New trends in γ-ray imaging with CdZnTe/CdTe at CEA-Leti

Increasing interest in CdTe/CZT for γ-ray imaging has marked the last 10 years with progress in crystal growth, device technology, integrated electronics and signal processing. The purpose of this paper is to present recent advances in these four fields at CEA-LETI. A new method to grow very large dimension CZT up to 300 mm in diameter is presented. MS-contact process control allows design of very small electrodes (100 μm pitch) and results on long-term stability are presented. The development of low-noise front-end integrated electronics and new interconnects technologies have made “pixel detectors” feasible. Significant effort has been focused on reaching high-energy resolution as well as high detection efficiency. The combination of signal processing such as bi-parametric (BP) approaches and electrode design presents an interest in charge loss compensation for a large range of μτ products, tailing reduction due to geometric effect and depth of interaction information. New digital approaches may give drastic advantages to push the limit of spectrometric performance. In the field of γ-ray application, single-channel device for per-operative probes and small 2-D imager for molecular imaging are the most promising ones. By using a tailored “mixed” electrode (small anode and capacitive grid Frich effect) and a BP correction, an energy resolution of 1% at 662 keV has been demonstrated with CZT based 8×8×15 mm3 detector. New results of 3-D CZT detectors for μPET imaging are presented with a measured coincidence time of 2.6 ns FWHM and an expected spatial resolution of 1 mm FWHM.