Conventional superconducting nanowire single-photon detectors(SNSPDs)have been typically limited in their applications due to their size,weight,and power consumption,which confine their use to laboratory settings.Howe...Conventional superconducting nanowire single-photon detectors(SNSPDs)have been typically limited in their applications due to their size,weight,and power consumption,which confine their use to laboratory settings.However,with the rapid development of remote imaging,sensing technologies,and long-range quantum communication with fewer topographical constraints,the demand for high-efficiency single-photon detectors integrated with avionic platforms is rapidly growing.We herein designed and manufactured the first drone-based SNSPD system with a system detection efficiency(SDE)as high as 91.8%.This drone-based system incorporates high-performance NbTiN SNSPDs,a self-developed miniature liquid helium dewar,and custom-built integrated electrical setups,making it capable of being launched in complex topographical conditions.Such a drone-based SNSPD system may open the use of SNSPDs for applications that demand high SDE in complex environments.展开更多
We demonstrate the photon-number resolution(PNR)capability of a 1.25 GHz gated InGaAs single-photon avalanche photodiode(APD)that is equipped with a simple,low-distortion ultra-narrowband interference circuit for the ...We demonstrate the photon-number resolution(PNR)capability of a 1.25 GHz gated InGaAs single-photon avalanche photodiode(APD)that is equipped with a simple,low-distortion ultra-narrowband interference circuit for the rejection of its background capacitive response.Through discriminating the avalanche current amplitude,we are able to resolve up to four detected photons in a single detection gate with a detection efficiency as high as 45%.The PNR capability is limited by the avalanche current saturation,and can be increased to five photons at a lower detection efficiency of 34%.The PNR capability,combined with high efficiency and low noise,will find applications in quantum information processing technique based on photonic qubits.展开更多
By analyzing the average percent of faults detected （APFD） metric and its variant versions, which are widely utilized as metrics to evaluate the fault detection efficiency of the test suite, this paper points out so...By analyzing the average percent of faults detected （APFD） metric and its variant versions, which are widely utilized as metrics to evaluate the fault detection efficiency of the test suite, this paper points out some limitations of the APFD series metrics. These limitations include APFD series metrics having inaccurate physical explanations and being unable to precisely describe the process of fault detection. To avoid the limitations of existing metrics, this paper proposes two improved metrics for evaluating fault detection efficiency of a test suite, including relative-APFD and relative-APFDc. The proposed metrics refer to both the speed of fault detection and the constraint of the testing source. The case study shows that the two proposed metrics can provide much more precise descriptions of the fault detection process and the fault detection efficiency of the test suite.展开更多
To improve the diagnostic efficiency of prostate cancer(PCa)and reduce unnecessary biopsies,we defined and analyzed the diagnostic efficiency of peripheral zone prostate-specific antigen(PSA)density(PZ-PSAD).Patients ...To improve the diagnostic efficiency of prostate cancer(PCa)and reduce unnecessary biopsies,we defined and analyzed the diagnostic efficiency of peripheral zone prostate-specific antigen(PSA)density(PZ-PSAD).Patients who underwent systematic 12-core prostate biopsies in Shanghai General Hospital(Shanghai,China)between January 2012 and January 2018 were retrospectively identified(n=529).Another group of patients with benign prostatic hyperplasia(n=100)were randomly preselected to obtain the PSA density of the non-PCa cohort(N-PSAD).Prostate volumes and transition zone volumes were measured using multiparameter magnetic resonance imaging(mpMRI)and were combined with PSA and N-PSAD to obtain the PZ-PSAD from a specific algorithm.Receiver operating characteristic(ROC)curve analysis was used to assess the PCa detection efficiency in patients stratified by PSA level,and the area under the ROC curve(AUC)of PZ-PSAD was higher than that of PSA,PSA density(PSAD),and transition zone PSA density(TZ-PSAD).PZ-PSAD could amend the diagnosis for more than half of the patients with inaccurate transrectal ultrasonography(TRUS)and mpMRI results.When TRUS and mpMRI findings were ambiguous to predict PCa(PIRADS score≤3),PZ-PSAD could increase the positive rate of biopsy from 21.7%to 54.7%,and help 63.8%(150/235)of patients avoid unnecessary prostate biopsy.In patients whose PSA was 4.0–10.0 ng ml^(−1),10.1–20.0 ng ml^(−1),and>20.0 ng ml^(−1),the ideal PZ-PSAD cut-off value for predicting clinically significant PCa was 0.019 ng ml^(−2),0.297 ng ml^(−2),and 1.180 ng ml^(−2),respectively(sensitivity>90%).Compared with PSA,PSAD,and TZ-PSAD,the efficiency of PZ-PSAD for predicting PCa is the highest,leading to fewer missed diagnoses and unnecessary biopsies.展开更多
For the problem of cooperative strike against multiple maneuvering targets,in order to improve the detection efficiency of multi-missile systems,this paper proposes a Group Cooperative Midcourse Guidance Law(GCMGL)for...For the problem of cooperative strike against multiple maneuvering targets,in order to improve the detection efficiency of multi-missile systems,this paper proposes a Group Cooperative Midcourse Guidance Law(GCMGL)for heterogeneous missile formation with optimal detection efficiency.Firstly,considering the adverse impact of target maneuvering on the guidance system,a Super-Twisting Disturbance Observer(STDO)is introduced to estimate target acceleration.Secondly,to avoid chattering in the system,a reaching law is combined with the design of the midcourse guidance law and cooperative detection control law for the leader missiles.This approach provides reference information for follower missiles and forms an optimal detection formation.Then,to achieve cooperative engagement of targets by follower missiles in groups,a group consensus protocol is introduced in the Line-of-Sight(LOS)direction to design the GCMGL.Simultaneously,in the direction normal to the LOS,when follower missiles cannot obtain the LOS angle combination information from the leader missiles,a distributed extended state observer is introduced to estimate it.Finally,a time-varying LOS angle Formation Tracking Midcourse Guidance Law(FTMGL)is designed based on this estimated information.The guidance law’s stability is validated using Lyapunov theory,and simulation experiments are performed to confirm its effectiveness and advantages.展开更多
