The space charge accumulation in CdZnTe crystals seriously affects the performance of high-flux pulse detectors.The influence of sub-bandgap illumination on the space charge distribution and device performance in CdZn...The space charge accumulation in CdZnTe crystals seriously affects the performance of high-flux pulse detectors.The influence of sub-bandgap illumination on the space charge distribution and device performance in CdZnTe crystals were studied theoretically by Silvaco TCAD software simulation.The sub-bandgap illumination with a wavelength of 890 nm and intensity of 8×10−8 W/cm2 were used in the simulation to explore the space charge distribution and internal electric field distribution in CdZnTe crystals.The simulation results show that the deep level occupation faction is manipulated by the sub-bandgap illumination,thus space charge concentration can be reduced under the bias voltage of 500 V.A flat electric field distribution is obtained,which significantly improves the charge collection efficiency of the CdZnTe detector.Meanwhile,premised on the high resistivity of CdZnTe crystal,the space charge concentration in the crystal can be further reduced with the wavelength of 850 nm and intensity of 1×10−7 W/cm2 illumination.The electric field distribution is flatter and the carrier collection efficiency of the device can be improved more effectively.展开更多
A kind of excellent CdZnTe crystal has been grown in Yinnel Tech, Inc. in recent years. Based on these CdZnTe crystals and some new techniques, a portable energy-dispersive spectrometer has been constructed which has ...A kind of excellent CdZnTe crystal has been grown in Yinnel Tech, Inc. in recent years. Based on these CdZnTe crystals and some new techniques, a portable energy-dispersive spectrometer has been constructed which has yielded good results. CdZnTe detector has a 3% relative resolution in high-energy field and can detect gamma rays at room temperature. An integrated circuit based on preamplifier and shaping amplifier chips is connected to the detector. Voltage pulses are transformed into digital signals in MCA (multichannel analyzer) and are then transmitted to com- puter via USB bus. Data process algorithms are improved in this spectrometer. Fast Fourier transform (FFT) and nu- merical differentiation (ND) are used in energy peak’s searching program. Sampling-based correction technique is used in X-ray energy calibration. Modified Gaussian-Newton algorithm is a classical method to solve nonlinear curve fitting problems, and it is used to compute absolute intensity of each detected characteristic line.展开更多
CdZnTe(CZT)capacitive Frisch grid detectors can achieve a higher detecting resolution.The anode structure might have an important role in improving the weighting potential distribution of the detectors.In this paper, ...CdZnTe(CZT)capacitive Frisch grid detectors can achieve a higher detecting resolution.The anode structure might have an important role in improving the weighting potential distribution of the detectors.In this paper, four anode structures of capacitive Frisch grid structures have been analyzed with FE simulation,based on a 3-dimensional weighting potential analysis.The weighting potential distributions in modified anode devices(Model B, C and D)are optimized compared with a square device(Model A).In model C and D,the abrupt weighting potential can be well modified.However,with increased radius of the circular electrode in Model C the weighting potential platform away from the anode becomes higher and higher and in Model D,the weighting potential does not vary too much.展开更多
Cadmium zinc telluride(CZT)is a preferred material for X-ray and gamma-ray detector.Thanks to the relatively high atomic number,high density and wide band-gap,CZT detector possesses sharp energy resolution and high de...Cadmium zinc telluride(CZT)is a preferred material for X-ray and gamma-ray detector.Thanks to the relatively high atomic number,high density and wide band-gap,CZT detector possesses sharp energy resolution and high detection efficiency without cryogenic cooling.We have developed a CdZnTe detector with an energy resolution of 3.45%(FWHM)at 59.54 keV at room temperature,and it is used for X-ray fluorescence analysis.In this paper, leakage current,energy resolution and long term stability of the CZT detector are discussed.展开更多
