The DESY Photon Science Users´ Meeting will take place online from 21 - 28 January 2022 in conjunction with the European XFEL Users´ Meeting 2022.
The week comprises satellite meetings, online sessions on research with free-electron laser and synchrotron radiation sources, scientific poster sessions and sessions on future developments at PETRA III and FLASH including the upgrade projects PETRA IV and FLASH 2020+.
The deadline for the registration of poster presentations: 17 January 2022.
Access online sessions: All registered participants will receive the login information via e-mail on the day of the event
Support: If there are any questions or problems, please contact: users.meeting2022@desy.de
Time zone: CET Europe/Hamburg
Biology is complex and has been described as soft, slow, squishy, and/or sticky. Life’s reactions are catalyzed by enzymes, which use an active site constellation of atoms from a relatively small fraction of each macromolecule. To achieve the correct outcome, the active site atoms must all be in the right place, at the right time, for long enough, and with sufficient energy to transcend the barriers encountered along each reaction coordinate. Consequently, enzyme function is profoundly supported by the entire macromolecule structure, its surrounding environment, and the dynamics of the whole.
Structural biologists have experimentally determined and released nearly 186,000 atomic models of macromolecules, representing a large cross section of biodiversity. Most derive from traditional crystallographic experimental data collected from samples at cryogenic temperature (e.g. 100 K). Cryocooling effectively “freezes” ground state configuration(s) and restricts dynamics. These ground-state structures and their functional insights are essential to life science R&D efforts globally.
For example, ground-state crystal structures were critical in the recent Pfizer medicinal chemistry campaign that led to the oral antiviral treatment for SARS-CoV-2, Paxlovid - a combination of two antiviral compounds, nirmatrelvir (PF-07321332) and ritonavir (to slow the metabolism of the former). Two SARS-CoV-2 proteases, i.e. the main protease (Mpro) and the papain-like protease (PLpro) hydrolyze the viral polypeptide chains to yield functional non-structural proteins. They are both essential for viral replication. Nirmatrelvir was designed to inhibit Mpro from the original SARS-CoV-2 strain, but it is also a potent inhibitor of the Mpro from Delta and Omicron variants.
Our community-based collaboration ([2695] Time-resolved SFX of Covid-19 proteins including Mpro and PLpro) focused on water soluble substrates or inhibitors ranging in size from 112 – 684 Daltons, used mix-inject flow focusing gas dynamic virtual nozzle methods. X-ray photons arrived at the interaction region with a 500 kHz intra-pulse rate. We collected 2020 images per second using the AGIPD 4M, which were bundled into five-minute runs. Calibration of the 606k AGIPD images within each run took ~ 40 minutes to prepare for further analysis. We developed versions of cctbx.xfel and DIALS to exploit parallel processing strategies distributed over many nodes at the Eu.XFEL. The calibrated virtual images were processed with cctbx.xfel and DIALS at 3500 Hz – to our knowledge, setting a world record. We made use of a 96-node computer cluster (80-140 cores per node) within the MAXWELL cluster at DESY, with a dedicated 100 node partition for the live experiment. We indexed and integrated 606k images in 2-3 minutes by sub-filing the run into 12 sequences, each run on 8 nodes. We therefore produced interpretable electron density maps about 4 minutes after calibration was complete. Further optimisation post-beamtime reduced the total nodes to 12-48 while achieving comparable speeds (8-16% of the MAXWELL cluster). This demonstrates that cctbx.xfel and DIALS can utilise the current Eu.XFEL compute resource to produce real-time datasets with minimal impact on other MAXWELL users. Importantly, it allows enough compute resource for other serial processing algorithms to run concurrently. Some of our tr-SFX results of small ligand binding to PLpro will be presented.
