B16-Test Beamline
Optics
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Open Access
Abstract: High-speed adaptive correction of optics, based on real-time metrology feedback, has benefitted numerous scientific communities for several decades. However, it remains a major technological challenge to extend this concept into the hard x ray regime due to the necessity for active mirrors with single-digit nanometer height errors relative to a range of aspheric forms. We have developed a high-resolution, real-time, closed-loop “adaptive” optical system for synchrotron and x ray free electron laser (XFEL) applications. After calibration of the wavefront using x ray speckle scanning, the wavefront diagnostic was removed from the x ray beam path. Non-invasive control of the size and shape of the reflected x ray beam was then demonstrated by driving a piezoelectric deformable bimorph mirror at ∼1Hz
. Continuous feedback was provided by a 20 kHz direct measurement of the optical surface with picometer sensitivity using an array of interferometric sensors. This enabled a non-specialist operator to reproduce a series of pre-defined x ray wavefronts, including focused or non-Gaussian profiles, such as flattop intensity or multiple split peaks with controllable separation and relative amplitude. Such changes can be applied in any order and in rapid succession without the need for invasive wavefront diagnostic sensors that block the x ray beam for scientific usage. These innovations have the potential to profoundly change how x ray focusing elements are utilized at synchrotron radiation and XFEL sources and provide unprecedented dynamic control of photon beams to aid scientific discoveries in a wide range of disciplines.
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Jan 2023
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Optics
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Abstract: With brighter synchrotron sources, automated sample changers, and faster detectors, there is a strong scientific need for rapid and precise variation of the X-ray beam profile, rather than the "set and forget" operation of years past. Piezoelectric bimorph deformable mirrors already allow quick beam profile changes without the heat generation and wear of mechanical devices. Now, their early technological limitations – excessively constraining holders, progressive "junction effect" distortion, and communication bottlenecks with power supplies – are being overcome by a collaboration of scientists and engineers both in industry and at Diamond Light Source. A new generation of bimorph mirrors maintains a stable figure over extended periods of operation. Improved holders and flexible electrical connectors are greatly reducing the mechanical strain imparted to bimorphs, thereby improving their speed, accuracy, and stability. A more sophisticated high voltage power supply has on-board signal processing capacity, allowing large focusing changes within seconds and providing programmable time-varying voltage profiles to counteract piezoelectric creep. The communication between beamline systems and power supplies is being freed of bottlenecks and now runs stably up to 1 Hz. Early tests have already shown that bimorph mirrors can repeatedly switch the size of an X-ray beam in well under 10 seconds. Bimorph mirrors at synchrotron beamlines are now growing beyond the largely static operation of the past and gaining a new dynamism through development projects that are now well advanced. We report on how these endeavours will make it easier for beamlines to utilise the full potential of bimorph mirrors.
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Dec 2022
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Optics
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Open Access
Abstract: We present the development of a Fizeau interferometer stitching system to characterize the surface profile of state-of-the-art X-ray optics for synchrotron and free electron laser sources. Controls and acquisition software precisely translate and rotate the surface under test in synchrony with data capture by a Zygo Verifire HDX interferometer. Overlapping sub-aperture images are combined into a composite, high-spatial resolution topographical image of the entire optical surface using PyLOSt stitching software produced by the MooNpics collaboration. After minimization of random and systematic measurement errors, system performance was quantified by characterizing two challenging optics. These optics represent extreme cases for synchrotron X-ray mirrors: an aspheric elliptical profile with a slope error of ∼50 nrad rms, and a corresponding height error of 0.2 nm rms; and a chirped periodic structure superimposed upon a strong curvature (radius ∼ 9.33 m). Results are in very good agreement with the Diamond-NOM slope profilometer and Bruker GTX stitching micro-interferometer. Without a specialist transmission reference, both optics could not be measured by the interferometer without pitch and translation stitching. Any individual HDX scan, relative to the average of the ensemble, has an average slope error repeatability of < 15 nrad rms. After calibration of the transmission reference flat and zoom factor, a reproducibility of ∼ 27 nrad rms compared to the Diamond-NOM, was achieved for the elliptically curved mirror.