Due to variable time for charge collection,energy resolution of nuclear detectors declines,especially compound semiconductor detectors like cadmium zinc telluride(CdZnTe) detector.To solve this problem,an analog rise-...Due to variable time for charge collection,energy resolution of nuclear detectors declines,especially compound semiconductor detectors like cadmium zinc telluride(CdZnTe) detector.To solve this problem,an analog rise-time discriminator based on charge comparison principle is designed.The reference charge signal after attenuation is compared with the deconvoluted and delayed current signal.It is found that the amplitude of delayed current signal is higher than that of the reference charge signal when rise time of the input signal is shorter than the discrimination time,thus generating gating signal and triggering DMCA(digital multi-channel analyzer) to receive the total integral charge signal.When rise time of the input signal is longer than discrimination time,DMCA remains inactivated and the corresponding total integral charge signal is abandoned.Test results show that combination of the designed rise-time discriminator and DMCA can reduce hole tailing of CdZnTe detector significantly.Energy resolution of the system is 0.98%@662 keV,and it is still excellent under high counting rates.展开更多
A test device for isotopic γ-ray imaging, which consists of an isotope γ-ray source, a CdZnTe γ-ray spec- trometer and other auxiliary equipment, is studied here. Compared with the conventional X-ray, the isotope ...A test device for isotopic γ-ray imaging, which consists of an isotope γ-ray source, a CdZnTe γ-ray spec- trometer and other auxiliary equipment, is studied here. Compared with the conventional X-ray, the isotope γ-ray, which is utilized in this project, has its own advantages in imaging. Furthermore, with a room-temperature high-energy-resolution CdZnTe detector and a modern imaging processing technique, this device is capable of effec- tively suppressing the background and gaining more information, thus it can obtain a better image than conventional X-ray devices. In the experiment of PCB imaging, all soldered points and chip components are sharply demonstrated.展开更多
In this paper, the design of a novel low-noise front-end readout circuit for Cadmium zinc telluride (CdZnTe) X-ray and γ-ray detectors is described. The front-end readout circuits include the charge sensitive amplifi...In this paper, the design of a novel low-noise front-end readout circuit for Cadmium zinc telluride (CdZnTe) X-ray and γ-ray detectors is described. The front-end readout circuits include the charge sensitive amplifier (CSA) and the CR-RC shaper is implemented in TSMC 0.35 μm mixed-signal CMOS technology. The die size of the prototype chip is 4.9 mm × 2.2 mm. The simulation results show that, the noise performance is 46 electrons + 10 electrons/pF, and power consumption is 1.65 mW per channel.展开更多
In this paper,we present the design and performances of a low-noise and radiation-hardened front-end readout application specific integrated circuit（ASIC） dedicated to CdZnTe detectors for a hard X-ray imager in spa...In this paper,we present the design and performances of a low-noise and radiation-hardened front-end readout application specific integrated circuit（ASIC） dedicated to CdZnTe detectors for a hard X-ray imager in space applications.The readout channel is comprised of a charge sensitive amplifier,a CR-RC shaping amplifier,an analog output buffer,a fast shaper,and a discriminator.An 8-channel prototype ASIC is designed and fabricated in TSMC 0.35-μm mixed-signal CMOS technology,the die size of the prototype chip is 2.2×2.2 mm^2.The input energy range is from 5 to 350 keV.For this 8-channel prototype ASIC,the measured electrical characteristics are as follows：the overall gain of the readout channel is 210 V/pC,the linearity error is less than 2%,the crosstalk is less than 0.36%,The equivalent noise charge of a typical channel is 52.9 e^- at zero farad plus 8.2 e^- per picofarad,and the power consumption is less than 2.4 mW/channel.Through the measurement together with a CdZnTe detector,the energy resolution is 5.9%at the 59.5-keV line under the irradiation of the radioactive source ^（241）Am.The radiation effect experiments show that the proposed ASIC can resist the total ionization dose（TID） irradiation of higher than200 krad（Si）.展开更多
Readout electronics, especially digital electronics, for two-element CdZnTe （CZT） detectors in parallel are developed. The preliminary results show the detection efficiency of the two-element CZT detectors in parall...Readout electronics, especially digital electronics, for two-element CdZnTe （CZT） detectors in parallel are developed. The preliminary results show the detection efficiency of the two-element CZT detectors in parallel with analog electronics is as many as 1.8 and 2.1 times the single ones, and the energy resolution （FWHM） is limited by that of the single one by the means of analog electronics. However, the digital method for signal processing will be sufficiently better by contrast with an analog method especially in energy resolution. The energy resolution by the means of digital electronics can be improved by about 26.67%, compared to that only with analog electronics, while their detection efficiency is almost the same. The cause for this difference is also discussed.展开更多