Diamond Light Source: Martin A. Walsh, Jos Kamps, Rob Bosman, Tiankun Zhou, Anna Bailey, Pierre Aller, Agata Butryn, Robin Owen, Sam Horrell, Petra Lukacik, Claire Strain-Damerell, David Owen, Nicholas Devenish, Gwyndaf Evans, Graeme Winter
Lawrence Berkeley National Laboratory: Aaron Brewster
University of Oxford: Christopher J. Schofield, Tika Malla, Lennart Brewitz, Tobias John, Siegfried Graf Thun-Hohenstein, Timothy Suits, Jurgen Brem, Patrick Rabe, Michael McDonough
European XFEL: Adrian Mancuso, Adam Round, Marcin Sikorski, Richard Bean, Johan Bielecki, Grant Mills, Kristina Lorenzen, Huijong Han, Joachim Schulz, Mohammad Vakili, Marco Kloos, Robin Schubert, Jolanta Sztuk-Dambietz, Fabio Dall'Antonia, Frank Schluenzen, Krzysztof Wrona, et al
University of Wisconsin-Milwaukee: Marius Schmidt, Tek Malla, Suraj Pande
Cornell University: Lois Pollack, Kara Zielinski
NERSC: Johannes Blaschke
The dream of imaging single molecules was instrumental to the construction of X-ray free-electron lasers (XFELs). The extremely bright and short pulses provided by XFELs make it possible to collect the diffraction pattern of a particle before its destruction (Neutze et al. 2000) which was successfully proved at FLASH more than a decade ago (Chapman et al. 2006). Since then, the method of flash X-ray imaging (FXI) has been used to image live cells (van der Schot et al. 2015), cell organelles (Hantke et al. 2014) and in particular the giant Mimivirus in both two dimensions (Seibert et al. 2011) and three dimensions (Ekeberg et al. 2015). The inauguration of the European XFEL marked the beginning of the high-intensity, high-repetition-rate and high data-rate era of XFELs, and it has been shown that FXI can take full advantage of those rates (Sobolev et al. 2020).
Yet, FXI has not yet fulfilled its promise of high-resolution sub-nanometer imaging. In this talk I will present our latest results from single-particle imaging experiments at the SQS beamline at the European XFEL. I will also discuss the future of single-particle imaging, how we are tantalizingly close to our goals and how several new technologies can help us get there.
High-energy and high-intensity lasers are essential for pushing the boundaries of science. Their development has allowed leaps forward in basic research areas including laser-plasma interaction, high-energy density science, metrology, biology and medical technology. The HiBEF user consortium contributes and operates two high-peak-power optical lasers at the HED instrument of the European XFEL facility. These lasers will be used to generate transient extreme states of density and temperature to be probed by the X-Ray beam. This contribution introduces the ReLaX laser, a short-pulse high-intensity Ti:Sa laser system, and discusses its characteristics as available for user experiments. As the outcome of internal commissioning experiments, we will as show unprecedented synchronization results for a 100 TW class laser and will validate the performance as laser-plasma driver with relativistic I > 1020 W/cm2 intensity on target by investigations of TNSA as laser-proton acceleration mechanism. Additionally, we have investigated the effect of EMP and laser generated secondary radiation and particle sources on several x-ray diagnostics, and have developed successful strategies to reduce their impacts. The commissioning of ReLaX is concluded by the successful run of the first user experiment “HED 2621: User community assisted commissioning of the UHI Laser at HED, impact of relativistic plasma environment on x-ray diagnostics”. The main goal of 2621 was to validate SAXS, PCI and x-ray spectroscopy on a variety of targets covering a multitude of science cases such as, hole boring, relativistic transparency, fast electron transport along extended target, isochoric heating of buried targets, EOS determination by shocked targets, plasma instabilities in relativistic intensity regime.
Toma Toncian, (HZDR)
on behalf of HED 2621 collaboration and HiBEF user consortium
Presentation of a short overview over the activities of the European XFEL User Organization Executive Committee during 2021, including the results of the recent user survey and the bestowal of this year's Young Scientist Award.
Again, in 2021 user operation at FLASH was heavily impacted by the COVID-19 pandemic. Nonetheless, a number of user experiments were very successfully completed, while new instrumentation and experimental developments were driven forward at the FLASH beamlines and endstations. A comprehensive overview will be given of what new opportunities will be available for FLASH users from autumn 2022 after the first FLASH2020+ shutdown.
The FLASH2020+ project implements major upgrades to the FLASH facility to meet the new requirements of the growing soft-x ray user community.
