Metrology
Optics
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Open Access
Abstract: Advanced metrology methods are continually being developed and refined to meet the demanding quality standards of high-performance X-ray mirrors. Among these, interferometric techniques are the most widely used for measuring the height maps of optical surfaces. However, they often encounter limitations when applied to strongly curved or freeform surfaces, primarily due to high fringe density caused by steep slope. To address these challenges, we have developed a laser Speckle-based Curvature Optical Metrology instrument (SCOM) for measuring the two-dimensional surface curvature maps. This technique offers an alternative for characterizing complex optical surfaces by using a digital image correlation algorithm to extract curvature information from the speckle pattern, which effectively acts as a set of wavefront markers. We have demonstrated the effectiveness of this method for measuring strongly curved mirrors with a radius of curvature from 10 m down to 100 mm. Additionally, we have applied this technique to online deterministic figuring of optical surfaces, in-situ stress measurements during multilayer deposition processes, and the characterization of deformable mirrors. This technique shows great promise not only for high precision metrology of X-ray mirrors used in synchrotron radiation facilities, free-electron lasers, and space and astronomical observatories, but also for freeform optical components in advanced industrial applications.
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Apr 2026
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B16-Test Beamline
Optics
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Yuanze
Xu
,
Vishal
Dhamgaye
,
Hongchang
Wang
,
Oliver
Fox
,
Futing
Yi
,
Ming
Li
,
Weiwei
Zhang
,
Junliang
Yang
,
David
Laundy
,
Dongni
Zhang
,
Kawal
Sawhney
,
Jing
Liu
,
He
Lin
Diamond Proposal Number(s):
[34816]
Open Access
Abstract: A novel aberration-free X-ray compound refractive kinoform lens design based on the Cartesian oval curve is presented, designated as the OVAL-OK (OVAL Overlap Kinoform) lens. Material infilling of the kinoform step structure maintains focal spot dimensions while reducing focal intensity and reproducibility of structures. A SU-8 OVAL-OK lens fabricated through X-ray lithography achieved vertical focal sizes of 70.8 nm (knife-edge scanning) and 56 nm (wavefront propagation analysis) under 15 keV X-ray illumination, using a 120 μm × 200 μm (horizontal × vertical) aperture and 40.8 mm working distance. The lens exhibits a horizontal structural depth of 170 μm and a minimum feature size of 5 μm. The observed discrepancy between direct knife-edge measurements and wavefront-derived values is attributable to the combined effects of geometric, diffraction, coherence, instrumental instability, etc. These results demonstrate the potential for achieving sub-50 nm 2D focusing in future iterations through enhanced structural depth and expanded aperture dimensions.
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Apr 2026
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Metrology
Optics
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Open Access
Abstract: High-performance synchrotron X-ray focusing mirrors require aspheric surfaces with nanoradian slope accuracy, which are challenging to provide for many manufacturers. Conventional grinding and polishing techniques typically introduce tooling marks to the surface during the fabrication process, and these marks can impose significant challenges for the deterministic figuring processes used as the final step in mirror fabrication, ultimately limiting the slope errors of the mirrors. To overcome this limitation, we present an alternative approach by using ion beam shaping to form an elliptical sub-microfocusing mirror from a flat mirror, followed by ion beam figuring to improve the remaining errors. Two mirrors fabricated using this approach achieved tangential slope errors below 200 nrad root mean squared (rms), in contrast to a conventionally pre-shaped mirror with identical ellipse parameters that was limited to > 500 nrad rms after ion beam figuring due to residual tooling marks. In X-ray focusing tests, the ion beam shaped mirrors are able to realise a spot size below 250 nm (full width half maximum), compared to 404 nm for the pre-shaped mirror. This demonstrates the excellent potential of ion beam shaping as a method for rapid, efficient and high-quality X-ray mirror fabrication.
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Feb 2026
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Optics
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Arindam
Majhi
,
Wadwan
Singhapong
,
Wai Jue
Tan
,
Andrey
Sokolov
,
Stefano
Agrestini
,
Mirian
Garcia-Fernandez
,
Ke-Jin
Zhou
,
Andrew C.
Walters
,
Chris
Bowen
,
Alexander J. G.
