Comparison of the charge sharing effect in two hybrid pixel detectors of different thickness

Abstract

Advances in semiconductor technologies, enable the design of hybrid pixel detectors with ever smaller pixel sizes while maintaining good performance of analogue circuits. Along with the decrease in the size of pixels new, previously unaddressed phenomena are beginning to play an important role. One such phenomenon is the charge sharing effect, where the charge generated by a particle in the vicinity of the pixel's border is collected by two or more different detector electrodes and processed in part by two or more independent pixels. In systems operating in the single photon counting (SPC) mode which compares the amplitude of the recorded signal with a predetermined threshold, this may reduce or increase the number of photons counted. In systems which measure the amplitude of the signal recorded, this phenomenon can lead to incorrect results of the amplitude measurements. In order to investigate the effect of charge sharing, measurements were conducted using silicon pixel detectors with the thickness of 300 μ m and 1 mm, 100 μ m × 100 μ m pixel size, connected to the PXD18k ASIC. The pixel array was scanned with 16 keV narrow pencil beam. The measurement setup and the results of the measurements are presented in the article.