The PICOSEC Micromegas(MM)is a precise timing gaseous detector based on a Cherenkov radiator coupled with a semi-transparent photocathode and an MM amplifying structure.It features a two-stage amplification process th...The PICOSEC Micromegas(MM)is a precise timing gaseous detector based on a Cherenkov radiator coupled with a semi-transparent photocathode and an MM amplifying structure.It features a two-stage amplification process that leads to a significant deterioration of non-uniformity when scaling up to larger areas.Since the performance of gaseous detectors is highly dependent on the choice of working gas,optimizing the gas mixture offers a promising solution to improve the uniformity performance.This paper addresses these challenges through a combined approach of simulation based on Garfield++and experimental studies.The simulation investigates the properties of different mixing fractions of gas mixtures and their impact on detector performance,including gain uniformity and time resolution.To verify the simulation results,experimental tests were conducted using a multi-channel PICOSEC MM prototype with different gas mixtures.The experimental results are consistent with the findings of the simulation,indicating that a higher concentration of neon significantly improves the detector’s gain uniformity.Furthermore,the influence of gas mixtures on time resolution was explored as a critical performance indicator.The study presented in this paper offers valuable insights for improving uniformity in large-area PICOSEC MM detectors and optimizing overall performance.展开更多
This study determined the lifetime of the first excited state(5∕2_(1)^(+))in ^(139)La via β-γ time-difference measurement using a LaBr_(3)+plastic scintillator array.This state is populated following the decay of ^...This study determined the lifetime of the first excited state(5∕2_(1)^(+))in ^(139)La via β-γ time-difference measurement using a LaBr_(3)+plastic scintillator array.This state is populated following the decay of ^(139)Ba produced in the^(138)Ba(n,γ)reaction.Compared with previous experiments using only stilbene/plastic crystals,this experiment separates the background contribution in the γ-ray spectrum owing to the high energy resolution of LaBr_(3).The L-forbidden M1 transition strength,B(M1,5∕2_(1)^(+)→7∕2_(1)^(+)),in^(139)La was measured and compared with detailed large-scale shell model calculations,with a special focus on the core-excitation effect.The results showed the importance of both proton and neutron core-excitations in explaining the M1 transition strength.Meanwhile,the effective g-factor for the tensor term of the M1 operator was smaller than the previously reported value in this region or around ^(208)Pb.展开更多
The problems of airport landside capacity assessment are of industry-wide interest. Evaluation of landside capacity enables airport operators and airport designers to identify passenger and baggage flow bottlenecks, i...The problems of airport landside capacity assessment are of industry-wide interest. Evaluation of landside capacity enables airport operators and airport designers to identify passenger and baggage flow bottlenecks, identify the primary cause of bottlenecks formation and take measures mitigating the impact of bottlenecks on the airport terminal operation. Many studies dealing with the problems of airport landside capacity are focused mainly on the processing part of the airport terminal and consider the airport terminal to be an isolated system. Even the most of models of airport landside operations developed using various simulation （both generic and dedicated） software packages （e.g., PaxSim, SLAM, WITNESS, ARENA or EXTEND） are designed for simulating the passenger and baggage flows only between curb-side and apron. Although this approach provides valuable data concerning capacity, delays or processing bottlenecks, in some cases identified capacity constraints are only the symptoms of the actual problem. In order to discover the cause of the problem, it is necessary to consider the airport terminal as an integral part of much more complex regional, national or international transportation system. This article reflects the above mentioned requirements and introduces an innovative approach to passenger and baggage flow simulation based on the fact that airport terminal is considered as an integral part of air passenger door-to-door transportation process.展开更多
基金supported by the National Natural Science Foundation of China(12125505).
文摘The PICOSEC Micromegas(MM)is a precise timing gaseous detector based on a Cherenkov radiator coupled with a semi-transparent photocathode and an MM amplifying structure.It features a two-stage amplification process that leads to a significant deterioration of non-uniformity when scaling up to larger areas.Since the performance of gaseous detectors is highly dependent on the choice of working gas,optimizing the gas mixture offers a promising solution to improve the uniformity performance.This paper addresses these challenges through a combined approach of simulation based on Garfield++and experimental studies.The simulation investigates the properties of different mixing fractions of gas mixtures and their impact on detector performance,including gain uniformity and time resolution.To verify the simulation results,experimental tests were conducted using a multi-channel PICOSEC MM prototype with different gas mixtures.The experimental results are consistent with the findings of the simulation,indicating that a higher concentration of neon significantly improves the detector’s gain uniformity.Furthermore,the influence of gas mixtures on time resolution was explored as a critical performance indicator.The study presented in this paper offers valuable insights for improving uniformity in large-area PICOSEC MM detectors and optimizing overall performance.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research (No. 2021B0301030006)Young Scientists Fund of the National Natural Science Foundation of China (No. 12405144)+3 种基金the National Natural Science Foundation of China (No. 12475129)the International Atomic Energy Agency Coordinatated Research Project F41034 (No. 28649)the computational resources from Sun Yat-sen University the National Supercomputer Center in Guangzhouthe Natural Science Foundation of Guangdong Province,China (No. 2025A1515012112)
文摘This study determined the lifetime of the first excited state(5∕2_(1)^(+))in ^(139)La via β-γ time-difference measurement using a LaBr_(3)+plastic scintillator array.This state is populated following the decay of ^(139)Ba produced in the^(138)Ba(n,γ)reaction.Compared with previous experiments using only stilbene/plastic crystals,this experiment separates the background contribution in the γ-ray spectrum owing to the high energy resolution of LaBr_(3).The L-forbidden M1 transition strength,B(M1,5∕2_(1)^(+)→7∕2_(1)^(+)),in^(139)La was measured and compared with detailed large-scale shell model calculations,with a special focus on the core-excitation effect.The results showed the importance of both proton and neutron core-excitations in explaining the M1 transition strength.Meanwhile,the effective g-factor for the tensor term of the M1 operator was smaller than the previously reported value in this region or around ^(208)Pb.
文摘The problems of airport landside capacity assessment are of industry-wide interest. Evaluation of landside capacity enables airport operators and airport designers to identify passenger and baggage flow bottlenecks, identify the primary cause of bottlenecks formation and take measures mitigating the impact of bottlenecks on the airport terminal operation. Many studies dealing with the problems of airport landside capacity are focused mainly on the processing part of the airport terminal and consider the airport terminal to be an isolated system. Even the most of models of airport landside operations developed using various simulation （both generic and dedicated） software packages （e.g., PaxSim, SLAM, WITNESS, ARENA or EXTEND） are designed for simulating the passenger and baggage flows only between curb-side and apron. Although this approach provides valuable data concerning capacity, delays or processing bottlenecks, in some cases identified capacity constraints are only the symptoms of the actual problem. In order to discover the cause of the problem, it is necessary to consider the airport terminal as an integral part of much more complex regional, national or international transportation system. This article reflects the above mentioned requirements and introduces an innovative approach to passenger and baggage flow simulation based on the fact that airport terminal is considered as an integral part of air passenger door-to-door transportation process.