The upgrades are grouped in two installation phases of which the first has started in November 21 and focusses on extending the capabilities of the superconducting linear accelerator. Among others the beam energy will be increased by 100 MeV to allow reaching a total of 1.35 GeV and thus reducing extending the available wavelength range even further into the water window. Additionally in FLASH2 a so called afterburner will be installed allowing to boost the intensity at the third harmonic while additionally allowing for variable polarisation at wavelength aslow as 1.33 nm.
In the second installation phase starting 2024 the FLASH1 beamline will be in focus. The existing beamline will be completely replaced by an externally seeded beamline allowing to exploit the full FLASH repetition rate of 1MHz in burst mode at variable polarisation. Together with the option of parallel THz generation, new pump-probe laser sources, an improved synchronisation and new endstations this will allow for the next generation of high quality user experiments.
Organic semiconductors constitute an important novel class of electronic materials, especially for applications requiring low power consumption and lightweight, flexible materials. The large variety of these compounds paired with relatively low cost and ease of processing as well as the possibility to design and modify them using synthetic organic chemistry have created high expectations for the development of new functional materials. In particular, their potential application in organic photo-electronic devices such as organic photovoltaic cells (OPVs), solar fuel generation or artificial photosynthesis has motivated numerous investigations. Preferential conductivity for electrons or holes in OPVs is usually achieved by mixing molecular compounds with different electronic functionalities. For example, adding C60 to an organic semiconductor improves the photoconductivity by orders of magnitude.
Here we present the first femtosecond time-resolved XPS (tr-XPS) measurement of charge transfer dynamics in a CuPc/C60 bi-layer system using the Free-Electron Laser FLASH at DESY. Tr-XPS offers the unique opportunity to investigate the dynamics underlying the charge transfer process with exquisite site-specificity by monitoring the time-resolved C 1s XPS from the CuPc/C60 system following optical excitation of the chromophore (Pc). We observe an energy-shifted C 1s XPS line of the C60 electron acceptor after optical excitation, which can be seen as a direct indicator for the electron transfer to the C60. A previously unobserved channel for interfacial charge-transfer (ICT) state separation into mobile charge carriers with an efficiency of 22% is identified, providing a direct measure of the internal quantum efficiency of the heterojunction for this channel.
Even after two decades of studies and debates, the mechanisms of ultrafast demagnetization remain disputed. To bring new experimental information into this field, and with the advent of femtosecond X-rays sources, I will present the results of our recent time-resolved soft X-ray resonant Magnetic Reflectivity experiment on an Fe thin film. First I will show how this technique allows probing simultaneously structural and magnetism dynamics, and how to perform it at FLASH. Second I will present our results and unravel the dynamics of the transient inhomogeneous depth magnetic profile of the Fe layer.
Spectroscopy on solids has fruitful applications, for example in the development of materials for future devices. Using the high intensity and coherence of free-electron lasers offers new opportunities to enhance the information content, but first, one needs to understand the underlying fundamental processes in the (core) electron dynamics, instrumental developments have to be established and methodological advancements in theory and experiment have to be scrutinized.
En route to useful non-linear X-ray spectroscopy applications, important steps have been made in the observation of stimulated processes and in the understanding of electron dynamics that can shield the experimental signatures. Further developments include the implementation of highly efficient intensity normalization schemes that open new opportunities also for other studies. The ultrahigh-vacuum chamber for multi-dimensional spectroscopy and inelastic X-ray scattering (MUSIX, [1]) has been built, offers enhanced flexibility and is being used in various experimental campaigns within many collaborations. New observations include first steps towards also mixing FEL photons with optical laser photons.
[1] Beye, M. et al. Non-linear soft x-ray methods on solids with MUSIX—the multi-dimensional spectroscopy and inelastic x-ray scattering endstation. J Phys Condens Matter 31, 014003 (2018).
Multidimensional photoemission spectroscopy (MPES) experiments using delay-line detectors generate data streams which resolve individual photoelectrons. This enables the correlation of each detected electron to the full state of the experimental apparatus. Such a detection scheme is ideal for SASE FELs such as FLASH, where the inherent intensity fluctuation and timing jitters can not only be corrected for but can also be further exploited, thereby increasing the measured parameter space.
