Smart*Light 2.0
A smarter Europe
High-quality X-ray analyses are crucial for medical applications, the preservation of cultural heritage, and the development of materials and processes that contribute to a more sustainable society. The aim of Smart*Light 2.0 is to expand a pilot instrument into a versatile research instrument.
Realisaties
Publicatie: Visibility retrieval and spatial dark-field resolution in DP-XGI
There has been a rising interest in multi-scale imaging of materials and structures. However, conventional X-ray-based imaging methods are fundamentally limited by the discretization of the image, causing a direct coupling between pixel size and field of view. Through small-angle scattering, X-ray dark-field (DF) imaging is sensitive to the sub-pixel structure of the sample being imaged, overcoming this limitation. In grating-based dark-field imaging, the DF signal is operationally defined as the relative change in visibility of the interference pattern in each pixel, which is commonly probed via the process called phase stepping. We show through simulations that the real-space DF resolution in dual-phase X-ray grating interferometry (DP-XGI), for which the interference pattern is directly resolvable, is limited by the fringe period, being larger than the pixel size. We therefore propose a single-shot visibility retrieval algorithm for DP-XGI, which does not require precise phase stepping and is by design restricted to the real-space resolution given by the fringe period. The simulation demonstrates that minimal physical information is lost with a single shot. It is argued that phase-stepping in DP-XGI has only limited benefit compared to single-shot, while it comes at the cost of more complex measurement.
Sinnaeve et al, Vol. 34, No. 18 / 7 Sep 2026 / Optics Express 33622 https://doi.org/10.1364/OE.600956
Publicatie: Optimizing the interaction geometry of inverse Compton scattering x-ray sources
Inverse Compton scattering (ICS) is a promising method for generating coherent and tunable x-rays in a compact setup. In this paper, we present a theoretical framework describing the output of an ICS x-ray source for arbitrary interaction angles between pulsed electron and laser beams in the Thomson regime. This allows for analytic optimization of the x-ray beam properties by varying the parameters defining the geometry. In general, different x-ray applications require optimization of different x-ray beam properties, such as energy spread for x-ray spectroscopy and angular spread for x-ray scattering measurements. In this paper, we restrict ourselves to optimization of the x-ray brilliance, which is a comprehensive figure of merit for x-ray beam quality. The framework can be used, however, to optimize other x-ray properties.We investigate two specific ICS interaction geometries in particular: head-on scattering of a laser beam off an electron beam and scattering of a laser beam off an electron beam in a co-propagating geometry, interacting under a grazing angle. For head-on scattering, we show that a tightly focused, cylindrically symmetric laser pulse, which balances laser intensity and interaction time, optimizes the x-ray brilliance. For a co-propagating, grazing angle geometry, an elliptical focus of the laser pulse is required to mitigate the geometric reduction of the interaction time.We find that the latter geometry is especially useful for soft x-ray generation.
Publicatie: The acid attack (1990) on Rembrandt’s The Night Watch (1642). Reassessing the painting’s condition through a multimodal analytical approach
In 1990, Rembrandt’s The Night Watch was attacked with concentrated sulphuric acid. This study reassesses the affected area and aims to identify and characterise any secondary degradation products, as well as any challenges for the conservation treatment. A comprehensive analytical approach, using macroscopic X-ray fluorescence (MA-XRF), macroscopic X-ray powder diffraction (MA-XRPD), optical coherence tomography (OCT), and light microscopy, scanning electron microscopy combined with energy-dispersive X-ray (SEM-EDX) analysis, micro attenuated total reflectance Fourier transform infrared (µ-ATR-FTIR) spectroscopy and synchrotron radiation micro X-ray powder diffraction (SR-µ-XRPD) of three paint cross-sections, permitted the confirmation of anglesite (PbSO4) and extensive lead soap formation in the affected areas. Additionally, mock-ups were prepared and analysed to reconstruct the entire sequence of events of the acid attack. Current estimations predict that some of the damage to the paint layers will become discernible after varnish removal and that local consolidation of the fragile surface might be required.
Raven, L., Gestels, A., van Loon, A. et al. The acid attack (1990) on Rembrandt’s The Night Watch (1642). Reassessing the painting’s condition through a multimodal analytical approach. npj Herit. Sci. 14, 130 (2026). https://doi.org/10.1038/s40494...
