Dear colleagues,

Approximately 35 years ago, I began my journey at PSI, which was then a newly established research institute. Since then, I have had the privilege of witnessing its remarkable growth into one of the world’s leading research institutions. I feel that, unlike me, PSI has never developed a single wrinkle and continues to remain perpetually youthful and strong. The true secret to this fountain of youth is, of course, our dedicated staff, whose talent and commitment are vital to imagining, developing, building, and maintaining our exceptional large-scale research facilities. 

The most recent proof of this was provided by the Swiss Parliament, which just approved our IMPACT project centred around the High Intensity Proton Accelerator (HIPA) complex. On one hand, IMPACT will enhance the production of so-called theranostic isotopes at PSI, while on the other, it will significantly increase the muon flux for particle physics and materials-science experiments. Looking ahead, the Center for Neutron and Muon Sciences is deeply involved in the construction of the Quantum Matter and Materials Discovery Center (QMMC), which will become a hub for cutting-edge research into materials with novel properties. The QMMC will consolidate PSI’s efforts in materials research and play a key role in the research programmes at our large-scale facilities. Beyond that, we will soon start planning the next generation of neutron instruments in the SINQ “North Hall” and ensure the continuous development of our beamlines for CHRISP and SµS.

I have always kept in mind Georges Clemenceau’s words, “the graveyards are full of indispensable men”, and I strongly believe that the older generation should make room for the younger one rather than clinging to an illusory sense of power. With this perspective, I am confident in the bright future of PSI and look forward to returning as an ordinary yet passionate user.

Alex Amato
PSI Center for Neutron and Muon Sciences CNM

A call for SLS proposals will be announced towards the end of the SLS 2.0 upgrade project. An overview of all proposal submission deadlines of the PSI facilities can be found here.

The miniaturisation of computer chips is one of the keys to the digital revolution. The leading lithography technique in CMOS mass production is extreme ultraviolet (EUV) lithography, and significant progress has been made in EUV interference lithography using transmission gratings. However, pushing the resolution well below 10 nm remains a formidable challenge. Now, a team of PSI researchers has developed a novel technique that uses mirror-based technology to overcome the inherent efficiency limitations of grating-based approaches. Using the standard EUV wavelength of 13.5 nm, the team was able to produce conductor tracks just 5 nm apart. As the process is compatible with shorter wavelengths beyond EUV, mirror-based interference lithography could pave the way to ultimate resolutions for photonic techniques. Currently, the new approach is too slow for industrial chip production though — and can only produce simple and periodic structures rather than a chip design — but it offers a method for early development of photoresists needed for future chip production at resolutions not possible in industry. The team plans to continue their research with a new EUV tool, which is expected by the end of 2025. Coupled with the SLS 2.0, the new hardware will provide significantly enhanced performance and capabilities.

I. Giannopoulos et al., Nanoscale 16, 15533 (2024)
DOI: 10.1039/D4NR01332H

In materials lacking lattice inversion symmetry, the emergence of topologically nontrivial magnetic structures, for example in the form of skyrmion lattices, is well established. However, understanding how such states can arise in centrosymmetric materials remains a challenge. In neutron-scattering experiments at PSI and ILL, a team led by TU Dresden has now discovered that the bilayer perovskite Sr₃Fe₂O₇, previously thought to have simple single-q spin-helical order, actually hosts three distinct magnetic phases, including a new ‘spin meta-cholesteric’ state. This intermediate phase, observed between 70 K and 110 K, exhibits an unusual combination of long-range helical magnetic order along one propagation vector while maintaining strongly fluctuating short-range correlations in the orthogonal direction — reminiscent of molecular arrangements in liquid crystals. By mapping the magnetic states in detail, the researchers found that unlike conventional multi-q magnetic phases, Sr₃Fe₂O₇ exhibits unequally intense spin modulations at the two ordering vectors in its ground state. Together with a theoretical analysis, these findings establish Sr₃Fe₂O₇ as an intriguing material in which the interplay between spiral order, a unique set of symmetry-breaking rules, and spin fluctuations suggests the potential emergence of novel properties.