We developed a distributed workflow pipeline which takes advantage of single-event resolution to correct and calibrate MPES data and to generate an open-source data structure ready for analysis and storage with complete metadata description. Initially designed for the HEXTOF end-station, this workflow is easily generalized to any electron-resolved data stream, increasing portability and usability across a large community.
The modular structure of the workflow combines high resolution, artifact-free post processing methods for offline analysis with fast on-site data evaluation. This structure enables users to make data driven decisions, effectively increasing the output of significant data from each beamtime.
Attosecond science is nowadays a well-established research field, which offers formidable tools for the realtime investigation of electronic processes including charge migration in bio-relevant molecules [1].
Here, I will present a time-resolved study of the correlation-driven charge migration process occurring in the DNA nucleobase adenine after ionisation by a 15-35 eV attosecond pulse. Our most intriguing observation is that a stable dication of the parent molecule can be produced if the probing NIR pulse is delayed of 2.3 fs from the XUV pulse. The delayed creation of the dication is the signature of a charge migration mechanism occurring on a sub-3 fs time scale [2].
I will then show that electronic coherences, created by a sub-2fs UV pulse [3] in the chiral molecule Methyl-lactate, can be used to modulate the chiral response of the molecule on a sub-15 fs time scale.
References
[1] F. Calegari et al 336, Science 346 (2014)
[2] E. Månnson et al, (Nature) Commun. Chem. 4, 73 (2021)
[3] M. Galli et al, Optics Letters, 44, 1308 (2019)
“Research with Photons – Light for the Future” is the title of the recent strategy brochure of the committee Research with synchrotron Radiation (KFS, Komitee Forschung mit Synchrotronstrahlung). The KFS is an elected body which represents the interest of more than 4000 synchrotron radiation users (including FELs) in Germany.
Our aim is to help to shape the future of German synchrotron radiation by acting as a link between users and facilities, between users and funding agencies, between Germany and Europe and international sources. In particular, we discuss and help to develop strategies for synchrotron radiation at national and international sources such as outlined in the recently published strategy paper. We further want to promote synchrotron research, networking and support especially young enthusiastic researchers and initiatives like NFDI, ErUM-Data and ErUM-Pro (former “BMBF-Verbundforschung“). DAPHNE4NFDI has recently started as a DFG funded project to establish an infrastructure for data storage with data repositories and metadata capture, re-use and joint data analysis software according to the FAIR (findable, accessible, interoperable, reusable) principle.
The KFS is elected every three years, and the last elections took place in autumn 2020. The following scientists were elected/coopted as members for this period:
Jan-Dierk Grunwaldt (chair, Karlsruhe Institute of Technology), Sarah Köster (vice chair, University of Göttingen), Bridget Murphy (University of Kiel), Birgit Kanngießer (Technical University of Berlin), Andrea Thorn (University of Hamburg), Christian Gutt (University of Siegen), Taisia Gorkhover (University of Hamburg), Dirk Lützenkirchen-Hecht (University of Wuppertal), Jochen Geck (TU Dresden), Bernd Hinrichsen (BASF), Manfred Rößle (TH Lübeck) and Max Wilke (University of Potsdam). In addition, guests representing the German photon facilities BESSY II, DELTA, KIT-Synchrotron, PETRA III, FLASH and the European facilities ESRF and the European XFEL, representatives from funding agencies, PT-DESY and further experts are members.
Do you have topics to be discussed? We are open for opinions, suggestions and questions. We look forward to the discussions during or after our talk at the DESY Photon Science Meeting, or at the KFS poster. Do not hesitate to contact us (Karin Griewatsch, kfsadmin@sni-portal.de).
