Subpixel resolution in CdTe Timepix3 pixel detectors

Abstract

Timepix3 (256  256 pixels with a pitch of 55 mm) is a hybrid-pixel-detector readout chip that implements a data-driven architecture and is capable of simultaneous time-of-arrival (ToA) and energy (ToT: time-over-threshold) measurements. The ToA information allows the unambiguous identification of pixel clusters belonging to the same X-ray interaction, which allows for full oneby-one detection of photons. The weighted mean of the pixel clusters can be used to measure the subpixel position of an X-ray interaction. An experiment was performed at the European Synchrotron Radiation Facility in Grenoble, France, using a 5 mm  5 mm pencil beam to scan a CdTe-ADVAPIX-Timepix3 pixel (55 mm  55 mm) at 8  8 matrix positions with a step size of 5 mm. The head-on scan was carried out at four monochromatic energies: 24, 35, 70 and 120 keV. The subpixel position of every single photon in the beam was constructed using the weighted average of the charge spread of single interactions. Then the subpixel position of the total beam was found by calculating the mean position of all photons. This was carried out for all points in the 8  8 matrix of beam positions within a single pixel. The optimum conditions for the subpixel measurements are presented with regards to the cluster sizes and beam subpixel position, and the improvement of this technique is evaluated (using the charge sharing of each individual photon to achieve subpixel resolution) versus alternative techniques which compare the intensity ratio between pixels. The best result is achieved at 120 keV, where a beam step of 4.4 mm AE 0.86 mm was measured.research papers

Single-shot, omni-directional x-ray scattering imaging with a laboratory source and single-photon localization

“…With the Timepix3 chip's fast time-stamping, each absorbed photon can accurately be localized below the pixel size at a hit rate of up to 40 Mhits s −1 cm −2 [18] by measuring the charge sharing distribution for each event [20]. In practice, the recorded photon subpixel positions are rebinned into virtual subpixels and the beamlets' intensity distribution can afterwards be analyzed at a resolution smaller than the physical pixel size.…”

Cadmium Zinc Telluride Detectors for a Next-Generation Hard X-ray Telescope

“…The interested reader may consult (Iniewski et al, 2007;Rana et al, 2009;Kitaguchi et al, 2011;Yin et al, 2011Yin et al, , 2013Yin et al, , 2014Veale et al, 2014;Montémont et al, 2014;Ocampo Giraldo et al, 2018;Khalil et al, 2018) for discussions of charge sharing in CZT detectors, and (Zhang et al, 2004;Benoit and Hamel, 2009;De Geronimo et al, 2008;Kim et al, 2011;Zhang et al, 2012;Beilicke et al, 2013;Yin et al, 2014;Kim et al, 2014;Wahl et al, 2015;Chen et al, 2018) for discussion of CZT detectors of different thicknesses and pixel sizes.…”

Characterization of Hybrid Pixel Detector With CdTe Sensor

“…It was required to push the boundaries of detector technology toward sensors capable of counting photons at higher rates and in a broader energy range. For that reason, materials with high atomic numbers Z, such as Gallium Arsenide (GaAs) [6], Cadmium Telluride (CdTe) [7,8], and Cadmium Zinc Telluride (CdZnTe) [9] were introduced to provide those features and enhance the experiment capabilities [10].…”