In the research and development of new silicon pixel detectors,a collimated monoenergetic charged-particle test beam equipped with a high-resolution pixel-beam telescope is crucial for prototype verification and perfo...In the research and development of new silicon pixel detectors,a collimated monoenergetic charged-particle test beam equipped with a high-resolution pixel-beam telescope is crucial for prototype verification and performance evaluation.When the beam energy is low,the effect of multiple Coulomb scattering on the measured resolution of the Device Under Test(DUT)must be considered to accurately evaluate the performance of the pixel chips and detectors.This study aimed to investigate the effect of multiple Coulomb scattering on the measured resolution,particularly at low beam energies.Simulations were conducted using Allpix^(2) to study the effects of multiple Coulomb scattering under different beam energies,material budgets,and telescope layouts.The simulations also provided the minimum energy at which the effect of multiple Coulomb scattering could be ignored.Compared with the results of a five-layer detector system tested with an electron beam at DESY,the simulation results were consistent with the beam test results,confirming the reliability of the simulations.展开更多
Carbon ions,commonly referred to as particle therapy,have become increasingly popular in the last decade.Accurately predicting the range of ions in tissues is important for the precise delivery of doses in heavy-ion r...Carbon ions,commonly referred to as particle therapy,have become increasingly popular in the last decade.Accurately predicting the range of ions in tissues is important for the precise delivery of doses in heavy-ion radiotherapy.Range uncertainty is currently the largest contributor to dose uncertainty in normal tissues,leading to the use of safety margins in treatment planning.One potential method is the direct relative stopping measurement(RSP)with ions.Heavy-ion CT(Hi′CT),a compact segmented full digital tomography detector using monolithic active pixel sensors,was designed and evaluated using a 430 MeV/u high-energy carbon ion pencil beam in Geant4.The precise position of the individual carbon ion track can be recorded and reconstructed using a 30μm×30μm small pixel pitch size.Two types of customized image reconstruction algorithms were developed,and their performances were evaluated using three different modules of CAT-PHAN 600-series phantoms.The RSP measurement accuracy of the tracking algorithm for different types of materials in the CTP404 module was less than 1%.In terms of spatial resolution,the tracking algorithm could achieve a 20%modulation transfer function normalization value of CTP528 imaging results at 5 lp/cm,which is significantly better than that of the fast imaging algorithm(3 lp/cm).The density resolution obtained using the tracking algorithm of the customized CTP515 was approximately 10.5%.In conclusion,a compact digital Hi'CT system was designed,and its nominal performance was evaluated in a simulation.The RSP resolution and image quality provide potential feasibility for scanning most parts of an adult body or pediatric patient,particularly for head and neck tumor treatment.展开更多
Lanthanum bromide(LaBr_(3))crystal has a high energy resolution and time resolution and has been used in Compton cameras(CCs)over the past few decades.However,LaBr_(3) crystal arrays are difficult to process because L...Lanthanum bromide(LaBr_(3))crystal has a high energy resolution and time resolution and has been used in Compton cameras(CCs)over the past few decades.However,LaBr_(3) crystal arrays are difficult to process because LaBr_(3) is easy to crack and break;thus,few LaBr_(3)-based CC prototypes have been built.In this study,we designed and fabricated a large-pixel LaBr_(3) CC prototype and evaluated its performance with regard to position,energy,and angular resolution.We used two 10×10 LaBr_(3) crystal arrays with a pixel size of 5 mm×5 mm,silicon photomultipliers(SiPMs),and corresponding decoding circuits to construct our prototype.Additionally,a framework based on a Voronoi diagram and a lookup table was developed for list-mode projection data acquisition.Monte Carlo(MC)simulations based on Geant4 and experiments were conducted to evaluate the performance of our CC prototype.The lateral position resolution was 5 mm,and the maximum deviation in the depth direction was 2.5 and 5 mm for the scatterer and absorber,respectively.The corresponding measured energy resolu-tions were 7.65%and 8.44%,respectively,at 511 keV.The experimental results of ^(137)Cs point-like sources were consistent with the MC simulation results with regard to the spatial positions and full widths at half maximum(FWHMs).The angular resolution of the fabricated prototype was approximately 6°when a point-like ^(137)Cs source was centrally placed at a distance of 5 cm from the scatterer.We proposed and investigated a large-pixel LaBr_(3) CC for the first time and verified its feasibility for use in accurate spatial positioning of radiative sources with a high angular resolution.The proposed CC can satisfy the requirements of radiative source imaging and positioning in the nuclear industry and medical applications.展开更多
The reconstruction of the tracks of charged particles with high precision is crucial for HEP experiments to achieve their physics goals.The BESⅢdrift chamber,which is used as the tracking detector of the BESⅢexperim...The reconstruction of the tracks of charged particles with high precision is crucial for HEP experiments to achieve their physics goals.The BESⅢdrift chamber,which is used as the tracking detector of the BESⅢexperiment,has suffered from aging effects resulting in degraded tracking performance after operation for approximately 15 years.To preserve and enhance the tracking performance of BESⅢ,one of the proposals is to add one layer of a thin cylindrical CMOS pixel sensor based on state-of-the-art stitching technology between the beam pipe and the drift chamber.The improvement in the tracking performance of BESⅢwith such an additional pixel detector compared to that with only the existing drift chamber was studied using the modern common tracking software Acts,which provides a set of detector-agnostic and highly performant tracking algorithms that have demonstrated promising performance for a few high-energy physics and nuclear physics experiments.展开更多
