First light at the renewed Advanced Photon Source !

• Laurent Chapon (APS)

Room: Saal G Following a year-long shutdown that began in April 2023, significant progress has been made in commissioning the new storage ring at the Advanced Photon Source. Multiple beamlines, including feature beamlines which form an integral part of the APS-U project, have entered technical commissioning and the facility as a whole is preparing to welcome back users. I will review activities at the APS in the last 18 months including the storage ring removal and installation phases and will highlight the milestones achieved during the commissioning to date, on the storage ring and beamlines. I will also present some of the strategic opportunities that emerge from combining the renewed APS and the Aurora exascale computer at Argonne.

SPring8-II and beyond -Challenge to a high-performance greener light source

• Hitoshi Tanaka

Room: Saal G Advanced light sources are expected to accelerate the transition to a sustainable society through a variety of outcomes that contribute to innovation in industrial and living human infrastructure. In response to these demands, light sources themselves need to change to greener systems compromising higher performance with energy and material savings. Along this direction, we have gradually and continuously developed accelerator-based light sources at the SPring-8 site. This talk will start with the background of promoting greener light sources and outline several approaches achieving more environmentally friendly light sources. Then, the talk will overview a roadmap for the long-term upgrade of light source complex at the SPring-8 site and the SPring-8-II project, on-going greener high-performance upgrade of current SPring-8. The talk will also introduce the concept, targets and ongoing R&D of SACLA-II following the SPring-8-II project.

Scandium-45 nuclear-clock isomer driven by X-ray laser (6. FELs: New facilities and opportunities)

• Yuri Shvyd'ko (Argonne National Laboratory)

Room: Saal G Precise timekeeping is indispensable in everyday life, science, and technology. It relies on reference oscillators with stable frequencies. Atomic clocks -- the most precise time-measurement devices at present -- use spectrally very narrow resonant transitions between electronic states in atoms as their reference oscillators [1]. With the advent of hard x-ray FELs, the use of extremely narrow resonant transitions in atomic nuclei as reference oscillators for ultra-high-precision clocks is now within reach. Nuclear oscillators are naturally more stable and more resilient to external perturbations than their atomic counterparts. Resonant excitation of an ultra-narrow transition in Scandium-45 nuclear isomer with hard x-rays became recently possible [2] due to the high spectral photon flux delivered by the European XFEL in self-seeded high-repetition-rate mode [3]. In this talk, the results of the Scandium-45 experiment [2] will be presented along with discussion of further developments of hard X-ray FELs required for ultra-high precision nuclear clocks in particular and for nuclear resonance studies in general. [1] Ludlow, A. D. et al. Optical atomic clocks. Rev. Mod. Phys. 87, 637–701 (2015). [2] Shvyd'ko, Yu. et al. Resonant x-ray excitation of the nuclear clock isomer 45Sc. Nature 622 (2023) 471. [3] Liu, S. et al. Cascaded hard X-ray self-seeded free-electron laser at MHz-repetition-rate. Nature Photon. 17 (2023) 984–99/1.

X-ray tomography for Circuit Neuroscience - Towards X-ray Connectomics

• Andreas T. Schaefer (Francis Crick Institute)

