A new photochemical reaction cell has been developed for the X-ray microscope at the PolLux beamline of SLS that allows mimicking sunlight-mediated chemical reactions in airborne particles. The setup was used to image the interior of photoactive organic particles — of the type we frequently inhale — to reveal the chemistry that produces a high concentration of persistent carbon-centred radicals and reactive oxygen species, which can cause damage to the respiratory tract. It was found that when the relative air humidity is below 60%, particles can become highly viscous or even glass-like, drastically reducing the mobility of molecules therein. At the same time, due to the combined effects of fast reaction and slow diffusion near the surface, oxygen does not penetrate such particles, so that the harmful radicals are effectively trapped, increasing their potential for doing harm.
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The famed Stern–Gerlach experiment has lost nothing of its appeal since it was first performed in 1922. As a beam of spin-bearing particles passes through a magnetic-field gradient, particles in different quantum states are spatially separated, making quantisation directly visible. But Stern–Gerlach-type splitting can be exploited without spatial beam separation, too, as an international team led by PSI researchers demonstrate. In their experiment, polarized neutrons in a centimetre-sized beam are split transversally by sub-micrometre distances according to their spin state. In Talbot–Lau interferometric imaging experiments recently pioneered at SINQ, the thus-split spin components create independent interference patterns whose destructive superposition leads to decreased visibility — which so far has been explained in the context of coherence loss. This insight might now open up new routes to imaging magnetic microstructures.
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Superconductivity and ferromagnetism are traditionally considered antagonistic states of matter. But when they can be made to co-exist, the combination of magnetic and superconducting properties could enable low-power electronics and spintronic functionality. An international team led by researchers form the University of Leeds (UK) now present a system in which emergent spin-ordering and diffusion of Cooper-pairs are achieved. They demonstrate that in heterostructures of superconductor and normal-metal thin-films a suitably designed layer of C60 molecules can mediate the leakage of Cooper-pair states via the proximity effect. Low-energy muon spin rotation experiments at SμS, combined with electron-transport measurements and magnetometry, establish that at such metallo-molecular interfaces, spin-singlet to triplet Cooper-pair conversion takes place, which in turn could be used for generating and controlling diffusion of spin-polarised dissipationless currents.
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Researchers at SwissFEL have demonstrated, for the first time, transient grating (TG) spectroscopy in the hard X-ray regime. TG spectroscopy is based on generating an interference pattern by crossing two simultaneous pulses in a solid sample. In this way, a grating of spatially modulated excitation is created, from which subsequently a time-delayed probe pulse is diffracted. This versatile, background-free technique for probing vibrational, magnetic and electronic degrees of freedom in the time domain has been established first in the optical domain, and has recently been demonstrated in the extreme ultraviolet (EUV) regime as well. The extension into the hard X-ray range now enables access to bulk properties of materials with atomic selectivity involving nanoscale TG spatial periods, and paves the way for X-ray ultrafast coherent four-wave-mixing techniques (graphics courtesy: Ella Maru Studio).
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From April 6–9 more than 120 scientists from Japan, Europe and America participated in a virtual workshop dedicated to preparing the science case of a future high-intensity muon beam (HIMB) at PSI. The main cases were presented in the plenary sessions, including the possibility of producing an ultralow-energy muon beam of high brilliance with the new muCool facility. On the particle-physics side, searches for charged lepton flavour violation, a possible measurement of the muon electric dipole moment, and muonium production featured prominently. For muon spin spectroscopy, fresh opportunities for advancing the technique with vertexing as well as sub-surface and pulsed beams were discussed. Elemental analysis with negative muons was considered as well. During the following parallel sessions more detailed discussions took place within smaller groups.
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During the week of March 15–19, we had the pleasure of welcoming 20 international PhD students, postdocs and assistant professors for the first virtual HERCULES School on Neutrons and Synchrotron Radiation. The participants attended online lectures, virtual tours, remote practicals at SLS beamlines and tutorials at SINQ. The school is dedicated to introducing scientists to new techniques and methods at large-scale facilities utilizing photons and neutrons, and covers multiple disciplines, including biology, chemistry, physics, material science and industrial applications. It runs for one month, of which one week is hosted by PSI.
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This year, the LEM event rate reached a new all-time record with 2600/sec, which translates - after correction for detection efficiencies - into a muon rate of 6000/sec at the sample, and 13000/sec at the moderator. This could be achieved due to the newly installed slanted muon production target and a high proton current of 2 mA. As these results were obtained with a solid argon moderator, even higher rates up to 21000/sec can be anticipated if a solid neon moderator with extraction voltages up to 10 kV will be used.

Also, SμS received a total of 83 new proposals that were submitted at the recent deadline on June 9. The call was open for the instruments GPD, GPS, HAL-9500 and LEM and the users asked for 426 days of beamtime for the period October - December 2021. Presently the proposals are being evaluated by the external proposal review committee and we will inform the users as soon as possible.

A new method for characterizing the transverse phase space of a strongly focused, ultra-relativistic electron beam with sub-micrometer resolution has been introduced and validated at SwissFEL. The approach is based on a series of measurements with nanofabricated wire scanners at different angles and locations along the beam waist. From these data, the transverse phase space is reconstructed using an iterative tomographic algorithm. The technique has been demonstrated in experiments with the ACHIP (Accelerator on a Chip International Program) chamber at SwissFEL, but should be applicable as well in other experiments in which focused high-brightness electron beams need to be characterized.
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PSI researchers, together with the company VACUUMSCHMELZE, have completed the construction of a 25-cubic-metre magnetically shielded room with a (for a walk-in room) record-low measured residual magnetic field of below 150 picotesla. This room will be the centre piece for the next-generation neutron EDM experiment n2EDM, which is due to be fully assembled in 2022.
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The PSI Facility Newsletter addresses the users of the PSI large facilities and appears quarterly in English. Any feedback is highly welcome! More information. 

Contact: PSI User Office, Phone: +41-56-310-4666, Email: useroffice@psi.ch