A new multi-detector array named HALIMA(Hybrid Array for LIfetime MeAsurement)has been developed at Lanzhou for nuclear structure studies in fission.The array comprises eight BGO-shielded High-Purity Germanium detecto...A new multi-detector array named HALIMA(Hybrid Array for LIfetime MeAsurement)has been developed at Lanzhou for nuclear structure studies in fission.The array comprises eight BGO-shielded High-Purity Germanium detectors and twenty fast Ce-doped Lanthanum Bromide[LaBr_(3)(Ce)]detectors shielded with CsI(Tl).HALIMA is further complemented by two ancillary detector systems:fission fragment(FF)detectors and β detectors.This configuration enables precise sub-nanosecond lifetime measurements using the fourfold FF/β-Ge-LaBr_(3)(Ce)-LaBr_(3)(Ce)coincidence technique.The performance and specifications of the detectors,associated electronics,and the data acquisition system are presented in detail.The advantage of FF selectivity is emphasized,which significantly enhances sensitivity to specific fission channels.Using this approach,the lifetimes of the nuclear excited states populated in the spontaneous fission of^(252)Cf were measured,showing good agreement with the established literature values.展开更多
To overcome the difficulty and high cost of some specific isotopic targets,a substitution method was proposed to measure the cross section of the(γ,n)reactions.Considering that the natural copper element(^(nat)Cu)onl...To overcome the difficulty and high cost of some specific isotopic targets,a substitution method was proposed to measure the cross section of the(γ,n)reactions.Considering that the natural copper element(^(nat)Cu)only has^(63)Cu and^(65)Cu isotopes,the^(65)Cu(γ,n)^(64)Cu reaction was taken as an example to test the substitution method.Using quasi-monoenergeticγbeams provided by the Shanghai Laser Electron Gamma Source(SLEGS)of the Shanghai Synchrotron Radiation Facility(SSRF),^(nat)Cu(γ,n)was measured from E_(γ)=11.09 MeV to 17.87 MeV.Furthermore,based on the^(63)Cu(γ,n)reaction measured using the same experimental setup at SLEGS,^(65)Cu(γ,n)^(64)Cu was extracted using the substitution method.The abundance variation of natural copper,showing a significant influence on the cross section,was also investigated.The results were compared to the existing experimental data measured by bremsstrahlung and positron annihilation in-flight sources,and the TALYS 2.0 predictions.Theγstrength function(γSF)of^(65)Cu was obtained from the^(65)Cu(γ,n)data,and the reaction cross section of^(64)Cu(n,γ)was further calculated.展开更多
The accurate photoneutron cross section of the^(27)Al nucleus has a significant impact on resolving differences in existing experimental data and enhancing the precision of nuclear reaction rate calculations for^(26)A...The accurate photoneutron cross section of the^(27)Al nucleus has a significant impact on resolving differences in existing experimental data and enhancing the precision of nuclear reaction rate calculations for^(26)Al in nuclear astrophysics.The photoneutron cross sections for the^(27)Al(γ,n)^(26)Al reaction,within the neutron separation energy range of 13.2-21.7 MeV,were meticulously measured using a new flat efficiency detector array at the Shanghai Laser-Electron Gamma Source.The uncertainty of the data was controlled to below 4%throughout the process,and inconsistencies between the present data and existing data from different gamma sources,as well as the TENDL-2021 data,are discussed in detail.These discussions provide a valuable reference for addressing discrepancies in the^(27)Al(γ,n)^(26)Al cross-section data and improving related theoretical calculations.展开更多
A reasonable prediction of photofission observables plays a paramount role in understanding the photofission process and guiding various photofission-induced applications,such as short-lived isotope production,nuclear...A reasonable prediction of photofission observables plays a paramount role in understanding the photofission process and guiding various photofission-induced applications,such as short-lived isotope production,nuclear waste disposal,and nuclear safeguards.However,the available experimental data for photofission observables are limited,and the existing models and programs have mainly been developed for neutron-induced fission processes.In this study,a general framework is proposed for characterizing the photofission observables of actinides,including the mass yield distributions(MYD) and isobaric charge distributions(ICD) of fission fragments and the multiplicity and energy distributions of prompt neutrons(n_(p)) and prompt γ rays(γ_(p)).The framework encompasses various systematic neutron models and empirical models considering the Bohr hypothesis and does not rely on the experimental data as input.These models are then validated individually against experimental data at an average excitation energy below 30 MeV,which shows the reliability and robustness of the general framework.Finally,we employ this framework to predict the characteristics of photofission fragments and the emissions of prompt particles for typical actinides including ^(232)Th,^(235,238)U and ^(240)Pu.It is found that the ^(238)U(γ,f) reaction is more suitable for producing neutron-rich nuclei compared to the ^(232)Th(γ,f) reaction.In addition,the average multiplicity number of both n_(p) and yp increases with the average excitation energy.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12275321,12121005,12475129,and 12335009)the Natural Science Foundation of Guangdong Province,China(No.2025A1515012112)+6 种基金the International Atomic Energy Agency Coordinated Research Project F41034(No.28649)the computational resources from Sun Yat-sen University the National Supercomputer Center in Guangzhouthe Open Project of Guangxi Key Laboratory of Nuclear Physics and Nuclear Technology(No.NLK2023-08)the Central Government Guidance Funds for Local Scientific and Technological Development,China(No.Guike ZY22096024)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)the National Key Research and Development Program(MOST 2022YFA1602304).
