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Description
The Medipix collaboration was formed in the 1990s at CERN with the intention of adapting hybrid pixel detector technology to fields outside of high energy physics. Since then there have been four generations of the Medipix detector, and four generations of the closely related Timepix detector. Silicon is a common sensor material for detecting X-rays in the 5-30 keV energy range. The response of silicon sensor detectors to X-rays in this range is well studied and understood, but the response to electrons of similar energies is not well documented. This energy range corresponds closely with typical energies used in scanning electron microscopy, one of the areas in which Medipix has found experimental and commercial use. Medipix3 is unique in the field of hybrid pixel detectors as it includes a charge summing mode which mitigates the effects of charge sharing. The performance of the charge summing algorithm has also not been well studied when comparing x-rays and electrons.
This research presents a systematic comparison study of a Medipix3 silicon sensor detector to both X-rays and electrons in the 5-30 keV energy range. At these energies electrons will lose a significant portion of their energy in the entrance window, making backside contact geometry an important factor. Experimental results show a consistent difference in response to X-rays and electrons in this energy range, with the electron response trending towards that of X-rays as the energy increases.
Measurements were conducted using X-ray fluorescence and an electron mirror, in both single pixel and charge summing modes, as well as for three gain modes. Additionally, simulations have been performed using AllPix2 which show a similar response to experiment, and are being used to guide development of a detector optimized for low energy electron detection.