References and links with further information:
[1] KFS-homepage: https://www.sni-portal.de/kfs
[2] Strategy brochure: https://www.sni-portal.de/en/files/KFS-brochure-201221-Web.pdf
[3] More information on DAPHNE4NFDI: https://www.daphne4nfdi.de/english
N. Thielemann-Kühn1, T. Amrhein1, W. Bronsch1, S. Jana2, N. Pontius2, R. Y. Engel3, P. S. Miedema3, D. Legut4, K. Carva5, U. Atxitia1, B. E. van Kuiken6, M. Teichmann6, R. E. Carley6, L. Mercadier6, A. Yaroslavtsev6,7, G. Mercurio6, L. Le Guyader6, N. Agarwal6, R. Gort6, A. Scherz6, S. Dziarzhytski3, G. Brenner3, F. Pressacco3, R. Wang3, J. Schunck3, M. Sinha3, M. Beye3, G.S. Chiuzbăian8, P. M. Oppeneer7, M. Weinelt1 and C. Schüßler-Langeheine2
1 Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
2 Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15,
12489 Berlin, Germany
3 Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
4 IT4Innovations-Czech National Supercomputing Centre, VSB - Technical University Ostrava, 17. listopadu 2172/15, 708 00 Ostrava, Czech Republic
5Charles University, Faculty of Mathematics and Physics, DCMP, Ke Karlovu 5, 12116 Prague 2, Czech Republic
6European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
7Uppsala University, Department of Physics and Astronomy, P.O. Box 516, 75120 Uppsala, Sweden 8Sorbonne Université, Laboratoire de Chimie Physique Matière et Rayonnement, 4 place Jussieu, 75252 Paris Cedex 05, France
Ultrafast magnetic response to optical excitation has been studied for many years; still, only very recently it has been appreciated that early electronic excitations may play a more important role than just being a transient step in the deposition of energy in the electron system [1,2]. An example is the optically induced spin transfer (OISTR) in 3d materials where the excited 3d electrons together with band structure effects directly lead to spin transfer processes. In the case of 4f metals, f-f electronic excitations within the 4f shell are dipole forbidden. Therefore, a variation of the 4f electronic structure was generally assumed to be negligible for the ultrafast 4f magnetic response to optical excitations. From pioneering experiments at the European XFEL [3] and FLASH where we combine time-resolved X-ray absorption and resonant inelastic X-ray scattering (RIXS), we learned that after exciting the 5d6s valence electrons in Tb metal with 800 nm laser pulses, the 4f electronic state actually can be affected on ultrashort time scales. The 4f electronic excitations are mainly driven by 5d-4f electron-electron scattering, but we also find indications of 5d-4f electron transfer contributing to the observed dynamics. The spin and orbital momenta derived from the 4f electronic state define the coupling of the magnetic system to the environment. We observe 20% of the Tb atoms with an altered orbital state, that results in a change of the magneto crystalline anisotropy. Our study gives a new dimension to the discussion about optically control of 4f magnetic dynamics, as it provides a femtosecond handle on the coupling between 4f magnetic system and environment.
[1] F. Willems et al., Optical inter-site spin transfer probed by energy and spin-resolved transient absorption spectroscopy, Nat. Commun. 11, 871 (2020).
[2] E. Golias et al., Ultrafast Optically Induced Ferromagnetic State in an Elemental Antiferromagnet Phys Rev Lett 126, 107202 (2021).
[3] N. Thielemann-Kühn et. al., Optical control of 4f orbital state in rare-earth metals, (2021) (https://arxiv.org/abs/2106.09999)
An externally seeded FEL combines the flexibility of photon energy tuning of a FEL amplifier with the control of the initial conditions of the amplification process, that are determined by the electron phase-space distribution at the entrance of the amplifier. This type of control allows the generation of light in a wide variety of pulse conditions. Some examples are the generation of multiple pulses, multiple colours, coherent control of the light properties, shaping of the pulse and some control on the pulse duration, in addition to a natural temporal synchronisation with the seed laser timing. In this communication an overview of some of the possibilities of pulse shaping and manipulation offered by external seeding will be presented.
An introduction to the European Synchrotron and FEL Users Organisation (ESUO) & User survey and questionnaire on impact of absence of Trans-National-Access (TNA) funding
Cormac McGuinness1*, Carla Bittencourt2, Federico Boscherini2, Tom Hase2, Rainer Lechner2, Derek Logan2, Bridget Murphy2, Moniek Tromp2.
1) President and 2) Executive Board Members of European Synchrotron and FEL Users Organisation (ESUO), www.esuo.eu (*Trinity College Dublin, Ireland.)
