Minimization of charge sharing effects in a counting type SOI pixel detector for synchrotron radiation

The charge sharing effect among adjacent pixels of a single photon counting detector, which comes from the lateral spread of charges generated from the interaction of X-ray quanta in silicon, has been a critical issue in the pixel detectors due to its influence on the count rate and resolution capability. Targeted on this issue, a single photon counting SOI pixel detector CNPTEG1 used for synchrotron radiation (SR) experiments was developed. It has 17k hexagonal pixels with 52 μm center-to-center pitch while keeping a circuit of charge sharing arbitration logic and 19-bit counter in each pixel. The effectiveness of the charge sharing arbitration logic was verified by using a micro beam with about 10 μm diameter scanning across pixels. The results showed that the count loss or multiple count in pixel boundary was effectively suppressed by the charge sharing arbitration logic with proper threshold setting. The impact of charge sharing on the pixel point spread function (PSF) has also been investigated.