News

Chalk River Unidentified Deposits (CRUD) are dissolved and suspended solids, product of the corrosion of structural elements in water circuits of nuclear reactors.  

The chemical composition of CRUD is variable as it depends on the composition of the reactor’s structural material, as well as the types of refueling cycles.  Recent internal investigations have found unexpected but significant Si-amount in CRUD. The chemical composition of CRUD holds key information for an improved understanding of CRUD formation and possible impact in fuel reliability and contamination prevention.

The standard analytical methods available in the hot laboratory did not allow an easy quantitative determination of the Si-amount in CRUD. A new innovative procedure has been developed and tested with synthetic CRUD name Syntcrud.

The adapted flex-fusion digestion method presented here is able to provide reliable concentrations of several elements within CRUD, including Si, which was not possible in methods used previously for ICPMS measurement.

Manipulating the spin state of thin layers of superconducting material is a promising route to generate dissipationless spin currents in spintronic devices. Approaches typically focus on using thin ferromagnetic elements to perturb the spin state of the superconducting condensate to create spin-triplet correlations. We have investigated simple structures that generate spin-triplet correlations without using ferromagnetic elements.

Kagome lattices are intriguing and rich platforms for studying the intertwining of topology, electron correlation, and magnetism. These materials have been subject to tremendous experimental and theoretical studies not only due to their exciting physical properties but also as systems that may solve critical technological problems. We will review recent experimental progress on superconductivity and magnetic fingerprints of charge order in several kagome-lattice systems from the local-magnetic probe point of view by utilizing muon-spin rotation under extreme conditions, i.e., hydrostatic pressure, ultra low temperature and high magnetic field.

Aliovalent doping is a way to optimize the electrical properties of semiconductors, but its impact on the phonon structure and propagation is seldom considered properly. Here we show that aliovalent doping can be much more effective in reducing the lattice thermal conductivity of thermoelectric semiconductors than the commonly employed isoelectronic alloying strategy. We demonstrate ...

The bones of the tree hollow toad tree frog are turquoise blue. Our team is currently investigating the nanostructure of the bone and its significance for the frog.

The helical magnetic structures of cubic chiral systems are well explained by the competition among Heisen- berg exchange, Dzyaloshinskii-Moriya interaction, cubic anisotropy, and anisotropic exchange interaction (AEI). Recently, the role of the latter has been argued theoretically to be crucial for the low-temperature phase diagram of the cubic chiral magnet Cu₂OSeO₃, which features tilted conical and disordered skyrmion states for a specific orientation of the applied magnetic field (μ₀H⃗ ∥ [001]). In this study ...

The current challenge to realizing continuously tunable magnetism lies in our inability to systematically change properties, such as valence, spin, and orbital degrees of freedom, as well as crystallographic geometry. Here, we demonstrate that ferromagnetism can be externally turned on with the application of low-energy helium implantation and can be subsequently erased and returned to the pristine state via annealing.

We are happy to announce the release of MUMOTT (multi-modal tensor tomography) 1.0, an all-Python package for the analysis of tensor tomography measurements! 

Stephan Burkhalter (PhD student in our group) is the recipient of this year’s Lab Award of the Physics Department at ETH Zurich.

Tiziano Bevilacqua (PhD student in our group) has been awarded a price for the best poster at the Large Hadron Collider Physics conference (LHCP) that took place in Belgrade this year.

Marino Missiroli (postdoctoral researcher in our group) will join the management team of the CMS experiment at CERN as Trigger Co-Coordinator in September 2023.

The translational project "PROGNOSTICS", proposed by a consortium led by Prof. Roger Schibli, received CHF 2 million funding from the PHRT initiative of the ETH Domain(https://www.sfa-phrt.ch/two-clinical-trial-projects-launched-transforming-clinical-care-with-eth-technologies/). The study is being conducted with the Co-applicants Prof. Dr. med. Damian Wild at the University Hospital Basel and Prof. Dr. Nicola Aceto of the ETHZ. The consortium will test a new radiopharmaceutical developed at the Center for Radiopharmaceutical Sciences in 36 patients with advanced prostate cancer.