A three-transistor active pixel sensor and its double sampling readout circuit implemented by a switch capacitor amplifier are designed. The circuit is embedded in a 64 × 64 pixel array CMOS image sensor and succ...A three-transistor active pixel sensor and its double sampling readout circuit implemented by a switch capacitor amplifier are designed. The circuit is embedded in a 64 × 64 pixel array CMOS image sensor and success-fully taped out with a Chartered 0.35μm process. The pixel pitch is 8μm × 8μm with a fill factor of 57%, the photo-sensitivity is 0.8V/（lux · s） ,and the dynamic range is 50dB. Theoretical analysis and test results indicate that as the process is scaled down, a smaller pixel pitch reduces the sensitivity. A deep junction n-well/p-substrate photodiode with a reasonable fill factor and high sensitivity are more appropriate for submicron processes.展开更多
Based on the analysis to the behavior of bad pixels, a statistics-based auto-detecting and compensation algorithm for bad pixels is proposed. The correcting process is divided into two stages： bad pixel detection and...Based on the analysis to the behavior of bad pixels, a statistics-based auto-detecting and compensation algorithm for bad pixels is proposed. The correcting process is divided into two stages： bad pixel detection and bad pixel compensation. The proposed detection algorithm is a combination of median filtering and statistic method. Single frame median filtering is used to locate approximate map, then statistic method and threshold value is used to get the accurate location map of bad pixels. When the bad pixel detection is done, neighboring pixel replacement algorithm is used to compensate them in real-time. The effectiveness of this approach is test- ed by applying it to I-IgCATe infrared video. Experiments on real infrared imaging sequences demonstrate that the proposed algorithm requires only a few frames to obtain high quality corrections. It is easy to combine with traditional static methods, update the pre-defined location map in real-time.展开更多
A detailed principle and a rigorous analysis of a new noise,the gate-induced noise,in pixel MOSFET of CMOS imagers are provided.The gate-induced noise of the MOSFET is more notable in the strong reversion region than...A detailed principle and a rigorous analysis of a new noise,the gate-induced noise,in pixel MOSFET of CMOS imagers are provided.The gate-induced noise of the MOSFET is more notable in the strong reversion region than that in the subthreshold region when the applied gate voltage is low.However,the applied gate voltage being up to 3V,the gate-induced noise is more notable with the ω/ω T increasing when the MOSFET operates in the subthreshold region than that in the strong reversion region.Between the photocurrent I D and the root mean square value of the gated-induced noise,current i 2 d presents the relation of i 2 d∝I D in the saturation region of the strong reversion and approximately i 2 d∝I D in the subthreshold region.A deta iled and rigorous study of the gate-induced noise in the reset MOSFET for the p hotodiode APS and improved photodiode APS are provided.The improvement of logari thmic response APS is analyzed and the simulation results show that the gate-in duced noise can be reduced.展开更多
This paper introduces certain innovative algorithms to mask for pixel defects seen in image sensors. Pixel defectivity rates scale with pixel architecture and process nodes. Smaller pixel and process nodes introduce m...This paper introduces certain innovative algorithms to mask for pixel defects seen in image sensors. Pixel defectivity rates scale with pixel architecture and process nodes. Smaller pixel and process nodes introduce more defects in manufacturing. Brief introduction to causes for pixel defectivity at lower pixel nodes is explained. Later in the paper, popular defect correction schemes used in image processing applications are discussed. A new approach for defect correction is presented and evaluated using images captured from an 8M Bayer image sensor. Experimentation for threshold evaluation is done and presented with practical results for better optimization of proposed algorithms. Experimental data shows that proposed defect corrections preserves a lot of edge details and corrects for bright and hot pixels/clusters, which are evaluated using histogram analysis.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11875274 and U1232202)。
文摘In the research and development of new silicon pixel detectors,a collimated monoenergetic charged-particle test beam equipped with a high-resolution pixel-beam telescope is crucial for prototype verification and performance evaluation.When the beam energy is low,the effect of multiple Coulomb scattering on the measured resolution of the Device Under Test(DUT)must be considered to accurately evaluate the performance of the pixel chips and detectors.This study aimed to investigate the effect of multiple Coulomb scattering on the measured resolution,particularly at low beam energies.Simulations were conducted using Allpix^(2) to study the effects of multiple Coulomb scattering under different beam energies,material budgets,and telescope layouts.The simulations also provided the minimum energy at which the effect of multiple Coulomb scattering could be ignored.Compared with the results of a five-layer detector system tested with an electron beam at DESY,the simulation results were consistent with the beam test results,confirming the reliability of the simulations.