Room: Saal G The brain is one of the most complex structures known. In order to understand how information is processed in mammalian brains, one needs to combine functional measurements with structural information across scales from cm to nm. In this talk, I will discuss our multi-modal, multiscale approaches, combining functional imaging in vivo in mice with different synchrotron X-ray tomography techniques[1,2]. I will illustrate how nano-holotomography can reveal circuit structure at scale, sufficient to describe input-output relationships in a brain area. Moreover, advanced sample preparation approaches[3,4] make it possible to not only prepare samples optimised for X-ray tomography but also to subsequently perform targeted volume electron microscopy with multiple samples. I will conclude by providing an outlook on what the key challenges are for X-ray tomography to delineate neural circuitry at microscopic level[5] and how to scale these approaches up to entire brains. References [1] - Bosch, C., Ackels, T., Pacureanu, A., Zhang, Y., Peddie, C.J., Berning, M., Rzepka, N., Zdora, M.C., Whiteley, I., Storm, M., ,,,, and A.T. Schaefer, Nature Communications 13, 2923. (2022). [2] - A. Laugros, J. Livingstone, P. Cloetens, A. Pacureanu , A. T. Schaefer. Program No. 144.05. 2023 Neuroscience Meeting Planner. Washington DC: Society for Neuroscience (2023). [3] - Bosch, C., Lindenau, J., Pacureanu, A., Peddie, C.J., Majkut, M., Douglas, A.C., Carzaniga, R., Rack, A., Collinson, L., Schaefer, A.T., and H. Steigmann. Appl Phys Lett 122, 143701. (2023) [4] - Zhang, Y., Ackels, T., Pacureanu, A., Zdora, M.-C., Bonnin, A., Schaefer, A.T., and Bosch, C. Frontiers in Cell and Developmental Biology 10. (2022) [5] - Bosch, C., Diaz, A., Holler, M., Guizar-Sicairos, M., Aidukas, T., Pacureanu, A., Mueller, E., Peddie, C.J., Collinson, L., Zhang, Y., … A. Diaz, A. Wanner and A.T. Schaefer. bioRxiv 2023.11.16.567403. (2023)

The recent status of High Energy Photon Source (HEPS) (11. Synchrotron radiation facilities: Facility updates and new facilities)

• Yuhui Dong (Institute of High Energy Physics, Chinese Academy of Sciences)

Room: Saal G One of the important tendencies in the development of synchrotron radiation sources is low emmitance. Low emmitance storage rings could provide higher brilliance and better coherence, which are very important for almost all kinds of experiments in synchrotron radiation facilities. The 4th generation synchrotron radiation facilities can provide 2 or 3 orders of higher brilliance and coherence comparing with 3rd generation ones. In the meantime, the successful construction of Shanghai Synchrotron Radiation Facility and the great achievements in the research in this facility, inspire the users to build the new and high-performance light sources in China. In the view point of regional factors, the vast in territory of China requires the reasonable distribution of synchrotron radiation facilities which support the scientific and technological research, in order to farthest satisfy the demands of users from different regions. Based on the above reasons, we are building a new synchrotron radiation facility in the region around Beijing: High Energy Photon Source (HEPS). The designed electron energy of HEPS is 6GeV and the emmitance is lower than 0.1nmrad. This machine can provide the hard X-ray with brilliance higher than 1022ph/s/mm2/mrad2/0.1%BW and photon energy higher than 300keV. The construction of HEPS started in June 2019, including a 500MeV LINAC, a 6GeV booster, a 1360m-circunference storage ring, 14 public beamlines and 1 test optical beamline, as well as the auxiliary facilities and building. Before the start-up of HEPS, the R&D project (HEPS-TF) was supported during 2016-2019. The Platform for Advanced Photon Source (PAPS) was supported in 2017 in order to provide a field for technology research and the assembling of the instruments of HEPS. The installation of LINAC started in March 2022, commissioning in March 2023. In June 2023, the electron energy of LINAC reached to 500MeV, and the bunch charge reached to 7nC. The installation of booster started in August 2022, commissioning in July 2023. By 4 months of debugging, the electron energy reached to 6GeV and bunch charge to 5nC, in November 2023. The installation of storage ring started in February 2023. Now all the magnets and girders are ready. The commissioning is planned in July 2024. All the FOEs and hutches of beamlines are ready. The instruments of beamlines and end-stations are in installation. The commissioning of beamlines will start with storage ring. In the meantime, the teams of beamlines and end-stations cooperate with users, to plan the day-one experiments and the construction of future beamlines. Several jointed research centers and laboratories are established to solve the problems of industries and explore the application of the unique experimental methods of 4th generation synchrotron radiation in frontier researches. We hope the users of HEPS can launch intensive research, instead of simple measurements in future. In order to support this purpose, the office & laboratory building as well as guesthouse, were completed. The whole facility will be in operating at the end of 2025.

