In this paper, we study how pixel size influences energy resolution for a proposed pixelated detector—a high sensitivity, low cost, and real-time radon monitor based on a Topmetal-Ⅱ^- time projection chamber(TPC). T...In this paper, we study how pixel size influences energy resolution for a proposed pixelated detector—a high sensitivity, low cost, and real-time radon monitor based on a Topmetal-Ⅱ^- time projection chamber(TPC). This monitor was designed to improve spatial resolution for detecting radon alpha particles using Topmetal-Ⅱ^- sensors assembled by a 0.35 lm CMOS integrated circuit process.Owing to concerns that small pixel size might have the side effect of worsening energy resolution due to lower signalto-noise ratio, a Geant4-based simulation was used to investigate the dependence of energy resolution on pixel sizes ranging from 60 to 600 lm. A non-monotonic trend in this region shows the combined effect of pixel size and threshold on pixels, analyzed by introducing an empirical expression. Pixel noise contributes 50 keV full-width at half-maximum energy resolution for 400 lm pixel size at 1–4σ threshold that is comparable to the energy resolution caused by energy fluctuations in the TPC ionization process( ~20 keV). The total energy resolution after combining both factors is estimated to be 54 keV for a pixel size of 400 lm at 1–4σ threshold. The analysis presented in this paper would help choosing suitable pixel size for future pixelated detectors.展开更多
Topmetal-Ⅱ^-is a low noise CMOS pixel direct charge sensor with a pitch of 83 μm.CdZnTe is an excellent semiconductor material for radiation detection.The combination of CdZnTe and the sensor makes it possible to bu...Topmetal-Ⅱ^-is a low noise CMOS pixel direct charge sensor with a pitch of 83 μm.CdZnTe is an excellent semiconductor material for radiation detection.The combination of CdZnTe and the sensor makes it possible to build a detector with high spatial resolution.In our experiments,an epoxy adhesive is used as the conductive medium to connect the sensor and cadmium zinc telluride（CdZnTe）.The diffusion coefficient and charge efficiency of electrons are measured at a low bias voltage of-2 V,and the image of a single alpha particle is clear with a reasonable spatial resolution.A detector with such a structure has the potential to be applied in X-ray imaging systems with further improvements of the sensor.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supported by the National Natural Science Foundation of China(No.U1732271)
文摘In this paper, we study how pixel size influences energy resolution for a proposed pixelated detector—a high sensitivity, low cost, and real-time radon monitor based on a Topmetal-Ⅱ^- time projection chamber(TPC). This monitor was designed to improve spatial resolution for detecting radon alpha particles using Topmetal-Ⅱ^- sensors assembled by a 0.35 lm CMOS integrated circuit process.Owing to concerns that small pixel size might have the side effect of worsening energy resolution due to lower signalto-noise ratio, a Geant4-based simulation was used to investigate the dependence of energy resolution on pixel sizes ranging from 60 to 600 lm. A non-monotonic trend in this region shows the combined effect of pixel size and threshold on pixels, analyzed by introducing an empirical expression. Pixel noise contributes 50 keV full-width at half-maximum energy resolution for 400 lm pixel size at 1–4σ threshold that is comparable to the energy resolution caused by energy fluctuations in the TPC ionization process( ~20 keV). The total energy resolution after combining both factors is estimated to be 54 keV for a pixel size of 400 lm at 1–4σ threshold. The analysis presented in this paper would help choosing suitable pixel size for future pixelated detectors.
基金Supported by National Natural Science Foundation of China(11375073,11305072,U1232206)
文摘Topmetal-Ⅱ^-is a low noise CMOS pixel direct charge sensor with a pitch of 83 μm.CdZnTe is an excellent semiconductor material for radiation detection.The combination of CdZnTe and the sensor makes it possible to build a detector with high spatial resolution.In our experiments,an epoxy adhesive is used as the conductive medium to connect the sensor and cadmium zinc telluride（CdZnTe）.The diffusion coefficient and charge efficiency of electrons are measured at a low bias voltage of-2 V,and the image of a single alpha particle is clear with a reasonable spatial resolution.A detector with such a structure has the potential to be applied in X-ray imaging systems with further improvements of the sensor.
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。