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Nov 2022
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Metrology
Optics
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Giuseppe
Mercurio
,
Jaromír
Chalupský
,
Ioana-Theodora
Nistea
,
Michael
Schneider
,
Věra
Hájková
,
Natalia
Gerasimova
,
Robert
Carley
,
Michele
Cascella
,
Loïc
Le Guyader
,
Laurent
Mercadier
,
Justine
Schlappa
,
Kiana
Setoodehnia
,
Martin
Teichmann
,
Alexander
Yaroslavtsev
,
Tomáš
Burian
,
Vojtĕch
Vozda
,
Luděk
Vyšín
,
Jan
Wild
,
David
Hickin
,
Alessandro
Silenzi
,
Marijan
Stupar
,
Jan
Torben Delitz
,
Carsten
Broers
,
Alexander
Reich
,
Bastian
Pfau
,
Stefan
Eisebitt
,
Daniele
La Civita
,
Harald
Sinn
,
Maurizio
Vannoni
,
Simon G.
Alcock
,
Libor
Juha
,
Andreas
Scherz
Open Access
Abstract: A real-time and accurate characterization of the X-ray beam size is essential to enable a large variety of different experiments at free-electron laser facilities. Typically, ablative imprints are employed to determine shape and size of µm-focused X-ray beams. The high accuracy of this state-of-the-art method comes at the expense of the time required to perform an ex-situ image analysis. In contrast, diffraction at a curved grating with suitably varying period and orientation forms a magnified image of the X-ray beam, which can be recorded by a 2D pixelated detector providing beam size and pointing jitter in real time. In this manuscript, we compare results obtained with both techniques, address their advantages and limitations, and demonstrate their excellent agreement. We present an extensive characterization of the FEL beam focused to ≈1 µm by two Kirkpatrick-Baez (KB) mirrors, along with optical metrology slope profiles demonstrating their exceptionally high quality. This work provides a systematic and comprehensive study of the accuracy provided by curved gratings in real-time imaging of X-ray beams at a free-electron laser facility. It is applied here to soft X-rays and can be extended to the hard X-ray range. Furthermore, curved gratings, in combination with a suitable detector, can provide spatial properties of µm-focused X-ray beams at MHz repetition rate.
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May 2022
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Metrology
Optics
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Open Access
Abstract: Reflective mirrors are used on most synchrotron and free electron laser (XFEL) beamlines to transport X-rays from the source to the sample. They are achromatic and provide larger acceptance and less absorption compared to compound refractive lenses. Mirrors whose surface profile can be controllably changed are called “active optics.” This enables users to vary the beam profile or focal position. X-ray beamlines use two categories of active optics: mechanically actuated mirrors, which typically use one or two independent bending motors for cylindrical or elliptical bending [1]; and piezoelectric bimorph deformable mirrors.
Bimorph deformable X-ray mirrors have been used to focus X-rays at synchrotron and XFEL beamlines since early research in the 1990s by Susini et al. [2] and Signorato et al. [3] at the European Synchrotron Radiation Facility (France). Soon afterwards, bimorph mirrors were commercialized by Thales-SESO (France) and deployed at several labs, including the Advanced Photon Source (USA) and Diamond Light Source (UK), called “Diamond” from here on. Research by Diamond’s Optics & Metrology (O&M) group shows that the widely held bad impression of bimorph mirrors as unreliable and excessively complex is outdated and unfounded. With fast, precise metrology techniques developed at Diamond, the difficulties encountered by the early users of bimorph mirrors have been overcome, and Diamond has combined bimorph actuators with specialized substrates for several novel applications. Finally, Diamond’s improvements can help realize the true potential of bimorph mirrors to act as closed-loop, adaptive X-ray optics with real-time correction. Such dynamic optics could match the profile of an X-ray beam to a series of rapidly changing samples of different shapes and sizes, or provide fast, stable wavefront correction.
