Optimization of quasi-hemispherical CdZnTe detectors by means of first principles simulation

Abstract

In this paper we present the development of quasi-hemispherical gamma-ray detectors based on CdZnTe. Among the possible single-polarity electrode configurations, such as coplanar, pixelated, or virtual Frisch-grid geometries, quasi-hemispherical detectors are the most cost-effective alternative with comparable raw energy resolution in the high and low energy range. The optimal configuration of the sensor in terms of dimension of the crystals and electrode specifications has been first determined by simulations, and successively validated with experimental measures. Spectra from different sources have been acquired to evaluate the detectors performances. Three types of detectors with different CZT volumes have been fabricated, namely 10 × 10 × 5 mm3, 15 × 15 × 10 mm3 and 20 × 20 × 10 mm3. In the case of 10 × 10 × 5 mm3 crystals, the optimum pixel size determined by our simulation tool was confirmed by experiments: the best spectroscopic resolution of 1.3% at 662 keV has been found for a 750 μm diameter pixel detector. The best energy resolution values obtained for the 15 × 15 × 10 mm3 and 20 × 20 × 10 mm3 detectors were respectively 1.7% and 2.7% at 662 keV.

Use of CdZnTe Quasi-Hemispherical Detectors under the Impact of Low Temperatures and High-Gamma Radiation Fluxes

“…Quasi-hemispherical detectors contain a large negative electrode on five sides and a positive dot electrode at the center of one of the large sides. The optimal diameter d of the dot electrode is determined by the size of the detector and the electrophysical characteristics of the CZT crystal used for detector fabrication [6]. Quasi-hemispherical detectors have slightly worse spectrometric characteristics then ideal hemispherical detectors [2] due to a deterioration of charge collection from corner regions of the detector where the electric field is significantly reduced.…”

“…A bias voltage was applied using a high-voltage power supply, allowing the measurement of detector leakage currents. Inside an electrically shielded case (9) around the detector, four IR LEDs (6) with different wavelengths of emitted light were placed. Each of the LEDs was powered by its own power source, allowing the illumination intensity to be adjusted by changing the direct consumption current of the LED.…”

“…These detectors exhibit different electrode configurations (coplanar grid, pixelated, Frish-ring and other types) employed for single-charge collection realization. Among them, quasihemispherical detectors are widely employed [1][2][3][4][5][6][7]. These detectors are relatively simple to manufacture but exhibit favorable spectrometric characteristics and do not require complex electronic circuits for their use.…”

Investigation of the Influence of Infrared Illumination on the Pulse Shapes of Output Signals of CdZnTe Detectors

“…They contained a large negative electrode on five sides and a positive dot electrode with a diameter of 2 mm at the center of one of the large sides. This optimal diameter of the dot electrode was determined by the size of the detector and the electrophysical characteristics of the CZT crystal used [14]. All detectors were produced with the same surface treatment.…”

“…Different types of CZT detectors with different contact configurations [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ] are used to achieve the most complete charge collection and high-energy resolution. Among all electrode configurations, the quasi-hemispherical configuration [ 2 , 10 , 11 , 12 , 13 , 14 , 15 ] provides spectrometric characteristics of detectors that are sufficiently high for many tasks and do not require complex and expensive electronics for their use.…”