Lunt
,
Hongchang
Wang
,
Kawal J.
Sawhney
Open Access
Abstract: Laterally graded multilayer optics play an important role in advanced X-ray applications, enabling precise control of beam properties for spectroscopic and focusing techniques. The Multilayer Deposition System (MDS) at Diamond Light Source (DLS) has demonstrated its ability to fabricate highly precise laterally graded X-ray optics. Developing such optics is challenging due to stringent requirements for precise lateral thickness variations and sagittal uniformity, achieved through optimized substrate speed profiles and advanced mask design. This study presents a comprehensive investigation into the design, fabrication, and characterization of laterally graded multilayers. An adjustable mask design improves sagittal uniformity and reduces optimization times. The structural and optical performance of the multilayers is evaluated, confirming their suitability for synchrotron applications. Two types of laterally graded multilayers were developed: one with a constant lateral gradient (0.005 nm/mm) for O-K edge polarizers, achieving sagittal thickness variations of approximately 0.3–0.4% across an 80 mm substrate, and another featuring a strong variable gradient from 0.037 to 0.112 nm/mm, designed to match the elliptical periodicity profile. The constant gradient multilayer polarizer has been successfully implemented on the state-of-the-art I21 beamline at DLS, highlighting the MDS's role in producing next-generation X-ray optics that meet the stringent demands of synchrotron beamlines.
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Jan 2026
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B07-B1-Versatile Soft X-ray beamline: High Throughput ES1
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
Optics
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Wai Jue
Tan
,
Arindam
Majhi
,
Wadwan
Singhapong
,
Andrew C.
Walters
,
Matthijs A.
Van Spronsen
,
Georg
Held
,
Burcu
Karagoz
,
David C.
Grinter
,
Pilar
Ferrer
,
Guru
Venkat
,
Qiushi
Huang
,
Zhe
Zhang
,
Zhanshan
Wang
,
Patrick Yuheng
Wang
,
Andrey
Sokolov
,
Hongchang
Wang
,
Kawal
Sawhney
Open Access
Abstract: X-ray Photoelectron Spectroscopy (XPS) is a powerful tool for probing the chemical and electronic states of materials with elemental specificity and surface sensitivity. However, its application in the tender X-ray range (1–5 keV) for synchrotron radiation has remained limited due to the limited choice of optics capable of maintaining high reflectivity and efficiency in this energy window. To address this, multilayer (ML) grating structures have become increasingly popular, offering significantly higher efficiency than SL coatings in the tender X-ray region. This paper presents the development of ML laminar gratings optimised for enhancing efficiency in the tender X-ray range, and capable of retaining performance under intense X-ray exposure in the oxygen partial pressure of 10 mbar. The ML coating quality was verified through X-ray reflectivity (XRR), XPS and near-edge X-ray absorption fine structures (NEXAFS) measurements, while the performance of the grating was validated through beamline flux transmission and XPS measurements. The MLLG demonstrated 22 higher intensity in flux and XPS, significantly improving the signal-to-noise ratio. Most importantly, the MLLGs outperformed traditional designs by offering improved spectral resolution while maintaining measurement capability at varying values without compromising the intensity. Furthermore, we demonstrated that the incorporation of nitrogen during deposition further enhances flux transmission.
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Oct 2025
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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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B16-Test Beamline
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B.
Cline
,
D.
Banks
,
M.
Bishop
,
A.
Davis
,
J.
Harris
,
M.
Hart
,
S.
Knowles
,
T.
Nicholls
,
J.
Nobes
,
S.
Pradeep
,
M.
Roberts
,
M. C.
Veale
,
M. D.
Wilson
,
V. P.
Dhamgaye
,
O. J. L.
Fox
,
K. J. S.
Sawhney
,
S.