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Apr 2022
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I21-Resonant Inelastic X-ray Scattering (RIXS)
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Ke-Jin
Zhou
,
Andrew
Walters
,
Mirian
Garcia-Fernandez
,
Thomas
Rice
,
Matthew
Hand
,
Abhishek
Nag
,
Jiemin
Li
,
Stefano
Agrestini
,
Peter
Garland
,
Hongchang
Wang
,
Simon
Alcock
,
Ioana
Nistea
,
Brian
Nutter
,
Nicholas
Rubies
,
Giles
Knap
,
Martin
Gaughran
,
Fajin
Yuan
,
Peter
Chang
,
John
Emmins
,
George
Howell
Open Access
Abstract: The I21 beamline at Diamond Light Source is dedicated to advanced resonant inelastic X-ray scattering (RIXS) for probing charge, orbital, spin and lattice excitations in materials across condensed matter physics, applied sciences and chemistry. Both the beamline and the RIXS spectrometer employ divergent variable-line-spacing gratings covering a broad energy range of 280–3000 eV. A combined energy resolution of ∼35 meV (16 meV) is readily achieved at 930 eV (530 eV) owing to the optimized optics and the mechanics. Considerable efforts have been paid to the design of the entire beamline, particularly the implementation of the collection mirrors, to maximize the X-ray photon throughput. The continuous rotation of the spectrometer over 150° under ultra high vacuum and a cryogenic manipulator with six degrees of freedom allow accurate mappings of low-energy excitations from solid state materials in momentum space. Most importantly, the facility features a unique combination of the high energy resolution and the high photon throughput vital for advanced RIXS applications. Together with its stability and user friendliness, I21 has become one of the most sought after RIXS beamlines in the world.
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Mar 2022
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Metrology
Optics
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Open Access
Abstract: We present recent advancements in the Optical Metrology Laboratory (OML) at Diamond Light Source. Improvements in optical manufacturing technology, and demands from beamlines at synchrotron and free electron laser facilities, have made it a necessity to routinely characterize X-ray mirrors with slope errors < 100 nrad rms. The Diamond-NOM profiler can measure large, fully assembled optical systems in a sideways, upwards, or downwards facing geometry. Examples are provided of how it has recently characterized several challenging systems, including: actively bent mirrors; clamped monochromator gratings in a downward-facing geometry; and four, state-of-the-art, elliptically bent, long mirrors with slope errors < 100 nrad rms. The NOM’s components and data analysis procedures are continuously updated to stay ahead of the ever-increasing quality of X-ray optics and opto-mechanics. The OML’s newest instrument is a Zygo HDX 6” Fizeau interferometer. A dedicated support frame and motorized translation and rotation stages enable sub-aperture images to be stitched together using in-house controls and automation software. Cross-comparison of metrology data, including as part of the MooNpics collaboration, provides a valuable insight into the nature of optical defects and helps to push optical fabrication to a new level of quality.
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Sep 2019
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Metrology
Optics
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Open Access
Abstract: There is growing interest at synchrotron light and X-ray free electron laser facilities to explore and improve the dynamic performance of piezoelectric bimorph deformable X-ray mirrors. Many beamlines, especially those dedicated to Macromolecular Crystallography, need to measure hundreds of samples per day. Shorter acquisition time requires rapid changes in the focus of the X-ray beam to condense the maximum photon density onto the sample. This is necessary to match the X-ray beam to the dimensions of the sample, or to probe variable sized regions of larger samples. Fine control of the X-ray beam becomes crucial for ensuring the highest quality of scientific data and increased throughput. Previous work at Diamond Light Source successfully changed the X-ray beam focus and stabilised it in under 10 seconds using piezoelectric bimorph deformable mirrors. Further updates to the controls software of the programmable HV-ADAPTOS high-voltage power supply (from CAEN / S.RI. Tech) now make it possible to control individual electrodes at 1 Hz using custom voltage profiles. This allows localized compensation of piezo creep, thus improving X-ray beam shape, significantly reducing stabilisation time, and eliminating curvature drift. For ex-situ validation, dynamic changes in the surface of the bimorph mirror need to monitored in real-time with sufficient spatial sensitivity. In this paper, we show that the active optical surface of a bimorph mirror (from Thales-SESO) can be accurately changed with sub-nanometre height sensitivity by dynamically monitoring the mirror’s surface using an array of high-speed (up to 200 kHz) Zygo ZPS™ absolute interferometric displacement sensors mounted in an independent metrology frame.
