CZT detectors with 3D readout for gamma-ray spectroscopy and imaging

Abstract

We are developing 10 mm thick CZT detectors with 3-D readout for ~100 keV to ~1.5 MeV gamma-rays. Multiple-site gamma-ray interactions are fully measured, i.e., the energy and 3-D position of each site are determined. Spatial resolution is 1 mm FWHM. Anode pixel readout with 1 mm pitch is used for x-and y-positions and charge drift times for z-positions. Drift time measurements are triggered by the cathode signal and end when each interaction site's charge cloud reaches an anode pixel. Post-event processing corrects for signal loss due to charge trapping and accurately determines gamma-ray energies, with a goal of 1% energy resolution at 662 keV. Compton kinematic analysis can identify the initial interaction site in most cases as well as constrain the incident gamma-ray direction. Tests were made with a prototype detector, measuring 10 x 10 x 10 mm 3 and operated at 1000 V bias. The measured drift time resolution of 25 nsec FWHM at 662 keV and 60 nsec at 122 keV corresponds to z-position resolution of 0.25 and 0.60 mm FWHM, respectively. The technique is described and results of modeling and tests are presented.

Simulation studies of CZT detectors as gamma-ray calorimeter

“…So far CZT detectors have mainly been studied in the photoelectric regime (10 keV-∼300 keV). Two different designs have been widely used, pixellated detectors and single sided strip detectors [1,2,3,4]. Excellent energy resolutions have been achieved with both designs.…”

Study of a high-resolution, 3D positioning cadmium zinc telluride detector for PET

“…The result is that when photon interactions occur within the volume subtended by the gaps between anode strips, the bent field lines steer the drifting charge carriers away from the gaps toward the anode strips (figure 3(b)). The steering electrodes therefore effectively funnel charge carriers towards anodes for more complete charge collection on anodes (Kalemci et al 1999, Matteson et al 2002). …”

“…Figure 3(a) shows interspersed anodes (thin) and steering electrodes (thick), and figure 3(b) shows the effect of steering electrodes on electric field lines (adapted from Matteson et al 2002). …”

“…The steering electrodes therefore effectively funnel charge carriers towards anodes for more complete charge collection on anodes (Kalemci et al 1999, Matteson et al 2002.…”