Characterisation of the Timepix4 silicon sensor detector for low energy X-ray applications

This study aims to provide a characterisation of the Timepix4 hybrid pixel detector (HPD) in terms of energy calibration, energy resolution, temperature response and angular response for low-energy photon applications (20–150 keV). The Timepix4 detector used in this study was bump-bonded to a 300 μ m thick silicon sensor. The characterisation was performed using X-ray fluorescence lines from several materials and 3 radioactive sources: 55 Fe, 109 Cd and 241 Am. In this context, the Timepix4 HPD shows excellent performances, with an energy resolution ranging from 43.52% at 5.89 keV to 7.84% at 59.54 keV. The measured energy resolution was slightly better than with previous versions of the detector. A strong angular dependence was observed, with a photon count ratio decreasing by up to a factor of 2 for 55 Fe and 85% for 241 Am with a 90 ° rotation. The detector should therefore be used with restricted angular ranges to limit incorrect photonic fluences. Temperature was observed over the tested range to have a minimal impact. The relative energy shift for the 241 Am 59.54 keV peak varied between 0.74% from 10 °C to 1% at 40 °C, showing a linear relationship between the temperature variation and the position of the photopeak. No correlation between the temperature variation and the number of counts in the photopeak was observed, but a small energy resolution loss with the increasing temperature was identified. The use of correction factors or the implementation of the associated uncertainty should be considered in the case of large temperature variations in between measurements. • Timepix4 is the latest version of the Timepix ASIC. • Timepix4 demonstrated strong spectroscopic performances. • Temperature (10-40 °C) minimally affects Timepix4 energy and fluence accuracy. • Timepix4 has limited angular response for low-energy X-rays.