Scully
Diamond Proposal Number(s):
[36472]
Open Access
Abstract: In this paper, results are presented from the characterisation of a 2 mm thick Redlen Technologies high-flux-capable Cadmium Zinc Telluride (HF-CZT) sensor hybridised to the small-pixel, spectroscopic-imaging HEXITEC_MHz ASIC. Dynamic datasets were taken on the B16 Test Beamline at the Diamond Light Source to study a previously-identified 'excess-leakage-current' phenomenon in HF-CZT, where additional leakage current was temporarily generated upon the application of an X-ray flux. A study of the response of the detector as a function of X-ray intensity demonstrated a measurable excess leakage current signal above 105 ph s-1 mm-2. At a 20 keV flux of 7.81 × 106 ph s-1 mm-2, this effect contributed a signal equivalent to 3.79 ± 1.59 nA mm-2in addition to the expected photocurrent. On removal of X-rays at this flux, this excess leakage current took ∼ 10 s to decay below the noise floor of the detector. This long lifetime has implications for detectors required to operate at high frame rates and fluxes. The use of a small-pixel detector also allowed the spatial variation of this effect to be studied. A per-pixel comparison between the magnitude of the excess leakage current and the spectroscopic performance of the pixel showed no correlation. This suggests that the phenomenon is less likely to be a bulk-crystal effect and more likely the result of the properties of the CZT surface or metal/semiconductor interface. An Arrhenius analysis of the temperature-dependence of the dark and excess leakage currents in the detector yielded values of 0.69 ± 0.04 eV and 0.13 ± 0.01 eV respectively. The change in dark current with temperature is consistent with deep levels pinning the Fermi level close to the mid band gap, whilst the activation energy of the excess leakage current suggests shallower defects at the metal-semiconductor interface are responsible.
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Oct 2025
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B16-Test Beamline
Optics
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Wadwan
Singhapong
,
Arindam
Majhi
,
Wai Jue
Tan
,
Vishal
Dhamgaye
,
Riley
Shurvinton
,
Paresh
Pradhan
,
Igor
Dolbnya
,
Lucia
Alianelli
,
Chris
Bowen
,
Alexander J. G.
Lunt
,
Hongchang
Wang
,
Kawal
Sawhney
Open Access
Abstract: Multilayer monochromators are crucial optical elements for monochromatizing intense X-ray beams in applications demanding high photon flux with moderate energy resolution. Achieving high-performance multilayer monochromators requires optimizing multilayer parameters, using high-quality substrates, and precisely controlling the deposition process to ensure high reflectivity and eliminate stripe artifacts. This paper presents the design and development, and characterization of double multilayer monochromators (DMM). These coatings are deposited using an optimized mask design to ensure <0.3% sagittal thickness uniformity and employing reactive sputtering in nitrogen gas (N2) - to enhance multilayer reflectivity. A high reflectivity of 88.7% at 14.0 keV and 85.6% at 22.4 keV is achieved. Furthermore, stripe-free imaging is achieved in double-reflection geometry via the use of high-quality substrates produced using the in-house ion beam figuring machine. These findings offer valuable insights for developing high-performance DMMs, paving the way for the next generation of synchrotron optics and instruments.
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Aug 2025
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B16-Test Beamline
Optics
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Open Access
Abstract: Multilayer (ML) monochromators are essential components in synchrotron radiation facilities, widely used for X-ray imaging and X-ray diffraction, as well as select X-ray spectroscopy techniques. However, ML monochromators introduce stripe artefacts to the reflected beam, which degrade the quality of the X-ray images. These stripe artefacts originate from figure errors on the monochromator’s surface, which are challenging to minimise for most manufacturers. In this study, we demonstrate stripe-free imaging from ultra-high-quality ML monochromators. We employed a state-of-the-art ion beam figuring (IBF) technique to produce multilayer substrates with a cutting-edge slope error of less than 30 nrad root mean squared (rms). These substrates were coated in an advanced multilayer deposition system, enabling the production of uniform multilayer coatings. The performance of the ML monochromators was tested at the B16 test beamline at the diamond light source. Speckle-based metrology was used to verify the theoretical link between wavefront curvature and the appearance of stripe artefacts. We obtained stripe-free X-ray images from the newly fabricated ML monochromators in both single-bounce and double-bounce configurations, with excellent image clarity and flat field uniformity. This represents a breakthrough in the production of ML monochromators.
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Aug 2025
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Metrology
Optics
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Simon G.
Alcock
,
Ioana-Theodora
Nistea
,
Murilo
Bazan Da Silva
,
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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