It is possible to understand the lightning activities in a specific region and compare test results of different apparatus only when a reliable evaluation of detection efficiency distribution pertaining to a particula...It is possible to understand the lightning activities in a specific region and compare test results of different apparatus only when a reliable evaluation of detection efficiency distribution pertaining to a particular lightning location system(LLS)is available. Based on the data in 1992.an approximate evaluation of detection efficiency spatial distribu- tion for single-station lightning location system(M-LDARS)and LLP three-station lightning loca- tion system in Beijing-Tianjin-Hebei area is presented in the paper,showing that the average detec- tion efficiencies are smaller than 48% and 46% respectively.In addition,the article offers an eval- uation of spatial distribution of ground stroke density(D_g)and positive stroke percentage,indicat- ing that six high stroke density zones exist along the southeastern sides of the Taihang and Yan- shan Mountains.The stroke density of mountainous region is higher than that of the plain region, in contrast to the case of positive stroke percentage.Also,it is shown that within a radius of 250 km,the average of D_g is 1.2(km^(-2) a^(-1))while the average positive stroke percentage is 10.9%. Finally,the paper proposes a possible test method of accurately evaluating the spatial distribution of detection efficiency(A).展开更多
In this paper, the detection efficiency of a large area neutron sensitive microchannel plate detector has been evaluated. A ^6LiF/ZnS scintillator detector 65 mm in diameter and 0.32 mm in thickness, with product code...In this paper, the detection efficiency of a large area neutron sensitive microchannel plate detector has been evaluated. A ^6LiF/ZnS scintillator detector 65 mm in diameter and 0.32 mm in thickness, with product code,EJ426HD2, produced by Eljen Technology, was employed as the benchmark detector. The TOF spectra of these two detectors were simultaneously measured and the energy spectra were then deduced to calculate the detection efficiency curve of the ^nMCP detector. Tests show the detection efficiency@25.3 me V thermal neutrons is 34% for this ^nMCP detector.展开更多
A high-efficiency fast neutron detector prototype based on a triple Gas Electron Multiplier（GEM） detector, which, coupled with a novel multi-layered high-density polyethylene（HDPE） as a neutron-to-proton converter...A high-efficiency fast neutron detector prototype based on a triple Gas Electron Multiplier（GEM） detector, which, coupled with a novel multi-layered high-density polyethylene（HDPE） as a neutron-to-proton converter for improving the neutron detection efficiency, is introduced and tested with the Am-Be neutron source in the Institute of Modern Physics（IMP） at Lanzhou in the present work. First, the developed triple GEM detector is tested by measuring its effective gain and energy resolution with55 Fe X-ray source to ensure that it has a good performance.The effective gain and obtained energy resolution is 5.0×104and around 19.2%, respectively. Secondly, the novel multi-layered HDPE converter is coupled with the cathode of the triple GEM detector making it a high-efficiency fast neutron detector. Its effective neutron response is four times higher than that of the traditional single-layered conversion technique when the converter layer number is 38.展开更多
The rapid growth of neutron flux has driven the development of^(3)He-free neutron detectors to satisfy the requirements of the neutron scattering instruments under construction or planned at the China Spallation Neutr...The rapid growth of neutron flux has driven the development of^(3)He-free neutron detectors to satisfy the requirements of the neutron scattering instruments under construction or planned at the China Spallation Neutron Source(CSNS).Position-sensitive neutron detectors with a high counting rate and large area play an important role in the instruments performing neutron measurements in or close to the direct beam.The ceramic gas-electron-multiplier(GEM)detector serves as a promising solution,and considerable work has been done using the small-area GEM neutron detectors.In this article,we designed and constructed a detector prototype utilizing ceramic GEM foils with an effective area of about307 mm×307 mm.To evaluate and investigate their basic characteristics,the Monte Carlo(MC)tool FLUKA was employed and several neutron beam tests were conducted at CSNS.The simulated spatial resolution was basically in agreement with the measured value of 2.50±0.01 mm(FWHM).The wavelength spectra measurement was verified through comparisons with a commercial beam monitor.In addition,a detection efficiency of 4.7±0.1%was achieved for monoenergetic neutrons of 1.59 A wavelength.This is consistent with the simulated result.The results indicate that the large-area ceramic GEM detector is a good candidate to implement neutron beam measurements.Its efficiency can be improved in a cascading manner to approach that reached by traditional^(3)He detectors.展开更多
To accurately reconstruct the tomographic gamma scanning(TGS)transmission measurement image,this study optimized the transmission reconstruction equation based on the actual situation of TGS transmission measurement.U...To accurately reconstruct the tomographic gamma scanning(TGS)transmission measurement image,this study optimized the transmission reconstruction equation based on the actual situation of TGS transmission measurement.Using the transmission reconstruction equation and the Monte Carlo program Geant4,an innovative virtual trajectory length model was constructed.This model integrated the solving process for the trajectory length and detection efficiency within the same model.To mitigate the influence of the angular distribution ofγ-rays emitted by the transmitted source at the detector,the transport processes of numerous particles traversing a virtual nuclear waste barrel with a density of zero were simulated.Consequently,a certain amount of information was captured at each step of particle transport.Simultaneously,the model addressed the nonuniform detection efficiency of the detector end face by considering whether the energy deposition of particles in the detector equaled their initial energy.Two models were established to validate the accuracy and reliability of the virtual trajectory length model.Model 1 was a simplified nuclear waste barrel,whereas Model 2 closely resembled the actual structure of a nuclear waste barrel.The results indicated that the proposed virtual trajectory length model significantly enhanced the precision of the trajectory length determination,substantially increasing the quality of the reconstructed images.For example,the reconstructed images of Model 2 using the“point-to-point”and average trajectory models revealed a signalto-noise ratio increase of 375.0%and 112.7%,respectively.Thus,the virtual trajectory length model proposed in this study holds paramount significance for the precise reconstruction of transmission images.Moreover,it can provide support for the accurate detection of radioactive activity in nuclear waste barrels.展开更多
