Diamond Light Source - Annual Review 2022/23

56 57 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 2 / 2 3 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 2 / 2 3 Spectroscopy Group Sofia Diaz-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 four spectrometers are complementary in the energy ranges they cover, the size of their focussed beam spots delivered to the sample, 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 through materials science, condensed matter physics, environmental and life science, energy materials and cultural heritage. Many technical developments that enhance the capabilities of the group for in situ and operando experiments have been implemented on the spectroscopy beamlines over the past year. Some of the efforts have been focussed on upgrading the infrastructure of the beamlines. A Local Exhaust Ventilation (LEV) system has been recently installed on I18 to enable experiments with toxic and/or flammable gases, while the existing B18 LEV system has been upgraded, to remove the limitations that the previous system imposed on the sample environment that could be used. In addition, permanent gas monitors for the most commonly used toxic and flammable gases have been added to B18, linking them to the beamline alarm panel to increase the safety for associated experiments. A new sample environment has also been deployed on the beamlines. A new capillary reactor to perform gas experiments at high pressure, up to 20 bars, has been recently used for a user experiment on B18, and this system is now available for the other beamlines in the group. In addition, an OctoBoost16000 booster has been procured for the IVIUMOctoStats potentiostat, increasing the maximum current achievable from 1 A up to 128 A. This will enable the study of electrochemical systems at current densities comparable to the optimised cell designs used in practical applications. I18 update The Microfocus Spectroscopy Beamline, I18, uses a finely focussed beam down to 2 µm in size to investigate heterogeneous samples with a variety of experimental X-ray techniques, such as Fluorescence (XRF) and Diffraction (XRD) imaging, micro Absorption Spectroscopy (µXAS), and XRF and XRDmicro- tomography (µCT). In the past few years, improvements in the beamline hardware have allowed a significant speed-up in data collection, which is particularly beneficial for techniques that required long measurement times such as µCT-XRF and µCT-XRD. To keep up with these developments, this year has seen significant efforts invested in optimising the automatic data reduction and processing routines, so that processed XRF and XRD maps can now be shown on the fly, while tomography measurements are displayed only seconds after the scan is finished. Transmission imaging capabilities have also been added to the plethora of techniques available in I18. This has been possible by the procurement of a new 5 Megapixel sCMOS 2D imaging camera that can record images at rates of up to 100 frames per second. The design of the new in-house X-ray emission spectrometer is completed, and the procurement is now underway. Unfortunately delays with the delivery of some of the components have had an impact on the commissioning and installation schedules, but it is expected that the instrument will be available for the user community early next year. 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 to perform experiments under in situ and operando conditions. Last year has seen a development in the fluorescence detection capabilities of the beamline. A new seven-element silicon drift detector has been procured to replace the four-element detector. The larger solid angle covered by the new detector, together with its faster pre-amplifiers, will reduce the collection time required to obtain the desired signal to noise ratios. In addition, a new Odin- based data acquisition software system has been developed for the 36-element Ge detector, allowing the XSPRESS-4 digital pulse processor readout system to be used to its full potential up to a data rate of 1 kHz. To facilitate experiments done in fluorescence detection mode, both fluorescence detectors have been motorised so that the sample to detector distance can now be optimised remotely, increasing the efficiency of beamtime usage. To enhance the capabilities of the beamline in the tender X-ray regime, effort has been devoted to the development of new sample environment. A transfer system has been designed so air sensitive samples can be loaded directly from the glove box into the tender X-ray chamber. In addition, a new sample stick for the tender X-ray chamber has been integrated, allowing measurements of multiple samples down to 77 K. To help users in the process of data acquisition and live analysis, an ISPyB webpage has been deployed for real time data reduction. Implementation of real time data analysis is in progress, including averaging of multiple repetitions and automatic outlier rejection. I20-Scanning update On I20-scanning, the high flux provided by the wiggler source is used in two end-stations. The X-ray emission end-station has been designed to perform high-energy-resolution fluorescence detection XAS (HERFD-XAS) and resonant and