 10.1038/s41467-025-65212-1

Vitamin B₁₂ is an organometallic cofactor found in enzymes in various organisms, including humans. A decade ago, it came as a surprise that B₁₂ derivatives had been repurposed for light sensing in a large family of bacteria. The way in which these B₁₂ photoreceptors function at a molecular level has remained a mystery ever since. Now, an international consortium led by scientists at the Institut de Biologie Structurale in Grenoble has combined experimental techniques using the X-ray free-electron lasers SwissFEL and SACLA, as well as synchrotron experiments, with quantum-chemical calculations to uncover the inner workings of the prototypical B₁₂ photoreceptor CarH. After triggering photoactivity, the researchers observed structural changes in CarH in real time. From the first moments after light absorption on the nanosecond timescale to the timescale at which the tetrameric architecture of CarH is lost, the study reveals the sequence of orchestrated molecular events that underpin its function. The researchers discovered an unanticipated intermediate state that the photoreceptor transiently adopts during the reaction process. This state is thought to prevent the photoreceptor from reverting to its initial dark state. Such an intermediate state has not been found in thermally activated B₁₂ enzymes — making it a plausible explanation for the light-sensing capability of CarH and related B₁₂ photoreceptors. 

R. Rios-Santacruz et al., Nature 650, 1045 (2026)
DOI: 10.1038/s41586-025-10074-2

Lattice vibrations are not usually thought of as magnetic objects. Yet in certain crystals, atomic motions can trace circular paths that carry angular momentum — producing so-called chiral phonons — and, under the right conditions, these rotating modes can also bear substantial magnetic moments. Until now, probing this magnetic character experimentally has been largely restricted to optical techniques, which cannot resolve the full energy and momentum dependence of the excitations. Neutron scattering, sensitive to both nuclear and magnetic signals simultaneously, offers a powerful alternative. A team led by researchers at Nanjing University has exploited this capability to study the ferrimagnetic compound Fe_1.75Zn_0.25Mo₃O₈. Using inelastic neutron scattering, the researchers found that below the magnetic ordering temperature, the low-energy phonon modes displayed markedly enhanced scattering intensity at small momenta — a signature of their magnetic character. Together with the observed out-of-plane intensity modulation, phonon and magnon mode splitting, and field-induced Zeeman shifts (measured using the EIGER triple-axis spectrometer at SINQ), these findings provide the first complete momentum-resolved mapping of truly chiral phonon dispersions in a magnetic material and establish neutron spectroscopy as a direct probe of the magnetic signatures of phonon modes.

S. Bao et al., Physical Review Letters 136, 096502 (2026) — Editors' Suggestion
DOI: 10.1103/pq5m-32wj

Quantum spin liquids are exotic states of matter in which magnetic moments remain disordered and fluctuating even at the lowest temperatures, defying conventional magnetic ordering. A central challenge in their experimental realization is disentangling the role of geometric frustration from that of chemical disorder, which can mimic spin-liquid behaviour. Y-kapellasite [Y₃Cu₉(OH)₁₉Cl₈] is a rare kagome antiferromagnet that is both geometrically frustrated and essentially free from site disorder, making it an ideal model system. At ambient pressure it exhibits long-range magnetic order, but its magnetic interactions place it close to a phase boundary with a spin liquid state. An international team including researchers from PSI has now used muon spin spectroscopy (μSR) at the GPD spectrometer of SμS, combined with high-pressure X-ray diffraction and optical phonon measurements, to study Y-kapellasite under hydrostatic pressure. At 2.3 GPa, static magnetic order is fully suppressed and replaced by a dynamical, spin-liquid-like ground state. Complementary structural measurements show that pressure gradually reduces the anisotropy of the kagome lattice — enhancing geometric frustration without triggering structural transitions. These results establish Y-kapellasite as a clean platform for studying pressure-tuned frustrated magnetism, and represent the first fingerprint for the realization of a quantum spin liquid without strong disorder.

D. Chatterjee et al., Physical Review Letters 136, 136701 (2026) — Editors' Suggestion
DOI: 10.1103/3pmg-b78n

An international team including PSI researchers has recorded the first high-resolution X-ray and gamma-ray spectrum of the medically important radionuclide ²²⁵Ac, using a metallic magnetic calorimeter (MMC). Operating at millikelvin temperatures, these detectors achieve an energy resolution more than an order of magnitude better than possible with conventional spectroscopy. The measurements allowed the identification of ²²⁵Ac and most of its daughter nuclides individually and with high sensitivity. This capability could enable improved monitoring of radionuclide redistribution and more accurate dosimetry in targeted alpha therapy. Based on these results, MMC technology emerges as a promising tool for future theranostic applications and the development of more personalized cancer treatments.

K. Maurer et al., Communications Medicine 6, 169 (2026)
DOI: 10.1038/s43856-026-01377-0

SINQ++ workshop at PSI

The SINQ++ workshop was held at PSI on 29 and 30 April 2026 to develop and refine the emerging science case that will define the future of SINQ. Around 120 participants took part, with strong representation from Swiss research institutions, international neutron facilities, and scientific communities that already rely on neutron methods or see clear future opportunities in them. The practical purpose of the meeting was to gather community input on the scientific priorities, capability gaps and strategic opportunities that should shape the next development phase at SINQ. Discussions were organized around the first version of the SINQ++ Science Case, in which the community sets out how SINQ could be strengthened as a next-generation platform for Swiss and European neutron science. Across the two days, speakers underlined the continuing importance of SINQ as a national research infrastructure. They also placed it in the wider European context, where a resilient network of complementary neutron facilities remains essential for scientific access, training, method development, and long-term capability. 

