Metrology Beamline Research Articles

Design and performance of the camera of the Micro-channel X-ray Telescope on-board the SVOM mission

The Microchannel X-ray Telescope (MXT) is part of the scientific payload of the SVOM Sino-French space mission to observe the early afterglow of gamma-ray bursts in the 0.2–10 keV energy range and localize them within 2 arcmin. For a total mass of 42 kg and a total power of 60 W, this instrument is composed of an optical system, a structural carbon fiber tube, a radiator, a camera and a data processing unit. The camera consists of a focal plane assembly with a detector ceramic board and thermoelectric coolers, a front-end electronics, a calibration wheel and a support structure. Spectral characterization tests of the focal plane assembly based on a 256 × 256 pixel pnCCD spectroscopic imager were performed in the laboratory, at the Metrology beamline of the SOLEIL synchrotron and at the PANTER X-ray facility. Energy resolution of 79 eV FWHM at 1.5 keV was demonstrated in the nominal flight configuration (−65 °C, real time event selection by the camera). The paper presents the design, the realization and the performance of the flight camera of MXT. It focuses on the technical challenges, the original implemented solutions and the custom-made setups for the validation tests.

Characterization of the focal plane of the microchannel X-ray telescope at the metrology beamline of SOLEIL synchrotron for the space astronomy mission SVOM

The Microchannel X-Ray Telescope is one of the four instruments of the SVOM Sino-French space mission to observe the afterglow of gamma-ray bursts in the 0.2–10 keV energy range and localize them within 2 arcmin. Inside the 9 kg camera, the detection chain consists of a detector assembly equipped with a fully depleted 256 × 256 pixels pnCCD and two CAMEX front-end ASICs, and a “US-free” front-end electronics unit to control the focal plane and extract photon events. The flight spare model was installed and characterized in November 2021 at SOLEIL synchrotron on the soft X-ray branch of Metrology beamline operating from 40 eV to 1800 eV. The goals of this campaign were to measure the quantum efficiency and characterize the spectral response, i.e., the energy calibration law, the charge transfer efficiency and the energy resolution at different positions on the detector. This implied the development of a full-custom cryostat to interface with the beam line and a special tuning of the beam line to get the appropriate photon flux for single photon counting in the pixels of 75 μm size without pile-up. This paper presents the configuration, the test plan, the test results, and the modeling of the detector response. This beam line was successfully used for spectral characterizations of the MXT detector from 300 to 1800 eV with excellent spectral purity and with a photon flux 7 orders of magnitude lower than the beamline nominal output.

Reference‐Free Combined X‐Ray Reflectometry−Grazing Incidence X‐Ray Fluorescence at the French Synchrotron SOLEIL

Chambre d'Analyse Spectrométrique en Transmission ou en Réflexion (Analysis Chamber for Transmission or Reflection Spectrometry) (CASTOR) is a new instrument, operated at the SOLEIL synchrotron facility, dedicated to the metrological characterization of thin films with thicknesses in the nanometer range. The instrument can combine two X‐ray techniques, namely, the reflectivity (XRR) measurements with fluorescence (XRF) acquisitions and especially total‐reflection X‐ray fluorescence (TXRF)‐related techniques such as grazing‐incidence XRF (GIXRF). The instrument is most often installed on the hard X‐ray branch of the Metrology beamline. Geometrical characterization is presented, reproducibility of measurements is studied, and the reference‐free GIXRF analysis is described. Some representative examples are given to illustrate the capabilities of the setup and the combined analysis procedure.

Characterization and performance evaluation of the XSPA-500k detector using synchrotron radiation.

