Timepix4 Based Detection Systems Characterization for X-Ray Imaging Applications

The Timepix4 is an Application-Specific Integrated Circuit (ASIC) developed by the Medipix4 Collaboration at CERN. It features a 448x512 pixel matrix that can be bump-bonded to semiconductor sensors of various materials and thicknesses, with a pixel pitch of 55 μm. Operating in data-driven ToA-ToT mode, the Timepix4 simultaneously measures the Time of Arrival (ToA) of each hit and the signal's Time over Threshold (ToT). In pixelated hybrid detectors, charge sharing between neighboring pixels can occur, and a single photon interaction may produce multiple hits. By combining the spatial coordinates of these hits with their ToA, the Timepix4 enables clustering of spatially and temporally correlated events, reconstructing information about the interacting photons. After calibration, the ToT provides a measurement of photon energy. The ability to correct charge-sharing effects and measure photon energies over a continuous spectrum makes Timepix4-based systems highly promising for X-ray and spectral imaging applications. In the first part of this work, two Timepix4-based detection systems, equipped with a 300 μm silicon sensor and a 1 mm CdTe sensor, were energy calibrated and characterized in terms of energy resolution, spatial resolution, and count linearity, to optimize performance for spectral X-ray imaging. In the second part, an example of spectral imaging acquisition and analysis is presented, involving a sample containing multiple contrast agents at different concentrations.