In cases of high radiation emergencies,we propose a surface contamination monitor(SCM)that can quickly measure and pinpoint the contamination distribution in the affected population.Thick gaseous electron multiplier(T...In cases of high radiation emergencies,we propose a surface contamination monitor(SCM)that can quickly measure and pinpoint the contamination distribution in the affected population.Thick gaseous electron multiplier(THGEM)has several advantages,including fast response time and good spatial resolution.Based on new THGEMs,a two-dimensional imaging detector was developed for alpha detection,with a position resolution greater than 3 mm.The detector design and test results are described in this paper.Fast radiation imaging SCMs,with a 40mm×40 mm sensitive area,are currently under development.展开更多
Purpose This work aims to study the increase in dead layer thickness of an HPGe N-type detector during its operational period from 2012 to 2018.Methods The dead layer was examined along three Ge-crystal surfaces,such ...Purpose This work aims to study the increase in dead layer thickness of an HPGe N-type detector during its operational period from 2012 to 2018.Methods The dead layer was examined along three Ge-crystal surfaces,such as outer frontal,outer lateral,and inner lateral.These parameters were optimized using response surface methodology(RSM)with a Box–Behnken design(BBD).The Monte Carlo calculations using the GAMOS(Geant4-based Architecture for Medicine-Oriented Simulations)code were performed to evaluate the detector’s efficiency at different values of the inactive germanium layer.Results and conclusion The optimal combination of dead layer thickness has been identified using the desirability function approach,which is a useful tool to optimize multi-response problems.To find the variation in dead layer thickness over the operational period,the optimization procedure was reiterated for both experimental efficiencies measured in 2012 and 2018.The obtained results show that dead layers thickness has increased from 0.6141 mm to 0.7447 mm,0.0803 mm to 2.2721 mm,and 1.5012 mm to 1.6091 mm for the outer frontal,outer lateral,and inner lateral surfaces,respectively.展开更多
The point-contact high-purity germanium detector(HPGe)has the advantages of low background,low energy threshold,and high energy resolution and can be applied in the detection of rare-event physics.However,the performa...The point-contact high-purity germanium detector(HPGe)has the advantages of low background,low energy threshold,and high energy resolution and can be applied in the detection of rare-event physics.However,the performance of HPGe must be further improved to achieve superior energy resolution,low noise,and long-term reliability.In this study,we combine computational simulations and experimental comparisons to deeply understand the passivation mechanism of Ge.The surface passivation effect is calculated and inferred from the band structure and density of interface states,and further con-firmed by the minority carrier lifetime.The first-principles method based on the density functional theory was adopted to systematically study the lattice structure,band structure,and density of state(DOS)of four different systems:Ge–H,Ge–Ge-NH 2,Ge-OH,and Ge-SiO_(x).The electronic char-acteristics of the Ge(100)unit cell with different passi-vation groups and Si/O atomic ratios were compared.This shows that H,N,and O atoms can effectively reduce the surface DOS of the Ge atoms.The passivation effect of the SiO_(x) group varied with increasing O atoms and Si/O atomic ratios.Experimentally,SiO and SiO_(2) passivation films were fabricated by electron beam evaporation on a Ge substrate,and the valence state of Si and resistivity was measured to characterize the film.The minority carrier lifetime of Ge-SiO_(2) is 21.3 ls,which is approximately quadruple that of Ge-SiO.The passivation effect and mechanism are discussed in terms of hopping conduction and surface defect density.This study builds a relationship between the passivation effect and different termination groups,and provides technical support for the potential passivation layer,which can be applied in Ge detectors with ultralow energy thresholds and especially in HPGe for rare-event physics detection experiments in future.展开更多
Tyvek is widely used as the inner lining material of water Cherenkov detectors. Therefore, infor- mation about its optical properties plays an important role in the simulation and reconstruction of particles passing t...Tyvek is widely used as the inner lining material of water Cherenkov detectors. Therefore, infor- mation about its optical properties plays an important role in the simulation and reconstruction of particles passing through water Cherenkov detectors. In this paper, a water tank experiment is performed to study the Tyvek reflectivity in water. The so-called UNIFIED model, which is an optical model of surface reflection in Geant4, is adopted to describe the Tyvek reflectivity. Two key optical parameters are obtained from a comparison between the measured data and a Monte Carlo simulation.展开更多