Hybrid photon counting (HPC) detectors are widely used at both synchrotron facilities and in-house laboratories. The features of HPC detectors, such as no readout noise, high dynamic range, high frame rate, excellent point spread function, no blurring etc. along with fast data acquisition, provide a high-performance detector with a low detection limit and high sensitivity. Several HPC detector systems have been developed around the world. A number of them are commercially available and used in academia and industry. One of theimportant features of an HPC detector is a fast readout speed. Most HPC detectors can easily achieve over 1000 frames s-1, one or two orders of magnitude faster than conventional CCD detectors. Nevertheless, advanced scientific challenges require ever faster detectors in order to study dynamical phenomena in matter. The XSPA-500k detector can achieve 56 kframes s-1 continuously, without dead-time between frames. Using `burst mode', a special mode of the UFXC32k ASIC, the frame rate reaches 1 000 000 frames s-1. XSPA-500k was fully evaluated at the Metrology beamline at Synchrotron SOLEIL (France) and its readout speed was confirmed by tracking the synchrotron bunch time structure. The uniformity of response, modulation transfer function, linearity, energy resolution and other performance metrics were also verified either with fluorescence X-rays illuminating the full area of the detector or with the direct beam.

Grazing-incidence X-ray fluorescence analysis of thin chalcogenide materials deposited on Bragg mirrors

Advanced chalcogenide materials are key for state-of-the art memories, energy harvesting materials and photonics. The properties of thin chalcogenide layers are highly driven by their chemical composition, chemical depth-profiles and surface/interface effects. The combination of Grazing-Incidence X-ray Fluorescence (GIXRF) and X-ray Reflectometry (XRR) techniques allows for non-destructive access to such information, in the lab or at dedicated beamlines. However, the accuracy of the GIXRF-deduced composition slightly degrades with depth, as the enhancement of the XRF signal by the X-ray Standing Wave (XSW) field is usually limited to the first nanometers at the surface of the probed sample. In this paper, we suggest the use of (Mo/Si)*N Bragg mirrors, rather than bare silicon substrates for thin chalcogenide deposition, to improve the sensitivity of GIXRF/XRR analysis to small process-driven modifications. The aim of such multilayered substrates is to maintain high values of X-ray reflected intensity even at angles significantly higher than the critical angle, therefore generating an XSW-induced enhancement of the XRF signal not only at the surface but also in the depth of the layer of interest. The simulation of GIXRF-XRR data, collected at SOLEIL Metrology beamline and in the lab on Rigaku SmartLab diffractometer, on arsenic-free Ovonic Threshold Switch materials (Ge, Se, Sb) for advanced Phase Change memory (PCRAM) applications illustrates the interest of this approach, which is fully-compatible with numbers of PCRAM materials elaborated with low-temperature physical vapor deposition process.

Efficient high-order suppression system for a metrology beamline.

High-quality metrology with synchrotron radiation requires in particular a very high spectral purity of the incident beam. This is usually achieved by a set of transmission filters with suitable absorption edges to suppress high-order radiation of the monochromator. The at-wavelength metrology station at a BESSY-II bending-magnet collimated plane-grating monochromator (c-PGM) beamline has recently commissioned a high-order suppression system (HiOS) based on four reflections from mirrors which can be inserted into the beam path. Two pairs of mirrors are aligned parallel so as not to disturb the original beam path and are rotated clockwise and counter-clockwise. Three sets of coatings are available for the different energy ranges and the incidence angle is freely tunable to find the optimum figure of merit for maximum suppression at maximum transmission for each photon energy required. Measured performance results of the HiOS for the EUV and XUV range are compared with simulations, and applications are discussed.

SOLEIL shining on the solution-state structure of biomacromolecules by synchrotron X-ray footprinting at the Metrology beamline

