Study of an X-ray/Gamma Ray Photon Counting Circuit Based on Charge Injection

A direct charge-to-digital converter (QDC) based on charge injection for an X-ray/gamma ray photon counting detector is introduced in this paper. The proposed circuit is a direct conversion circuit unlike conventional indirect circuits. Direct charge signal processing does not lose time because it a...

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Bibliographic Details
Published in:Sensors and materials 2018-01, Vol.30 (7), p.1611
Main Authors: Takagi, Katsuyuki, Terao, Tsuyoshi, Koike, Akifumi, Aoki, Toru
Format: Article
Language:English
Subjects:
Charge injection
Circuit design
Coincidence circuits
Converters
Counting
Counting circuits
Dark current
Direct conversion
Electronic components
Gamma rays
Sensors
Signal processing
Simulation
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Summary:A direct charge-to-digital converter (QDC) based on charge injection for an X-ray/gamma ray photon counting detector is introduced in this paper. The proposed circuit is a direct conversion circuit unlike conventional indirect circuits. Direct charge signal processing does not lose time because it accomplishes conversion and resets simultaneously and starts the conversion without waiting for all the photon energy to be converted into charge. This conversion behavior was verified by simulating a direct QDC circuit. Moreover, in the simulation, the effect of the dark current in the detector was taken into consideration and an appropriate compensation method for this was proposed. An experimental circuit was built and tested with discrete components to confirm coincidence with the simulated results. Direct conversion is simpler than indirect conversion, and the resultant circuit contains fewer electronic components than an indirect converter. This circuit is suitable for high-density imaging sensor design. In addition, this architecture ideally counts generated charges individually, which is valuable for the analysis of charge drift inside the detector.
ISSN:0914-4935
DOI:10.18494/SAM.2018.1925