N. D. Andriushin et al., npj Quantum Materials 9, 84 (2024)
DOI: 10.1038/s41535-024-00698-4

Altermagnets, a novel class of magnetic materials, have attracted considerable interest due to their unique properties combining aspects of both ferro- and antiferromagnets. The metallic rutile oxide RuO₂ has recently been proposed as a prototypical altermagnet, based on resonant X-ray and neutron scattering studies suggesting magnetic ordering. However, while several experiments seemed to support altermagnetism in RuO₂, the existence and strength of its magnetic order remained controversial, especially as theoretical calculations naturally converge to a non-magnetic state. An international team of scientists has now revisited the question of ordered magnetic moments in RuO₂. They combined muon spectroscopy at SμS, complemented by density functional theory, with new neutron diffraction measurements at ISIS. Their finding: RuO₂ is not magnetic, neither in bulk nor in epitaxial thin films. They determined an upper bound on magnetic moments that is two orders of magnitude smaller than values found in antecedent studies, with the new values essentially reflecting the detection limits of the spectrometers used. Regarding the altermagnetic signatures reported in several other publications, they suggest that these are likely of extrinsic origin.

P. Keßler et al., npj Spintronics 2, 50 (2024)
DOI: 10.1038/s44306-024-00055-y

Spins carried by atoms are the building blocks of magnetism. In contrast to, say, ferromagnets and antiferromagnets, the spins in a spin liquid fluctuate and do not form an ordered magnetic state, despite local interactions. A team of PSI scientists has now shown that the electromagnetic field of short THz pulses imprints its coherence onto the orbital wavefunctions of the terbium atoms in the correlated quantum material Tb₂Ti₂O₇, which forms an interacting spin-liquid ground state. As a result, the spins of 10¹⁵ excited terbium ions in the material move in synchrony. The spins align in less than a picosecond, creating a magnetic field inside the material, which was detected at the Bernina experimental station of SwissFEL using ultrashort X-ray pulses. The temporal shape and profile of the magnetic field is defined by the THz pulse. For linearly polarized THz fields, the generated magnetic field oscillates until coherence is lost. Circularly left and right polarized THz fields are predicted to create magnetic fields with opposite field directions. As the fields can be induced on ultrashort femtosecond to picosecond timescales, they could find applications in new, fast data storage or, more generally, in the control of material properties such as electrical conductivity or magnetic state. 

R. Mankowsky et al., Nature Communications 15, 7183 (2024)
DOI: 10.1038/s41467-024-51339-0

In 2016, a group of researchers at the ATOMKI laboratories in Hungary reported an anomaly found in the relative angle distribution of the electron–positron pairs from the internal conversion of gamma rays from the ⁷Li(p,γ)⁸Be reaction. The anomaly was later confirmed in two additional processes, helium and carbon, and the so-found excess of events is compatible with the hypothesis of a new boson of mass 17 MeV/c² — the X17 boson. Although the anomaly was measured independently by another group at the University of Hanoi, all these measurements have been performed using the same detection scheme, making it hard to evaluate the weight of possible systematic effects. The MEG II experiment at PSI uses the same lithium-to-beryllium transition to calibrate its liquid-xenon calorimeter and can provide an independent measurement in a wider angular acceptance with a different experimental technique. After a successful data-taking run at the beginning of 2023, the signal box was unblinded and the result is now public. No significant excess was found in the signal region and an upper limit of 1.2×10^-5 was set on the branching ratio to the X17 boson at a 90% confidence level, to be compared with the 6.0×10^-6 branching ratio measured at ATOMKI, meaning that the hypothesis of an X17 boson is rejected at a 94% level.

The MEG II collaboration, Preprint at arXiv: 2411.07994 (2024)
DOI: 10.48550/arXiv.2411.07994

SLS: Excited About SLS 2.0

After 22 years of brilliant science, the SLS went into temporary shutdown on 30 September 2023 and the SLS 2.0 upgrade began. In the video series #ThankYouSLS, seven PSI beamline scientists looked back on a few of the many discoveries made possible by light from the SLS. Now in a new video series #ExcitedAboutSLS, the same researchers tell us why they can’t wait for the SLS 2.0 upgrade. Across the diverse applications, stretching from molecular biology to quantum materials, the researchers look forward to faster experiments, higher resolution, and more realistic conditions. With this, the light of SLS 2.0 — and the thousands of scientists from around the world who will use it — will address societal challenges such as health and the energy transition.