In this paper we present a model system built out of artificially layered materials, allowing us to understand the interrelation of magnetic phases with the metallic-insulating phase at long length scales, and enabling new strategies for the design and control of materials in devices. The artificial model system consists of superlattices made of SmNiO₃ and NdNiO₃ layers, – two members of the fascinating rare earth nickelate family, having different metal-to-insulator and magnetic transition temperatures. By combining two complementary techniques ....

We report resonant elastic x-ray scattering of long-range magnetic order in EuPtSi₃, combining different scattering geometries with full linear polarization analysis to unambiguously identify magnetic scattering contributions. At low temperatures, EuPtSi₃ stabilizes type A antiferromagnetism featuring various long- wavelength modulations. For magnetic fields applied in the hard magnetic basal plane, well-defined regimes of cycloidal, conical, and fanlike superstructures may be distinguished that encompass a pocket of commensurate type A order without superstructure.

Muon spin rotation with low-energy muons (LE-μSR) is a powerful nuclear method where electrical and magnetic properties of surface-near regions and thin films can be studied on a length scale of ≈200 nm. This study shows the potential of utilizing low-energy muons for a depth-resolved characterization of oxide-semiconductor interfaces, i.e., for silicon (Si) and silicon carbide (4H-SiC). The performance of semiconductor devices relies heavily on the quality of the oxide-semiconductor interface; thus, investigation of defects present in this region is crucial to improve the technology.

Professor Dr. Cristina Müller.

Prof. Roger Schibli was awarded an Honorary Fellow of the Society of Radiopharmaceutical Sciences (SRS) “in recognition of substantial contribution to the SRS”.

Prof. Roger Schibli (third person from the left).

In a study published in Nature Photonics, researchers at the Ben-Gurion University of the Negev, Israel, explain the bright, white-colored stripes from Pacific cleaner shrimps, one of the most efficient white reflectors found in nature.

On June 7, 2023, the PXIII project team successfully shone the first light into the optics hutch at the upgraded X06DA-PXIII beamline. It is an essential first step for testing new hardware and software solutions that will be implemented at SLS2.0.

Control of magnetization and electric polarization is attractive in relation to tailoring materials for data storage and devices such as sensors or antennae. In magnetoelectric materials, these degrees of freedom are closely coupled, allowing polarization to be controlled by a magnetic field, and magnetization by an electric field, but the magnitude of the effect remains a challenge in the case of single-phase magnetoelectrics for applications. 

Gas attenuators are important devices providing accurate variation of photon intensity for soft X-ray beamlines. In the SwissFEL ATHOS beamline front-end the space is very limited and an innovative approach has been taken to provide attenuation of three orders of magnitude up to an energy of 1200 eV. Additive manufacturing of a differential pumping system vacuum manifold allowed a triple pumping stage to be realized in a space of less than half a meter. Measurements have shown that the response of the device is as expected from theoretical calculations.

Dr Christian Wäckerlin (*1983), currently Research and Teaching Associate at EPFL and Project Leader at the Paul Scherrer Institute (PSI), as Assistant Professor of Physics in the School of Basic Sciences. Christian Wäckerlin’s research focuses on nanoscience and quantum engineering.

Operando X-ray diffraction was used to measure process zone temperatures in laser powder bed fusion and compared with finite element simulations.

Zirconium-containing metal-organic framework (MOF) with UiO-66 topology is an extremely versatile material, which finds applications beyond gas separation and catalysis.  By means of in situ time-resolved high-resolution mass spectrometry, Zr K-edge X-ray absorption spectroscopy, magic-angle spinning nuclear magnetic resonance spectroscopy, and X-ray diffraction it is showed that the nucleation of UiO-66 occurs via a solution-mediated hydrolysis of zirconium chloroterephthalates, whose formation appears to be autocatalytic.

Researchers led by the University of Málaga show the Portland cement early age hydration with microscopic detail and high contrast between the components. This knowledge may contribute to more environmentally friendly manufacturing processes.

