Abstract
This project is focused on the development of a hybrid pixel detector for X-ray spectral imaging applied to cultural heritage. The aim of this Project is the development and construction of a hybrid pixel detector for X-ray spectral imaging in the field of cultural heritage with performances beyond the state-of-the-art. This detector is based on the flip-chip bonding assembly of the Timepix4 ASIC to pixelated semiconductor sensors. The present Project will apply the Timepix4 ASIC technology to perform photon-counting energy-resolved X-ray imaging applied to cultural heritage, for the determination of the distribution of elements in artistic objects and manufacts. Expected results: If successful, the results of this Project will represent a major breakthrough in the field of cultural heritage non-destructive analysis. It will solve the problem of performing energy-resolved X-ray imaging using a standard (polychromatic) X-ray source, and will therefore allow a non-destructive and non-invasive inspection of a wide range of materials and objects of art. This analysis will be empowered by the single photon-counting capability of the Timepix4 ASIC, in combination with high-rate capability and the possibility to measure the energy of each individual X-ray photon interacting with the sensor (with 1 keV resolution), in addition to a time-stamping resolution of the order of 100 ps. Thanks to the detector system developed in this Project it will be possible to perform Multi Energy Computed Tomography (MECT) in an interval of photon energy previously not reachable. Benefits will be given mostly to material detection and classification purposes. Selection of the optimal energy band for material detection (enhanced contrast) and quasi-monochromatic CT with consequent typical polychromatic beam
Results achieved
: The project aimed at developing and experimentally validating a hybrid pixel detector system based on the Timepix4 ASIC for photon-counting, energy-resolved X-ray imaging in cultural heritage applications. The scientific objective was to move beyond conventional integrating X-ray detectors by exploiting single-photon sensitivity, high spatial resolution and spectrometric capability, with the long-term goal of enabling Energy Resolved Radiography and Multi-Energy Computed Tomography using standard polychromatic X-ray sources. During the project, substantial progress was achieved towards this objective through the design, construction and commissioning of a complete laboratory prototype. The detector system was developed by coupling the Timepix4 ASIC with a CdTe semiconductor sensor, thereby providing the basis for high-efficiency X-ray detection in an energy range relevant to cultural heritage diagnostics. The detector module was integrated with dedicated readout electronics, FPGA-based data acquisition hardware and a software framework for detector control, data handling and preliminary image formation. The complete system was then installed at the Department of Physics and Astronomy of the University of Bologna, where the first functional tests were carried out. The system includes the detector head, readout and acquisition chain, cooling system, X-ray tube, mechanical supports, shielding elements and a remotely controlled multi-axis motion system for detector translation, alignment and sample rotation. Dedicated software libraries were implemented to control the motion stages and to synchronize scan procedures, allowing the acquisition of organized datasets suitable for radiographic and tomographic imaging. The detector was experimentally characterized in terms of imaging response, signal-to-noise behaviour, spatial resolution and preliminary energy response. Linearity tests of the detector response as a function of X-ray tube current were performed, together with signal-to-noise ratio evaluations under different acquisition conditions. Pixel-by-pixel sensitivity calibration was implemented and shown to improve image uniformity and SNR behaviour. Spatial resolution measurements were also successfully carried out using the sharp-edge method. The resulting Modulation Transfer Function showed a behaviour compatible with the expected performance of the detector, with values around 6.5 lp/mm at 10% MTF and 8 lp/mm at 5% MTF, close to the theoretical limit imposed by the 55 micron pixel size. This result confirms the suitability of the detector for high-resolution X-ray imaging of small objects and fine structural details, which is particularly relevant for cultural heritage diagnostics. Low-energy X-ray radiographs of small benchmark objects were successfully obtained, demonstrating the capability of the acquisition line to produce coherent images of physical samples. A first computed tomography experiment was performed using the Timepix4-based system on a plastic test tube filled with beads. demonstrating the feasibility of CT acquisition with the developed prototype. Although full Multi-Energy Computed Tomography on cultural heritage benchmarks and real objects still requires further improvements, this result confirms that the core hardware and software chain for Timepix4-based CT imaging has been successfully established. The project also identified and clarified the main technical challenges that must be addressed to fully exploit the detector’s spectrometric capabilities. Preliminary measurements of the detector response to the X-ray energy spectrum showed that further work is required on energy calibration and charge collection in order to obtain accurate photon-energy measurements. These findings are important outcomes in themselves, as they define the next development steps needed to achieve reliable material-sensitive imaging and energy-band selection. Overall, the project achieved a significant result by delivering a functioning Timepix4-based imaging prototype, integrating it into a dedicated CT setup, validating its basic imaging performance and demonstrating both radiographic and first tomographic acquisitions. These results provide the experimental foundation for future energy-resolved X-ray imaging and Multi-Energy CT applications in cultural heritage. While the final application to real artworks and fully calibrated spectral MECT remains to be completed, the project has successfully established the detector platform, acquisition infrastructure and experimental know-how required to progress towards non-destructive material identification and classification in complex heritage objects. Dissemination activities were also initiated through presentations at scientific events, including Technart 2025 in Perugia and PD2025 Workshop in Bologna, contributing to the communication of the project’s progress within the scientific community.Project details
Unibo Team Leader: Maria Pia Morigi
Unibo involved Department/s:
Dipartimento di Fisica e Astronomia "Augusto Righi"
Coordinator:
Università degli Studi di Ferrara - Amministrazione Centrale(Italy)
Total Unibo Contribution: Euro (EUR) 89.173,00
Project Duration in months: 24
Start Date:
28/09/2023
End Date:
28/02/2026