基金the National Natural Science Foundation of China(Nos.11975292,12205374,U2032209,and 12222512)Beijing Hope Run Special Fund of Cancer Foundation of China(No.LC2021B23)+1 种基金the CAS“Light of West China”Program,the CAS Pioneer Hundred Talent Program,the Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030008)the National Key Research and Development Program of China(No.2021YFA1601300 and 2020YFE0202002).
文摘Carbon ions,commonly referred to as particle therapy,have become increasingly popular in the last decade.Accurately predicting the range of ions in tissues is important for the precise delivery of doses in heavy-ion radiotherapy.Range uncertainty is currently the largest contributor to dose uncertainty in normal tissues,leading to the use of safety margins in treatment planning.One potential method is the direct relative stopping measurement(RSP)with ions.Heavy-ion CT(Hi′CT),a compact segmented full digital tomography detector using monolithic active pixel sensors,was designed and evaluated using a 430 MeV/u high-energy carbon ion pencil beam in Geant4.The precise position of the individual carbon ion track can be recorded and reconstructed using a 30μm×30μm small pixel pitch size.Two types of customized image reconstruction algorithms were developed,and their performances were evaluated using three different modules of CAT-PHAN 600-series phantoms.The RSP measurement accuracy of the tracking algorithm for different types of materials in the CTP404 module was less than 1%.In terms of spatial resolution,the tracking algorithm could achieve a 20%modulation transfer function normalization value of CTP528 imaging results at 5 lp/cm,which is significantly better than that of the fast imaging algorithm(3 lp/cm).The density resolution obtained using the tracking algorithm of the customized CTP515 was approximately 10.5%.In conclusion,a compact digital Hi'CT system was designed,and its nominal performance was evaluated in a simulation.The RSP resolution and image quality provide potential feasibility for scanning most parts of an adult body or pediatric patient,particularly for head and neck tumor treatment.
文摘Lanthanum bromide(LaBr_(3))crystal has a high energy resolution and time resolution and has been used in Compton cameras(CCs)over the past few decades.However,LaBr_(3) crystal arrays are difficult to process because LaBr_(3) is easy to crack and break;thus,few LaBr_(3)-based CC prototypes have been built.In this study,we designed and fabricated a large-pixel LaBr_(3) CC prototype and evaluated its performance with regard to position,energy,and angular resolution.We used two 10×10 LaBr_(3) crystal arrays with a pixel size of 5 mm×5 mm,silicon photomultipliers(SiPMs),and corresponding decoding circuits to construct our prototype.Additionally,a framework based on a Voronoi diagram and a lookup table was developed for list-mode projection data acquisition.Monte Carlo(MC)simulations based on Geant4 and experiments were conducted to evaluate the performance of our CC prototype.The lateral position resolution was 5 mm,and the maximum deviation in the depth direction was 2.5 and 5 mm for the scatterer and absorber,respectively.The corresponding measured energy resolu-tions were 7.65%and 8.44%,respectively,at 511 keV.The experimental results of ^(137)Cs point-like sources were consistent with the MC simulation results with regard to the spatial positions and full widths at half maximum(FWHMs).The angular resolution of the fabricated prototype was approximately 6°when a point-like ^(137)Cs source was centrally placed at a distance of 5 cm from the scatterer.We proposed and investigated a large-pixel LaBr_(3) CC for the first time and verified its feasibility for use in accurate spatial positioning of radiative sources with a high angular resolution.The proposed CC can satisfy the requirements of radiative source imaging and positioning in the nuclear industry and medical applications.