A team of scientists from the Paul Scherrer Institut, the University of Basel and DESY have demonstrated the first-ever realization of apochromatic X-ray focusing using a tailored combination of a refractive lens and a Fresnel zone plate. This innovative approach enables the correction of the chromatic aberration suffered by both refractive and diffractive lenses over a wide range of X-ray energies. This groundbreaking development in X-ray optics have been just published in the scientific journal Light: Science & Applications.

The newly discovered kagome superconductors represent a promising platform for investigating the interplay between band topology, electronic order and lattice geometry. Despite extensive research efforts on this system, the nature of the superconducting ground state remains elusive. In particular, consensus on the electron pairing symmetry has not been achieved so far, in part owing to the lack of a momentum-resolved measurement of the superconducting gap structure. Here we report ...

The visual pigment rhodopsin plays a critical role in the process of low-light vision in vertebrates. It is present in the disk membranes of rod cells in the retina and is responsible for transforming the absorption of light into a physiological signal. Rhodopsin has a unique structure that consists of seven transmembrane (TM) α-helices with an 11-cis retinal chromophore covalently bound to the Lysine sidechain of 7^th TM helix. A negatively charged amino acid (glutamate) forms a salt bridge with the protonated Schiff base (PSB) of the chromophore to stabilize the receptor in the resting state.

Rhodopsin transforms the absorption of light into a physiological signal through conformational changes that activate the intracellular G protein transducin—a member of the Gi/o/t family—initiating a signaling cascade, resulting in electrical impulses sent to the brain and ultimately leading to visual perception. Although previous studies have provided valuable insights into the mechanism of signal transduction in rhodopsin, methods that provide both a high spatial and temporal resolution are necessary to fully understand the activation mechanism at the atomic scale from femtoseconds to milliseconds. This study presents the first experimentally-derived picture of the rhodopsin activation mechanism at the atomic scale using time-resolved serial femtosecond crystallography in association with hybrid quantum mechanics/molecular mechanics (QM/MM) simulations. The results show that light-induced structural changes in rhodopsin occur on a timescale of hundreds of femtoseconds, and they reveal new details about the conformational changes that occur during activation.

It has long been hoped that spin liquid states might be observed in materials that realize the triangular-lattice Hubbard model. However, weak spin–orbit coupling and other small perturbations often induce conventional spin freezing or magnetic ordering. Sufficiently strong spin–orbit coupling, however, can renormalize the electronic wavefunction and induce anisotropic exchange interactions that promote magnetic frustration.

Neutron scattering experiments at three-axes spectrometers (TAS) investigate magnetic and lattice excitations by measuring intensity distributions to understand the origins of materials properties. The high demand and limited availability of beam time for TAS experiments however raise the natural question whether we can improve their efficiency and make better use of the experimenter’s time. 

The Smart Digital User (SDU) software for unattended data collection has been deployed at the macromolecular crystallography beamlines at the Swiss Light Source. 

Coacervation via liquid-liquid phase separation provides an excellent oppor- tunity to address the challenges of designing nanostructured biomaterials with multiple functionalities. Protein-polysaccharide coacervates, in particular, offer an appealing strategy to target biomaterial scaffolds, but these systems suffer from the low mechanical and chemical stabilities of protein-based condensates. Here we overcome these limitations by transforming native proteins into amyloid fibrils and demonstrate ...

Mobility of water, sodium and gas molecules within a smectite nanopore

Various gases are produced by metal corrosion and organic material degradation in deep gelological repository for nuclear waste. To ensure repository safety, it's important to demonstrate that gases can be dissipated by diffusion in host rocks and prevent pressure buildup in repository near field. Smectite mineral particles form a pore network that is usually saturated with water, making gas diffusion the primary transport mechanism. Molecular simulations have shown that the diffusion of gases through the pore network depends on various factors, including pore size and temperature. For instance, smaller pores and lower temperatures tend to reduce gas diffusion. Interestingly, hydrogen and helium have been found to diffuse faster than argon, carbon dioxide, and methane, possibly due to interactions with the clay surface and water molecules. Ultimately, the diffusion coefficients for different gases and pore sizes can be predicted using an empirical relationship, which is useful for macroscopic simulations of gas transport.

