Metrology
Optics
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Abstract: Autocollimators are used in profilometers for the precise form measurement of beam-shaping optics for synchrotron light sources and x-ray free-electron lasers. This application requires using an aperture stop, typically 2.5 mm in diameter, which limits the footprint of the autocollimator’s measuring beam on the optics to achieve a sufficiently high lateral resolution. Central to the development of profilometry has been the availability of commercial autocollimators, such as the Elcomat 3000 from Möller–Wedel Optical. Although autocollimators are generally not designed for use with small apertures, this device has proven capable and has become the de facto standard. Now that it has been replaced by the Elcomat 5000, we evaluate the performance of several autocollimators of this type at small apertures, including the characterization of instrument transfer functions with a chirped height profile. We demonstrate that the Elcomat 5000 is capable of repeatable angle measurements with a standard deviation of 0.014 arcsec at an aperture diameter of 1.6 mm, whereas the Elcomat 3000 achieves 0.03 arcsec at 2.5 mm, comparing models with modified reticle designs. We also investigate the influence of optical aberrations of the autocollimator’s objective and their changes with the path length to the surface under test. We characterize the sensitivity of the angle measurement to changes in environmental parameters, in particular, barometric pressure. These efforts are aimed at approaching fundamental limits in the characterization of the shape of optical surfaces with autocollimator-based profilometers so that these are ready for characterizing the next generation of synchrotron and XFEL beamline optics.
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Jan 2026
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Metrology
Optics
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Open Access
Abstract: A new Optics Metrology Laboratory for assembling and characterizing beamline x-ray optical systems has been built. This replaces the old laboratory, which was demolished to make space for construction of a new flagship beamline for the forthcoming Diamond-II facility upgrade. The new cleanroom laboratory is located between several beamlines and laboratories, which intermittently generate significantly higher levels of acoustic noise and floor vibrations. A threefold design strategy was employed to create an ultra-stable environment for the sensitive, optical metrology instruments. First, the walls, ceiling and doors of the laboratory were constructed to attenuate acoustic noise. Second, the air handling systems were designed to minimize self-production of noise and vibrations. Finally, engineering solutions were developed to further isolate the metrology instruments from environmental fluctuations. Overall, despite higher levels of external disturbances, this strategy enables nano-metrology to be successfully conducted in the new laboratory. The shielded environment around each instrument achieves noise rating NR30, which is 5–25 dB quieter than the old laboratory. Over 60-h, the temperature inside the Diamond-NOM’s enclosure varied by only 0.004 °C rms, and humidity changed by <1% RH. All optical metrology instruments are now performing better than in the old laboratory: the slope error repeatability of Diamond-NOM is improved from 15 to 9 nrad rms; the GTX micro-interferometer has measured super-polished substrates with micro-roughness <40 pm rms; the new gantry for Speckle Angular Measurement is commissioned; and the HDX Fizeau interferometer has measured mirrors with slope errors <50 nrad.
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Oct 2025
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Metrology
Optics
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Simon G.
Alcock
,
Ioana-Theodora
Nistea
,
Murilo
Bazan Da Silva
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Kawal
Sawhney
,
Norman
Niewrzella
,
Holger
Lasser
,
Amparo
Vivo
,
Ray
Barrett
,
Jana
Buchheim
,
Grzegorz
Gwalt
,
Frank
Siewert
,
Sibylle
Spielmann
,
Uwe
Flechsig
,
Silja
Schmidtchen
,
Maurizio
Vannoni
,
Josep
Nicolas
,
Muriel
Thomasset
,
Francois
Polack
Open Access
Abstract: The surface quality of x-ray mirrors is a major constraint on optical performance at synchrotron light and free electron laser facilities. A limiting factor for creating state-of-the-art optics is the accuracy of metrology data to deterministically guide the polishing tool to correct surface errors. The “MooNpics” (Metrology On One-Nanometer-Precise Optics) collaboration aims to improve optical metrology capabilities at European facilities to enable reproducible measurement of long or curved optics with height errors <1 nm rms and slope errors <100 nrad rms. Three challenging x-ray optics were measured by several labs using a variety of instruments. The mirrors, chosen to challenge and explore different aspects of optical metrology, were as follows: a 1 m-long, ultra-flat (radius of curvature R > 100 km); an ellipse with added parabolic arcs; and a strongly curved sphere (R ∼ 9.3 m) with an added spatially varying chirp. This study highlighted calibration issues with several instruments, which were subsequently corrected. In this paper, we present results about the ellipse mirror. Based on metrology data provided by the collaboration, two cycles of ion beam figuring improved all aspects of the mirror, including correcting the ellipse parameters, reducing high- and mid-frequency spatial polishing errors, and refining the shape of the parabolic arcs. Overall, the slope and height errors were improved by a factor of ∼10. We also show how the round-robin measurement exercise helped refine “best practice” procedures for mounting optics, alignment, and data acquisition and analysis methods. It is hoped that this collaborative project will ignite further improvements in the production quality of x-ray optics to benefit many scientific communities around the world.