Over the past decade, ultraviolet(UV) detection has been a subject of major interest for both research scientists and engineers because of its important applications in both the civil and military fields. The rapid de...Over the past decade, ultraviolet(UV) detection has been a subject of major interest for both research scientists and engineers because of its important applications in both the civil and military fields. The rapid development of interdisciplinary research has enabled the realization of UV detectors based on a variety of principles. Among these devices, UV detectors based on surface acoustic wave(SAW) technology offer unique advantages of remote wireless operation capability and zero power consumption. This article provides a comprehensive review of the working principles, important parameters, and the acoustic wave and materials types used in SAW-based UV detectors. The research and development status of these detectors are discussed and the most commonly used methods to optimize device performance are also summarized. Novel types of acoustic UV detectors based on thin film bulk acoustic resonators(FBARs)and Lamb wave resonators(LMRs) are briefly introduced. Finally, future development challenges are proposed and suggestions for future directions are provided to aid the development of this important research field.展开更多
Three-dimensional surface scanning(3DSS)and multi-detector computed tomography(MDCT)are two techniques that are used in legal medicine for digitalizing objects,a body or body parts such as bones.While these techniques...Three-dimensional surface scanning(3DSS)and multi-detector computed tomography(MDCT)are two techniques that are used in legal medicine for digitalizing objects,a body or body parts such as bones.While these techniques are more and more commonly employed,surprisingly little information is known about the quality rendering of digitalized three-dimensional(3D)models provided by each of them.This paper presents findings related to the measurement precision of 3D models obtained through observation of a study case,where a fractured skull reconstructed by an anthropologist was digitalized using both post-mortem imaging methods.Computed tomography(CT)scans were performed using an 8-row MDCT unit with two different slice thicknesses.The variability of 3D CT models superimposition allowed to assess the reproducibility and robustness of this digitalization technique.Furthermore,two 3D surface scans were done using a professional high resolution 3D digitizer.The comparison of 3D CT-scans with 3D surface scans by superimposition demonstrated several regions with significant differences in topology(average difference between+1.45 and-1.22 mm).When comparing the reproducibility between these two digitalizing techniques,it appeared that MDCT 3D models led in general to greater variability for measurement precision between scanned surfaces.Also,the reproducibility was better achieved with the 3D surface digitizer,showing 3D models with fewer and less pronounced differences(from+0.32 to-0.31 mm).These experiments suggest that MDCT provides less reproducible body models than 3D surface scanning.But further studies must be undertaken in order to corroborate this first impression,and possibly explain the reason for these findings.展开更多
A TiO_(2)-based multi-color photodetector with controlled photoelectric response to ultraviolet(UV)and visible light is developed by using band regulation technologies such as multi-junction synergy and surface adsorp...A TiO_(2)-based multi-color photodetector with controlled photoelectric response to ultraviolet(UV)and visible light is developed by using band regulation technologies such as multi-junction synergy and surface adsorption.This photodetector is manufactured via a continuous process including magnetron sputtering,hydrothermal growth,hydrogen annealing,spin coating and thermal evaporation assembly to form a structure of N-doped TiO_(2)/hydrogenated-TiO_(2)/p-Si heterojunction.These synergistic effects form electronic potential wells in the device to control the electrical transport and spectral response of photo-generated carriers.In the air,the device exhibits a controllable photodetection ability that responds to visible light at positive voltages and UV light at negative voltages.But in vacuum(<0.1 Pa),the photodetection ability of the device at negative voltages is greatly reduced due to the lack of barrier effect caused by surface adsorption.On the contrary,the photodetection ability at positive voltage(e.g.,4 V)has been greatly improved,and the quantum efficiency reaches 206.6%under the 480 nm wavelength light.The device has a controllable ability to detect UV and visible light depending on the environments,which is very useful in the fields of environmental detection,chemical sensing and multi-color communication,etc.展开更多
