Diamond Annual Review 2020/21

92 93 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 0 / 2 1 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 0 / 2 1 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 (Extended X-ray Absorption Fine Structure) beamline, B18, and the two independently operating branches of the Versatile X-ray Absorption Spectroscopy beamline, I20-Scanning and I20-EDE (Energy Dispersive EXAFS). These four spectrometers are complementary in the energy ranges they cover,thesizeoftheirfocussedbeamspotsdeliveredtothesample,andthetimeresolutionstheyareabletoreach.Thiscomplementaritymeans that they can support research across many different scientific disciplines, from chemistry and catalysis through materials science, condensed matter physics, environmental and life science, energymaterials and cultural heritage. During last year, the activities of the Spectroscopy Group have been heavily impacted by the restrictions imposed by the COVID-19 pandemic, affecting both operations and technical developments. Thanks to the effort invested by the beamline staff, we have continued to support the spectroscopy user community and as far as possible, maintain its research programmes. Several initiatives have been dedicated to enhancing the capabilities of the beamlines in the group to perform remote experiments, and to mitigate the challenges of operating under the COVID-19 restrictions, some of which are described below. Besides maintaining the user programme on the beamlines, several technical developments and improvements have also been realised during the last year. At B18, the replacement of the 4-element silicon drift detector for a 7-element instrument with faster pre-amplifiers is underway and will significantly increase thethroughputoverthetenderenergyregime.Theprocurementofamultichannel potentiostat for I20-EDE will enable fast electrochemical measurements. An IR-DRIFTS instrument that will be integrated into B18 and I20-EDE, has been procured to complement the time-resolved X-ray Absorption Spectroscopy (XAS) measurements performed on these instruments. I18 update The Microfocus Spectroscopy beamline, I18, uses a finely focused X-ray beam to study heterogeneous material on the micrometre scale using a variety of techniques, such as X-Ray Fluorescence (XRF) mapping, XAS, X-ray Diffraction (XRD), and fluorescence and diffraction ComputedTomography (CT). Several changes in the I18 experimental setup have been implemented over the last year to allow remote experiments, as well as to maximise the data collection efficiency. The need for human intervention for sample changing was reduced by the design of a new holder able to hold many samples. Using motion stages that were already available at the beamline, a sample carousel solutionwas implemented. The sample carousel allows uninterrupted data collection from 12 hoursuptoseveraldays,dependingontheexperimentalrequirements,andcanbe controlledremotely.Thebeamlinedataacquisitionsoftwarehasalsobeenupdated and user-friendly scripting capabilities are now available, so data collection sequences can be programmed. A similar multiple sample carousel compatible with the cryojet is being designed, to allow low temperature measurements for beam-sensitive samples. All these developments have allowed I18 to run 27 remote experiments and one industrial session. Significant effort has also been dedicated to improving the automated post-processing of the collected experimental data. Reconstructed computed tomography and reduced X-ray diffraction data can now be viewed within minutes of the end of a data collection, without the need of staff input.The current automated post-processing system also allows the use of custom user Python scripts. Beside the described efforts dedicated to ease remote operations of the beamline, other developments have been carried out. A newmonochromator that will improve the position stability of the microfocus beam has been procured.The monochromator has been designed in-house and the assembly is well advanced. This new instrument is expected to be installed on the beamline and ready for user operations after the summer. B18 update The Core EXAFS (Extended X-ray Absorption Fine Structure) beamline, B18, is characterised by a wide energy range, a focused beam and a continuous scanning monochromator. The availability of a flexible experimental space combined with a large range of sample environment equipment make this beamline ideal to performexperiments under real conditions of operation. Last year significant efforts were dedicated to enhancing the capabilities of B18 to perform remote experiments with the minimum of human interaction. Although the B18 long-term strategy included the increased use of automation, this development has been accelerated by the need to address the challenges posed by the pandemic. For example, a multiple-sample motorised cryostat has been commissioned, enabling low temperature remote experiments. In addition, a 6-axis compact industrial robot has been procured, and it is in an advanced stage of software integration. This system will give additional flexibility in automated positioningandorientingchallengingsamples.Inparallel,the interfacetothedata acquisition has been improved so that a large number of samples can be handled. Experimentalprogrammetableswithbasic informationregardingsample location and required absorption edges can be prepared in advance and can be directly imported into an automatic series of scans. In the meanwhile, and to ensure that B18 continued to support the spectroscopy user community during the last year, a series of additional developments have been carried out. Soon after experiments with remote users were approved, a system able to measure up to 200 pellets was designed. The system comprises a 3D printed sample holder and a large manipulator system that was put together using available motorised stages. This setup has been used to run intense experimental sessions during the Catalysis Hub and Energy BAG (Beamtime Allocation Group) visits. A further