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Sep 2019
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Metrology
Optics
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Carolyn
Atkins
,
William
Brzozowski
,
Naomi
Dobson
,
Maria
Milanova
,
Stephen
Todd
,
David
Pearson
,
Cyril J.
Bourgenot
,
David
Brooks
,
Robert M.
Snell
,
Wenjuan
Sun
,
Peter
Cooper
,
Simon G.
Alcock
,
Ioana-Theodora
Nistea
Abstract: Additive manufacturing (AM; 3D printing) is a fabrication process that builds an object layer-upon-layer and promotes the use of structures that would not be possible via subtractive machining. Prototype AM metal mirrors are increasingly being studied in order to exploit the advantage of the broad AM design-space to develop intricate lightweight structures that are more optimised for function than traditional open-back mirror lightweighting. This paper describes a UK Space Agency funded project to design and manufacture a series of lightweighted AM mirrors to fit within a 3U CubeSat chassis. Six AM mirrors of identical design will be presented: two in aluminium (AlSi10Mg), two in nickel phosphorous (NiP) coated AlSi10Mg, and two in titanium (Ti64). For each material mirror pair, one is hand-polished and the other is diamond turned. Metrology data, surface form error and surface roughness, will be presented to compare and contrast the different materials and post-processing methods. To assess the presence of porosity, a frequent concern for AM materials, X-ray computed tomography measurements will be presented to highlight the location and density of pores within the mirror substrates; methods to mitigate the distribution of pores near the optical surface will be described. As a metric for success the AlSi10Mg + NiP and AlSi10Mg mirrors should be suitable for visible and infrared applications respectively.
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Sep 2019
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Metrology
Optics
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Giuseppe
Mercurio
,
Carsten
Broers
,
Robert
Carley
,
Jan Torben
Delitz
,
Natalia
Gerasimova
,
Loïc
Le Guyarder
,
Laurent
Mercadier
,
Alexander
Reich
,
Justine
Schlappa
,
Martin
Teichmann
,
Alexander
Yaroslavtsev
,
Michele
Cascella
,
Kiana
Setoodehnia
,
Michael
Schneider
,
Bastian
Pfau
,
Stefan
Eisebitt
,
Vojtech
Vozda
,
Anna
Hajkova
,
Ludek
Vysin
,
Tomas
Burian
,
Jaromir
Chalupský
,
Libor
Juha
,
Simon G.
Alcock
,
Ioana-Theodora
Nistea
,
Daniele
La Civita
,
Harald
Sinn
,
Maurizio
Vannoni
,
Andreas
Scherz
Abstract: The Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL is a soft X-ray beamline aiming to unravel electronic, spin and structural properties of materials in ultrafast processes at the nanoscale. Various experimental techniques offered at SCS have different requirements in terms of beam size at the sample. Kirkpatrick-Baez (KB) refocusing optics equipped with mechanical benders allows for independent change of the horizontal and vertical beam size. We report here on the first characterization of the SCS KB mirrors by means of a novel diffraction-based technique which images the beam profile on a 2D pixelated detector. This approach provides a quick characterization of micrometer beam sizes. Results are compared with metrology measurements obtained with a non-contact slope profiler.
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Sep 2019
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