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Aug 2025
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I13-1-Coherence
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Diamond Proposal Number(s):
[29218, 23409, 32637, 34164]
Abstract: In conventional x-ray ptychography, diffraction data are collected by scanning a sample through a monochromatic and spatially coherent x-ray beam. A high-resolution image is then retrieved using an iterative algorithm. Combined with a scan of the incident photon energy, it is also possible to access chemical and elemental information. Although powerful, the high brilliance required currently constrains the method to third and fourth generation synchrotron sources and long scanning times. An alternative approach is to use broadband illumination in combination with an energy resolving detector. These detectors record the data in a series of energy channels simultaneously, creating stacks of coherent data suitable for a ptychographic reconstruction. This approach promises to unlock the full power of the radiation source and provide spectral imaging at a higher rate and in a single acquisition. However, these detectors currently saturate well below reaching the flux rates produced at synchrotrons, which is preventing the uptake of this approach. Furthermore, current monochromatic synchrotron setups typically employ Fresnel zone plates for pre-sample focusing due to their stability, flexibility, and affordability, but these diffractive optics limit the spectral bandwidth that the setup can accept. In this article, we analyze the problem and consider alternative optics that can both maximize the total photon detection rates and broaden the tolerable bandwidth. Broadband x-ray ptychography has the potential to dramatically reduce data collection times at synchrotron sources but also to harness the full power of lower brilliance sources and transition x-ray ptychography into a laboratory technique.
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Aug 2025
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[31385]
Open Access
Abstract: A free-standing and compact reaction cell for combined in situ/operando x-ray spectroscopy, scattering, and imaging measurements at high pressures and high temperatures is described. The cell permits measurements under realistic operating conditions (up to 50 bar and 1000 °C), under static and flow conditions (up to 100 ml/min), over a wide range of hard x-ray energies, variable detection modes (transmission, fluorescence, and scattering), and at all angles of rotation. An operando XAS, x-ray fluorescence, x-ray computed tomography, and x-ray diffraction computed tomography case study on the reduction of a heterogeneous catalyst is presented to illustrate the performance of the reaction cell.
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Oct 2024
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I05-ARPES
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Diamond Proposal Number(s):
[25083]
Open Access
Abstract: Our understanding of quantum materials is commonly based on precise determinations of their electronic spectrum by spectroscopic means, most notably angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy. Both require atomically clean and flat crystal surfaces, which are traditionally prepared by in situ mechanical cleaving in ultrahigh vacuum chambers. We present a new approach that addresses three main issues of the current state-of-the-art methods: (1) Cleaving is a highly stochastic and, thus, inefficient process; (2) fracture processes are governed by the bonds in a bulk crystal, and many materials and surfaces simply do not cleave; and (3) the location of the cleave is random, preventing data collection at specified regions of interest. Our new workflow is based on focused ion beam machining of micro-strain lenses, in which shape (rather than crystalline) anisotropy dictates the plane of cleavage, which can be placed at a specific target layer. As proof-of-principle, we show ARPES results from micro-cleaves of Sr2RuO4 along the ac plane and from two surface orientations of SrTiO3, a notoriously difficult to cleave cubic perovskite.
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Mar 2024
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I22-Small angle scattering & Diffraction
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M.
Hassan Sk
,
S.
Agrawal
,
M.
Woolley
,
S. M.
Clarke
,
A.
Osundare
,
D.
Craske
,
Robert
Lindsay
,
Andrew J.
Smith
,
T.
Snow
,
T.
Zinn
,
N.