A new electrode structure CdZnTe(Cadmium Zinc Telluride) detector named Binode CdZnTe has been proposed in this paper.Together with the softwares of MAXWELL,GEANT4,and ROOT,the charge collection process and its gamma ...A new electrode structure CdZnTe(Cadmium Zinc Telluride) detector named Binode CdZnTe has been proposed in this paper.Together with the softwares of MAXWELL,GEANT4,and ROOT,the charge collection process and its gamma spectrum of the detector have been simulated and the detector structure has been optimized.In order to improve its performance further,Compton scattering effect correction has been used.The simulation results demonstrate that with refined design and Compton scattering effect correction,Binode CdZnTe detectors is capable of achieving 3.92%FWHM at 122 keV,and 1.27%FWHM at 662 keV.Compared with other single-polarity(electron-only) detector configurations,Binode CdZnTe detector offers a cost effective and simple structure alternative with comparable energy resolution.展开更多
Surface defects caused during cutting and polishing in the fabrication of cadmium zinc telluride (CdZnTe) nuclear detectors limit their spectral performance. Chemical treatments are often used to remove surface damage...Surface defects caused during cutting and polishing in the fabrication of cadmium zinc telluride (CdZnTe) nuclear detectors limit their spectral performance. Chemical treatments are often used to remove surface damages and defects. In this paper, we present the analysis of Te and TeO2 species on the surfaces of CdZnTe nuclear detectors treated with hydrogen bromide and ammonium-based solutions. The CdZnTe wafers were chemo-mechanically polished in a mixture of hydrogen bromide in hydrogen peroxide and ethylene glycol, followed by a chemical passivation in a mixture of ammonium fluoride and hydrogen peroxide solution. X-ray photoelectron spectroscopy showed significant conversion of Te to TeO2, thus producing a more chemically stable surface. The resistivity of the CdZnTe samples is in the order of 1010 ohms-cm. The current for a given applied voltage increased following the passivation and decreased after a 3-hour period. Results from spectral response measurements showed that the 59.5-keV gamma-peak of Am-241 was stable under the same channel for the surface treatment processes.展开更多
Cadmium zinc telluride (CdZnTe) semiconductor has applications in the detection of X-rays and gamma-rays at room temperature without having to use a cooling system. Chemical etching and chemo-mechanical polishing are ...Cadmium zinc telluride (CdZnTe) semiconductor has applications in the detection of X-rays and gamma-rays at room temperature without having to use a cooling system. Chemical etching and chemo-mechanical polishing are processes used to smoothen CdZnTe wafer during detector device fabrication. These processes reduce surface damages left after polishing the wafers. In this paper, we compare the effects of etching and chemo-mechanical polishing on CdZnTe nuclear detectors, using a solution of hydrogen bromide in hydrogen peroxide and ethylene glycol mixture. X-ray photoelectron spectroscopy (XPS) was used to monitor TeO2 on the wafer surfaces. Current-voltage and detector-response measurements were made to study the electrical properties and energy resolution. XPS results showed that the chemical etching process resulted in the formation of more TeO2 on the detector surfaces compared to chemo-mechanical polishing. The electrical resistivity of the detector is of the order of 1010 Ω-cm. The chemo-mechanical polishing process increased the leakage current more that chemical etching. For freshly treated surfaces, the etching process is more detrimental to the energy resolution compared to chemo-mechanically polishing.展开更多
本文采用CdZnTe单晶制成像素探测器,并对其能谱响应特性及均匀性进行了系统表征。通过I-V和能谱响应测试,测定了晶体的电阻率和载流子迁移率与寿命的积,并用红外透过显微成像观察了晶体内Te夹杂的分布特性。采用光刻、剥离和真空蒸镀技...本文采用CdZnTe单晶制成像素探测器,并对其能谱响应特性及均匀性进行了系统表征。通过I-V和能谱响应测试,测定了晶体的电阻率和载流子迁移率与寿命的积,并用红外透过显微成像观察了晶体内Te夹杂的分布特性。采用光刻、剥离和真空蒸镀技术,在CdZnTe晶片上制备了8×8的像素电极,用丝网印刷和贴片技术通过导电银胶实现像素电极与读出电路的准确连接,制备出CdZnTe像素探测器。对像素探测器的测试表明,-300V下单像素最大漏电流小于0.7nA,对241 Am 59.5keV的能量分辨率可达5.6%,优于平面探测器。进一步分析了晶体内Te夹杂等缺陷对探测器漏电流和能谱响应特性的影响规律,结果表明,Te夹杂的聚集会显著增加漏电流,并降低探测器的能量分辨率。展开更多
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant Nos.51702271 and 61904155)the Natural Science Foundation of Fujian Province,China(Grant No.2020J05239).