Herein we report a prototypical electronic substrate specifically designed to serve the weakly interacting massive particles(WIMPs)detectors at the China Dark Matter Experiment(CDEX).Because the bulky high-purity germ...Herein we report a prototypical electronic substrate specifically designed to serve the weakly interacting massive particles(WIMPs)detectors at the China Dark Matter Experiment(CDEX).Because the bulky high-purity germanium(HPGe)detectors operate under liquid-nitrogen temperatures and ultralow radiation backgrounds,the desired electronic substrates must maintain high adhesivity across different layers in such cold environment and be free from any radioactive nuclides.To conquer these challenges,for the first time,we employed polytetrafluoroethylene((C2F4)n)foil as the base substrate,in conjunction with ion implantation and deposition techniques using an independently developed device at Beijing Normal University for surface modification prior to electroplating.The remarkable peeling strengths of 0.88±0.06 N/mm for as-prepared sample and 0.75±0.05 N/mm for that after 2.5-days of soaking inside the liquid nitrogen were observed,while the regular standards commonly require 0.4 N/mm^0.6 N/mm for electronic substrates.展开更多
In experiments searching for rare signals,background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever mo...In experiments searching for rare signals,background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever more essential.We propose to develop a gaseous time projection chamber(TPC)with a Micromegas readout for radio screening.The TPC records three-dimensional trajectories of charged particles emitted from a flat sample placed in the active volume of the detector.The detector can distinguish the origin of an event and identify the particle types with information from trajectories,which significantly increases the screening sensitivity.For a particles from the sample surface,we observe that our proposed detector can reach a sensitivity higher than 100 l Bq m-2 within two days.展开更多
Sulfur dioxide and its derivative sulfite widely existed in air,water as the environment pollutant.Sulfite is also commonly used as preservative and additive in fresh fruits,vegetables,wines and pharmaceutical materia...Sulfur dioxide and its derivative sulfite widely existed in air,water as the environment pollutant.Sulfite is also commonly used as preservative and additive in fresh fruits,vegetables,wines and pharmaceutical materials.Due to sulfite is closely related with human diseases,it is very urgent for the sensitive and rapid quantification of sulfite in various samples.In our study,a turn-on near infrared(NIR)fluorescent probe(MDQ)was developed for sulfite detection based on a Michael addition reaction,with high sensitivity(LOD 4.16 nmol/L),selectivity and fast response time(400 s).Using MDQ,a quantify method for sulfite in traditional Chinese medicines(TCMs)was developed with the advantages of high precision,accuracy and convenient operation.Furthermore,according to the photophysical property of MDQ,a portable fluorescence detector is designed to quantify sulfite for TCMs and surface water in Dalian city of China.Therefore,the developed fluorescent probe MDQ and portable fluorescent detector as a rapid inspection instrument were successfully used to real-time monitor the sulfite in various complex samples.展开更多
基金supported by the China Institute of Atomic Energy and University of Chinese Academy of SciencesNational Natural Science Foundation of China(Nos.11575193 and U1732266)+2 种基金Key Research Program of Frontier Sciences,CAS(No.QYZDB-SSWSLH039)the Youth Innovation Promotion Association of CAS(No.2016153)the Natural Science Key Foundation of Guangxi(No.2015GXNSFDA139002)
文摘In cases of high radiation emergencies,we propose a surface contamination monitor(SCM)that can quickly measure and pinpoint the contamination distribution in the affected population.Thick gaseous electron multiplier(THGEM)has several advantages,including fast response time and good spatial resolution.Based on new THGEMs,a two-dimensional imaging detector was developed for alpha detection,with a position resolution greater than 3 mm.The detector design and test results are described in this paper.Fast radiation imaging SCMs,with a 40mm×40 mm sensitive area,are currently under development.
文摘Purpose This work aims to study the increase in dead layer thickness of an HPGe N-type detector during its operational period from 2012 to 2018.Methods The dead layer was examined along three Ge-crystal surfaces,such as outer frontal,outer lateral,and inner lateral.These parameters were optimized using response surface methodology(RSM)with a Box–Behnken design(BBD).The Monte Carlo calculations using the GAMOS(Geant4-based Architecture for Medicine-Oriented Simulations)code were performed to evaluate the detector’s efficiency at different values of the inactive germanium layer.Results and conclusion The optimal combination of dead layer thickness has been identified using the desirability function approach,which is a useful tool to optimize multi-response problems.To find the variation in dead layer thickness over the operational period,the optimization procedure was reiterated for both experimental efficiencies measured in 2012 and 2018.The obtained results show that dead layers thickness has increased from 0.6141 mm to 0.7447 mm,0.0803 mm to 2.2721 mm,and 1.5012 mm to 1.6091 mm for the outer frontal,outer lateral,and inner lateral surfaces,respectively.