Terrill
Diamond Proposal Number(s):
[23699, 28693, 32669]
Open Access
Abstract: Here, we report the design and successful implementation of an ultra-low oxygen sample cell for use on the SAXS-WAXS (small-wide angle x-ray scattering) beamline I22 at DIAMOND. The rigorous exclusion of oxygen is found to require double jacketing with purge gas throughout the entire system, pipework, pumps, and the sample cell itself. This particularly includes a “double-window” arrangement at the sample location to accommodate the very tight geometrical restrictions of the sample position. The in situ cell design also requires the additional complexity of heating the sample/solution and real-time electrochemical measurements. We demonstrate the successful implementation of this arrangement with real-time in situ characterization of an iron foil corrosion evolving under the “sweet-scale environment,” very anoxic conditions common, in particular, commercial situations. The formation of iron carbonate, siderite, rather than iron oxide, indicates that our system is oxygen free down very low levels (<35 ppb at 80 °C).
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Apr 2023
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Accelerator Physics
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Vladimir A.
Chernov
,
Ivan A.
Bataev
,
Yakov V.
Rakshun
,
Yuri V.
Khomyakov
,
Maksim V.
Gorbachev
,
Andrei E.
Trebushinin
,
Nikolay I.
Chkhalo
,
Dmitry A.
Krasnorutskiy
,
Viktor S.
Naumkin
,
Artem N.
Sklyarov
,
Nikolay A.
Mezentsev
,
Alexander M.
Korsunsky
,
Igor P.
Dolbnya
Abstract: Over the next decade, the extremely brilliant fourth generation synchrotron radiation sources are set to become a key driving force in materials characterization and technology development. In this study, we present a conceptual design of a versatile “Materia” diffraction and imaging beamline for a low-emittance synchrotron radiation facility. The beamline was optimized for operation with three main principal delivery regimes: parallel collimated beam ∼1 mm beam size, micro-focus regime with ∼10 μm beam spot size on the sample, and nano-focus regime with <100 nm focus. All regimes will operate in the photon energy range of 10–30 keV with the key feature of the beamline being fast switching between them, as well as between the various realizations of diffraction and imaging operation modes while maintaining the target beam position at the sample, and with both spectrally narrow and spectrally broad beams up to the energy band ΔE/E of 5 × 10−2. The manuscript presents the details of the principal characteristics selected for the insertion device and beamline optics, the materials characterization techniques, including the simulations of thermal load impact on the critical beamline optics components. Significant efforts were made to design the monochromators to mitigate the very high beam power load produced by a superconducting undulator source. The manuscript will be of interest to research groups involved in the design of new synchrotron beamlines.
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Jan 2023
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Insertion Devices
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Open Access
Abstract: The APPLE-Knot undulator has been proposed to reduce the large on-axis heat load of the APPLE-II at very low photon energy. However, the current designs have an inherent non-zero second field integral due to the Knot sections, resulting in a transverse deflection of the electron beam throughout the undulator. For a long device, such a deviation can degrade the brightness and power distribution of the outgoing beam. Here, a new end-Knot section is presented to compensate for the electron trajectory, and the undulator is symmetrized to balance the output power distribution. The performance of the APPLE-Knot with symmetric power distribution is investigated. The partial power, flux, and polarization are compared with the APPLE-II. In the linear mode, APPLE-Knot shows a pronounced reduction of the partial power, with a similar flux to the APPLE-II. The symmetric power density distribution reduces the hotspot by 41%, with a flux loss of less than 5%. In the circular mode and at low photon energies, the flux is limited by the phase error of the symmetric design.
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Sep 2022
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B22-Multimode InfraRed imaging And Microspectroscopy
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Open Access
Abstract: We present an in-vacuum mechanical chopper running at high speed and integrated into a magnetic levitating motor for modulating optical beams up to 200 kHz. The compact chopper rotor allows fast acceleration (10 kHz s−1 as standard) for rapid tuning of the modulation frequency, while 1 mm diameter slots provide high optical throughput for larger infrared beams. The modulation performances are assessed using a reference visible laser and the high brightness, broadband, infrared (IR) beam of synchrotron radiation at the MIRIAM beamline B22 at Diamond Light Source, UK. For our application of IR nanospectroscopy, minimizing the temporal jitter on the modulated beam due to chopper manufacturing and control tolerances is essential to limit the noise level in measurements via lock-in detection, while high modulation frequencies are needed to achieve high spatial resolution in photothermal nanospectroscopy. When reaching the maximum chopping frequency of 200 kHz, the jitter was found to be 0.9% peak-to-peak. The described chopper now replaces the standard ball-bearing chopper in our synchrotron-based FTIR photothermal nanospectroscopy system, and we demonstrate improved spectroscopy results on a 200 nm thickness polymer film.
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Aug 2022
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