non-resonant X-ray emission spectroscopy (RXES and XES) studies, looking at the electronic state of materials. The XAS end-station is optimized for studying the structure of low concentration samples. In October last year, the three-analyser crystal spectrometer used at the XES end-station was replaced by a fourteen-analyser crystal instrument (Figure 1). The beamline re-opened to users in January 2023, so several XAS experiments wereperformedwhile extensive cablingand commissioningof the spectrometer continued. The with-beam spectrometer commissioning took place last month, and HERFD-XAS, RXES and XES data were taken from reference samples. While the energy resolution achieved by the spectrometer is comparable to that of the old spectrometer, the intensity of the radiation collected is significantly higher. This will enable the study of more dilute systems, especially for experiments using Kβ emission lines, that are approximately one order of magnitude weaker than the Kα lines. The first user of the new spectrometer is scheduled for April 2023. A project to develop a new four-bouncemonochromator has begun; this will use liquid nitrogen direct cooling of the first crystal tomaintain thermal stability and for the first time enable the beamline to utilise a Si(311) monochromator, reaching energies above 20 keV. The project will be undertaken in-house, capitalising on Diamond’s expertise in building monochromators. I20-EDE final 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. EDE experiments are very specialisedand, due to theuniquedispersive setup, the sample quality requirements aremuchmore stringent than for conventional XAS beamlines, as changes in background can compromise the normalisation procedure. This has meant that the I20-EDE branchline largely remained the tool of choice for research in a select number of scientific areas. A decision has been taken to close the I20-EDE beamline in April 2023 (Figure 2), so Diamond’s limited resources can be deployed towards areas that are more in tune with user demand and anticipating the arrival of SWIFT in a few years (see below). The dedicated beamline team worked hard to maximise the beamline’s output until the end of operations and there were thirteen experimental sessions in the final allocation period. In particular, the provision of an XRD detector on the beamline proved popular with users, giving them the possibility to interrogate their samples using two techniques simultaneously. SWIFT update The fast-scanning capabilities of the I20-EDE beamline will be covered by the new spectroscopy beamline that will be built as part of the Diamond-II upgrade programme. The new beamline, called SWIFT (Spectroscopy WithIn Fast Timescales) will be a wiggler-based, quick-scanning EXAFS beamline dedicated to operando studies, also at micrometric scale. SWIFT will become operational on Diamond-II immediately after the dark period that is currently expected to last for 18 months from December 2026. SWIFT’s design is progressing well. The layout, optics and specifications of the beamline are now defined, including the functionalities of the acquisition, controls and analysis software which will be based on the new Diamond-II stack. A preliminary engineering analysis of the Quick-EXAFS monochromator design has already been performed and the project is showing great promise. Community Support and Development As part of our on-going role to support the development of the spectroscopy user community, the Spectroscopy Group organized the annual three-day X-ray Absorption Spectroscopy workshop in June 2022. After running the workshop remotely the previous year, we were able to run it in-person, as one of the first on-site meetings organised at Diamond after the COVID pandemic. As in previous years, the workshop was in high demand, with more than 150 applications, although required staff to student ratios limited the successful applications to 32 participants. On this occasion, as well as a brief introduction to the spectroscopy beamlines at Diamond and the methods to process and analyse spectroscopy data, the workshop included a brief introduction to XANES modelling using DFT approaches. The group is also invested in expanding further the capabilities for advance spectroscopy data analysis. With this aim, Diamond, though the Spectroscopy Group, is involved on the UK High-End Computing Consortium for X-ray Spectroscopy (HPC-CONEXS), an Engineering and Physical Sciences Research Council (EPSRC) funded High End Computing Consortium that will take the lead in the development and distribution of computational tools to advance the detailed analysis of experimental spectroscopy data. This consortium is an evolution of the very successful COllaborative NEtwork for X-ray Spectroscopy (CONEXS) project, started three years ago and is coming to an end at the end of April 2023. Many technical developments that enhance the capabilities of the group for in situ and operando experiments have been implemented on the spectroscopy beamlines over the past year. Figure 1. Science and engineering teamwho delivered the new I20 14-crystal spectrometer. Figure 2. Diamond staff who designed, delivered and operated I20-EDE over its 10 year life-cycle.