文摘The space charge accumulation in CdZnTe crystals seriously affects the performance of high-flux pulse detectors.The influence of sub-bandgap illumination on the space charge distribution and device performance in CdZnTe crystals were studied theoretically by Silvaco TCAD software simulation.The sub-bandgap illumination with a wavelength of 890 nm and intensity of 8×10−8 W/cm2 were used in the simulation to explore the space charge distribution and internal electric field distribution in CdZnTe crystals.The simulation results show that the deep level occupation faction is manipulated by the sub-bandgap illumination,thus space charge concentration can be reduced under the bias voltage of 500 V.A flat electric field distribution is obtained,which significantly improves the charge collection efficiency of the CdZnTe detector.Meanwhile,premised on the high resistivity of CdZnTe crystal,the space charge concentration in the crystal can be further reduced with the wavelength of 850 nm and intensity of 1×10−7 W/cm2 illumination.The electric field distribution is flatter and the carrier collection efficiency of the device can be improved more effectively.
文摘A kind of excellent CdZnTe crystal has been grown in Yinnel Tech, Inc. in recent years. Based on these CdZnTe crystals and some new techniques, a portable energy-dispersive spectrometer has been constructed which has yielded good results. CdZnTe detector has a 3% relative resolution in high-energy field and can detect gamma rays at room temperature. An integrated circuit based on preamplifier and shaping amplifier chips is connected to the detector. Voltage pulses are transformed into digital signals in MCA (multichannel analyzer) and are then transmitted to com- puter via USB bus. Data process algorithms are improved in this spectrometer. Fast Fourier transform (FFT) and nu- merical differentiation (ND) are used in energy peak’s searching program. Sampling-based correction technique is used in X-ray energy calibration. Modified Gaussian-Newton algorithm is a classical method to solve nonlinear curve fitting problems, and it is used to compute absolute intensity of each detected characteristic line.
基金Supported by National Natural Science Foundation of China(Grant No.60676002 and No.10675080).
文摘CdZnTe(CZT)capacitive Frisch grid detectors can achieve a higher detecting resolution.The anode structure might have an important role in improving the weighting potential distribution of the detectors.In this paper, four anode structures of capacitive Frisch grid structures have been analyzed with FE simulation,based on a 3-dimensional weighting potential analysis.The weighting potential distributions in modified anode devices(Model B, C and D)are optimized compared with a square device(Model A).In model C and D,the abrupt weighting potential can be well modified.However,with increased radius of the circular electrode in Model C the weighting potential platform away from the anode becomes higher and higher and in Model D,the weighting potential does not vary too much.
文摘Cadmium zinc telluride(CZT)is a preferred material for X-ray and gamma-ray detector.Thanks to the relatively high atomic number,high density and wide band-gap,CZT detector possesses sharp energy resolution and high detection efficiency without cryogenic cooling.We have developed a CdZnTe detector with an energy resolution of 3.45%(FWHM)at 59.54 keV at room temperature,and it is used for X-ray fluorescence analysis.In this paper, leakage current,energy resolution and long term stability of the CZT detector are discussed.