基金supported by the National Natural Science Foundation of China Youth Fund(No.12005017)。
文摘The point-contact high-purity germanium detector(HPGe)has the advantages of low background,low energy threshold,and high energy resolution and can be applied in the detection of rare-event physics.However,the performance of HPGe must be further improved to achieve superior energy resolution,low noise,and long-term reliability.In this study,we combine computational simulations and experimental comparisons to deeply understand the passivation mechanism of Ge.The surface passivation effect is calculated and inferred from the band structure and density of interface states,and further con-firmed by the minority carrier lifetime.The first-principles method based on the density functional theory was adopted to systematically study the lattice structure,band structure,and density of state(DOS)of four different systems:Ge–H,Ge–Ge-NH 2,Ge-OH,and Ge-SiO_(x).The electronic char-acteristics of the Ge(100)unit cell with different passi-vation groups and Si/O atomic ratios were compared.This shows that H,N,and O atoms can effectively reduce the surface DOS of the Ge atoms.The passivation effect of the SiO_(x) group varied with increasing O atoms and Si/O atomic ratios.Experimentally,SiO and SiO_(2) passivation films were fabricated by electron beam evaporation on a Ge substrate,and the valence state of Si and resistivity was measured to characterize the film.The minority carrier lifetime of Ge-SiO_(2) is 21.3 ls,which is approximately quadruple that of Ge-SiO.The passivation effect and mechanism are discussed in terms of hopping conduction and surface defect density.This study builds a relationship between the passivation effect and different termination groups,and provides technical support for the potential passivation layer,which can be applied in Ge detectors with ultralow energy thresholds and especially in HPGe for rare-event physics detection experiments in future.
基金Supported by Ministry of Science and Technology of the People's Republic of China (2006CB808102)
文摘Tyvek is widely used as the inner lining material of water Cherenkov detectors. Therefore, infor- mation about its optical properties plays an important role in the simulation and reconstruction of particles passing through water Cherenkov detectors. In this paper, a water tank experiment is performed to study the Tyvek reflectivity in water. The so-called UNIFIED model, which is an optical model of surface reflection in Geant4, is adopted to describe the Tyvek reflectivity. Two key optical parameters are obtained from a comparison between the measured data and a Monte Carlo simulation.
基金This work was supported by China Scholarship Council,the National Natural Science Foundation of China(61974107)Hubei Provincial Major Program of Technological Innovation(2019AAA052,2017AAA121).
文摘Over the past decade, ultraviolet(UV) detection has been a subject of major interest for both research scientists and engineers because of its important applications in both the civil and military fields. The rapid development of interdisciplinary research has enabled the realization of UV detectors based on a variety of principles. Among these devices, UV detectors based on surface acoustic wave(SAW) technology offer unique advantages of remote wireless operation capability and zero power consumption. This article provides a comprehensive review of the working principles, important parameters, and the acoustic wave and materials types used in SAW-based UV detectors. The research and development status of these detectors are discussed and the most commonly used methods to optimize device performance are also summarized. Novel types of acoustic UV detectors based on thin film bulk acoustic resonators(FBARs)and Lamb wave resonators(LMRs) are briefly introduced. Finally, future development challenges are proposed and suggestions for future directions are provided to aid the development of this important research field.
文摘Three-dimensional surface scanning(3DSS)and multi-detector computed tomography(MDCT)are two techniques that are used in legal medicine for digitalizing objects,a body or body parts such as bones.While these techniques are more and more commonly employed,surprisingly little information is known about the quality rendering of digitalized three-dimensional(3D)models provided by each of them.This paper presents findings related to the measurement precision of 3D models obtained through observation of a study case,where a fractured skull reconstructed by an anthropologist was digitalized using both post-mortem imaging methods.Computed tomography(CT)scans were performed using an 8-row MDCT unit with two different slice thicknesses.The variability of 3D CT models superimposition allowed to assess the reproducibility and robustness of this digitalization technique.Furthermore,two 3D surface scans were done using a professional high resolution 3D digitizer.The comparison of 3D CT-scans with 3D surface scans by superimposition demonstrated several regions with significant differences in topology(average difference between+1.45 and-1.22 mm).When comparing the reproducibility between these two digitalizing techniques,it appeared that MDCT 3D models led in general to greater variability for measurement precision between scanned surfaces.Also,the reproducibility was better achieved with the 3D surface digitizer,showing 3D models with fewer and less pronounced differences(from+0.32 to-0.31 mm).These experiments suggest that MDCT provides less reproducible body models than 3D surface scanning.But further studies must be undertaken in order to corroborate this first impression,and possibly explain the reason for these findings.
基金This work was financially supported by the National Natural Science Foundation of China(No.51972055)the Shenzhen Science and Technology Research Project(No.JCYJ20180508152903208)+5 种基金the Guangdong Basic and Applied Basic Research Foundation(No.2020A1515010258)the Stable Support Project for Shenzhen High Education Institutions(No.SZWD2021001)the Shenzhen Bay Laboratory Open Program(No.SZBL2020090501002)the Natural Science Foundation of Top Talent of SZTU(No.20200201)the Homemade Experimental Equipment Foundation of SZTU(No.2020XZY002)the Shenzhen Pengcheng Scholar Program.