Promoting the development of deep-sea mineral exploration instrumentation can help alleviate the global resource shortage faced by mankind.X-ray fluorescence(XRF)spectrometry has been widely used in the in situ analys...Promoting the development of deep-sea mineral exploration instrumentation can help alleviate the global resource shortage faced by mankind.X-ray fluorescence(XRF)spectrometry has been widely used in the in situ analysis of deep-sea minerals owing to its fast analytical speed,nondestructive nature,and wide analytical range.This study focused on the structural safety and detection efficiency of X-ray fluorescence in situ measurement equipment under high pressure for deep-sea XRF analysis.This study first combined finite element analysis and experiments to design and optimize the structure of an X-ray probe tube required for deep-sea mineral exploration and to determine the Be window thickness to ensure stress safety.Subsequently,the Monte Carlo method was used to analyze and optimize the Be window thickness on the X-ray probe tube to improve the accuracy of the elemental analyses.Finally,the effect of seawater thickness between the transmitter outer tube and rock wall was also considered.The results show that based on ocean depth in different detection environments,Be windows with a thickness of 1.5 mm or 2.0 mm can be selected to improve the detection efficiency of the device while ensuring the structural safety of the instrument.According to the design features and detection requirements of the device,in deep-sea exploration of minerals with characteristic peak energies below 10 keV,the transmitter outer tube should be as close as possible to the rock wall inside the logging.When the characteristic peak energy of the minerals is more than 10 keV,the distance between the transmitter outer tube and rock wall inside the logging should be controlled to approximately 2 mm.This study provides feasible solutions for future deep-sea mineral resource development and a useful reference for elemental analysis of minerals in the deep-sea or other extreme working environments.展开更多
Based on lightning location data of lightning monitoring network in Guizhou Province in recent eight years,the effective detection radius of a station and the effective detection range of lightning monitoring network ...Based on lightning location data of lightning monitoring network in Guizhou Province in recent eight years,the effective detection radius of a station and the effective detection range of lightning monitoring network in Guizhou Province were analyzed. The results show that the effective detection radius of a lightning monitoring sub-station in Guizhou Province is 160 km; some counties in the southwest,northwest and northeast of Guizhou were not detected. To improve the detector efficiency of lightning monitoring network in Guizhou Province,it is suggested that nine sub-stations should be built in Weining,Shuicheng,Qinglong,Pingtang,Rongjiang,Yuping,Songtao,Tongren and Renhuai,so that the effective detection efficiency will reach more than 95%.展开更多
Onlineγ-spectrometry systems for inland waters,most of which extract samples in situ and in real time,are able to produce reliable activity concentration measurements for waterborne radionuclides only when they are d...Onlineγ-spectrometry systems for inland waters,most of which extract samples in situ and in real time,are able to produce reliable activity concentration measurements for waterborne radionuclides only when they are distributed relatively uniformly and enter into a steady-state diffusion regime in the measurement chamber.To protect residents’health and ensure the safety of the living environment,better timeliness is required for this measurement method.To address this issue,this study established a mathematical model of the online waterγ-spectrometry system so that rapid warning and activity estimates can be obtained for water under non-steady-state(NSS)conditions.In addition,the detection efficiency of the detector for radionuclides during the NSS diffusion process was determined by applying the computational fluid dynamics technique in conjunction with Monte Carlo simulations.On this basis,a method was developed that allowed the online waterγ-spectrometry system to provide rapid warning and activity concentration estimates for radionuclides in water.Subsequent analysis of the NSS-mode measurements of^(40)K radioactive solutions with different activity concentrations determined the optimum warning threshold and measurement time for producing accurate activity concentration estimates for radionuclides.The experimental results show that the proposed NSS measurement method is able to give warning and yield accurate activity concentration estimates for radionuclides 55.42 and 69.42 min after the entry of a 10 Bq/L^(40)K radioactive solution into the measurement chamber,respectively.These times are much shorter than the 90 min required by the conventional measurement method.Furthermore,the NSS measurement method allows the measurement system to give rapid(within approximately 15 min)warning when the activity concentrations of some radionuclides reach their respective limits stipulated in the Guidelines for Drinking-water Quality of the WHO,suggesting that this method considerably enhances the warning capacity of in situ online waterγ-spectrometry systems.展开更多
Objective:To assess the detection efficiencies of liquid radioisotopes in a well-type NaI(Tl)gamma spectrometer,focusing on the short-lived isotopes^(99)Tcm,^(131)I,and^(18)F.Methods:The detection efficiencies of liqu...Objective:To assess the detection efficiencies of liquid radioisotopes in a well-type NaI(Tl)gamma spectrometer,focusing on the short-lived isotopes^(99)Tcm,^(131)I,and^(18)F.Methods:The detection efficiencies of liquid 99Tcm,131I,and 18F in a well-type NaI(Tl)gamma spectrometer were systematically investigated through calibration experiments and Monte Carlo simulations,and accounting for the coincidence-summing effect.Results:The results indicated that the detection efficiencies of^(99)Tcm,^(131)I,and^(18)F varied from 64.4%to 72.3%,34.8%-43.1%and 27.3%-28.5%for different sample volumes ranging from 15 mL to 80 mL,respectively.The simulated detection efficiencies were highly consistent with the experimental results,with a largest relative deviation of 5%for the 3 radionuclides and 4 different sample volumes.Conclusion:The consistent results between the calibration experiments and Monte Carlo simulations reveal that this measuring device possesses high detection efficiencies of 99Tcm,131I,and 18F,making it suitable for measuring low-level activity radioactive liquids,such as radioactive waste liquids to be discharged.展开更多
The nuclides inhaled during nuclear accidents usually cause internal contamination of the lungs with low activity.Although a parallel-hole imaging system,which is widely used in medical gamma cameras,has a high resolu...The nuclides inhaled during nuclear accidents usually cause internal contamination of the lungs with low activity.Although a parallel-hole imaging system,which is widely used in medical gamma cameras,has a high resolution and good image quality,owing to its extremely low detection efficiency,it remains difficult to obtain images of inhaled lung contamination.In this study,the Monte Carlo method was used to study the internal lung contamination imaging using the MPA-MURA coded-aperture collimator.The imaging system consisted of an adult male lung model,with a mosaicked,pattern-centered,and anti-symmetric MURA coded-aperture collimator model and a CsI(Tl)detector model.The MLEM decoding algorithm was used to reconstruct the internal contamination image,and the complementary imaging method was used to reduce the number of artifacts.The full width at half maximum of the I-131 point source image reconstructed by the MPAMURA coded-aperture imaging reached 2.51 mm,and the signal-to-noise ratio of the simplified respiratory tract source(I-131)image reconstructed through MPA-MURA coded-aperture imaging was 3.98 dB.Although the spatial resolution of MPA-MURA coded-aperture imaging is not as good as that of parallel-hole imaging,the detection efficiency of PMA-MURA coded-aperture imaging is two orders of magnitude higher than that of parallel-hole collimator imaging.Considering the low activity level of internal lung contamination caused by nuclear accidents,PMA-MURA coded-aperture imaging has significant potential for the development of lung contamination imaging.展开更多