基金supported by the National Natural Science Foundation of China(Nos.U2032203,12275296,12275297,12075142,12175256,12035009)National Key R&D Program of China(No.2020YFA0406302)。
文摘The reconstruction of the tracks of charged particles with high precision is crucial for HEP experiments to achieve their physics goals.The BESⅢdrift chamber,which is used as the tracking detector of the BESⅢexperiment,has suffered from aging effects resulting in degraded tracking performance after operation for approximately 15 years.To preserve and enhance the tracking performance of BESⅢ,one of the proposals is to add one layer of a thin cylindrical CMOS pixel sensor based on state-of-the-art stitching technology between the beam pipe and the drift chamber.The improvement in the tracking performance of BESⅢwith such an additional pixel detector compared to that with only the existing drift chamber was studied using the modern common tracking software Acts,which provides a set of detector-agnostic and highly performant tracking algorithms that have demonstrated promising performance for a few high-energy physics and nuclear physics experiments.
文摘A three-transistor active pixel sensor and its double sampling readout circuit implemented by a switch capacitor amplifier are designed. The circuit is embedded in a 64 × 64 pixel array CMOS image sensor and success-fully taped out with a Chartered 0.35μm process. The pixel pitch is 8μm × 8μm with a fill factor of 57%, the photo-sensitivity is 0.8V/（lux · s） ,and the dynamic range is 50dB. Theoretical analysis and test results indicate that as the process is scaled down, a smaller pixel pitch reduces the sensitivity. A deep junction n-well/p-substrate photodiode with a reasonable fill factor and high sensitivity are more appropriate for submicron processes.
基金Sponsored by the National Natural Science Foundation of China(60877060)
文摘Based on the analysis to the behavior of bad pixels, a statistics-based auto-detecting and compensation algorithm for bad pixels is proposed. The correcting process is divided into two stages： bad pixel detection and bad pixel compensation. The proposed detection algorithm is a combination of median filtering and statistic method. Single frame median filtering is used to locate approximate map, then statistic method and threshold value is used to get the accurate location map of bad pixels. When the bad pixel detection is done, neighboring pixel replacement algorithm is used to compensate them in real-time. The effectiveness of this approach is test- ed by applying it to I-IgCATe infrared video. Experiments on real infrared imaging sequences demonstrate that the proposed algorithm requires only a few frames to obtain high quality corrections. It is easy to combine with traditional static methods, update the pre-defined location map in real-time.
文摘A detailed principle and a rigorous analysis of a new noise,the gate-induced noise,in pixel MOSFET of CMOS imagers are provided.The gate-induced noise of the MOSFET is more notable in the strong reversion region than that in the subthreshold region when the applied gate voltage is low.However,the applied gate voltage being up to 3V,the gate-induced noise is more notable with the ω/ω T increasing when the MOSFET operates in the subthreshold region than that in the strong reversion region.Between the photocurrent I D and the root mean square value of the gated-induced noise,current i 2 d presents the relation of i 2 d∝I D in the saturation region of the strong reversion and approximately i 2 d∝I D in the subthreshold region.A deta iled and rigorous study of the gate-induced noise in the reset MOSFET for the p hotodiode APS and improved photodiode APS are provided.The improvement of logari thmic response APS is analyzed and the simulation results show that the gate-in duced noise can be reduced.
文摘This paper introduces certain innovative algorithms to mask for pixel defects seen in image sensors. Pixel defectivity rates scale with pixel architecture and process nodes. Smaller pixel and process nodes introduce more defects in manufacturing. Brief introduction to causes for pixel defectivity at lower pixel nodes is explained. Later in the paper, popular defect correction schemes used in image processing applications are discussed. A new approach for defect correction is presented and evaluated using images captured from an 8M Bayer image sensor. Experimentation for threshold evaluation is done and presented with practical results for better optimization of proposed algorithms. Experimental data shows that proposed defect corrections preserves a lot of edge details and corrects for bright and hot pixels/clusters, which are evaluated using histogram analysis.
