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Recent progress in two-proton radioactivity

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Nuclear Science and Techniques 2022年第8期33卷 118-146页

作者： Long Zhou Si-Min Wang de-qing fang Yu-Gang Ma Key Laboratory of Nuclear Physics and Ion-beam Application(MOE) Institute of Modern PhysicsFudan UniversityShanghai 200433China Shanghai Research Center for Theoretical Nuclear Physics NSFC and Fudan UniversityShanghai 200438China

During the last few decades,rare isotope beam facilities have provided unique data for studying the properties of nuclides located far from the beta-stability *** nuclei are often accompanied by exotic structures and radioactive modes,which represent the forefront of nuclear *** them,two-proton(2p)radioactivity is a rare decay mode found in a few highly proton-rich *** 2p decay lifetimes and properties of emitted protons hold invaluable information regarding the nuclear structures in the presence of a low-lying proton continuum;as such,they have attracted considerable research *** this review,we present some of the recent experimental and theoretical progress regarding the 2p decay,including technical innovations for measuring nucleon-nucleon correlations and developments in the models that connect their structural aspects with their decay *** impressive progress should play a significant role in elucidating the mechanism of these exotic decays,probing the corresponding components inside nuclei,and providing deep insights into the open quantum nature of dripline systems.

关键词： Exotic decay Two-proton radioactivity Nucleon-nucleon correlation Experimental and theoretical development

design and performance of a high-speed and low-noise preamplifier for SiPM

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Nuclear Science and Techniques 2023年第11期34卷 93-102页

作者： Xi‑Yang Wang Hong‑Yu Zhang de‑qing fang Wan‑Bing He Xiao‑Long Wang Qi‑Bin Zheng Shi‑Ming Zou Key Laboratory of Nuclear Physics and Ion‑beam Application(MOE)and Institute of Modern Physics Fudan UniversityShanghai 200433China Shanghai Research Center for Theoretical Nuclear Physics NSFC and Fudan UniversityShanghai 200438China Laboratory of Radiation detection and Medical Imaging and School of Health Science and Engineering University of Shanghai for Science and TechnologyShanghai 200093China

Considering the R&D for upgrading the K^(0)_(L) andμdetectors in the Belle II experiment using a scintillator and silicon pho-tomultiplier(SiPM),we designed a compact high-speed and low-noise *** preamplifier demonstrated a good gain stability,bandwidth of 426 MHz,baseline noise level ofσ≈0.6 mV,dynamic range of up to170 mV of the input signal amplitude,good time resolution of 20 ps,and it can be comprehensively applied to *** pole-zero-cancelation in the preamplifier reduces both the rise and fall times of the SiPM signal,which can significantly improve the time resolution and reduce the pile-up when using a large SiPM or an array of *** combinations of the preamplifier and several types of SiPMs demonstrated time resolutions better than 50 ps for most cases;when the number of detected photons was larger than 60,a time resolution of approximately 25 ps was achieved.

关键词： Silicon photomultiplier High-speed amplifier Low noise High time resolution

Effect of source size and emission time on the p–p momentum correlation function in the two-proton emission process

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Nuclear Science and Techniques 2020年第5期31卷 64-69页

作者： Long Zhou de-qing fang Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Nuclear Physics and Ion-beam Application(MOE) Institute of Modern PhysicsFudan UniversityShanghai 200433China

The effect of source size and emission time on the proton-proton(p-p)momentum correlation function(Cpp(q))has been studied *** a spherical Gaussian source with space and time profile according to the function S(r,t)~exp(-r2/2 r02-t/τ)in the correlation function calculation code(CRAB),the results indicate that one Cpp(q)distribution corresponds to a unique combination of source size r0 and emission timeτ.Considering the possible nuclear deformation from a spherical nucleus,an ellipsoidal Gaussian source characterized by the deformation parameter∈=ΔR/R has been *** is almost no difference of Cpp(q)between the results of spherically and ellipsoidally shaped sources with small *** results indicate that a unique source size r0 and emission time could be extracted from the p-p momentum correlation function,which is especially important for identifying the mechanism of twoproton emission from proton-rich ***,considering the possible existence of cluster structures within a nucleus,the double Gaussian source is *** results show that the p-p momentum correlation function for a source with or without cluster structures has large systematical differences with the variance of r0 andτ.This may provide a possible method for experimentally observing the cluster structures in proton-rich nuclei.

关键词： Two-proton emission p–p momentum correlation function Source size Emission time

determination of the neutron skin thickness from interaction cross section and charge-changing cross section for B,C,N,O,F isotopes

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Nuclear Science and Techniques 2016年第3期27卷 153-158页

作者： Xiu-fang Li de-qing fang Yu-Gang Ma Shanghai Institute of Applied Physics Chinese Academy of Sciences University of Chinese Academy of Sciences

The effective neutron and proton root-meansquare radius of stable and unstable nuclei(^(12-15,17)B,^(12-20)C,^(14-21)N,^(16-24)O and ^(18-21,23-26)F) were deduced from the charge-changing cross section,σ_(cc),and the interaction cross sections,σ_I,by using a statistical abrasion-ablation model *** extracted proton radii are in good agreement with the data from the Atomic Data and Nuclear Data Tables within the ***,we can observe that the neutron skin thickness increases monotonously with the increasing neutron number in these isotopes,which is consistent with the systematical trend of theoretical calculations.

