Characterization of the H3D ASIC Readout System and 6.0 cm$^{3}$ 3-D Position Sensitive CdZnTe Detectors

Abstract

Two 20 mm 20 mm 15 mm pixelated CZT detectors made by eV-Products were characterized using the new H3D Application Specific Integrated Circuits (ASIC) readout system developed by the Instrumentation Division at Brookhaven National Laboratory. The ASIC is capable of reading out energy and timing signals from 121 anode pixels and the planar cathode electrode of one CZT detector simultaneously. The system has a measured electronic noise of 2.2 keV FWHM with a dynamic range from 20 keV to 3.0 MeV. The two detectors achieved energy resolution of 0.48% FWHM and 0.60% FWHM, respectively, at 662 keV for single-pixel events from the entire 6.0 cm detection volume at room temperature with an un-collimated Cs source. The average of both detectors were measured to be cm /V. The detection efficiency of the two detectors was evaluated at several different energies up to 1.3 MeV by comparing with simulated data. It was found that the total counts agree well between the measured data and the simulated data over the studied energy range. However, the measured photopeak counts were 10-15% lower than simulated photopeak counts at high gamma-ray energies. The analysis shows that the loss of photopeak efficiency is likely due to the charge loss from peripheral pixels to the boundary of detectors.

Three‐Dimensional Position‐Sensitive Wide Bandgap Semiconductor Gamma‐Ray Imaging Detectors

“…Our group proposed the threedimensional (3D) position-sensing technology in 1998 5 and subsequently demonstrated better than 1% F WHM energy resolution for 662 keV gamma rays on CdZnTe detectors with dimensions up to 2x2x1.5 cm 3 . 6 Energy resolutions of about 1.6% F WHM have been demonstrated on Hgl 2 detectors with dimensions of up to 1.8x1.8x1.5 cm 3 . 7 Figure 1.…”

A Correction Factor to the Two-Bias Method for Determining Mobility-Lifetime Products in Pixelated Detectors

“…Note that for a constant electric field, (8) reduces to (2). While there is currently no technique to measure the electric field profile in thick semiconductor detectors with the fidelity required to use (8), the profile can be approximated with continuous functions comparable to profiles obtained from cathode waveform analysis [10]. These electric field profiles can be used to estimate the magnitude of the non-uniform electric field effect on the μ e τ e measurement.…”

“…Because of the simplicity and accuracy of the two-bias method, many researchers have used it to characterize μ e τ e in pixelated detectors [8], [11]- [14]. However, the original two-bias method assumes an ideal weighting potential for single-polarity charge sensing; specifically, zero throughout the bulk and a rapid increase to one at the anode surface (see Fig.…”

Use of virtual Frisch-grid CdZnTe detectors to attain sub-millimeter spatial resolution

“…The assembled VFGD module was connected to the hardware in the test box that contains the readout electronics based on the 3D ASIC (H3D); this was developed jointly by BNL's Instrumentation Division and the University of Michigan [2]. Figs.…”