complementary development to enhance automation on the beamline has been the construction of a motorised gantry and cassette system that offers improved flexibility in sample positioning. The system holds up to 36 sample frames of nine pellets and has nowbeen integrated into the beamline.The cassette systemwill also be usedwith the advanced robot system in the future. These developments have enabled B18 to host 40 experimental sessions in remote access mode, including five industrial beamtimes. I20-Scanning update The Scanning branch of I20 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. Last year has seen a rapid adaptation of the beamline to undertake remote experiments on samples that did not require extensive on-site preparation. Sample plates have been made for both the XAS and XES end stations, that allow up to nine room temperature samples to be mounted for measurement without manual intervention. The first remote experiment with users from Germany was performed at the end of June 2020. Since then, 23 remote experiment sessions have run, including the first industry session using XES, and one supporting a user group based in Australia. Besidesmaintaining operations, a project to replace the current three analyser crystal spectrometer with a 14-crystal spectrometer has been approved, and the new spectrometer is in the design phase. This new instrument will enable faster data collection times and substantially reduce the concentration of samples that can be studied, which is particularly relevant for weak emission lines. The spectrometer has been designed so a two ‘colour’ running mode will also be available, where half of the analyser crystals will measure at one emission line while the other half is aligned to collect a different energy.This should enable two different emission spectra to be taken simultaneously as well as facilitate rapid switching for high energy resolution data collection fromdifferent edges. As part of the process to build a new four-bounce monochromator for the beamline, a liquid nitrogen direct cooled first monochromator crystal has been tested. This technology will be key for the new instrument to ensure that the beamline can operate at high energies. The design of the new monochromator will start in the summer of 2021. 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 studieswithtimeresolutionsrangingfromsecondsdowntomilliseconds or even microseconds.The very nature of these studies imposes the need for users to be on-site to prepare the samples and control the operating conditions of their systems. Furthermore, an additional constraint is that toxic/explosive gases are frequently required, which means experiments cannot be safely run by a lone worker. Remote experiments under pandemic operating conditions were thus deemed infeasible at the beamline.When the operating restrictions were partially lifted in October 2020 the beamlinemanaged to run one user experiment. Several developments started last year to improve the quality of the data collected by the beamline, but unfortunately progress has been seriously hindered by the pandemic. A 12-week programme to replace the beamline harmonic rejectionmirrors was initiated inMarch 2020, but when the restrictions for working on-sitewereput inplaceasaresponsetothepandemic,theworkhadtobestopped as the mirror replacement needed the support of a large group of people. At that time,itwasdecidedtoreversetheworkthathadalreadybeenstarted.Thisreversion could not be completed before lockdown restrictions kicked in, and it took until early August 2020 to get the system returned to the original state. Unfortunately, it will not be possible to replace the mirrors until social distancing requirements are substantially relaxed. More positively, progress has been achieved on the development of a sample spinning system so that samples in a tube furnace can be spun in the beam path to present a more homogeneous sample to the beam. The systemwas commissioned and optimised during last year. Community support and development As part of our ongoing role to support the development of the spectroscopy user community, the Spectroscopy Group organised the annual three-day X-ray Absorption Spectroscopy (XAS) workshop in March 2020.The workshop covered a brief introduction to the spectroscopy beamlines at Diamond, as well as methods to process and analyse spectroscopy data. As was the case in previous years, the workshop was in high demand, withmore than 150 applications, although venue limitations and required staff to student ratios limited the successful applications to 30 participants. This year, the workshop will be held in June, and will be run remotely for the first time. 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 areworking 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, a Summer School and an International conference were organised. The Summer School was originally scheduled to take place in September 2020, but it had to be postponed to March 2021, when it was run just before the International Conference. Both events were run remotely, and theywereverywellattended.Morethan90applicantsregisteredfortheworkshop and over 190 for the conference. The network also runs monthly webinars where international speakers give an overviewof the fundamentals of X-ray spectroscopy fromthe experimental and theoretical points of view.Thewebinars have proven to be very popular over the pandemic year. As part of the Diamond-II (proposed upgrade programme) activities, the Spectroscopy Group organised a series of webinars from September to November 2020 to discuss with the user community the two flagship beamline projects that were presented in late 2020 to the Diamond Scientific Advisory Committee (SAC) and the Diamond Industrial Science Committee (DISCo) for prioritisation. The webinars for each project attracted a large number of participants and served to gather information from the community that helped shape the proposals. The sample spinning system on I20-EDE. Attendees of the XAS workshop at Diamond in March 2020.