Status of the Hard X-ray Self-Seeding at the EuXFEL (11. Synchrotron radiation facilities: Facility updates and new facilities)

• Shan Liu (DESY)

Room: Saal G As a scheme to increase longitudinal coherence in SASE based FELs, hard X-ray self-seeding (HXRSS) has demonstrated its capability of delivering above 1mJ/eV peak pulse intensity at MHz repetition rate in the SASE2 beam line at the EuXFEL. The delivery of HXRSS started in 2021 at the EuXFEL. With the increasing user requests with stringent requirements, we explored different methods for bandwidth and background controls. Additionally, we are investigating advanced HXRSS operation schemes to further expand our operational capabilities. This presentation will provide an overview of HXRSS status, current capabilities, and future prospects.

Computed X-ray microtomography (7. Imaging and coherence applications)

• Manuel Guizar-Sicairos (PSI/EPFL)

Room: Saal G Ptychography is a coherent lensless imaging technique that incorporates scanning of the sample. As such, it relies heavily on computations and has benefitted from advances in algorithms since its original conception in 1969 [1] and its more modern iterative implementation from 2004 [2]. Leveraging the coherence of X-ray sources, it does away with imaging lenses and their limitations in resolution and efficiency, that are inherent to their challenging manufacturing. It has been shown to work with perfect as well as aberrated, or partially coherent, illuminations, as well as being able to correct for multiple scattering effects, and even figure out and correct for inaccurate positioning of the sample due to scanning-stage errors. It may seem that for ptychography all that matters is the reconstruction algorithms and all instrumental errors and other imperfections can be accounted for in post-processing. This is to some extent true due to the richness of information in a ptychogram. However, these postprocessing corrections come at the cost of signal-to-noise ratio, or in other words, of photon statistics. Joint improvements both in algorithms and instrumentation can yield significantly more efficient imaging. Years of research into optimizing ptychographic tomography [3, 4] have led to important advances in instrumentation that enable high throughput and resolution. These include using optical interferometry for accurate sample positioning, design X-ray illuminations with engineered wavefront aberrations, and implementing hybrid scanning approaches of optics and sample. In this presentation I will showcase some important advances in instrumentation as well as algorithms that have allowed a sustained improvement in imaging throughput at the cSAXS beamline of about 3 times per year over 10 years. References [1] W. Hoppe, "Beugung im inhomogenen Primarstrahlwellenfeld. I. Prinzip einer Phasenmessung von Elektronenbeungungsinterferenzen," Acta Crystallographica Section A 25, 495-501 (1969). https://doi.org/doi:10.1107/S0567739469001045 [2] H. M. L. Faulkner and J. M. Rodenburg, "Movable aperture lensless transmission microscopy: A novel phase retrieval algorithm," Physical Review Letters 93, 023903 (2004). https://doi.org/10.1103/PhysRevLett.93.023903 [3] M. Holler, M. Guizar-Sicairos, E. H. R. Tsai, R. Dinapoli, E. Müller, O. Bunk, J. Raabe, and G. Aeppli, "High-resolution non-destructive three-dimensional imaging of integrated circuits," Nature 543, 402-406 (2017). https://doi.org/10.1038/nature21698 [4] M. Holler, M. Odstrcil, M. Guizar-Sicairos, M. Lebugle, E. Müller, S. Finizio, G. Tinti, C. David, J. Zusman, W. Unglaub, O. Bunk, J. Raabe, A. F. J. Levi, and G. Aeppli, "Three-dimensional imaging of integrated circuits with macro- to nanoscale zoom," Nature Electronics 2, 464-470 (2019). https://doi.org/10.1038/s41928-019-0309-z

