A 12-bit 1MS/s SAR-ADC for multi-channel CdZnTe detectors

This paper presents a low power, area-efficient and radiation-hardened 12-bit 1 MS/s successive approx- imation register （SAR） analog-to-digital converter （ADC） for multi-channel CdZnTe （CZT） detector applications. In order to improve the SAR-ADC＇s accuracy, a novel comparator is proposed in which the offset voltage is self- calibrated and also a new architecture for the unit capacitor array is proposed to reduce the capacitance mismatches in the charge-redistribution DAC. The ability to radiation-harden the SAR-ADC is enhanced through circuit and layout design technologies. The prototype chip was fabricated using a TSMC 0.35 μm 2P4M CMOS process. At a 3.3/5 V power supply and a sampling rate of 1 MS/s, the proposed SAR-ADC achieves a peak signal to noise and distortion ratio （SINAD） of 67.64 dB and consumes only 10 mW power. The core of the prototype chip occupies an active area of 1180 ×1080μm2.

A reference voltage in capacitor–resister hybrid SAR ADC for front-end readout system of CZT detector

An on-chip reference voltage has been designed in capacitor-resister hybrid SAR ADC for CZT detec- tor with the TSMC 0.35 μm 2P4M CMOS process. The voltage reference has a dynamic load since using variable capacitors and resistances, which need a large driving ability to deal with the current related to the time and sampling rate. Most of the previous articles about the reference for ADC present only the bandgap part for a low temperature coefficient and high PSRR. However, it is not enough and overall, it needs to consider the output driving ability. The proposed voltage reference is realized by the band-gap reference, voltage generator and output buffer. Apart from a low temperature coefficient and high PSRR, it has the features of a large driving ability and low power con- sumption. What is more, for CZT detectors application in space, a radiation-hardened design has been considered. The measurement results show that the output reference voltage of the buffer is 4.096 V. When the temperature varied from 0 to 80 ℃, the temperature coefficient is 12.2 ppm/℃. The PSRR was -70 dB @ 100 kHz. The drive current of the reference can reach up to 10 mA. The area of the voltage reference in the SAR ADC chip is only 449 × 614μm2. The total power consumption is only 1.092 mW.

A novel CZT detector using strengthened electric field line anode

In this paper, we report on the design, simulation and testing of a novel CZT detector with an electrode named the Strengthened Electric Field Line Anode（SEFLA）. The Strengthened Electric Field（SEF） technique and Single Polarity Charge Sensing（SPCS） technique are implemented. It could achieve the same performance as Coplanar Grid, Pixel Array CZT detectors but requires only a simple readout system. Geant4, Ansoft Maxwell and a self-developed Induced Current Calculator（ICC） package are used to develop an understanding of how the energy spectrum is formed, and the parameters of the detector are optimized. A prototype is fabricated. Experimental results demonstrate the effectiveness of this design. The test shows that the SEFLA detector achieves a FWHM of6.0% @59.5 ke V and 1.6% @662 ke V, which matches well with the simulations.

Charge sharing effect on 600 μm pitch pixelated CZT detector for imaging applications

We are currently investigating the spatial resolution of highly pixelated Cadmium Zinc Telluride （CZT） detector for imaging application. A 20 mm × 20 mm× 5 mm CZT substrate was fabricated with 600 μm pitch pixels （500μm anode pixels with 100 μm gap） and coplanar cathode. Charge sharing between two pixels was studied using collimated a 122 keV gamma ray source. Experiments show a resolution of 125 μm FWHM for double-pixel charge sharing events when the 600 μm pixelated and 5 mm thick CZT detector biased at -1000 V. In addition, we analyzed the energy response of the 600 μm pitch pixelated CZT detector.

Alpha particle detection with a planar CdZnTe detector and relative simulations

Purpose The performance of CZT inγ-ray and X-ray detection is growing rapidly in these years.However,there are only a few reports on its utilization inαparticle detection.Therefore,to study the properties of CZT for detection ofαparticle,a detection system has been manufactured,and a series of simulations have been done.Methods A 22×22×0.7mm^(3) planar CZT detector is deployed to detect theαparticles from a radiation source containing Am-241 and Pu-239,while COMSOL MultiPhysics and GEANT4 are employed in the simulation of charge collection and interaction betweenαparticles and CZT.Results An energy resolution of 1.47%FWHM at 5.486MeV and 1.32%at 5.157MeV has been achieved.A simulated spectrum has been created,and it is analogous to the one from experiment.Conclusion The experiment results show the potential of CZT inαdetection.The simulations are confirmed effective and will guide a better design of the detecting system.

Experiment validation of the high stability of long-term transmitted gamma photon counting of a new CdZnTe semiconductor detector and its preliminary applications

Purpose To develop a detector system with high stability in counting the detection of transmitted gamma photons,which can be applied in the area of non-destructive testing.Method We used the cadmium zinc telluride(CZT)detector with single-polarity electrodes to substitute the traditional scintillator detector and front-end read-out electronics based on our self-designed low-noise charge-sensitive amplifier.Results and conclusion The energy resolution of 662 keV from 137Cs radioactive source was improved to 1.9%,and the relative standard deviation of different total counts of transmitted photons detected decreased to 0.05%when the counts were more than 5×107,which means the impact from the statisticalfluctuation of long-term gamma photons counting will not be a main obstacle to achieving high precision in the area of non-destructive testing.The preliminary experiment of inspecting the inner gaps in the metal rodsfilled with samples also proved to have good prospects for the CZT detector in non-destructive testing.