Real-time monitoring of the 14-MeV D-T fusion neutron yield is urgently required for the triton burnup study on the Experimental Advanced Superconducting Tokamak (EAST). In this study, we developed an optimal design o...Real-time monitoring of the 14-MeV D-T fusion neutron yield is urgently required for the triton burnup study on the Experimental Advanced Superconducting Tokamak (EAST). In this study, we developed an optimal design of a fast-neutron detector based on the scintillating fiber (Sci-Fi) to provide D-T neutron yield through Geant4simulation. The effect on the detection performance is concerned when changing the number of the Sci-Fis embedded in the probe head, minimum distance between the fibers, length of the fibers, or substrate material of the probe head. The maximum number of scintillation photons generated by the n/γ source particles and output by the light guide within an event (event:the entire simulation process for one source particle) was used to quantify the n/γ resolution of the detector as the main basis. And the intrinsic detection efficiency was used as another evaluation criterion. The results demonstrate that the optimal design scheme is to use a 5 cm probe head whose substrate material is pure aluminum, in which 463 Sci-Fis with the same length of 5 cm are embedded, and the minimum distance between the centers of the two fibers is 2 mm. The optimized detector exhibits clear directionality in the simulation, which is in line with the expectation and experimental data provided in the literature. This study presents the variation trends of the performance of the SciFi detector when its main parameters change, which is beneficial for the targeted design and optimization of the Sci-Fi detector used in a specific radiation environment.展开更多
Chinese Spallation Neutron Source(CSNS) has successfully produced its first neutron beam in 28th August 2017. It has been running steadily from March, 2018. According to the construction plan, the engineering material...Chinese Spallation Neutron Source(CSNS) has successfully produced its first neutron beam in 28th August 2017. It has been running steadily from March, 2018. According to the construction plan, the engineering materials diffractometer(EMD) will be installed between 2019–2023. This instrument requires the neutron detectors with the cover area near3 m2in two 90° neutron diffraction angle positions, the neutron detecting efficiency is better than 40%@1A, and the spatial resolution is better than 4 mm×200 mm in horizontal and vertical directions respectively. We have developed a onedimensional position-sensitive neutron detector based on the oblique6Li F/Zn S(Ag) scintillators, wavelength shifting fibers,and Si PMs(silicon photomultipliers) readout. The inhomogeneity of the neutron detection efficiency between each pixel and each detector module, which caused by the inconsistency of the wave-length shifting fibers in collecting scintillation photons, needs to be mitigated before the installation. A performance optimization experiment of the detector modules was carried out on the BL20(beam line 20) of CSNS. Using water sample, the neutron beam with Φ5 mm exit hole was dispersed related evenly into the forward space. According to the neutron counts of each pixel of the detector module, the readout electronics threshold of each pixel is adjusted. Compared with the unadjusted detector module, the inhomogeneity of the detection efficiency for the adjusted one has been improved from 69% to 90%. The test result of the diffraction peak of the standard sample Si showed that the adjusted detector module works well.展开更多
The detection of low-level light is a key technology in various experimental scientific studies. As a photon detector, the silicon photomultiplier （SiPM） has gradually become an alternative to the photomultiplier tu...The detection of low-level light is a key technology in various experimental scientific studies. As a photon detector, the silicon photomultiplier （SiPM） has gradually become an alternative to the photomultiplier tube （PMT） in many applications in high-energy physics, astroparticle physics, and medical imaging because of its high photon detection efficiency （PDE）, good resolution for single-photon detection, insensitivity to magnetic field, low operating voltage, compactness, and low cost. However, primarily because of the geometric fill factor, the PDE of most SiPMs is not very high; in particular, for those SiPMs with a high density of micro cells, the effective area is small, and the bandwidth of the light response is narrow. As a building block of the SiPM, the concept of the backside-illuminated avalanche drift detector （ADD） was first proposed by the Max Planck Institute of Germany eight years ago; the ADD is promising to have high PDE over the full energy range of optical photons, even ultraviolet light and X-ray light, and because the avalanche multiplication region is very small, the ADD is beneficial for the fabrication of large-area SiPMs. However, because of difficulties in design and fabrication, no significant progress had been made, and the concept had not yet been verified. In this paper, preliminary results in the design, fabrication, and performance of a backside-illuminated ADD are reported; the difficulties in and limitations to the backside-illuminated ADD are analyzed.展开更多
Mobile Ad Hoc Networks consist of nodes which are wireless and get organized based on the transmission requirement. These nodes are mobile nodes, so they communicate with each other without any fixed access point. Thi...Mobile Ad Hoc Networks consist of nodes which are wireless and get organized based on the transmission requirement. These nodes are mobile nodes, so they communicate with each other without any fixed access point. This type of network faces several attacks because of its mobility nature. In MANET, black hole attacks may cause packet dropping or misrouting of packets during transmission from sender to receiver. This may lead to performance degradation in the network. To surmount this issue, we propose the modified secret sharing scheme to provide the data protection from unauthorized nodes, consistency of data and genuineness. In this algorithm, initially the identification of black hole attacks is achieved and followed by data protection from malicious nodes and also this scheme checks for the reality of the data. Here, we detect the misbehaviour that is dropping or misrouting using verifiable secret sharing scheme. The proposed algorithm achieves the better packet delivery ratio, misbehaviour detection efficiency, fewer packets overhead and end-to-end delay than the existing schemes. These can be viewed in the simulation results.展开更多
We discuss the efficiency of an electro-optic （EO） polymer sensor with interdigitated coplanar electrodes. The developed EO sensor is used to detect terahertz radiation via EO sampling. Results show that the sensor ...We discuss the efficiency of an electro-optic （EO） polymer sensor with interdigitated coplanar electrodes. The developed EO sensor is used to detect terahertz radiation via EO sampling. Results show that the sensor improves more significantly detection sensitivity than does a sensor with sandwich configurations.展开更多
基金the Innovation Program for Quantum Science and Technology(Grant No.2023ZD0300100)the National Key Research and Development Program of China(Grant Nos.2023YFB3809600 and 2023YFC3007801)+1 种基金the National Natural Science Foundation of China(Grant Nos.62301543 and U24A20320)the Shanghai Sailing Program(Grant No.21YF1455700).