The European Synchrotron and FEL Users Organisation (ESUO) was established for the purposes of advocating on behalf of European SR and FEL users of European facilities. ESUO’s vision is to support a thriving (European) synchrotron & FEL user community with equal opportunities of access and participation for all scientists based solely on the scientific merit of their ideas.
European users have benefitted over two decades from the availability of financial support via successive Framework/ Horizon 2020 Integrating Activities programmes providing Trans-National-Access (TNA) funding in accessing SR and FEL facilities, paying travel and accommodation costs for one or more members on a beamtime. Earlier, in 2014, ESUO had been successfully in helping lobby for continuation of TNA in Horizon 2020 via a general access activity giving the CALIPSOplus programme. However, the TNA which was funded by CALIPSOplus ended with the project on 31st October 2021. At present there is no direct replacement by the European Commission in the form of a general access curiosity driven programme that would continue to provide TNA to all researchers from across Europe no matter the topic.
ESUO has initiated a user survey on the possible impacts of the absence of Trans-National-Access (TNA) funding for the user community. This can be completed by going to the following link: https://www.esuo.eu/possible-impacts-of-the-absence-of-transnational-access-funding-support-for-the-user-community/
All researchers, young and old, whether Master or PhD students, postdoctoral researchers, academic staff, group leaders or professors are encouraged to complete the survey and to circulate it. Using the survey results, ESUO will continue to advocate to the European Commission, in cooperation with LEAPS facilities, for TNA funding for all science topics and all scientists.
ESUO first established in 2010, in 2021 has become an International non-profit organisation, and is composed of national delegates from all European nations and their National User Organisations (NUOs) and/or Facility User Organisations (FUOs).
PETRA III is a 6 GeV synchrotron radiation source and delivers X-ray beams from 100eV to 200keV with very high brightness and small emittance. 25 beamlines with specialized experiments are accepting beamtime proposals from the international user community. Despite of the Corona pandemic in 2021, reliable operation with on-site users has been achieved and users published their results in high impact journals.
Additionally, mail-in and remote access has been successfully introduced at many beamlines for off-site users. The planning, construction and commissioning of new PETRA III beamlines proceeds as planned. With the start of the user operation at the beamlines P62 for small angle scattering and P66 for luminescent spectroscopy the PETRA III extension project has been completed.
The key to fabricating complex, hierarchical materials is the control of chemical reactions at various length scales. To this end, the classical model of nucleation and growth fails to provide sufficient information. Here, we illustrate how a combination of in situ X-ray spectroscopic, scattering and microscopic studies bridge the molecular- and macro- length scales. Moreover, we will present how synchrotron methods, far from merely providing new tools, are extending the ways we study, understand and design such complex structures. It gives complementary information about chemical reaction in solution and nucleation, growth and crystal phase transition of nanoparticles and their functionality in devices. [1-4] Finally, we will discuss the advantages and the pitfalls of the synchrotron methods for in situ and operando studies.
News from the DESY Photon Science User Committee
The DESY Photon Science User Committee (DPS-UC) is a direct link between the users and the DESY Photon Science management to assist the communication and the exchange of information. New DPS-UC members will be nominated and elected by all users for a term of 3 years.
The User committee will take note of the needs and concerns of individual users and/or groups regarding daily affairs of on-site work during beamtimes, operating procedures, general user support and other related topics. The committee will discuss these issues and propose appropriate actions to the management. All information is regarded as confidential unless otherwise agreed.
If you have any questions or suggestions for improvement of the DESY facilities, please contact us, the chair or any other member of the DPS-UC, directly: https://photon-science.desy.de/about_us/committees/dps_uc/members/index_eng.html
RNA-based nanomedicines have proven to be a promising new class of drugs, with their broad field of potential applications ranging from protein substitution, over tumour immunotherapy, up to the recent success of being the first approved Covid-19 vaccines. The basic concept for all mRNA drugs is to deliver protein-encoding mRNA, like tumour or virus antigens, into target cells in order to be transfected into the protein and for example induce antitumoral responses. To make intravenous application of mRNA possible, formulations are required that protect the mRNA from degradation through the ubiquitous nucleases, deliver it to the target site and promote cellular uptake and translation. Non-viral lipid-based delivery vehicles have demonstrated to be suitable for this purpose.