The LCLS-II: High Repetition Rate Free Electron Laser driven by a Superconducting CW Linac

• Mike Dunne (SLAC National Accelerator Laboratory)

Room: Saal G A major upgrade to the Linac Coherent Light Source (LCLS) Free Electron Laser facility has recently been completed. The LCLS-II project delivered a 4 GeV superconducting CW linac, capable of supplying pulses at up to 1 MHz rates in a continuous stream, marking the culmination of a 10-year, $1 billion project. This beam is used to drive a pair of undulators capable of delivering FEL pulses from 250 eV to 5000 eV, with pulse durations down to the sub-femtosecond level. A suite of instruments has been built to make use of the new beam, including TMO (time-resolved atomic, molecular and optical science instrument), ChemRIXS (liquid-phase chemical sciences using Resonant Inelastic X-ray Scattering), qRIXS (materials science using time- and momentum (q)- resolved RIXS), and TXI (a dual-beam tender X-ray instrument). This talk will provide an overview of the current status of the LCLS facility with these new developments, including data from the commissioning and early science programs at the level of 8 to 32 kHz. The talk will also describe the next phase of upgrades that are currently underway, including the extension to 8 GeV via the LCLS-II-HE Project. Finally, the talk will offer a perspective on future plans for a next-generation facility known as LCLS-X, and commentary on the anticipated directions for FEL science.

Application of Deep Learning Methods for Beam Size Control at the Advanced Light Source

• Thorsten Hellert (MPY (Beschleunigerphysik))

Room: Saal G Past research at the Advanced Light Source (ALS) provided a proof-of-principle demonstration that deep learning methods could be effectively employed to compensate for the significant perturbations to the transverse electron beam size induced by user-controlled adjustments of the insertion devices. However, incorporating these methods into the ALS' daily operations has faced notable challenges. The complexity of the system's operational requirements and the significant upkeep demands have restricted their sustained application during user operation. In this talk, we introduce the development of a more robust neural network (NN)-based algorithm that utilizes a novel online fine-tuning approach and its systematic integration into the day-to-day machine operations.

Big data handling

• Jana Thayer (SLAC National Accelerator Laboratory)

Room: Saal G

Attosecond Pump-Probe Spectroscopy of Liquid Water (11. Synchrotron radiation facilities: Facility updates and new facilities)

• Linda Young (Eur.UPEX)

Room: Saal G Electronic motion in nature underlies chemical reactions and occurs on the attosecond timescale. Attosecond snapshots of evolving electronic structure during light-induced chemical reactions have been captured with high-harmonic generation probes [1]. However, all x-ray attosecond-pump/attosecond-probe experiments that directly observe electron dynamics in real time with all nuclear motions frozen awaited the advent of intense, attosecond pulses from free-electron lasers [1] delivered as synchronized pairs [2]. Such x-ray pump-probe experiments represent a means to understand, with site- and chemical-selectivity, ionization-induced electronic dynamics in simple gas-phase to complex condensed-phase systems. Employing synchronized two-color x-ray pulse pairs we experimentally developed and theoretically modelled observables for all x-ray attosecond transient absorption spectroscopy (AX-ATAS) where spectroscopic snapshots free from nuclear motion are acquired [4]. Our initial study on pure liquid water resolved a long-standing debate concerning the interpretation of the 1b1 x-ray emission doublet, demonstrating the power of attosecond experiments to also reveal equilibrium structure information. An outlook for studying radiation-induced chemistry from sub-femtosecond to much longer timescales in complex aqueous systems will be presented. [1] P. Kraus et al., *Nature Reviews Chemistry* **2,** 82–94 (2018). [2] J. Duris et al., *Nature Photonics* **14**, 30–36 (2020). [3] Z. Guo et al., *Nature Photonics* (2024). [4] S. Li et al., *Science* **383**, 1118-1122 (2024).