关键词：中子皮厚度作用截面同位素变化截面电荷均方根半径测定不稳定核

decay modes of highly excited nuclei

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Nuclear Science and Techniques 2018年第6期29卷 9-18页

作者： Zhen-fang Zhang de-qing fang Yu-Gang Ma Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China University of Chinese Academy of Sciences Beijing 100049China

The deexcitation of single excited ^(112) Sn nuclei at T = 1–30 MeV is simulated using the isospin-dependent quantum molecular dynamics(IQMD) model and GEMINI model. The fragmentation mechanism, critical behavior,and kinematic characteristics are investigated within these two models. The results show that the IQMD model can be applied to the analysis of fragmentation processes, critical points, and slope temperature extraction. The results of IQMD are generally consistent with experimental - Z_(bound) data. However, GEMINI can reproduce the experimental data better than IQMD for isotopic distributions.

关键词：原子核腐烂 IQMD 破碎过程双子座试验性动力学模型

Study on the performance of a large-size CsI detector for high energy γ-rays

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Nuclear Science and Techniques 2018年第1期29卷 58-64页

作者： He Dong de-qing fang Chen Li Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China University of Chinese Academy of Sciences Beijing 100049China

The measurement of high-energy γ-rays is an important experimental method to study the giant resonance in a nucleus, c reaction in nuclear astrophysics, and so on. The performance of a large-size Cs I detector for crays detection is studied by comparison between the experimental measurements and GEANT4 simulation. The reliability of the simulated efficiency for low-energy γ-rays is verified by comparing with the experimental data. The efficiency of the Cs I detector for high-energy γ-rays was obtained by the GEANT4 simulation. The simulation shows that the detection efficiency of 20 Me V γ-rays can reach 3.8%.

关键词： CsI:Tl Scintillation detector Full absorption efficiency Energy resolution GEANT4 simulation

Investigation of the symmetry energy of nuclear matter using isospin-dependent quantum molecular dynamics

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Nuclear Science and Techniques 2020年第6期31卷 83-89页

作者： Hao Yu de-qing fang Yu-Gang Ma Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of the Chinese Academy of Sciences Beijing 100080China Key Laboratory of Nuclear Physics and Ion-beam Application(MOE) Institute of Modern PhysicsFudan UniversityShanghai 200433China

Simulations of infinite nuclear matter at different densities,isospin asymmetries and temperatures are performed using the isospin-dependent quantum molecular dynamics(IQMD)model to study the equation of state and symmetry energy.A rigorous periodic boundary condition is used in the *** energies are extracted from the binding energies under different conditions and compared to the classical molecular dynamics(CMD)model using the same *** results show that both models can reproduce the experimental results for the symmetry energies at low densities,but IQMD is more appropriate than CMD for nuclear matter above the saturation *** indicates that IQMD may be a reliable model for the study of the properties of infinite nuclear matter.

关键词： Infinite nuclear matter Symmetry energy IQMD model

Helmholtz decomposition with a scalar Poisson equation in elastic anisotropic media

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Petroleum Science 2024年第3期21卷 1597-1610页

作者： Xin-Yu fang Gang Yao qing-qing Zheng Ping-Min Zhang Di Wu Feng-Lin Niu State Key Laboratory of Petroleum Resources and Engineering China University of Petroleum(Beijing)Beijing102249China Unconventional Petroleum Research Institute China University of Petroleum(Beijing)Beijing102249China department of Mathematics College of ScienceChina University of Petroleum(Beijing)Beijing102249China College of Geophysics China University of Petroleum(Beijing)Beijing102249China department of Earth Environmental and Planetary SciencesRice UniversityHoustonTX77005UA

P-and S-wave separation plays an important role in elastic reverse-time *** can reduce the artifacts caused by crosstalk between different modes and improve image *** addition,P-and Swave separation can also be used to better understand and distinguish wave types in complex *** present,the methods for separating wave modes in anisotropic media mainly include spatial nonstationary filtering,low-rank approximation,and vector Poisson *** of these methods require multiple Fourier transforms or the calculation of large matrices,which require high computational costs for problems with large *** this paper,an efficient method is proposed to separate the wave mode for anisotropic media by using a scalar anisotropic Poisson operator in the spatial *** 2D problems,the computational complexity required by this method is 1/2 of the methods based on solving a vector Poisson ***,compared with existing methods based on pseudoHelmholtz decomposition operators,this method can significantly reduce the computational *** examples also show that the P and S waves decomposed by this method not only have the correct amplitude and phase relative to the input wavefield but also can reduce the computational complexity significantly.

关键词： Anisotropic media Scalar anisotropic Poisson equation Improved elastic wavefield decomposition

Flexible,efficient,and accurate tests for epidemics

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Science China Mathematics 2024年第8期67卷 1881-1898页

作者： Linjiajie fang Bing-Yi Jing Shen Ling Qiyue Wang qing Yang Data Science and Analytics Thrust The Hong Kong University of Science and TechnologyHong KongChina department of Statistics and Data Science Southern University of Science and TechnologyShenzhen 518055China department of Mathematics and Statistics Dalhousie UniversityHalifaxNS B 3H 4R 2Canada department of Mathematics The Hong Kong University of Science and TechnologyHong KongChina

Group testing involves discovering a small subset of distinguished subjects from a large population while efficiently reducing the total number of *** has been widely used for industrial testing,information technology,and biology,especially epidemic ***,in reality,are noisy for the presence of false *** tests are accurate but time-consuming,while others are cheaper but less *** which test to use is constrained by various considerations,such as availability,cost,accuracy,and *** this paper,we propose flexible,efficient,and accurate tests(FEATs).FEATs are based on group testing with simple but careful designs by incorporating ideas such as close contact cliques and repeated *** could dramatically improve the efficiency or accuracy of existing *** example,for accurate but slow tests,the FEAT can improve efficiency multiple times without compromising *** the other hand,for fast but inaccurate tests,the FEAT can sharply reduce the false-negative rate(FNR)and significantly increase *** justifications are *** point out some scenarios where the FEAT can be effectively employed.

关键词： epidemiology control blood testing testing efficiency testing accuracy

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