20 international students visited PSI as part of the renowned Hercules School to learn about our state-of-the-art techniques and methodologies at our large scale facilities.

How do you get from A to B in the most environmentally friendly way? This question can now be answered quite easily with the latest version of the "mobitool". Read the article to learn more.

During the last decades, computing power has been subject to tremendous progress due to the shrinking of transistor size as predicted by Moore’s law. However, as we approach the physical limits of this scaling, alternative techniques have to be deployed to increase computing performance. In this regard, the next big advance is envisioned to be the usage of approximate computing hardware based on field-programmable gate arrays and/or digital-analogue in-memory circuits. Such approximate computing can provide disproportional gain (x1000) in energy efficiency and/or execution time for acceptable loss of simulation accuracy. This could be highly beneficial in order to accelerate computational intensive simulations such as reactor core analyses with higher resolution multi-physics models. On the other hand, the execution of programming codes on low-precision hardware may result in inadequate outcomes due to quality degradation and/or algorithm divergence. To address these questions, studies on the stability and the performance of advanced reactor simulation algorithms as function of reduced floating-point arithmetic precision are being conducted at the laboratory for reactor physics and thermal-hydraulics. Results obtained so far indicate a large room for the acceleration of nuclear engineering applications using mixed-precision hardware. Therefore, research is now being enlarged towards assessing multiprecision computing methods for reactor core simulations with higher spatial resolution.

Nanoscale thin films are widely implemented across a plethora of technological and scientific areas, and form the basis for many advancements that have driven human progress, owing to the high degree of functional tunability based on the chemical composition. Pulsed laser deposition is one of the multiple physical vapour deposition routes to fabricate thin films, employing laser energy to eject material from a target in the form of a plasma ...

Using operando time-resolved X-ray absorption spectroscopy, we investigated the origin of volcano-shaped ethanol oxidative dehydrogenation activity trend of VOx/CeO2 catalysts as a function of VOx surface coverage. Vanadium and cerium synergistically change their oxidation states during the catalytic cycle. The catalytic activity correlates with the concentration of reversible Ce4+/3+species.

The ability to study in situ the formation and consumption of Pd hydrides (PdH) in liquid environments is a significant challenge hampering a deeper understanding of catalyzed liquid-phase hydrogenation reactions. Here, using quick scanning X-ray absorption spectroscopy (QEXAFS), we present a detailed kinetic study of Pd hydride formation and reactivity on Pd/Al₂O₃ in 2-propanol solvent. 

Oxynitrides are promising materials for visible light-driven water splitting. However, limited information regarding their electron-momentum resolved electronic structure exists. Here, with the advantage of the enhanced probing depth and chemical state specificity of soft-X-ray ARPES, we determine the electronic structure of the photocatalyst oxynitride LaTiO₂N and monitor its evolution as a consequence of the oxygen evolution reaction. After the photoelectrochemical reactions, we observe a partial loss of Ti- and La-N 2p states, distortions surrounding the local environment of titanium atoms and, unexpectedly, an indication of an electron accumulation layer at or near the surface, which may be connected with either a large density of metallic surface states or downward band bending. The distortions and defects associated with the titanium 3d states lead to the trapping of electrons and charge recombination, which is a major limitation for the oxynitride LaTiO₂N. The presence of an accumulation layer and its evolution suggests complex mechanisms of the photoelectrochemical reaction, especially in cases where co-catalysts or passivation layers are used.

“Soft” x-rays are notoriously hard to detect. Particularly, in the context of high-performance synchrotron and free electron laser (FEL) experiments, suitable detector options for low-energy x-rays are highly sought after. Currently available options only provide limited area, readout speed, and dynamic range. Now, a team of scientists from the Laboratory for X-Ray Nanoscience and Technologies (LXN) at PSI are challenging these limitations. They combined a detector made at PSI with newly developed silicon sensors to push the resolution toward the soft x-ray limit. A first version of this detector system is now in operation at the SwissFEL endstation Maloja. And it points to further possibilities to refine the detector technology to eventually catch the elusive soft x-rays.