Speaker
Description
The Medipix4 collaboration has recently introduced the Timepix4, a cutting-edge application-specific integrated circuit (ASIC) designed for single-particle detection in hybrid pixel detectors, which features a 448 × 512 pixel matrix with a 55 µm pitch [1].
The Timepix4 architecture supports a data-driven operating mode where pixel hits trigger the generation of data packets. These packets contain both Time of Arrival (ToA) and Time over Threshold (ToT) data for each event. The ToT is correlated to the charge collected by the pixel, which in turn reflects the energy deposited by the incident photon. By applying pixel-wise energy calibration, it is possible to obtain full spectral information to implement multi-energy X-ray imaging applications.
Timepix4 detector assemblies were fabricated by bump-bonding the ASIC to pixelated 1 mm-thick CdTe and 500 µm-thick GaAs sensors, aimed at spectral X-ray imaging applications. To calibrate and evaluate the spectral performance of these assemblies, measurements were conducted at the METROLOGIE beamline of the SOLEIL Synchrotron (Paris, France), with monochromatic photon beams in an energy range from 12 keV to 38 keV. Data acquisition was managed via the SPIDR4 (Nikhef) readout system and DataPix4 software [2]. The experimental setup is shown in Figure 1.
The acquisitions with monochromatic X-rays at different energies were used to calibrate the energy response from ToT measurements through a hybrid calibration strategy. This method integrates the experimental data obtained from monochromatic radiation with internal charge test-pulse sequences generated by the ASIC, following a procedure established in previous works [3,4].
In this contribution, we will report the results of the energy calibration and energy resolution measured for both sensor materials. Clustering of hits, for event reconstruction, based on ToA and spatial coincidence will be also discussed as a means to mitigate charge sharing and X-ray fluorescence escape effects. The results of this characterization provide essential parameters for the calibration and computational modeling of Timepix4-based systems that are instrumental in the development of high-resolution spectral imaging detectors for X-ray imaging applications.