Synchrotron X-ray footprinting complements the techniques commonly used to define the structure of molecules such as crystallography, small-angle X-ray scattering and nuclear magnetic resonance. It is remarkably useful in probing the structure and interactions of proteins with lipids, nucleic acids or with other proteins in solution, often better reflecting the in vivo state dynamics. To date, most X-ray footprinting studies have been carried out at the National Synchrotron Light Source, USA, and at the European Synchrotron Radiation Facility in Grenoble, France. This work presents X-ray footprinting of biomolecules performed for the first time at the X-ray Metrology beamline at the SOLEIL synchrotron radiation source. The installation at this beamline of a stopped-flow apparatus for sample delivery, an irradiation capillary and an automatic sample collector enabled the X-ray footprinting study of the structure of the soluble protein factor H (FH) from the human complement system as well as of the lipid-associated hydrophobic protein S3 oleosin from plant seed. Mass spectrometry analysis showed that the structural integrity of both proteins was not affected by the short exposition to the oxygen radicals produced during the irradiation. Irradiated molecules were subsequently analysed using high-resolution mass spectrometry to identify and locate oxidized amino acids. Moreover, the analyses of FH in its free state and in complex with complement C3b protein have allowed us to create a map of reactive solvent-exposed residues on the surface of FH and to observe the changes in oxidation of FH residues upon C3b binding. Studies of the solvent accessibility of the S3 oleosin show that X-ray footprinting offers also a unique approach to studying the structure of proteins embedded within membranes or lipid bodies. All the biomolecular applications reported herein demonstrate that the Metrology beamline at SOLEIL can be successfully used for synchrotron X-ray footprinting of biomolecules.

CASTOR, a new instrument for combined XRR‐GIXRF analysis at SOLEIL

A new instrument called CASTOR is operated at the SOLEIL synchrotron facility and is dedicated to the characterization of thin films with thicknesses in the nanometer range. The instrument can combine X‐ray reflectivity measurements with fluorescence (XRF) acquisitions and especially total reflection X‐ray fluorescence‐related techniques such as grazing incidence XRF. The instrument was successfully installed and operated on the two branches of the metrology beamline making possible experiments over a wide range of photon energies (45 eV to 40 keV). A heating sample holder was developed to allow the sample temperature to be controlled up to 300° C. Some examples of the first studies are given to illustrate the capabilities of the setup. Copyright © 2017 John Wiley & Sons, Ltd.

High-efficiency B_4C/Mo_2C alternate multilayer grating for monochromators in the photon energy range from 07 to 34 keV

An alternate multilayer (AML) grating has been prepared by coating an ion etched lamellar grating with a B4C/Mo2C multilayer (ML) having a layer thickness close to the groove depth. Such a structure behaves as a 2D synthetic crystal and can reach very high efficiencies when the Bragg condition is satisfied. This AML coated grating has been characterized at the SOLEIL Metrology and Tests Beamline between 0.7 and 1.7 keV and at the four-crystal monochromator beamline of Physikalisch-Technische Bundesanstalt (PTB) at BESSY II between 1.75 and 3.4 keV. A peak diffraction efficiency of nearly 27% was measured at 2.2 keV. The measured efficiencies are well reproduced by numerical simulations made with the electromagnetic propagation code CARPEM. Such AML gratings, paired with a matched ML mirror, constitute efficient monochromators for intermediate energy photons. They will extend the accessible energy for many applications as x-ray absorption spectroscopy or x-ray magnetic circular dichroism experiments.

Characterization of subnanometric layers by grazing incidence X-ray reflectometry

We present a method to characterize subnanometric layers based on grazing incidence X-ray reflectometry. For this purpose, we propose to use a “Fabry–Pérot” type multilayer structure in order to improve the sensitivity of the measurement to the layer thickness. For our study, this structure consists of a thin layer of scandium inserted between two periodic chromium (Cr)/scandium (Sc) multilayers. We describe the principle and estimate the sensitivity of the method by simulation. Experiments were performed on two optimized Fabry–Pérot structures with 0.6 and 1.2nm Sc layer thicknesses using a laboratory grazing incidence reflectometer at 8.048keV (Cu Kα radiation). Fitting of experimental data allows determining the Sc layer thickness. Finally, the structural parameters used in the fit were confirmed by measurements at 3keV on the hard X-ray branch of the synchrotron SOLEIL Metrology and Tests beamline.