Abstract see above (Talk - Part 1)
Phase-contrast X-ray imaging uses the refraction of X-rays to generate the contrast. It has been demonstrated to provide superior soft-tissue contrast in comparison to conventional attenuation-based X-ray imaging. However, quantitative imaging of biomedical soft tissue at high spatial resolution and high image quality still remains challenging. Some existing methods require assumptions on the composition of the specimen (e.g., single material and low attenuation) to retrieve the phase information and show less sensitivity in resolving small changes in electron density within the sample. Specimens violating these assumptions become impossible to image. Within a long-term proposal at the imaging beamline P05, we successfully designed and built an imaging setup based on 2D Talbot array illuminators (TAI) (Gustschin et al., 2021) and a speckle-tracking technique (Unified Modulated Pattern Analysis, UMPA) (Zdora et al., 2017), which overcomes these challenges. Our method accurately extracts the electron density distribution with higher sensitivity than comparable techniques and is compatible with a wide energy range. Here, we will review the potential of this new quantitative imaging method by highlighting the recent results on biomedical applications.
Gustschin, A., Riedel, M., Riedel, M., Taphorn, K., Petrich, C., Gottwald, W., Noichl, W., Busse, M., Francis, S. E., Beckmann, F., Hammel, J. U., Moosmann, J., Thibault, P., & Herzen, J. (2021). High-resolution and sensitivity bi-directional x-ray phase contrast imaging using 2D Talbot array illuminators. Optica, Vol. 8, Issue 12, Pp. 1588-1595, 8(12), 1588–1595. https://doi.org/10.1364/OPTICA.441004
Zdora, M. C., Thibault, P., Zhou, T., Koch, F. J., Romell, J., Sala, S., Last, A., Rau, C., & Zanette, I. (2017). X-ray Phase-Contrast Imaging and Metrology through Unified Modulated Pattern Analysis. Physical Review Letters, 118(20), 203903. https://doi.org/10.1103/PhysRevLett.118.203903
P. Müller-Buschbaum
Technische Universität München, Physik-Department, Lehrstuhl für Funktionelle Materialien, James-Franck-Str. 1, 85748 Garching, Germany (E-mail: muellerb@ph.tum.de)
The first application of hybrid organo-metal halide perovskites as sensitizer in hybrid solar cells marked the cornerstone for what has now become a broad field of extensive research. After overcoming initial challenges, power conversion efficiencies (PCE) of hybrid perovskite photovoltaics strongly increased to above the 25 % mark and now outperform many conventional inorganic thin film technologies for solar cell fabrication. The easy and versatile processing towards an improved stability and reproducibility further increases the massive interest in this type of material. The abundance of precursor materials in combination with the wet chemical processing are rendering hybrid organo-metal halide perovskites as candidates for a low-cost, mass-producition photovoltaic technology. Moreover, perovskite solar cells are lightweight, show mechanical flexibility, are well working at diffuse light conditions and proof to be suited for an in-door use.
Extensive studies have focused on improving the operational stability of perovskite solar cells, but few have surveyed the fundamental degradation mechanisms. One aspect overlooked in earlier works is the effect of the atmosphere on device performance during operation. Here we investigate the degradation mechanisms of perovskite solar cells operated under vacuum and under a nitrogen atmosphere using synchrotron radiation-based operando grazing-incidence X-ray scattering methods. [1]
[1] R.Guo, D.Han, W.Chen, L.Dai, K.Ji, Q.Xiong, S.Li, L.K.Reb, M.A.Scheel, S.Pratap, N.Li, S.Yin, T.Xiao, S.Liang, A.L.Oechsle, C.L.Weindl, M.Schwartzkopf, H.Ebert, P.Gao, K.Wang, M.Yuan, N.C.Greenham, S.D.Stranks, S.V.Roth, R.H.Friend, P.Müller-Buschbaum
Degradation mechanisms of perovskite solar cells under vacuum and one atmosphere of nitrogen
Nature Energy 6, 977-986 (2021)