Multi-channel detector module for multi-energy computed gamma ray tomography

In this paper an enhanced signal processing electronics for an existing multi-channel detector module for gamma ray computed tomography is presented. The detector electronics is able to evaluate gamma photon energies by measuring pulse duration times, which makes it perfectly suitable for attenuation measurements with multi-energy and/or multiple isotopic sources.
The duration time of each voltage pulse generated by a gamma photon within the radiation detector is measured using a complex programmable logic device (CPLD). A sophisticated logic circuit for eight detector channels is designed to acquire the pulse duration time spectra in a total of 256 channels per detector channel. This paper introduces the basic concept, describes the general and the specific CPLD design, provides an analysis of the accuracy and presents measured pulse duration time spectra.