Publicatie: High-resolution compound-specific mapping in works of art via data fusion of MA-XRPD with hyperspectral data (part 2: case studies)
Background: This study is the second part of an investigation into enhancing high-resolution compound-specific mapping for artworks using multi-modal chemical imaging and machine learning. It builds upon the previously introduced framework, part one: method evaluation, by the authors that integrates macroscopic X-ray powder diffraction (MA-XRPD) macroscopic X-ray fluorescence (MA-XRF) or reflectance imaging spectroscopy (RIS). While MA-XRPD is time-consuming, the unique advantage of the technique lies in its ability to visualize the distributions of crystalline phases (e.g., pigments, degradation products) at the surface of artworks and estimate in a quantitative manner their relative concentrations. By leveraging data fusion and predictive modeling, this study aims to enhance the spatial resolution and efficiency of compound-specific mapping of artworks.
Results: This paper applies the previously established machine learning approach to three case studies, demonstrating its feasibility in analyzing heterogenous, complex artworks. The first case study validates the method on a 17th-century Dutch still life painting, comparing the predicted high-resolution compound-specific maps against experimental data. The second case study examines the potential to reduce MA-XRPD scanning time through lower resolution scans and predictive modeling while maintaining accuracy, which is assessed using root mean square error (RMSE) and structural similarity index measure (SSIM). The third case study explores model transferability, evaluating whether predictive models trained on one artwork can accurately predict compound distributions in another. Results confirm the efficacy of the machine learning approach in improving spatial resolution and reducing data acquisition constraints.
Significance: This study addresses the time-intensive nature of MA-XRPD by demonstrating a scalable approach for generating high-resolution, compound-specific maps through data fusion and predictive modeling. By integrating the high specificity of MA-XRPD with the spatial efficiency of faster hyperspectral imaging techniques (MA-XRF and RIS), and applying a random forest regression framework, the method significantly enhances the efficiency and interpretability of chemical imaging in cultural heritage research, enabling more accessible and large-scale non-invasive analysis of complex artworks.
Publicatie: High-resolution compound-specific mapping in works of art via data fusion of MA-XRPD with hyperspectral data (part 1: Method evaluation)
Background: Hyperspectral imaging techniques have emerged as powerful tools for non-invasive investigation of artworks. This paper employs either reflectance imaging spectroscopy (RIS) or macroscopic X-ray fluorescence (MA-XRF) imaging in combination with macroscopic X-ray powder diffraction (MA-XRPD) for state-of-the-art chemical imaging of painted cultural heritage artefacts. While RIS can provide molecular information and MA-XRF can offer elemental distribution maps of paintings of high lateral resolution, the unique advantage of MA-XRPD lies in its ability to visualize the distributions of specific pigments and estimate in a quantitative manner the relative concentrations of the crystalline phases at the surface of artworks. However, MA-XRPD is more time-consuming and offers a lower lateral resolution than RIS and MA-XRF.
Results: This study introduces a machine learning (ML) approach to obtain the distribution of specific compounds on the surface of artworks with a resolution that is comparable to that of RIS and MA-XRF data but with the compound specificity of MA-XRPD. The general aim is to expedite non-destructive artwork imaging analysis by fusing data from different imaging modalities via machine learning models. The effect of preprocessing techniques to enhance the predictive accuracy of the models is explored. The paper demonstrates the method’s efficacy on a 16th-century illuminated manuscript, showcasing the feasibility of predicting compound-specific distribution maps. Three evaluation methods—visual examination of the predicted distribution, root mean square errors (RMSE), and feature permutation importance (FPI)—are employed to assess model performance. Fusing MA-XRF with MA-XRPD led to the best RMSE scores overall. However, fusing the RIS and MA-XRPD data blocks also yield very satisfactory and easily interpretable high-resolution compound maps. Significance: While MA-XRPD allows for highly specific imaging of artworks, its time-consuming nature and limited resolution presents a bottleneck during non-invasive imaging of painted works of art. By integrating data from more time-efficient hyperspectral techniques such as MA-XRF and RIS, and employing machine learning, we expedite the process without compromising accuracy. The fusion process can also denoise the distribution maps, improving their readability for heritage professionals and art historical scholars. https://doi.org/10.1016/j.tala...
