Spectroscopy Village

A key development for the Spectroscopy Village has been the Mapping and the Stepper and Piezo Motor Scanning projects, which have focused on improving the data acquisition hardware and software for users at the village.

The mapping project is concerned with improving and unifying the mapping processes across beamlines. The initial rollout of a preliminary version of the project is planned for June 2016 on I18, followed by I08 then I14. Near full implementation on I18 is expected in December 2016. It has also been tested on I05 in the Surfaces and Interfaces Village, and will be deployed on I13 in the Materials Village when ready. The mapping project aims to provide a framework that is flexible and can be used to provide a consistent interface and lower level implementation across as many beamlines as possible. It is anticipated that every beamline at Diamond has the potential to benefit from this work.

Originally considered as part of the mapping project, the scanning project is specifically engaged with upgrading the I08-SXM controls hardware. This complex task will allow integration into the mapping project and ensure the hardware is compatible with that of the other beamlines. The Stepper and Piezo Motor Scanning project addresses interferometric control of scans with combined coarse (stepper motors) and fine (piezo) scans with a multi-detector geometry that are specific to I08 as well as I14.

Together, these two projects provide an improved user interface for scanning probe beamlines, and have led to higher efficiency and faster speeds. Both software and hardware have been upgraded to simplify data use and analysis for new users. Across the affected beamlines data is now portrayed in a more user-friendly way and users are offered a more flexible and wider range of scans.

Construction of new beamlines

With two of the six beamlines in the village currently under construction significant progress has been made over the last year to bring these beamlines closer to operational use. Both the Hard X-ray Nanoprobe beamline (I14) and the Inelastic Soft X-ray Scattering beamline (I21) achieved first light over the last year with further commissioning due in 2016.

Figure 1: Silvia da Graça Ramos, Software Engineer in the Data Acquisition group at Diamond, on beamline I08.

The 185 m long beamline of I14 will run via a vacuum pipe from an internal building, housing the optics hutches, to an external building accommodating the experimental end station. In April 2015 the beamline achieved first light in the optics hutch and over the next four months installation of the monochromator and mirrors was finalised. This included extensive offline testing to characterise parasitic motions and performance and to minimise vibrations in the mechanisms. This led to the development of a gravity fed cooling system for the mirror in order to minimise vibrations. A new cryocooler with integrated liquid nitrogen top up was also installed to improve the stability of the monochromator. From October 2015, the optics hutch mirrors and monochromator were commissioned down to a 5 mm undulator gap and performance was demonstrated across the 4.5 to 26 keV energy range. The beamline team is now working to optimise performance. 

Building work for the internal and external buildings of I14 was completed in February 2016, followed by the construction of the vacuum pipe in March 2016. Four months of fitting out the offices and labs with the necessary equipment are now scheduled, with installation of the beamline due to take place between June and September 2016. It is expected that first light to the external building will take place by early September 2016.

I21 has made significant progress over the last 14 months. The installation of the internal beamline started from April 2015 including the plane grating monochromator, mirror mechanics and slits as key beamline components. The measured vibrational stability of the monochromator is in the order of 30 - 50 nrads which provides the foundation for achieving ultra-high energy resolving power. First light was achieved in December 2015, two months ahead of the original milestone. Significant design and manufacturing progress has been made on the end station and RIXS spectrometer including optics, the sample vessel, the grating mechanics, and the detector assembly. All in vacuum mechanics in the sample vessel were delivered in 2015 with the sample vessel and grating mechanics delivered in March 2016. The grating mechanics has demonstrated a vibrational stability of 10 – 20 nrads, which is key to the final energy resolving power.

Having taken over the completion of the I21 building, Diamond was able to successfully deliver and install 32 tonnes of granite floor in February 2016. The design for the remainder of the spectrometer will soon be completed. This year will see staged X-ray commissioning from the internal beamline towards the exit slit in spring, the sample vessel by autumn. Final X-ray commissioning in the grating and detector assembly is expected by January 2017.

Additional village upgrades

Along with these major developments for the village as a whole, a number of beamlines have reported updates to their instrumentation, sample environments and experimental capabilities.

Figure 2: The I20 beamline team.

Most of the time and effort invested in the scanning branch of I20 during the last year has been directed towards solving the instability problems encountered in the performance of the monochromator. In order to achieve this, a complete change of the control electronic chain has been implemented, using new components from different manufacturers, some never used before at Diamond. In addition, the whole electrical installation of the monochromator was modified. The final tests of the beamline performance were successfully completed during the last run of 2015 and subsequently the decision to restart the user programme with a restricted energy range (up to 20 keV) was taken. In order to extend the energy range to 34 keV, a new monochromator will be procured for the beamline. This development project has already started.

 
Figure 3: Beamline I21 external building under construction.

The main developments made on the dispersive branch of I20 have been directed at improving and optimising the performance of the beamline. A new gravity compensation mechanism for the first vertical focussing mirror of the beamline has been designed and is currently being tested. This is hoped to deliver an improved beam focus at the sample position. A Si(311) polychromator crystal that increases the energy range covered by the beamline to 26 keV has also been commissioned. Significant effort has been invested in the integration of the FReLoN detector into the beamline data acquisition, while the commissioning of the faster germanium micro-strip detector with the X-ray beam took place in April 2016. The coming year will see the development of a turbo-XAS system to allow fluorescence measurements to be performed on the dispersive branch.

