84 85 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 1 / 2 2 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 1 / 2 2 Spectroscopy Group Sofia Díaz-Moreno, Science Group Leader T he Diamond Spectroscopy Group consists of four beamlines; the Microfocus Spectroscopy beamline (I18), the Core EXAFS beamline (B18), and the two independently operating branches of the Versatile X-ray Absorption Spectroscopy beamline, I20-Scanning and I20- EDE. These spectrometers are highly complementary, most notably in the energy ranges they cover, the size of their focussed beam spots, and the time resolutions they are able to reach. This complementarity means that they can support research across many different scientific disciplines, from chemistry and catalysis throughmaterials science, condensedmatter physics, environmental and life science, and cultural heritage. Two new flagship beamlines will be added to the portfolio of instruments of the Spectroscopy Group as part of the Diamond-II programme. SWIFT (Spectroscopy WithIn Fast Timescales) is a high flux beamline optimised for the study of samples under operando conditions, and with the added potential to investigate sample heterogeneities at the 20 μm length scale. The design of the beamline is progressing very well. The conceptual design review took place successfully in December 2021, and we are now preparing the technical design review. BERRIES (Bright Environment for X-ray Raman, Resonance Inelastic and Emission Spectroscopies), that will be built as part of phase-II of the upgrade programme, will be offering two new techniques to the Diamond user community: pink-beam X-ray Emission Spectroscopy (pink-XES) and X-ray Raman Scattering (XRS). Last year has seen the return to normal operations for the spectroscopy beamlines, with most of the experiments performed with users on-site, although with limited numbers. This has been challenging at times, especially for those experiments that require permanent on-site supervision. Maintaining the momentum acquired during operations in 2020, efforts have continued towards enhancing the level of automation on the beamlines. Aside of supporting the user programme, many technical developments and improvements have also been realised on the beamlines over the last year. New detectors procured for B18 and I20-EDE have enhanced the capabilities of the beamlines to collect complementary XRD data. The photon-in/photon- out capabilities of the group will significantly expand with the on-going development of the emission spectrometers for I20-Scanning and I18. This year has also seen the integration of the IR-DRIFTS instrument into B18 and I20- EDE, to complement the time-resolved X-ray Absorption Spectroscopy (XAS) measurements performed on these instruments. I18 update The Microfocus Spectroscopy Beamline, I18, uses a focussed beam, variable between 2 µmto 50 µm in size, to study heterogeneous sampleswith a variety of experimental techniques such as X-ray Fluorescence (XRF) and X-ray Diffraction (XRD) imaging, micro X-ray Absorption Spectroscopy (microXAS), and XRF and XRD micro-tomography (microCT). A new in-house designed double-crystal monochromator (DCM) was installed and commissioned last year. The monochromator has not only improved significantly the positional stability of the micron-size beam at the sample position, but the additional Si(311) crystal set will enable the collection of spectroscopy datawith enhanced energy resolution.We are currentlyworking towards implementing continuous scanning with the new monochromator, enabling fast XAS measurements that will reduce damage in sensitive samples caused by the X-ray beam. The monochromator has been designed so it will be compatible with operations after the Diamond-II upgrade, including the extension of the operational energy range of the beamline to 27 keV, that will be achieved by using the additional crystal set. Another major beamline upgrade has been the installation of the new motorised sample motion stages, allowing faster and reliable operations. The high speeds that the new sample stages can operate at (up to 5 mm/sec) together with the increased translation ranges enable scanning large sample areas very quickly. The throughput of the beamline is significantly increased when combined with the XRF and XRD detector data collection rates of up to 1kHz and up to 200 Hz, respectively. This is especially relevant for time- consuming measurements such as tomography and XANES mapping. In the upcoming year, the capabilities of the beamline will be enhanced by the addition of a new X-ray emission spectrometer based on a 0.5m diameter Rowland circle, that operates in the Johann configuration in the vertical plane. This instrument will expand the photon-in/photon-out capabilities of the group towards the tender energy regime, and the small focal spot of the beamline will enable spatially resolved measurements B18 update The Core EXAFS beamline, B18, is optimised for the efficient collection of XAS data over all elements heavier than phosphorous. The focussing optics and the capability of the monochromator for continuous scanning, together with a flexible experimental space that supports a large range of sample environment equipment, make this beamline ideal for experiments that are performed under in situ and operando conditions During the last year, efforts at B18 have been focussed on enhancing automation of the beamline. A 6-axis compact industrial robot is now fully integrated into the beamline data acquisition system. The robot is able to handle more than 300 samples and has a small footprint, so it does not interfere with the diverse sample environments available on the beamline. Another important step towards automationhas been themotorisationof thefluorescencedetector, that will enable measuring samples in fluorescence detection mode with different concentrations without the need of manual intervention. In parallel, work has been