Catching Catalysts in Action (2. Beamline Innovations)

• Serena DeBeer (MPI CEC)

Room: Saal G The ability to activate and functionalize C-H bonds in controlled and sustainable fashion remains one of the holy grails of chemistry. It is here that nature provides much inspiration, with enzymes such as methane monooxygenases enabling the direct and selective oxidation of methane to methanol - utilizing either a copper active site in the particulate form or a dinuclear iron site in the soluble form of the enzyme. Our understanding of the nature of these active sites and their mechanisms has greatly benefited from spectroscopic developments. Herein, I will present recent work utilizing both rapid freeze quench and microfluidic mixers to characterize these enzymatic intermediates in methane monooxygenases and lytic polysaccharide monooxygenases. In addition, recent static and time-resolved spectroscopic studies of homogeneous C-H bond activating catalysts will be presented. These will include 2p3d resonant inelastic X-ray scattering (RIXS) spectroscopic studies as a probe of two-state reactivity and femtosecond X-ray absorption (XAS) and X-ray emission (XES) spectroscopic studies of high-valent iron oxos. The implications of these studies for rational catalytic design will be discussed.

Overview Detector developments

• Gabriella Carini (Brookhaven National Laboratory)

Room: Saal G While we observe continuous progression of x-ray facilities, detectors remain often a limiting factor in exploiting the potential of these improved sources. This talk will provide an overview of detector developments with focus on new technologies and experimental needs. Further it will link the evolution of detector concepts to their success and impact in achieving science goals. The increased necessity to integrate approaches for data flow optimization will be discussed. At the end a perspective on the opportunities to develop a common vision and strategy between facilities as well as community building will be presented.

Science and Innovation at SIRIUS (11. Synchrotron radiation facilities: Facility updates and new facilities)

• Harry Westfahl (Brazilian Synchrotron Light Laboratory (SIRIUS) / CNPEM)

Room: Saal G SIRIUS, Brazil's fourth-generation storage ring light source, is managed by the Brazilian Synchrotron Light Laboratory (LNLS) at CNPEM and funded by the Ministry of Science, Technology, and Innovations (MCTI). As Latin America's only synchrotron, SIRIUS offers beamlines spanning from infrared to hard X-rays, accessible to researchers worldwide. SIRIUS storage ring, operating at 3 GeV with a 100 mA current, features a 5BA magnet lattice designed for high transverse coherence. It supports up to 38 beamlines, with ten currently operational, two in commissioning and two in installation. The initial set of beamlines covers scientific programs and experimental techniques such as CDI, XPCS, μ and nano-CT, μ and nano-XRD, XAFS, SAXS, ARPES, RIXS, PEEM, and XMCD. Innovative advancements in optics, precision mechatronics, detectors, and computing technology support these experimental capabilities. Since its inception in 2012, SIRIUS has leveraged expertise from UVX, Latin America's first synchrotron. By 2019, SIRIUS had achieved its first stored beam, and by the end of 2021, it had operated at 100 mA with six beamlines open for user commissioning. Regular operations for users began in 2023. Aligned with Brazil's green economy strategy, SIRIUS prioritizes sustainable innovation and facilitates agriculture, energy, environment, and health research. Early publications highlight a commitment to sustainable development. In 2023, the Brazilian government approved SIRIUS's second phase that will add ten more beamlines, extending SIRIUS's spectral range into the THz gap and harder X-rays; technical upgrades, such as the current increase to 350 mA; and infrastructure improvements. Additionally, CNPEM's ORION project will establish Latin America's first Biosafety Level 4 (BLS4) laboratory, integrating advanced synchrotron X-ray bio-imaging techniques to allow scientists to see, in tri-dimensions, how pathogens infect animals and cause diseases, from the cellular up to the organism level. This presentation will overview current and future advancements in synchrotron science enabled by SIRIUS, highlighting its potential for groundbreaking scientific breakthroughs.