Last year Diamond saw the first soft X-ray diffraction (ptychography) measurements carried out at the Scanning X-ray Microscopy beamline (I08) in preparation for the technique to be opened up to all users in 2017. Soft X-ray ptychography can provide optical resolution in the region of sub-10 nm, a scale that is of particular interest to biology-related applications among others. The technique has the ability to extend its use from absorption to phase spectroscopy, opening up an entirely new scientific field with unknown potential. A second branchline and end station is being considered to support these studies at I08.

Over the last year the adoption of a 36-element Ge fluorescent detector has had an impact on the efficiency of experiments at the Core XAS beamline (B18), leading to an increased throughput for dilute systems. Several in situ experiments were run with user-developed systems. The use of a SPACI-MS experimental system, from Queen’s University Belfast, has also allowed time and spatially resolved investigations in catalytic systems on the beamline. Future developments for B18 include a plan to adopt a von Hamos spectrometer which will help studies of samples with overlapping fluorescence lines and allow measurements using secondary spectroscopy.

Figure 4: Installation of the Double Crystal Monochromator (DCM) on I14.

Four of the village's beamlines are open to users, with a further two beamlines achieving first light during 2015. The last year also saw significant progress made in both the Diamond Mapping and the Stepper and Piezo Motor Scanning Projects, which are working to improve data acquisition hardware and software for users at the village.

During the last year the Core XAS beamline (B18) continued to host a high number of users. B18 is a high-throughput beamline that runs at energies of 2 to 35 keV and supports quick XAFS (QXAFS) time-resolved measurements of all elements heavier than phosphorus (P). The beamline can follow chemical processes from a few seconds through to a few minutes and is particularly suited to in situ applications such as investigating the evolution of catalysts at different temperatures or gas mixtures. B18 can run samples down to mMol dilutions and its flexible setup allows users to incorporate their own specialised equipment and run other techniques such as infrared (IR) spectroscopy.

The Microfocus Spectroscopy beamline (I18) uses X-ray beams as small as 2x2 μm to study samples that are heterogeneous on the micron scale. Using energies ranging from 2 to 20 keV it covers the whole gamut of science, from geological and earth science to chemistry and biological research. Users are able to study elements from phosphorus and above using XRF, XAS and diffraction techniques. This year saw the beamline continue to develop its 3D imaging capability as well as carrying out the first cryo-tomography measurements. The research I18 supported this year included studies on nanoparticle toxicity, the effect of metal distribution on eyes during ageing, and radiation damage in nuclear waste storage facilities, leading to a total of 30 published papers from this beamline in the last 12 months.

The Scanning X-ray Microscopy beamline (I08) uses soft X-rays of 250 eV to 4.2 keV to provide morphological, chemical and elemental information about samples. I08 is optimised for the analysis of the interaction of organic and inorganic matter and offers a range of imaging techniques as well as XAS and XRF. It is unique in its ability to offer a broad energy photon range with cryogenic cooled specimen environments. The past year has seen I08 demonstrate an improved Near Edge X-ray Absorption Fine Structure (NEXAFS) performance for low mass elements, especially carbon, oxygen and nitrogen. In Autumn 2015 the first soft X-ray diffraction (ptychography) measurements were carried out on the beamline in preparation for the technique to be opened up to all users in 2016.

The Versatile X-ray Spectroscopy beamline (I20) is a double beamline split into two branches: scanning (I20-scanning) and dispersive (I20-EDE). The two branchlines operate independently and simultaneously, as the X-rays are produced from two independent insertion devices.

After a challenging year during which significant effort has been invested into solving the instability problems in the monochromator, I20-scanning has been brought back into operation in January 2016. The beamline provides capabilities for XAS in transmission and fluorescence mode, as well as X-ray Emission Spectroscopy (XES) on two end stations. The first is optimised to carry out experiments on very low concentration samples while the second end station enables high resolution studies of the electronic structure of samples.

The second branch, I20-EDE uses energy dispersive EXAFS to give users the ability to follow processes that happen on time scales ranging upwards from microseconds, making it particularly suitable for chemistry. It hosted its first user in April 2015. The branchline is optimised for in situ and operando studies, often combined with complementary techniques such as Raman and UV-Vis spectroscopy. A new commissioning call for users was opened in April 2016, whilst the beamline team continues to optimise its capabilities.

The Hard X-ray Nanoprobe beamline (I14) remains under construction. Comprising of a 185 m beamline running from internal to external buildings, the construction of both sets of buildings was completed in February 2016 with first light to the internal side taking place in 2015. The next year will see this work continue with first users expected in 2017. I14 is a scanning probe beamline that uses a combination of spectroscopic and diffraction techniques to determine the chemical composition of samples. When it comes online I14 will produce X-ray beams of 30-50 nm – a factor of 100 times smaller in terms of beam size than I18. The beams will use X-rays with energies higher than 4 keV, giving better penetration depth for thick or wet samples. This will open up the possibility of studying micron scale samples in greater detail, such as biological cells that are generally on the scale of 1-5 μm.

I21, the Inelastic X-ray Scattering (IXS) beamline is also under construction, with completion of the internal beamline and first light both occurring in 2015, two months ahead of schedule. I21 will use X-ray beams with energies ranging from 250-3000 eV and demonstrate an ultrahigh energy resolving power (a few tens of thousands at 1 keV) thanks to high precision optics and mechanics. It is suited to investigate the electronic, magnetic and lattice dynamics of samples particularly those with magnetic and electronic interactions. In order to achieve extremely high energy resolving power I21 will be 81 m long with a 15 m long Resonant IXS spectrometer housed in an external building. The vacuum pipe that bridges the internal and external sites was completed in February 2016. Staged X-ray commissioning to the external building is due later this year with first users in April 2017.