done to support the increased rate of data collection, improving data analysis automation. A system of automatic experimental logs, including scan parameters, averaging of multiple repetitions, and data processing using larch and jupyter notebooks is being implemented and will soon be accessible on a dedicated webpage. The monochromator crystal cage based on direct water cooling has been successfully replaced last December. The new cage, where the crystals are indirectly cooled, will enhance the reliability of the device, avoiding the need for regular interventions to change the failing water seals. The new crystal cage has been operating since January, showing solid performance in terms of thermal stability and energy resolution. A new Pilatus 300KW detector has been procured for acquisition of X-ray diffraction/scattering data. The newdetector will replace theMythenmicrostrip, offering an improved signal to noise ratio and wider sensor area. The capability of faster readout, with further integration, will also enable collection of XRD images while continuously scanning the monochromator in the future, introducing the possibility to perform DAFS experiments. I20-Scanning update The Scanning branch of I20, I20-Scanning, exploits the high flux provided by the wiggler source through two different end-stations. The XAS end-station is optimised to examine the structure of very low concentration samples. The X-ray Emission Spectroscopy (XES) end-station is dedicated to the performance of high-energy resolution studies of the electronic structure of samples. The year has been a busy one with the beamline fully scheduled, mainly with users doing their experiments in person but with only limited numbers allowed per experiment. We also conducted several remote experiments, particularly for users from overseas who found it difficult to travel to the UK. The project to replace the current 3 analyser crystal emission spectrometer with a 14-crystal instrument has moved from the design phase to the build phase late in 2021. The 14 multi-axis stages that will move the analyser crystals have been built and work is continuing on the rest of the assembly before a programme of motion and software testing begins in late spring 2022. This new instrument will enable faster data collection times and substantially reduce the concentration of samples that can be studied. The instrument is due to be installed in the experimental hutch at the end of 2022. In order to reach higher energies on I20-Scanning, an innovative new first crystal has been designed for the four-bounce monochromator. The design aims to minimise any distortion in the crystal surface when the high-power X-ray beam produced by the wiggler source hits the surface. This crystal has now been procured and will be thermally tested in spring 2022 to determine if the expected performance matches the calculations. I20-EDE update The Energy Dispersive EXAFS (EDE) branch of I20 uses a polychromator to perform XAS experiments in a dispersive geometry. It is designed for in situ and operando studies with time resolutions ranging from seconds down to milliseconds or even microseconds. Due to the nature of the research programme, remote experiments are not possible on I20-EDE but, with the return of users on-site, the regular experimental programme has been restarted. During the last year, a Mar345 imaging plate detector has been repurposed from the crystallography group and integrated into the beamline, allowing the collection of complementary XRD data. This is particularly useful for the high- pressure users of the beamline, but will also be useful for thematerials scientists looking at material developments such as metal-organic framework synthesis. Community support and development Aside of supporting the beamlines and the operational science programmes, the Spectroscopy Group has continued its effort to support the development of the spectroscopy user community. The annual three-day X-ray Absorption Spectroscopy workshop was run remotely for the first time in June 2021, due to the restrictions imposed by the COVID pandemic. As was the case in previous years, the workshop was in high demand, with more than 180 applications, although required staff to student ratios limited the successful applications to 36 participants. Although the hands- on sessions were not as productive as when the workshop takes place in person, the feedback received was very positive. Diamond, through the Spectroscopy Group, together with the University of Newcastle, are the principal partners of the COllaborative NEtwork for X-ray Spectroscopy (CONEXS), an Engineering and Physical Sciences Research Council (EPSRC) funded network that aims to bring together experimentalists and theoreticians who are working in the area of X-ray spectroscopy. The network aims to improve members’ abilities to fully exploit and interpret experimental data. As part of the activities of the network, the third Summer School was organised in the last week of March 2022, immediately before the third international conference. Both events were run at Newcastle University, and they were very well attended. The network also runs monthly webinars where international speakers give an overview of the fundamentals of X-ray spectroscopy from the experimental and theoretical points of view. The webinars have proven to be very popular, with more than 1,000 visits to our YouTube channel. To increase the group’s capabilities on advanced data analysis, Joshua Elliott, an expert in ab-initio modelling, has joined the Spectroscopy Group this year. This will help us better support the spectroscopy users with the interpretation of their data. Joshua Elliott - Post doctoral research associate (Spectroscopy Computational Scientist). Diego Gianolio - Principal Beamline Scientist at B18. Two newflagship beamlines will be added to the portfolio of instruments of the Spectroscopy Group as part of the Diamond-II programme.