文摘Conventional superconducting nanowire single-photon detectors(SNSPDs)have been typically limited in their applications due to their size,weight,and power consumption,which confine their use to laboratory settings.However,with the rapid development of remote imaging,sensing technologies,and long-range quantum communication with fewer topographical constraints,the demand for high-efficiency single-photon detectors integrated with avionic platforms is rapidly growing.We herein designed and manufactured the first drone-based SNSPD system with a system detection efficiency(SDE)as high as 91.8%.This drone-based system incorporates high-performance NbTiN SNSPDs,a self-developed miniature liquid helium dewar,and custom-built integrated electrical setups,making it capable of being launched in complex topographical conditions.Such a drone-based SNSPD system may open the use of SNSPDs for applications that demand high SDE in complex environments.
基金supported by the National Natural Science Foundation of China(62250710162 and 12274406)the National Key Research and Development Program of China(2022YFA1405100).
文摘We demonstrate the photon-number resolution(PNR)capability of a 1.25 GHz gated InGaAs single-photon avalanche photodiode(APD)that is equipped with a simple,low-distortion ultra-narrowband interference circuit for the rejection of its background capacitive response.Through discriminating the avalanche current amplitude,we are able to resolve up to four detected photons in a single detection gate with a detection efficiency as high as 45%.The PNR capability is limited by the avalanche current saturation,and can be increased to five photons at a lower detection efficiency of 34%.The PNR capability,combined with high efficiency and low noise,will find applications in quantum information processing technique based on photonic qubits.
基金The National Natural Science Foundation of China(No.61300054)the Natural Science Foundation of Jiangsu Province(No.BK2011190,BK20130879)+1 种基金the Natural Science Foundation of Higher Education Institutions of Jiangsu Province(No.13KJB520018)the Science Foundation of Nanjing University of Posts&Telecommunications(No.NY212023)
文摘By analyzing the average percent of faults detected （APFD） metric and its variant versions, which are widely utilized as metrics to evaluate the fault detection efficiency of the test suite, this paper points out some limitations of the APFD series metrics. These limitations include APFD series metrics having inaccurate physical explanations and being unable to precisely describe the process of fault detection. To avoid the limitations of existing metrics, this paper proposes two improved metrics for evaluating fault detection efficiency of a test suite, including relative-APFD and relative-APFDc. The proposed metrics refer to both the speed of fault detection and the constraint of the testing source. The case study shows that the two proposed metrics can provide much more precise descriptions of the fault detection process and the fault detection efficiency of the test suite.
基金This study was supported by the National Natural Science Foundation of China(No.81772746,No.81870516)Natural Science Foundation of Xinjiang Province(2019D01C091).
文摘To improve the diagnostic efficiency of prostate cancer(PCa)and reduce unnecessary biopsies,we defined and analyzed the diagnostic efficiency of peripheral zone prostate-specific antigen(PSA)density(PZ-PSAD).Patients who underwent systematic 12-core prostate biopsies in Shanghai General Hospital(Shanghai,China)between January 2012 and January 2018 were retrospectively identified(n=529).Another group of patients with benign prostatic hyperplasia(n=100)were randomly preselected to obtain the PSA density of the non-PCa cohort(N-PSAD).Prostate volumes and transition zone volumes were measured using multiparameter magnetic resonance imaging(mpMRI)and were combined with PSA and N-PSAD to obtain the PZ-PSAD from a specific algorithm.Receiver operating characteristic(ROC)curve analysis was used to assess the PCa detection efficiency in patients stratified by PSA level,and the area under the ROC curve(AUC)of PZ-PSAD was higher than that of PSA,PSA density(PSAD),and transition zone PSA density(TZ-PSAD).PZ-PSAD could amend the diagnosis for more than half of the patients with inaccurate transrectal ultrasonography(TRUS)and mpMRI results.When TRUS and mpMRI findings were ambiguous to predict PCa(PIRADS score≤3),PZ-PSAD could increase the positive rate of biopsy from 21.7%to 54.7%,and help 63.8%(150/235)of patients avoid unnecessary prostate biopsy.In patients whose PSA was 4.0–10.0 ng ml^(−1),10.1–20.0 ng ml^(−1),and>20.0 ng ml^(−1),the ideal PZ-PSAD cut-off value for predicting clinically significant PCa was 0.019 ng ml^(−2),0.297 ng ml^(−2),and 1.180 ng ml^(−2),respectively(sensitivity>90%).Compared with PSA,PSAD,and TZ-PSAD,the efficiency of PZ-PSAD for predicting PCa is the highest,leading to fewer missed diagnoses and unnecessary biopsies.
基金supported by the National Natural Science Foundation of China(Nos.61973253 and 62003264).
文摘For the problem of cooperative strike against multiple maneuvering targets,in order to improve the detection efficiency of multi-missile systems,this paper proposes a Group Cooperative Midcourse Guidance Law(GCMGL)for heterogeneous missile formation with optimal detection efficiency.Firstly,considering the adverse impact of target maneuvering on the guidance system,a Super-Twisting Disturbance Observer(STDO)is introduced to estimate target acceleration.Secondly,to avoid chattering in the system,a reaching law is combined with the design of the midcourse guidance law and cooperative detection control law for the leader missiles.This approach provides reference information for follower missiles and forms an optimal detection formation.Then,to achieve cooperative engagement of targets by follower missiles in groups,a group consensus protocol is introduced in the Line-of-Sight(LOS)direction to design the GCMGL.Simultaneously,in the direction normal to the LOS,when follower missiles cannot obtain the LOS angle combination information from the leader missiles,a distributed extended state observer is introduced to estimate it.Finally,a time-varying LOS angle Formation Tracking Midcourse Guidance Law(FTMGL)is designed based on this estimated information.The guidance law’s stability is validated using Lyapunov theory,and simulation experiments are performed to confirm its effectiveness and advantages.