Muoniverse kick-off meeting

The National Centre of Competence in Research (NCCR) Muoniverse officially kicked off with its first community-wide meeting on 11 May 2026. Muoniverse is co-led by PSI and the University of Zurich and builds on the muon facility at PSI. It brings together universities, industry and museums to push advances in fields ranging from quantum technologies and renewable energy to archaeology and cultural heritage. More than 80 members from 11 institutions gathered at PSI for the kick-off event to launch the collaboration and shape its next steps. PhD students and senior researchers, cultural heritage experts, materials scientists, detector specialists and many others spent the day exchanging ideas and building new connections across disciplines, with conversations flowing from the plenary into the breakout sessions — and well beyond the official programme.

SLS — Improved focusing at PX III after the SLS 2.0 upgrade

The X06DA-PXIII beamline is a crystallography beamline on a superbend magnet at the SLS. Since 2008, it has served the scientific community, contributing to 2650 Protein Data Bank structures before the SLS shutdown began in autumn 2023. Just before the upgrade of the storage ring, the beamline was 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 the upgraded SLS and an advanced optical layout to focus the X-ray beam as sharply as possible onto the crystallography samples. First results from commissioning the beamline before and after the storage-ring upgrade already show clear, consistent gains in optical performance at the PXIII beamline. The X-ray beam is more stable over time, and the focusing capabilities increased significantly. As reported in a recent publication, the X-ray beam that was spread out over more than 100 µm before the upgrade is now contained within a focus of the order of 20 µm. Both effects — stability and focus size — are directly usable in crystallographic experiments, bringing the average time for obtaining a complete crystallographic set of data down to less than thirty seconds. 

SwissFEL — An upgrade pathway towards full coherence

SwissFEL produced first light in 2016 in the Aramis hard X-ray line and in 2020 in the Athos soft X-ray line. Although it is still a young and growing facility, it has already firmly established itself as a leading X-ray free-electron laser on the international landscape and has developed unique features. Concurrently, the demands of the photon science community have evolved towards tailored control over the X-ray pulse characteristics. Considering the current funding environment and existing commitments at PSI, the decision was taken to follow a two-stage approach for a SwissFEL upgrade. The first stage, called SwissFELplus and envisioned for the funding period 2029–2032, focuses on immediate improvements of the existing facility and prepares for the third undulator line. The addition of the third line, called Porthos, is planned for the 2033–2036 funding period. The SwissFELplus Conceptual Design Report has now been made available. It outlines an upgrade pathway for the Swiss X-ray free-Electron laser towards a fully coherent X-ray laser source with extended pulse control and harder X-ray energies — with all existing SwissFEL pulse modes set to benefit from improved accelerator performance and diagnostic tools. 

SINQ — AiiDAlab comes to CAMEA

The software platform AiiDAlab was originally developed to simplify computer simulations in materials research. A paper now describes its use in new areas — including streamlining experimental data analysis at SINQ. Running experiments at a neutron instrument combines scientific exploration with online data analysis. Visiting researchers typically install and configure data treatment and analysis software locally, which can be a cumbersome process at the start of an experiment. Similarly, after the beamtime, access to raw data often becomes fragmented, and expert input from beamline scientists may be limited, as staff need to focus on their next experiment. To address these challenges, PSI researchers have deployed AiiDAlab at the Multiplexing Spectrometer CAMEA. AiiDAlab provides user-friendly graphical interfaces for configuring and executing computational workflows, giving beamline scientists the possibility of timely, collaborative online data-analysis support. The platform integrates directly with PSI's institutional authentication infrastructure, and experimental data are streamed in real time to a shared file system accessible from within each user's secure, containerized environment. The system has already provided significant time savings in user experiments, and plans are in place to extend the approach to further instruments at SINQ. 

SμS — "We're pulling out all the stops"

The upgrade of two high-intensity muon beams within the framework of the IMPACT project is entering its critical phase. For many years, SμS has been delivering the world's most powerful muon beams — and with IMPACT, PSI aims to extend that lead. In an interview, Thomas Prokscha, interim head of the Laboratory for Muon Spin Spectroscopy, explains how a hundredfold increase in muon beam intensity will be achieved through a newly developed magnet system and advanced silicon pixel detectors, and what this will mean for research. For example, the upgrade will enable 3D magnetic tomography of materials with unprecedented speed and resolution, and will make muon spin spectroscopy accessible for samples as small as one millimetre in diameter. These advances will open the door to novel quantum and superconducting materials that are currently out of reach due to their small sample sizes. A major operational shutdown is planned from 2028 to mid-2029 to carry out the renovations. 

The ongoing high demand for muon beamtime is again reflected by the recent submission of 116 new proposals, which is a new record for the SμS June call.

CHRISP — McMule, a versatile beast of burden

The McMule collaboration just celebrated its tenth anniversary. McMule (Monte Carlo for Muons and other Leptons) is a framework that was initially developed at PSI and now typically involves about 15 scientists all over Europe. It has become a versatile tool that is used by numerous particle physics experiments at PSI and worldwide. The precision frontier of particle physics requires flexible theoretical predictions that can be adapted to specific experimental situations. It is a long, laborious and slippery path from a theoretical model (i.e., a Lagrangian) to the prediction of a measured observable. McMule carries the user along this path for low-energy processes involving leptons, pions and protons. It includes QED effects up to next-to-next-to-leading order (NNLO), and for pions and protons, the composite hadronic structure is taken into account. Ten years on, development continues apace: current developments include improvements in the hadronic effects and the extension to NNNLO in QED for selected processes.

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