Optical design of the NSLS-II metrology beamline

The article describes the optical design of the NSLS-II test beamline, dedicated to at-wavelength metrology, in situ surface figuring, crystal optics, radiometry, detectors and instrumentation testing. A key aspect of the beamline design is configuration flexibility, providing as wide as possible range of photon energy, beam size, and divergence, including the optimum trading of SR flux to a required degree of coherence. For this application we propose to use the chromatic properties of compound refractive lens (for hard x-ray) or zone plate (for soft x-ray) to provide band-pass energy filtering and variable spatial coherence. Using such a scheme, it is possible to efficiently vary the transverse coherence from 10 μm to 10 mm at ~1% monochromaticity. The flux extracted permits real-time phase imaging and at-wavelength metrology, even at the bending magnet beamline.

High efficiency multilayer gratings for monochromators in the energy range from 500 eV to 2500 eV

Multilayer (ML) gratings have been prepared by coating shallow ion etched lamellar gratings with a Mo2C/B4C multilayer having a layer thickness close to the groove depth. It was shown that such a structure behaves as a 2D synthetic crystal and can reach very high efficiencies when the Bragg condition is satisfied. A ML coated grating has been characterized at the SOLEIL Metrology beamline between 700 and 1700 eV and a beamline of PTB at BESSY II between 1750 and 3500 eV. A peak diffraction efficiency of nearly 27 % was measured at 2200 eV. The measured efficiencies are well reproduced by numerical simulations made with the electromagnetic propagation code CARPEM, This grating will be used in the Deimos beamline at SOLEIL together with a matched multilayer mirror.

Characterization of the Metrology beamline at the SOLEIL synchrotron and application to the determination of mass attenuation coefficients of Ag and Sn in the range 3.5 ≤ E ≤ 28 keV

This work presents the new Metrology beamline at the SOLEIL synchrotron facility and a first attempt to quantitative measurements of mass attenuation coefficients for Ag and Sn performed on the hard X‐ray branch. We first describe the beamline itself and the characterization performed of the unfocused monochromatic beam running mode. We performed a first experimental measurement of mass attenuation coefficients in the range 3.5 ≤ E ≤ 28 keV and we also derived the K‐absorption and L‐absorption jump ratios. The results are compared with theoretical values as well as with other experimental data and agree well with previous published values. Copyright © 2011 John Wiley & Sons, Ltd.

Optical metrology at the NSLS-II

Rapid progress in synchrotron optics performance places a high demand on optical characterization techniques used to validate surface parameters prior to installation of the X-ray optics. It is now necessary to characterize optical surface figure and slope errors and roughness on meter-long optics over spatial frequencies as short as 0.1 {micro}m The new NSLS-II Optical Metrology Laboratory (OML) includes instruments for measuring: (1) long spatial frequency figure errors with a ZYGO MST Fizeau-type 4* interferometer, capable of 0.1 nm sensitivity, (2) mid spatial frequencies with an upgraded ZYGO NewView 6300 white light interferometric microscope, capable of reaching 0.1 nm accuracy at a lateral resolution of 1 {micro}m, (3) high frequency roughness with an AFM (Nanosurf AG) with linearity better than 0.2% over the 80 {micro}m measurement area and sensitivity approaching 0.01 nm, and (4) slope errors with a long trace profiler currently under development that will be able to reach 50 nrad slope error accuracy. At present, the OML supports the NSLS-II R&D efforts and provides ongoing testing for NSLS optics. Future plans include the construction of a specialized metrology beamline for at-wavelength metrology, radiometry, in situ surface figuring, crystal optics characterization, and instrumentation development.

Development of in situ, at-wavelength metrology for soft X-ray nano-focusing

At the Advanced Light Source (ALS), we are developing broadly applicable, high-accuracy, in situ, at-wavelength wavefront slope measurement techniques for Kirkpatrick-Baez (KB) mirror nano-focusing. We describe here details of the metrology beamline endstation, the at-wavelength tests, and an original alignment method that have already allowed us to precisely set a bendable KB mirror to achieve a FWHM focused spot size of ~;;120 nm, at 1-nm soft x-ray wavelength.