文摘A TiO_(2)-based multi-color photodetector with controlled photoelectric response to ultraviolet(UV)and visible light is developed by using band regulation technologies such as multi-junction synergy and surface adsorption.This photodetector is manufactured via a continuous process including magnetron sputtering,hydrothermal growth,hydrogen annealing,spin coating and thermal evaporation assembly to form a structure of N-doped TiO_(2)/hydrogenated-TiO_(2)/p-Si heterojunction.These synergistic effects form electronic potential wells in the device to control the electrical transport and spectral response of photo-generated carriers.In the air,the device exhibits a controllable photodetection ability that responds to visible light at positive voltages and UV light at negative voltages.But in vacuum(<0.1 Pa),the photodetection ability of the device at negative voltages is greatly reduced due to the lack of barrier effect caused by surface adsorption.On the contrary,the photodetection ability at positive voltage(e.g.,4 V)has been greatly improved,and the quantum efficiency reaches 206.6%under the 480 nm wavelength light.The device has a controllable ability to detect UV and visible light depending on the environments,which is very useful in the fields of environmental detection,chemical sensing and multi-color communication,etc.
基金Project supported by the Central University Basic Scientific Research Business Expenses Special Funds under the project name of Research on Applied Physics under Low Radiation Background(Grant No.2018NTST07)the National Natural Science Foundation Joint Fund Key Project,China(Grant No.U1865206)。
文摘Herein we report a prototypical electronic substrate specifically designed to serve the weakly interacting massive particles(WIMPs)detectors at the China Dark Matter Experiment(CDEX).Because the bulky high-purity germanium(HPGe)detectors operate under liquid-nitrogen temperatures and ultralow radiation backgrounds,the desired electronic substrates must maintain high adhesivity across different layers in such cold environment and be free from any radioactive nuclides.To conquer these challenges,for the first time,we employed polytetrafluoroethylene((C2F4)n)foil as the base substrate,in conjunction with ion implantation and deposition techniques using an independently developed device at Beijing Normal University for surface modification prior to electroplating.The remarkable peeling strengths of 0.88±0.06 N/mm for as-prepared sample and 0.75±0.05 N/mm for that after 2.5-days of soaking inside the liquid nitrogen were observed,while the regular standards commonly require 0.4 N/mm^0.6 N/mm for electronic substrates.
基金the Ministry of Science and Technology of China(No.2016YFA0400302)the National Natural Sciences Foundation of China(Nos.11775142 and U1965201)the Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP).
文摘In experiments searching for rare signals,background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever more essential.We propose to develop a gaseous time projection chamber(TPC)with a Micromegas readout for radio screening.The TPC records three-dimensional trajectories of charged particles emitted from a flat sample placed in the active volume of the detector.The detector can distinguish the origin of an event and identify the particle types with information from trajectories,which significantly increases the screening sensitivity.For a particles from the sample surface,we observe that our proposed detector can reach a sensitivity higher than 100 l Bq m-2 within two days.
基金supported financially by Distinguished Professor Program of Liaoning Province(No.XLYC2002008)Dalian Science and Technology Leading Talents Project(Nos.2019RD15,2020RJ09 and 2020RQ076)+2 种基金Liaoning Provincial Natural Science Foundation(No.20180550761)Liaoning Revitalization Talents Program(No.XLYC1907017)the Open Research Fund of the School of Chemistry and Chemical Engineering,Henan Normal University(No.2021YB07).
文摘Sulfur dioxide and its derivative sulfite widely existed in air,water as the environment pollutant.Sulfite is also commonly used as preservative and additive in fresh fruits,vegetables,wines and pharmaceutical materials.Due to sulfite is closely related with human diseases,it is very urgent for the sensitive and rapid quantification of sulfite in various samples.In our study,a turn-on near infrared(NIR)fluorescent probe(MDQ)was developed for sulfite detection based on a Michael addition reaction,with high sensitivity(LOD 4.16 nmol/L),selectivity and fast response time(400 s).Using MDQ,a quantify method for sulfite in traditional Chinese medicines(TCMs)was developed with the advantages of high precision,accuracy and convenient operation.Furthermore,according to the photophysical property of MDQ,a portable fluorescence detector is designed to quantify sulfite for TCMs and surface water in Dalian city of China.Therefore,the developed fluorescent probe MDQ and portable fluorescent detector as a rapid inspection instrument were successfully used to real-time monitor the sulfite in various complex samples.