文摘It is possible to understand the lightning activities in a specific region and compare test results of different apparatus only when a reliable evaluation of detection efficiency distribution pertaining to a particular lightning location system(LLS)is available. Based on the data in 1992.an approximate evaluation of detection efficiency spatial distribu- tion for single-station lightning location system(M-LDARS)and LLP three-station lightning loca- tion system in Beijing-Tianjin-Hebei area is presented in the paper,showing that the average detec- tion efficiencies are smaller than 48% and 46% respectively.In addition,the article offers an eval- uation of spatial distribution of ground stroke density(D_g)and positive stroke percentage,indicat- ing that six high stroke density zones exist along the southeastern sides of the Taihang and Yan- shan Mountains.The stroke density of mountainous region is higher than that of the plain region, in contrast to the case of positive stroke percentage.Also,it is shown that within a radius of 250 km,the average of D_g is 1.2(km^(-2) a^(-1))while the average positive stroke percentage is 10.9%. Finally,the paper proposes a possible test method of accurately evaluating the spatial distribution of detection efficiency(A).
基金Supported by National Natural Science Foundation of China(11375095,11175098)
文摘In this paper, the detection efficiency of a large area neutron sensitive microchannel plate detector has been evaluated. A ^6LiF/ZnS scintillator detector 65 mm in diameter and 0.32 mm in thickness, with product code,EJ426HD2, produced by Eljen Technology, was employed as the benchmark detector. The TOF spectra of these two detectors were simultaneously measured and the energy spectra were then deduced to calculate the detection efficiency curve of the ^nMCP detector. Tests show the detection efficiency@25.3 me V thermal neutrons is 34% for this ^nMCP detector.
基金Supported by National Natural Science Foundation of China(11135002,11305232,11175076)
文摘A high-efficiency fast neutron detector prototype based on a triple Gas Electron Multiplier（GEM） detector, which, coupled with a novel multi-layered high-density polyethylene（HDPE） as a neutron-to-proton converter for improving the neutron detection efficiency, is introduced and tested with the Am-Be neutron source in the Institute of Modern Physics（IMP） at Lanzhou in the present work. First, the developed triple GEM detector is tested by measuring its effective gain and energy resolution with55 Fe X-ray source to ensure that it has a good performance.The effective gain and obtained energy resolution is 5.0×104and around 19.2%, respectively. Secondly, the novel multi-layered HDPE converter is coupled with the cathode of the triple GEM detector making it a high-efficiency fast neutron detector. Its effective neutron response is four times higher than that of the traditional single-layered conversion technique when the converter layer number is 38.
基金Project supported by the National Key R&D Program of China(Grant No.2023YFC2206502)the National Natural Science Foundation of China(Grant Nos.12175254 and 12227810)+1 种基金Guangdong Major Project of Basic and Applied Basic Research(Grant No.2023B0303000003)Guangdong Provincial Key Laboratory of Advanced Particle Detection Technology(Grant No.2024B1212010005)。
文摘The rapid growth of neutron flux has driven the development of^(3)He-free neutron detectors to satisfy the requirements of the neutron scattering instruments under construction or planned at the China Spallation Neutron Source(CSNS).Position-sensitive neutron detectors with a high counting rate and large area play an important role in the instruments performing neutron measurements in or close to the direct beam.The ceramic gas-electron-multiplier(GEM)detector serves as a promising solution,and considerable work has been done using the small-area GEM neutron detectors.In this article,we designed and constructed a detector prototype utilizing ceramic GEM foils with an effective area of about307 mm×307 mm.To evaluate and investigate their basic characteristics,the Monte Carlo(MC)tool FLUKA was employed and several neutron beam tests were conducted at CSNS.The simulated spatial resolution was basically in agreement with the measured value of 2.50±0.01 mm(FWHM).The wavelength spectra measurement was verified through comparisons with a commercial beam monitor.In addition,a detection efficiency of 4.7±0.1%was achieved for monoenergetic neutrons of 1.59 A wavelength.This is consistent with the simulated result.The results indicate that the large-area ceramic GEM detector is a good candidate to implement neutron beam measurements.Its efficiency can be improved in a cascading manner to approach that reached by traditional^(3)He detectors.
基金supported by The Youth Science Foundation of Sichuan Province(Nos.2022NSFSC1230,2022NSFSC1231,and 23NSFSC5321)the Science and Technology Innovation Seedling Project of Sichuan Province(No.MZGC20230080)+2 种基金the General project of national Natural Science Foundation of China(No.12075039)the Youth Science Foundation of China(No.12105030)the Key project of the National Natural Science Foundation of China(No.U19A2086)。
文摘To accurately reconstruct the tomographic gamma scanning(TGS)transmission measurement image,this study optimized the transmission reconstruction equation based on the actual situation of TGS transmission measurement.Using the transmission reconstruction equation and the Monte Carlo program Geant4,an innovative virtual trajectory length model was constructed.This model integrated the solving process for the trajectory length and detection efficiency within the same model.To mitigate the influence of the angular distribution ofγ-rays emitted by the transmitted source at the detector,the transport processes of numerous particles traversing a virtual nuclear waste barrel with a density of zero were simulated.Consequently,a certain amount of information was captured at each step of particle transport.Simultaneously,the model addressed the nonuniform detection efficiency of the detector end face by considering whether the energy deposition of particles in the detector equaled their initial energy.Two models were established to validate the accuracy and reliability of the virtual trajectory length model.Model 1 was a simplified nuclear waste barrel,whereas Model 2 closely resembled the actual structure of a nuclear waste barrel.The results indicated that the proposed virtual trajectory length model significantly enhanced the precision of the trajectory length determination,substantially increasing the quality of the reconstructed images.For example,the reconstructed images of Model 2 using the“point-to-point”and average trajectory models revealed a signalto-noise ratio increase of 375.0%and 112.7%,respectively.Thus,the virtual trajectory length model proposed in this study holds paramount significance for the precise reconstruction of transmission images.Moreover,it can provide support for the accurate detection of radioactive activity in nuclear waste barrels.
