Since June 5, external SLS users are allowed on site and the guesthouse reopened. Persons with right of free movement - in particular from Schengen states - are now allowed to enter Switzerland subject to the customary requirements. For third-country nationals who do not have rights of free movement, entry restrictions continue to apply. The safety concept for our users relies on proven measures like distance keeping in combination with reduced numbers of persons on site. Fully remote controlled or mixed remote/local experiments are becoming the new standard. The rapid access call for COVID-19 research has been very successful (see below) and is open until September.

Scientists from the Goethe University Frankfurt have published the first MX results of our priority COVID-19 call. Working - remotely - at the macromolecular crystallography beamline X06SA-PXI of SLS, they studied papain-like protease (PLpro), an essential enzyme of the SARS-CoV-2 coronavirus. The crystallographic-data collection happened on 9 April, as the planned Easter shutdown of SLS was cancelled for this specific experiment. PLpro is required for the processing of viral polypeptides and the assembly of new viral particles within human cells. The researchers have demonstrated that pharmaceutical targeting of PLpro by a specific non-covalent inhibitor blocks virus spread and increases anti-viral immunity in human epithelial cells, the prime site of pathogen entry. The paper reporting these results was submitted within one month of answering the priority COVID-19 call.

With the first application of stroboscopic neutron diffraction to studying lithium-ion batteries during operation, PSI scientists, in collaboration with colleagues at the Université Grenoble Alpes and an industrial partner, have established a new approach to unravelling the complex processes playing out in energy-storage materials. Neutron diffraction has long been recognised as a powerful modality for monitoring structural modifications of individual battery components. However, during fast charging and discharging, there is typically not enough time to acquire sufficient data for extracting structural information about intermediate states. Working at the HRPT diffractometer of SINQ, the team has now demonstrated that with a stroboscopic technique - whereby the same stage of a periodic process is sampled over several iterations - they can obtain appropriate statistics to characterise short-lived states during fast cycling.

An international team led by scientists from Leeds University has demonstrated a path to generating spin-polarized charges and storing them for up to hours at room temperature. They show that hybrid devices incorporating interfaces at which C₆₀ molecules hybridise with manganese-oxide surfaces can be charged with a magnetic electrode and subsequently store spin polarization in stable, localized states. By combining X-ray absorption spectroscopy data, obtained at the ALBA synchrotron near Barcelona, low-energy muon spin rotation measurements performed at PSI and DFT calculations, the researchers establish that an interplay between stray fields, spin-polarized interfacial dipole formation and interface-limited transport facilitates spin-dependent trapping of optically or electrically generated charges for periods long enough to be of interest for practical applications.

High-resolution snapshots throughout the photocycle of a light-driven sodium pump, obtained at SwissFEL, provide unique insight into the structural changes associated with active transport of sodium ions across biological membranes. An international collaboration led by PSI researchers studied the structural evolution in the prototypical sodium pump Krokinobacter eikastus rhodopsin 2 (KR2), covering a wide temporal window from 800 fs to 20 ms after activation. With these snapshots they assembled the first molecular movie of structural changes in KR2 ‘in action’ and, combined with spectroscopic data and quantum chemical calculations, propose a basic mechanistic model of light-driven sodium transport. The importance of these findings might extend to applications, in particular for the further development of optogenetic tools for neuroscience.
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During the whole COVID-19 crisis the SLS was in 'user operation without users on site'. Until the end of May SLS was operational in 24/5 mode and since June 5 we resumed normal 24/7 operation mode with users on campus. For the MX community we operate the three SLS MX beamlines in 100% remote mode and we cover Dewar shipping costs for European academic users (due to the present situation, delivery delays are expected).

The corona pandemic reached Switzerland in spring, exactly when the major neutron guide upgrade program of the Swiss neutron source SINQ was on the home straight. Thanks to the extraordinarily professional and dedicated efforts of both PSI and external staff, the most critical milestone - the installation of the new neutron guides - was nevertheless completed according to schedule. The remaining work to conclude the upgrade is currently being finalized with minimum delays.
During the first proposal round, we received more than 200 new proposals distributed across currently 9 available instruments (with the remaining instruments following suite soon), asking for a total of more than 900 beam days. This impressively highlights the continuing need for neutrons at PSI and we are looking forward to resuming SINQ operation by the end of July and to welcoming external users starting from September 1.

Due to the corona crisis, the restart of operation of the PSI high intensity proton accelerator (HIPA) has been delayed. It is expected now for July 13. The pandemic team of PSI approved in-house research at the SµS from this date on. According to the current situation, external/foreign users at the SµS will be allowed starting from September 1. In the coming days, a new experimental schedule will be published.
We have shifted the approved experiments of foreign users to a date as late as possible in the year and we assume that those users will be able to conduct their experiments at PSI. However, for all experiments foreign travel restrictions and entry requirements into Switzerland and PSI need to be carefully considered. Some experiments (especially for DOLLY) had to be scheduled before September 1. For these experiments and for those where travel restrictions prevent travelling to PSI, the PSI team offers to conduct the experiments for the users. For experiments that cannot be conducted in this way, it might be possible to shift the beamtime to next year.

The ATHOS team at SwissFEL has reached a further milestone. On June 24 the soft X-ray FEL beam passed down the beamline to the experimental hutch, where it was detected on a photon screen a few meters before the experimental chamber. The measured pulse energy was 180 µJ at 35 Å (357 eV). Six undulators were in operation, producing circularly polarized light contributing to the lasing. The next target for the photon beam is the experimental chamber of the Maloja endstation.

Surface muons - the workhorse of muon experiments at PSI - are created by the decay of pions stopped very close to the surface of the production target. As such, their yield is strongly affected by the target geometry. In an extensive study, as part of the High-intensity Muon Beam project (HiMB), we have found that slanting the graphite target at an angle of a few degrees allows the overall surface area of the target to be enlarged (while keeping the interaction length with the protons constant) thereby increasing the yield of surface muons by 40-50% depending on beamline. The new target was successfully tested during the last 3.5 weeks of operation at the 590 MeV proton accelerator HIPA in 2019 and the increased yields were confirmed by measurements in the experimental areas. The new target will also be installed this year in order to benefit from the increased surface muon yields and test its long-term performance.

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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