基金supported by the Natural Science Foundation of China(NSFC)(No.41474159)National High-tech R&D Program of China(863 Program)(Nos.2012AA061803 and 2014AA093403)Open Foundation of Applied Nuclear Techniques in Geosciences Key Laboratory of Sichuan Province(No.gnzds2014006)
文摘Due to variable time for charge collection,energy resolution of nuclear detectors declines,especially compound semiconductor detectors like cadmium zinc telluride(CdZnTe) detector.To solve this problem,an analog rise-time discriminator based on charge comparison principle is designed.The reference charge signal after attenuation is compared with the deconvoluted and delayed current signal.It is found that the amplitude of delayed current signal is higher than that of the reference charge signal when rise time of the input signal is shorter than the discrimination time,thus generating gating signal and triggering DMCA(digital multi-channel analyzer) to receive the total integral charge signal.When rise time of the input signal is longer than discrimination time,DMCA remains inactivated and the corresponding total integral charge signal is abandoned.Test results show that combination of the designed rise-time discriminator and DMCA can reduce hole tailing of CdZnTe detector significantly.Energy resolution of the system is 0.98%@662 keV,and it is still excellent under high counting rates.
基金Supported by National Science Foundation of China (No.10475074)
文摘A test device for isotopic γ-ray imaging, which consists of an isotope γ-ray source, a CdZnTe γ-ray spec- trometer and other auxiliary equipment, is studied here. Compared with the conventional X-ray, the isotope γ-ray, which is utilized in this project, has its own advantages in imaging. Furthermore, with a room-temperature high-energy-resolution CdZnTe detector and a modern imaging processing technique, this device is capable of effec- tively suppressing the background and gaining more information, thus it can obtain a better image than conventional X-ray devices. In the experiment of PCB imaging, all soldered points and chip components are sharply demonstrated.
文摘In this paper, the design of a novel low-noise front-end readout circuit for Cadmium zinc telluride (CdZnTe) X-ray and γ-ray detectors is described. The front-end readout circuits include the charge sensitive amplifier (CSA) and the CR-RC shaper is implemented in TSMC 0.35 μm mixed-signal CMOS technology. The die size of the prototype chip is 4.9 mm × 2.2 mm. The simulation results show that, the noise performance is 46 electrons + 10 electrons/pF, and power consumption is 1.65 mW per channel.
基金supported by the National Key Scientific Instrument and Equipment Development Project(No.2011YQ040082)the National Natural Science Foundation of China(Nos.11475136,11575144,61176094)the Shaanxi Natural Science Foundation of China(No.2015JM1016)
文摘In this paper,we present the design and performances of a low-noise and radiation-hardened front-end readout application specific integrated circuit（ASIC） dedicated to CdZnTe detectors for a hard X-ray imager in space applications.The readout channel is comprised of a charge sensitive amplifier,a CR-RC shaping amplifier,an analog output buffer,a fast shaper,and a discriminator.An 8-channel prototype ASIC is designed and fabricated in TSMC 0.35-μm mixed-signal CMOS technology,the die size of the prototype chip is 2.2×2.2 mm^2.The input energy range is from 5 to 350 keV.For this 8-channel prototype ASIC,the measured electrical characteristics are as follows：the overall gain of the readout channel is 210 V/pC,the linearity error is less than 2%,the crosstalk is less than 0.36%,The equivalent noise charge of a typical channel is 52.9 e^- at zero farad plus 8.2 e^- per picofarad,and the power consumption is less than 2.4 mW/channel.Through the measurement together with a CdZnTe detector,the energy resolution is 5.9%at the 59.5-keV line under the irradiation of the radioactive source ^（241）Am.The radiation effect experiments show that the proposed ASIC can resist the total ionization dose（TID） irradiation of higher than200 krad（Si）.
