Optimum spectroscopic performance from CZT γ- and X-ray detectors with pad and strip segmentation

We describe a method for obtaining optimum spectroscopic performance from CZT gamma- and X-ray detectors with segmented readout. This method allows to circumvent the effects of incomplete charge collection and to obtain energy resolution approaching the limitation due to detector and electronic noise. It is insensitive to hole trapping over most of the detector volume, while a modest amount of electron trapping can be tolerated. The method requires segmentation of the positive electrode. Signals from the common electrode, taken in coincidence with those of the segmented positive electrode, provide a measure of the depth of interaction. A distinct correlation profile exists between the signals of the segmented element and the common electrode. These profiles can be linearized to yield very sharp energy lines with high photopeak efficiency. Additional cuts can be made to improve peak-to-valley ratio, with small toss in efficiency. We present measurements taken with CZT detectors with pad segmentation. Illuminating with a Ba-133 source, we obtain for the 356 keV line a FWHM of 1.0-1.5%, with a peak-to-valley ratio of similar to 100/1, (C) 1999 Elsevier Science B.V. All rights reserved.