基金supported by the National Major Scientific Research Instrument Development Projects(No.42127807)the National Natural Science Foundation of China(No.12105030)。
文摘Promoting the development of deep-sea mineral exploration instrumentation can help alleviate the global resource shortage faced by mankind.X-ray fluorescence(XRF)spectrometry has been widely used in the in situ analysis of deep-sea minerals owing to its fast analytical speed,nondestructive nature,and wide analytical range.This study focused on the structural safety and detection efficiency of X-ray fluorescence in situ measurement equipment under high pressure for deep-sea XRF analysis.This study first combined finite element analysis and experiments to design and optimize the structure of an X-ray probe tube required for deep-sea mineral exploration and to determine the Be window thickness to ensure stress safety.Subsequently,the Monte Carlo method was used to analyze and optimize the Be window thickness on the X-ray probe tube to improve the accuracy of the elemental analyses.Finally,the effect of seawater thickness between the transmitter outer tube and rock wall was also considered.The results show that based on ocean depth in different detection environments,Be windows with a thickness of 1.5 mm or 2.0 mm can be selected to improve the detection efficiency of the device while ensuring the structural safety of the instrument.According to the design features and detection requirements of the device,in deep-sea exploration of minerals with characteristic peak energies below 10 keV,the transmitter outer tube should be as close as possible to the rock wall inside the logging.When the characteristic peak energy of the minerals is more than 10 keV,the distance between the transmitter outer tube and rock wall inside the logging should be controlled to approximately 2 mm.This study provides feasible solutions for future deep-sea mineral resource development and a useful reference for elemental analysis of minerals in the deep-sea or other extreme working environments.
基金Supported by the Foundation for Young Scholars of Guizhou Meteorological Bureau,China(QN[2012]13)
文摘Based on lightning location data of lightning monitoring network in Guizhou Province in recent eight years,the effective detection radius of a station and the effective detection range of lightning monitoring network in Guizhou Province were analyzed. The results show that the effective detection radius of a lightning monitoring sub-station in Guizhou Province is 160 km; some counties in the southwest,northwest and northeast of Guizhou were not detected. To improve the detector efficiency of lightning monitoring network in Guizhou Province,it is suggested that nine sub-stations should be built in Weining,Shuicheng,Qinglong,Pingtang,Rongjiang,Yuping,Songtao,Tongren and Renhuai,so that the effective detection efficiency will reach more than 95%.
基金supported by the National Natural Science Foundation of China(No.42127807)Natural Science Foundation of Sichuan Province of China(Project No.2023NSFSC0008)+1 种基金Uranium Geology Program of China Nuclear Geology(No.202205-6)the Sichuan Science and Technology Program(No.2021JDTD0018)。
文摘Onlineγ-spectrometry systems for inland waters,most of which extract samples in situ and in real time,are able to produce reliable activity concentration measurements for waterborne radionuclides only when they are distributed relatively uniformly and enter into a steady-state diffusion regime in the measurement chamber.To protect residents’health and ensure the safety of the living environment,better timeliness is required for this measurement method.To address this issue,this study established a mathematical model of the online waterγ-spectrometry system so that rapid warning and activity estimates can be obtained for water under non-steady-state(NSS)conditions.In addition,the detection efficiency of the detector for radionuclides during the NSS diffusion process was determined by applying the computational fluid dynamics technique in conjunction with Monte Carlo simulations.On this basis,a method was developed that allowed the online waterγ-spectrometry system to provide rapid warning and activity concentration estimates for radionuclides in water.Subsequent analysis of the NSS-mode measurements of^(40)K radioactive solutions with different activity concentrations determined the optimum warning threshold and measurement time for producing accurate activity concentration estimates for radionuclides.The experimental results show that the proposed NSS measurement method is able to give warning and yield accurate activity concentration estimates for radionuclides 55.42 and 69.42 min after the entry of a 10 Bq/L^(40)K radioactive solution into the measurement chamber,respectively.These times are much shorter than the 90 min required by the conventional measurement method.Furthermore,the NSS measurement method allows the measurement system to give rapid(within approximately 15 min)warning when the activity concentrations of some radionuclides reach their respective limits stipulated in the Guidelines for Drinking-water Quality of the WHO,suggesting that this method considerably enhances the warning capacity of in situ online waterγ-spectrometry systems.
基金supported by the State Administration for Market Regulation Innovation Talent Program(No.QNBJ202304)Shanghai Municipal Health Commission(No.GWVI-11.1-40)Science and Technology Program of the Shanghai Municipal Administration for Market Regulation,(No.2022–07),China.
文摘Objective:To assess the detection efficiencies of liquid radioisotopes in a well-type NaI(Tl)gamma spectrometer,focusing on the short-lived isotopes^(99)Tcm,^(131)I,and^(18)F.Methods:The detection efficiencies of liquid 99Tcm,131I,and 18F in a well-type NaI(Tl)gamma spectrometer were systematically investigated through calibration experiments and Monte Carlo simulations,and accounting for the coincidence-summing effect.Results:The results indicated that the detection efficiencies of^(99)Tcm,^(131)I,and^(18)F varied from 64.4%to 72.3%,34.8%-43.1%and 27.3%-28.5%for different sample volumes ranging from 15 mL to 80 mL,respectively.The simulated detection efficiencies were highly consistent with the experimental results,with a largest relative deviation of 5%for the 3 radionuclides and 4 different sample volumes.Conclusion:The consistent results between the calibration experiments and Monte Carlo simulations reveal that this measuring device possesses high detection efficiencies of 99Tcm,131I,and 18F,making it suitable for measuring low-level activity radioactive liquids,such as radioactive waste liquids to be discharged.
基金the Ministry of Science and Technology,People’s Republic of China(No.2012YQ180118)the National Natural Science Foundation of China(No.41874121)the Sichuan Science and Technology Program(No.2018JY0181).