基金Project supported by the National Natural Science Foundation of China(No.50902091)the Program for Changjiang Scholars,Innovative Research Team in University,China(No.IRT0739)the Shanghai Leading Academic Disciplines,China(No.S30107)
文摘Readout electronics, especially digital electronics, for two-element CdZnTe （CZT） detectors in parallel are developed. The preliminary results show the detection efficiency of the two-element CZT detectors in parallel with analog electronics is as many as 1.8 and 2.1 times the single ones, and the energy resolution （FWHM） is limited by that of the single one by the means of analog electronics. However, the digital method for signal processing will be sufficiently better by contrast with an analog method especially in energy resolution. The energy resolution by the means of digital electronics can be improved by about 26.67%, compared to that only with analog electronics, while their detection efficiency is almost the same. The cause for this difference is also discussed.
文摘A new electrode structure CdZnTe(Cadmium Zinc Telluride) detector named Binode CdZnTe has been proposed in this paper.Together with the softwares of MAXWELL,GEANT4,and ROOT,the charge collection process and its gamma spectrum of the detector have been simulated and the detector structure has been optimized.In order to improve its performance further,Compton scattering effect correction has been used.The simulation results demonstrate that with refined design and Compton scattering effect correction,Binode CdZnTe detectors is capable of achieving 3.92%FWHM at 122 keV,and 1.27%FWHM at 662 keV.Compared with other single-polarity(electron-only) detector configurations,Binode CdZnTe detector offers a cost effective and simple structure alternative with comparable energy resolution.
文摘Surface defects caused during cutting and polishing in the fabrication of cadmium zinc telluride (CdZnTe) nuclear detectors limit their spectral performance. Chemical treatments are often used to remove surface damages and defects. In this paper, we present the analysis of Te and TeO2 species on the surfaces of CdZnTe nuclear detectors treated with hydrogen bromide and ammonium-based solutions. The CdZnTe wafers were chemo-mechanically polished in a mixture of hydrogen bromide in hydrogen peroxide and ethylene glycol, followed by a chemical passivation in a mixture of ammonium fluoride and hydrogen peroxide solution. X-ray photoelectron spectroscopy showed significant conversion of Te to TeO2, thus producing a more chemically stable surface. The resistivity of the CdZnTe samples is in the order of 1010 ohms-cm. The current for a given applied voltage increased following the passivation and decreased after a 3-hour period. Results from spectral response measurements showed that the 59.5-keV gamma-peak of Am-241 was stable under the same channel for the surface treatment processes.
文摘Cadmium zinc telluride (CdZnTe) semiconductor has applications in the detection of X-rays and gamma-rays at room temperature without having to use a cooling system. Chemical etching and chemo-mechanical polishing are processes used to smoothen CdZnTe wafer during detector device fabrication. These processes reduce surface damages left after polishing the wafers. In this paper, we compare the effects of etching and chemo-mechanical polishing on CdZnTe nuclear detectors, using a solution of hydrogen bromide in hydrogen peroxide and ethylene glycol mixture. X-ray photoelectron spectroscopy (XPS) was used to monitor TeO2 on the wafer surfaces. Current-voltage and detector-response measurements were made to study the electrical properties and energy resolution. XPS results showed that the chemical etching process resulted in the formation of more TeO2 on the detector surfaces compared to chemo-mechanical polishing. The electrical resistivity of the detector is of the order of 1010 Ω-cm. The chemo-mechanical polishing process increased the leakage current more that chemical etching. For freshly treated surfaces, the etching process is more detrimental to the energy resolution compared to chemo-mechanically polishing.
文摘本文采用CdZnTe单晶制成像素探测器,并对其能谱响应特性及均匀性进行了系统表征。通过I-V和能谱响应测试,测定了晶体的电阻率和载流子迁移率与寿命的积,并用红外透过显微成像观察了晶体内Te夹杂的分布特性。采用光刻、剥离和真空蒸镀技术,在CdZnTe晶片上制备了8×8的像素电极,用丝网印刷和贴片技术通过导电银胶实现像素电极与读出电路的准确连接,制备出CdZnTe像素探测器。对像素探测器的测试表明,-300V下单像素最大漏电流小于0.7nA,对241 Am 59.5keV的能量分辨率可达5.6%,优于平面探测器。进一步分析了晶体内Te夹杂等缺陷对探测器漏电流和能谱响应特性的影响规律,结果表明,Te夹杂的聚集会显著增加漏电流,并降低探测器的能量分辨率。
