Characterization of CdTe and CdZnTe detectors for gamma-ray imaging applications

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 458; no. 1; pp. 297 - 309
• Main Authors: Verger, L, Boitel, M, Gentet, M.C, Hamelin, R, Mestais, C, Mongellaz, F, Rustique, J, Sanchez, G
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2001
• Subjects: Bi-parametric spectrum; CdTe; CdZnTe; Detection efficiency; Energy resolution; Gamma camera detector; HBM; HPBM; Lifetime; Mobility; Pulse height; Rise time; Scatter rejection; THM; TOF; Transport properties; VBM; VBM; Rise time; Transport properties; Scatter rejection; Mobility; Bi-parametric spectrum; TOF; CdTe; HPBM; HBM; Lifetime; Energy resolution; Pulse height; THM; Gamma camera detector
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/S0168-9002(00)00874-3

CEA-LETI in association with Bicron and Crismatec has been developing solid-state gamma camera technology based on CZT. The project included gamma camera head systems development including front-end electronics with an integrated circuit (ASIC), material growth, and detector fabrication and characterization. One feature of the work is the use of linear correlation between the amplitude and the fast rise time of the signal – which corresponds to the electron transit time in the detector, a development that was reported previously and which allows more than 80% of the 122 keV γ-photons incident on HPBM material to be recovered in a ±6.5% 2D window. In the current work, we summarize other methods to improve CZT detector performance and compare them with the Bi-Parametric Spectrum (BPS) method. The BPS method can also be applied as a diagnositic. BPS curve shapes are shown to vary with electric field, and with electron transport properties, and the correction algorithims are seen to be robust over a range of values. In addition, the technique is found to improve detectors from a variety of sources including some with special electrode geometries. In all cases, the BPS method improves efficiency (>75%) without degrading energy resolution (± 6.5% 2D window) even for a monolithic detector. The method does not overcome bulk inhomogeneity nor noise which comes from low resistivity.