文摘The nuclides inhaled during nuclear accidents usually cause internal contamination of the lungs with low activity.Although a parallel-hole imaging system,which is widely used in medical gamma cameras,has a high resolution and good image quality,owing to its extremely low detection efficiency,it remains difficult to obtain images of inhaled lung contamination.In this study,the Monte Carlo method was used to study the internal lung contamination imaging using the MPA-MURA coded-aperture collimator.The imaging system consisted of an adult male lung model,with a mosaicked,pattern-centered,and anti-symmetric MURA coded-aperture collimator model and a CsI(Tl)detector model.The MLEM decoding algorithm was used to reconstruct the internal contamination image,and the complementary imaging method was used to reduce the number of artifacts.The full width at half maximum of the I-131 point source image reconstructed by the MPAMURA coded-aperture imaging reached 2.51 mm,and the signal-to-noise ratio of the simplified respiratory tract source(I-131)image reconstructed through MPA-MURA coded-aperture imaging was 3.98 dB.Although the spatial resolution of MPA-MURA coded-aperture imaging is not as good as that of parallel-hole imaging,the detection efficiency of PMA-MURA coded-aperture imaging is two orders of magnitude higher than that of parallel-hole collimator imaging.Considering the low activity level of internal lung contamination caused by nuclear accidents,PMA-MURA coded-aperture imaging has significant potential for the development of lung contamination imaging.
基金supported by the Users with Excellence Program of Hefei Science Center CAS(No.2020HSC-UE012)the Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228)the Institute of Energy,Hefei Comprehensive National Science Center(No.21KZS205,21KZL401).
文摘Real-time monitoring of the 14-MeV D-T fusion neutron yield is urgently required for the triton burnup study on the Experimental Advanced Superconducting Tokamak (EAST). In this study, we developed an optimal design of a fast-neutron detector based on the scintillating fiber (Sci-Fi) to provide D-T neutron yield through Geant4simulation. The effect on the detection performance is concerned when changing the number of the Sci-Fis embedded in the probe head, minimum distance between the fibers, length of the fibers, or substrate material of the probe head. The maximum number of scintillation photons generated by the n/γ source particles and output by the light guide within an event (event:the entire simulation process for one source particle) was used to quantify the n/γ resolution of the detector as the main basis. And the intrinsic detection efficiency was used as another evaluation criterion. The results demonstrate that the optimal design scheme is to use a 5 cm probe head whose substrate material is pure aluminum, in which 463 Sci-Fis with the same length of 5 cm are embedded, and the minimum distance between the centers of the two fibers is 2 mm. The optimized detector exhibits clear directionality in the simulation, which is in line with the expectation and experimental data provided in the literature. This study presents the variation trends of the performance of the SciFi detector when its main parameters change, which is beneficial for the targeted design and optimization of the Sci-Fi detector used in a specific radiation environment.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11975255 and 11875273)Guangdong Basic and Applied Basic Research Foundation (Grant No. 2020B1515120025)。
文摘Chinese Spallation Neutron Source(CSNS) has successfully produced its first neutron beam in 28th August 2017. It has been running steadily from March, 2018. According to the construction plan, the engineering materials diffractometer(EMD) will be installed between 2019–2023. This instrument requires the neutron detectors with the cover area near3 m2in two 90° neutron diffraction angle positions, the neutron detecting efficiency is better than 40%@1A, and the spatial resolution is better than 4 mm×200 mm in horizontal and vertical directions respectively. We have developed a onedimensional position-sensitive neutron detector based on the oblique6Li F/Zn S(Ag) scintillators, wavelength shifting fibers,and Si PMs(silicon photomultipliers) readout. The inhomogeneity of the neutron detection efficiency between each pixel and each detector module, which caused by the inconsistency of the wave-length shifting fibers in collecting scintillation photons, needs to be mitigated before the installation. A performance optimization experiment of the detector modules was carried out on the BL20(beam line 20) of CSNS. Using water sample, the neutron beam with Φ5 mm exit hole was dispersed related evenly into the forward space. According to the neutron counts of each pixel of the detector module, the readout electronics threshold of each pixel is adjusted. Compared with the unadjusted detector module, the inhomogeneity of the detection efficiency for the adjusted one has been improved from 69% to 90%. The test result of the diffraction peak of the standard sample Si showed that the adjusted detector module works well.
基金Project supported by the National Natural Science Foundation of China(Grant No.11005010)
文摘The detection of low-level light is a key technology in various experimental scientific studies. As a photon detector, the silicon photomultiplier （SiPM） has gradually become an alternative to the photomultiplier tube （PMT） in many applications in high-energy physics, astroparticle physics, and medical imaging because of its high photon detection efficiency （PDE）, good resolution for single-photon detection, insensitivity to magnetic field, low operating voltage, compactness, and low cost. However, primarily because of the geometric fill factor, the PDE of most SiPMs is not very high; in particular, for those SiPMs with a high density of micro cells, the effective area is small, and the bandwidth of the light response is narrow. As a building block of the SiPM, the concept of the backside-illuminated avalanche drift detector （ADD） was first proposed by the Max Planck Institute of Germany eight years ago; the ADD is promising to have high PDE over the full energy range of optical photons, even ultraviolet light and X-ray light, and because the avalanche multiplication region is very small, the ADD is beneficial for the fabrication of large-area SiPMs. However, because of difficulties in design and fabrication, no significant progress had been made, and the concept had not yet been verified. In this paper, preliminary results in the design, fabrication, and performance of a backside-illuminated ADD are reported; the difficulties in and limitations to the backside-illuminated ADD are analyzed.
文摘Mobile Ad Hoc Networks consist of nodes which are wireless and get organized based on the transmission requirement. These nodes are mobile nodes, so they communicate with each other without any fixed access point. This type of network faces several attacks because of its mobility nature. In MANET, black hole attacks may cause packet dropping or misrouting of packets during transmission from sender to receiver. This may lead to performance degradation in the network. To surmount this issue, we propose the modified secret sharing scheme to provide the data protection from unauthorized nodes, consistency of data and genuineness. In this algorithm, initially the identification of black hole attacks is achieved and followed by data protection from malicious nodes and also this scheme checks for the reality of the data. Here, we detect the misbehaviour that is dropping or misrouting using verifiable secret sharing scheme. The proposed algorithm achieves the better packet delivery ratio, misbehaviour detection efficiency, fewer packets overhead and end-to-end delay than the existing schemes. These can be viewed in the simulation results.
基金supported by the National Natural Science Foundation of China(Nos.60871073 and 61201075)China Postdoctoral Science Foundation(No.2012M511507)
文摘We discuss the efficiency of an electro-optic （EO） polymer sensor with interdigitated coplanar electrodes. The developed EO sensor is used to detect terahertz radiation via EO sampling. Results show that the sensor improves more significantly detection sensitivity than does a sensor with sandwich configurations.
