<title>Progress in the study of CdZnTe strip detectors</title>

Abstract

We report new performance measurements and computer simulations of a sub-millimeter pitch CdZnTe strip detector under study as a prototype imaging spectrometer for astronomical X-ray and 7-ray observations. The prototype is 1.5 mm thick with 375 micron strip pitch in both the x and y dimensions. Previously reported work included demonstrations of half-pitch spatial resolution ( 190 microns) and good energy resolution and spectral uniformity. Strip detector efficiency measurements have also been presented. A model that includes the photon interaction, carrier transport and the electronics was developed that qualitatively reproduced the measurements.The new studies include measurements of the CdZnTe transport properties for this prototype in an effort to resolve quantitative discrepancies between the measurements and the simulations. Measurements of charge signals produced by laser pulses and a-rays are used to determine these transport properties. These are then used in the model to predict 7-ray efficiencies that are compared with the data. The imaging performance of the detector is studied by scanned laser and gamma beam spot measurements. The results support the model's prediction of nearly linear sharing of the charge for interactions occurring in the region between electrodes. The potential for strip detectors with spatial resolution much finer than the strip pitch is demonstrated. A new design scheme for strip detectors is shortly discussed.

Weighting potentials in CdZnTe /spl gamma/-ray detectors with segmented electrodes

“…Indeed, when the bias VC was raised from +200 Volts to 4 0 0 Volts, the measured value of the sum in the center of the gap increased from 82% to 90% of the calculated sum'with a clear indication of a saturation ratio close to unity. Figure 4 shows similar data obtained by scanning a collimated laser beam on the cathode surface of a strip detector [4]. Again the shape of Vu; agrees with the simulation, including the observation of small satellite structures in the subsequent gaps, similar to those shown in Figure 1 (top).…”

<title>Three-dimensional imaging and detection efficiency performance of orthogonal coplanar CZT strip detectors</title>

“…In earlier work, we reported on studies of double-sided CZT strip detectors with orthogonal anode and cathode strips. [9][10][11][12][13] In those publications we recognized that the poor transport of the hole charge carriers restricts the effective thickness of detectors that have their signal contacts on both the anode and cathode surfaces. In double-sided strip detectors events interacting far from the cathode may not generate large enough signals to trigger the cathode strip electronics to identify the second coordinate of the interaction location.…”

Transport properties and performance of CdZnTe strip detectors

“…A. Charge transport model O UR model for charge transport and signal generation has already been described, along with comparisons to experimental signals 14,15,7,2,8]. The model successfully reproduced signals from CdTe detectors 15,16].…”

“…I. INTRODUCTION G OOD energy resolution, spectral uniformity and sub-millimeter spatial resolution have been demonstrated with CdZnTe strip detectors 1,2,4,6,7,8]. Recent laser scans accross our strip detector showed a potential for position resolution much smaller than the strip pitch, possibly as good as 10 m 8].…”

“…An appropriate model for the charge transport and signal generation processes in CdZnTe detectors is an essential tool for understanding the detector performance characteristics and can be used to help specify optimum detector geometries and signal processing electronics for each application 2,3,7,8,9,10,12,13,14,15]. Our model is intended to be an end-to-end tool for simulating all detection and measurement processes from the radiation interaction down to the electronic chain.…”