Use of synchrotron radiation for studying multilayer nanostructures

We describe methods for using synchrotron radiation to study the metrological characteristics of multilayer nanostructures to be used as optical filters in the extreme vacuum ultraviolet range for solving nanoelectronics problems. For the synchrotron radiation metrology beamline, we have developed working standards for spectral irradiance and integrated irradiance.

Status of the metrology light source

The Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute, has set up in close cooperation with the Helmholtz-Zentrum Berlin (HZB, formerly BESSY) the 630 MeV electron storage ring metrology light source (MLS). This electron storage ring is in regular user operation since April 2008 and is dedicated to synchrotron-radiation-based metrology and technological developments in the far-IR/THz, IR, UV, VUV and EUV spectral range. Of special importance for PTB is the operation of the MLS as a primary radiation source standard from the near IR up to the soft X-ray region. Moreover, as a dedicated THz source the MLS can be operated in a special mode for the generation of short electron bunches. In this mode, the MLS delivers coherent radiation in the far-IR/THz spectral range with enhanced intensity as compared to the normal mode of operation. Several beamlines are in operation or in construction, including one undulator beamline, bending magnet beamlines for the calibration of radiation sources and detectors, an EUV metrology beamline and several IR/THz beamlines.

Quantitative research on higher order harmonics in metrology beamline

The synchrotron radiation spectra of the spherical grating monochromator (SGM) working in the soft X-ray and VUV region are often contaminated by significant amounts of higher order harmonics. They cannot be suppressed completely by suitable filters. Higher order contributions in the spectral radiation standard and metrology beamline were researched using transmission grating (made in-house) and IRD AXUV100G (USA) photodiode detector. The exit beam was dispersed with the transmission grating behind the exit slit of the monochromator, and the contributions of the different orders were analyzed. The higher order distributions were quantitatively determined for three gratings with line densities of 1800, 600 and 200 l/mm. Experiment results show that in wavelengths between 5 nm and 15 nm the contributions of the higher orders to the detector signal are restricted to less than 7% even without the use of filters. In wavelength regions between 5 nm and 34 nm, the contributions of the higher orders to the detector signal are less than 14% with proper A1, Si3N4 and Zr filters, and after being modified by quantum efficiency of the detector, the higher order contributions are restricted to less than 6.5%. The study also shows that higher orders are almost totally suppressed by MgF2 filter when the wavelength ranges between 115–140 nm.

Technical Report: Metrology and Test Beamline at SOLEIL

We propose to build at SOLEIL a facility for the accurate measurement of the properties of optical elements and detectors from the extreme ultraviolet (EUV), soft X-ray spectral regions up to the hard X-rays. The beamline will serve as a standard for such measurements and hence we call it a calibration and standards beamline, or alternatively, a metrology beamline. This beamline will also be valuable as a general-purpose beamline to prepare, test and set up a wide range of experiments. A complementary important aspect of this installation is the realization of a primary standard (as in BESSY II) [1]: in this case, the metrology beamline of SOLEIL could become the national primary standard source in collaboration with the Laboratoire National d'Essais (LNE) partner of this project. In another field, this installation will be used in the design and characterization of several diagnostics for the Megajoule Laser in Bordeaux in collaboration with the CEA DIF, also a partner of this project.

Future metrology needs for synchrotron radiation grazing-incidence optics

An International Workshop on Metrology for X-ray and Neutron Optics, the first of its kind, was held on March 16–17, 2000, at the Advanced Photon Source at Argonne National Laboratory. Metrology specialists, beamline engineers and scientists, and vendors from around the world met to evaluate current metrology instrumentation and methods used to characterize the surface figure and finish off long grazing-incidence optics used in synchrotron radiation beamlines, and to consider future needs for synchrotron, free-electron laser, and neutron sources. This paper summarizes the discussions on mirror and metrology requirements for the current and next-generation X-ray sources. Some recommended strategies for the needs of the future are also given.