SINQ: Planned upgrades of POLDI and NEUTRA and many new proposals

The AM-UP project, which will be realized over the next few years at SINQ, aims to modernize and upgrade two key instruments for applied materials research. The strain scanner POLDI will finally receive a second 90-degree detector bank and a replacement for the failing original 90-degree bank, enabling the simultaneous measurement of two principal strain directions in in-situ experiments. Further improvements to the neutron guide and shielding will provide additional performance. The ageing benchmark thermal neutron imaging station NEUTRA will be rebuilt to allow not only the use of advanced techniques but also access to a high-flux position for operando studies. Together with the new hydrogen safety installations, this will strengthen in particular unique studies in energy research.

At the most recent submission deadline in November 2024 (call I-25), more than 230 new SINQ proposals were submitted, collectively requesting over 1000 days of beam time. As in previous calls, the SANS instrument was the most requested, with 47 new proposals. The review process is currently underway, and the results of the evaluations and panel meetings are expected to be announced by the end of February 2025.

SμS: Strong demand for muon beamtime in 2025

In early December, the final proposal submission deadline for the PSI user facilities in 2024 passed with the conclusion of the SμS proposals call I-25. A total of 112 new proposals were submitted — a remarkable number, especially considering that the GPD instrument was not available for proposals this time (see PSI Facility Newsletter III-24). Combined with the first call earlier this year, the PSI User Office received a total of 216 SμS proposals in 2024.

As in previous years, the GPS (General Purpose Surface-Muon Instrument) received the highest demand, with 34 new proposals, followed by FLAME with 28 and LEM (Low-Energy Muon Facility) with 23 proposals. The proposals are currently under review. The evaluation panel will convene at the end of January, and the results are expected to be announced in February 2025.

SwissFEL: Eliminating the scourge of light contamination in fixed-target pump–probe SFX

X-ray free-electron lasers (XFELs) are uniquely suited to studying ultrafast dynamics on femtosecond to microsecond timescales. While fixed targets promise high sample efficiency, they have not yet been widely used for time-resolved serial femtosecond crystallography (TR-SFX) studies at XFELs. To address this gap, the SwissMX fixed-target sample-delivery system has been developed at the Cristallina station of SwissFEL, along with dedicated micro-structured polymer (MISP) chips for pump–probe experiments. One challenge was to avoid the accidental exposure of crystals mounted in wells adjacent to those illuminated by the pump laser. In a commissioning experiment, a team led by PSI researchers demonstrated that opaque MISP chips, when properly oriented, successfully prevent light contamination between adjacent crystal wells. Their method achieved ‘clean’ pump–probe measurements while reducing sample consumption ten-fold compared to traditional high-viscosity extrusion methods. 

CHRISP: MSetPoint, a novel system for secondary beamline control

The secondary beamlines at the HIPA accelerator are currently controlled through the ‘SetPoint’ programme. However, this system has reached its end of life and will be replaced by a new system based on the MIDAS DAQ system. The new system, called ‘MSetPoint’, will not only cover the functionality of the previous system but will also provide additional features, including a history display of beamline parameters as well as access and configurability through a web interface that enables easy remote access. Experiments that have already been using the MIDAS system can monitor and access the beamline through their DAQ system. This has been successfully demonstrated in the MEG II experiment during 2024, allowing for complex operations such as synchronizing beamline changes with individual measurements. The deployment of MSetPoint for all secondary beamlines is expected to take place in 2025. The next step will be the development of a new system to replace the ‘Optima’ programme, using innovative machine-learning algorithms.

Dear colleagues,

The current JUSAP Committee will complete its term of office in December 2024 and the election of the new JUSAP members for the next four years will take place at the beginning of 2025. As a note of farewell, we wish to thank the PSI user community for their support and their trust in the Board. 

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