Publicatie: Advanced X-ray techniques to study the alteration of pigments in paintings
The application of X-ray methods (using conventional sources or synchrotron radiation) for investigating degradation phenomena in paintings has significantly increased in the last two decades. This rise is due to their ability to provide spatially resolved elemental, molecular, and structural information from the macroscopic to the nanoscopic levels. This review will focus on the application of latest-generation X-ray techniques, including X-ray fluorescence (XRF), X-ray absorption spectroscopy (XAS), and X-ray diffraction (XRD), to study the alteration processes of pigments in paintings. The first part outlines the fundamentals of XRF, XAS, and XRD techniques and then describes the corresponding instrumental set-ups used for non-invasive macro-scale mapping of paintings and synchrotron radiation-based X-ray analysis of paint micro-samples. Subsequent sections will cover advancements in X-ray data analysis software, workflow management systems, Open Science and FAIR data initiatives, alongside practical aspects of sample preparation and issues concerning X-ray-induced damage to paints. The final section will review degradation phenomena resulting from chemical changes of selected classes of pigments. This will involve describing key findings obtained from paintings, related micro-samples, and artificially aged paint mock-ups. The outcomes discussed in this review highlight their crucial role in developing effective monitoring and preventive conservation strategies for artworks highly susceptible to degradation within heritage sites and museums.
Monico, L., Janssens, K., Cotte, M. et al. Advanced X-ray techniques to study the alteration of pigments in paintings. Riv. Nuovo Cim. 48, 315–434 (2025). https://doi.org/10.1007/s40766...
Publicatie: Optics for broadband x-ray ptychography
In conventional x-ray ptychography, diffraction data is 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 3rd and 4th generation synchrotron sources and long scanning times. An alternative approach is to use a broadband illumination in combination with an energy resolving detector. These detectors record the data in a series of energy channels simultaneously, creating a stack 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.
Stolp et al. Rev. Sci. Instrum. 96, 083707 (2025) https://doi.org/10.1063/5.0274...
Publicatie: A traveling wave X-band accelerating structure with low-beta front end for a compact inverse Compton scattering x-ray source.
Smart*Light is a table-top inverse Compton scattering X-ray source under development at Eindhoven University of Technology. The linac-based source aims for a very compact design through the use of X-band technology operating at accelerating gradients exceeding 60 MV/m. The heart of the linac is an X-band accelerating structure whose design is based on the T24 structure developed as a prototype for the Compact Linear Collider. To allow for the capture and acceleration of sub-relativistic electron bunches to energies of ∼ 30 MeV two adjustments have been made to the structure: the first is a reduction in the length of the first cells to match the injected particle velocities, and the other is to add additional cells to efficiently use RF power that would otherwise be dissipated within a load. Here we present the design, manufacturing, and commissioning of the Smart*Light accelerating structure, together with an analysis of the generated x-rays showing that the parameters of the accelerated electron bunches are in good agreement with the design values.
Stragier, X.F.D., Grudiev, A., Nijhof, D. et al. A traveling wave X-band accelerating structure with low-beta front end for a compact inverse Compton scattering x-ray source.
Eur. Phys. J. Spec. Top. 234, 8113–8123 (2026). https://doi.org/10.1140/epjs/s...
Publicatie: Broadband Ptychotomography with a Hyperspectral Detector
X-ray ptychography is a robust microscopy technique with nanoscale resolution that requires a spatially and temporally coherent illumination. In a typical setup, the temporal coherence requirements are satisfied by monochromating the x-ray source, e.g., using a crystal monochromator. Recent studies have shown that energy resolving, or hyperspectral, detectors can to some extent replace the role of the monochromator to perform, e.g., edge-subtraction ptychographic imaging with broadband radiation in a single acquisition. Scaling this capability from two dimensions (2D) to three dimensions (3D), and from a single absorption edge to multiple edges, is critical for its applications in structural and elemental characterisation. The method is hitherto limited by the inherently lower maximum count rate of hyperspectral detectors and the chromaticity of the optics often used in x-ray ptychography experiments, namely Fresnel zone plates. In this work, we design an optimized broadband spectroscopic ptychography setup and use it to perform 3D hyperspectral imaging of particles of battery material containing various percentages of nickel, manganese, cobalt (NMC). We show that we can identify different compositions based on their spectral response. We discuss the results and provide guidelines for future exploitation of the method in laboratory settings.
Stolp et al, PHYSICAL REVIEW LETTERS 134, 257001 (2025) DOI: 10.1103/kbrf-gb9c