The old Italian master violin makers Antonio Stradivari and Guarneri del Gesù relied on unexpected chemical additives to bring forth the extraordinary sound of their instruments. This has been revealed by an international team of researchers in experiments covering a wide range of spectroscopic, microscopic, and chemical techniques, including X-ray spectroscopy at the PHOENIX beamline of SLS. The researchers studied wood shavings left over from repairs of the valuable violins and found unnatural elemental compositions and oxidation patterns in the spruce wood used. These suggest artificial manipulation before the mechanical work, for the purpose of wood preservation or acoustic tuning. The extensive treatment included borax and metal sulfates (possibly for fungal suppression), table salt (for moisture control), alum (for molecular crosslinking), and potash or quicklime (for alkaline treatment). 
 
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Evaporation and condensation at liquid–vapour interfaces are ubiquitous mass-transport phenomena that are of interest both for basic studies and industrial applications. However, existing in-situ methods encounter important limitations when it comes to assessing the spatiotemporal distribution of multiple components and phases. Fresh insights could come from high-resolution neutron imaging, as proof-of-concept experiments at the ICON beamline of SINQ demonstrate. The team made use in particular of the large difference in neutron cross-section between hydrogen and its physicochemically similar isotope deuterium, and thus quantitatively characterized how a sessile 7.7-ml heavy-water droplet evaporates while absorbing light-water vapour from the ambient air — monitoring in situ both geometrical changes of the droplet and its H₂O–D₂O fraction, at a resolution of ~20 μm and 60 s per frame. 
 
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Within the family of platinum pnictide superconductors, LaPt₃P is quite an outlier. Its transition temperature of 1.1 K is significantly lower than that of its two isostructural counterparts SrPt₃P and CaPt₃P. And whereas the latter two are conventional Bardeen–Cooper–Schrieffer superconductors, LaPt₃P is not. The nature of its unconventional superconductivity remained, however, unresolved. Now, in a comprehensive μSR study performed at PSI and ISIS (UK) an international team of researchers has established that LaPt₃P is a rare example of a chiral singlet superconductor. They observed spontaneous time-reversal symmetry breaking in the superconducting state at T_c, with line nodes in the superconducting order parameter. These findings are shown to be consistent with a chiral d-wave singlet superconducting ground state in LaPt₃P with topologically protected Majorana Fermi arcs and a Majorana flat band. 

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At the Bernina endstation of the hard X-ray beamline Aramis, a chamber optimized for high-field THz excitation and (resonant) X-ray diffraction at sample temperatures between 5 and 500 K has been commissioned. The chamber is directly connected to the beamline vacuum and features a Beryllium window and an in-vacuum detector covering the full 2–12.7-keV energy range of the femtosecond X-ray pulses available. This means that absorption edges ranging from M (Dy to U), L (Rb to Tl) to K (P to Se) can be accessed. The ability to perform such element-specific experiments in a cryogenic sample environment should enable a variety of time-domain studies of correlated materials. The new capabilities were highlighted in commissioning experiments tracking selectively the dynamics of the structural, magnetic and orbital order of Ca₂RuO₄ and Tb₂Ti₂O₇ at the Ru (2.96 keV) and Tb (7.55 keV) L-edges, respectively.

Particle-physics results of lasting value and significant impact have been obtained at PSI over the past decades, and several efforts are presently ongoing and expected to deliver new findings in the near future. The results of these studies have been published in numerous articles and journals over the years, and many have found their way into the Particle Data Group review. However, in order to collect the scientific output of particle physics experiments at PSI's high-intensity beams of pions, muons and ultracold neutrons in one place, a special SciPost volume, entitled “Review of Particle Physics at PSI”, has recently been completed, containing also a description of the facilities. Ideas for future facility upgrades or completely new experimental efforts are not yet included, but there are plans to extend this volume in the years to come.

The established instruments for high-resolution 3D ptychography are complemented by LamNI (Laminography Nano Imaging), which operates in laminography geometry rather than tomography. It allows the measurement of extended flat specimens. An area of 10x10 mm² is accessible with the setup, and the measurement position and size can then be freely selected.
We have demonstrated high-resolution ptychographic X-ray laminography (PyXL) by measuring an integrated circuit where the only sample preparation was to polish the substrate for achieving sufficient transmissivity. The demonstrated 3D resolution was 18.9 nm, measured in a circular area of 40 μm. PyXL has also proved beneficial for imaging with magnetic contrast via X-ray magnetic circular dichroism. In this case the experimental geometry allowed for in-situ studies of domain wall dynamics. LamNI is now open to user proposals at the cSAXS beamline. Please discuss your project with beamline staff prior to submission.

After a successful commissioning phase, the multiplexing spectrometer CAMEA welcomes first users in the current cycle. The high-performance 2D detector for the DMC diffractometer was delivered and assembled, and enters now the test phase. First test measurements are planned towards the end of the year. The Selene guide system, chopper, polarizer and spin flipper for the reflectometer AMOR have successfully passed the tests and show the expected performance. The team is now working hard to complete the upgrade of the secondary part of the instrument.

Time-resolved pump–probe experiments provide valuable insight into the out-of-equilibrium response of a system. Such experiments become now feasible at the GPS instrument, thanks to pulsed microwave excitation during μSR observation. A key feature is that microwave pulses can be injected at variable times relative to the muon arrival time. This enables schemes such as two-pulse sequences where the first pulse excites the system and the second one returns it back to the initial state. Repeating the experiment with different delays between pulses and comparing the μSR signal before the first and after the second pulse, we can obtain insight into the time evolution of the microwave-excited state. For states that undergo phase-coherent microwave oscillations, this procedure yields Ramsey interference fringes. Such fringes have been observed in pilot experiments with muonium, a system with coupled paramagnetic electron and muon spin. Besides bespoke Ramsey fringes, various other excitation schemes become feasible with this novel tool, extending the capabilities of μSR to addressing open scientific questions regarding driven systems.

In another milestone on the path to full operation of SwissFEL, the Furka experiment station at the soft X-ray beamline Athos has seen ‘first light’. Diffraction and absorption test experiments are currently under way, and first scientific experiments with external users are planned for 2022. Whereas at the other experiment station of Athos, Maloja, work focusses on liquid and gaseous samples (Maloja has seen first light in mid-2020 and is now open for users), Furka is dedicated to the study of solid quantum materials using time-resolved resonant inelastic and elastic X-ray scattering (tr-RIXS and tr-REXS) as well as X-ray absorption (tr-XAS) spectroscopy.
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For the first time all the core components of the Mu3e experiment were all gathered at the πE5 beamline and operated in concert. The pixel vertex detector, a core component of Mu3e, produces up to 110 W of dissipated heat. To keep the temperature controllably below ~50°C, a novel cooling principle using gaseous helium at ambient pressure is used. This system has been developed over the past few years in a highly successful collaboration between PSI, the University of Applied Sciences Northwestern Switzerland at Brugg-Windisch, and industrial partners. The prototype setup uses a custom turbo compressor from the Swiss company Celeroton to propel a closed-loop helium flow of 2 g/s (11 L/s) at up to 240,000 rpm. The differential pressure across the loop was only around 40 mbar and cooling was maintained successfully for the full operation period, thus reaching an important milestone.

 

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