文摘A new multi-detector array named HALIMA(Hybrid Array for LIfetime MeAsurement)has been developed at Lanzhou for nuclear structure studies in fission.The array comprises eight BGO-shielded High-Purity Germanium detectors and twenty fast Ce-doped Lanthanum Bromide[LaBr_(3)(Ce)]detectors shielded with CsI(Tl).HALIMA is further complemented by two ancillary detector systems:fission fragment(FF)detectors and β detectors.This configuration enables precise sub-nanosecond lifetime measurements using the fourfold FF/β-Ge-LaBr_(3)(Ce)-LaBr_(3)(Ce)coincidence technique.The performance and specifications of the detectors,associated electronics,and the data acquisition system are presented in detail.The advantage of FF selectivity is emphasized,which significantly enhances sensitivity to specific fission channels.Using this approach,the lifetimes of the nuclear excited states populated in the spontaneous fission of^(252)Cf were measured,showing good agreement with the established literature values.
基金supported by the National key R&D program(Nos.2022YFA1602404 and 2023YFA1606901)the National Natural Science Foundation of China(Nos.12375123 and 12388102)the Natural Science Foundation of Henan Province(No.242300422048).
文摘To overcome the difficulty and high cost of some specific isotopic targets,a substitution method was proposed to measure the cross section of the(γ,n)reactions.Considering that the natural copper element(^(nat)Cu)only has^(63)Cu and^(65)Cu isotopes,the^(65)Cu(γ,n)^(64)Cu reaction was taken as an example to test the substitution method.Using quasi-monoenergeticγbeams provided by the Shanghai Laser Electron Gamma Source(SLEGS)of the Shanghai Synchrotron Radiation Facility(SSRF),^(nat)Cu(γ,n)was measured from E_(γ)=11.09 MeV to 17.87 MeV.Furthermore,based on the^(63)Cu(γ,n)reaction measured using the same experimental setup at SLEGS,^(65)Cu(γ,n)^(64)Cu was extracted using the substitution method.The abundance variation of natural copper,showing a significant influence on the cross section,was also investigated.The results were compared to the existing experimental data measured by bremsstrahlung and positron annihilation in-flight sources,and the TALYS 2.0 predictions.Theγstrength function(γSF)of^(65)Cu was obtained from the^(65)Cu(γ,n)data,and the reaction cross section of^(64)Cu(n,γ)was further calculated.
基金supported by the National key R&D program(Nos.2023YFA1606901 and 2022YFA1602404)the National Natural Science Foundation of China(Nos.12375123 and 12388102)the Natural Science Foundation of Henan Province(No.242300422048)。
文摘The accurate photoneutron cross section of the^(27)Al nucleus has a significant impact on resolving differences in existing experimental data and enhancing the precision of nuclear reaction rate calculations for^(26)Al in nuclear astrophysics.The photoneutron cross sections for the^(27)Al(γ,n)^(26)Al reaction,within the neutron separation energy range of 13.2-21.7 MeV,were meticulously measured using a new flat efficiency detector array at the Shanghai Laser-Electron Gamma Source.The uncertainty of the data was controlled to below 4%throughout the process,and inconsistencies between the present data and existing data from different gamma sources,as well as the TENDL-2021 data,are discussed in detail.These discussions provide a valuable reference for addressing discrepancies in the^(27)Al(γ,n)^(26)Al cross-section data and improving related theoretical calculations.
基金Supported by the National Natural Science Foundation of China (11675075)Independent research project of key laboratory of plasma physics,CAEP(JCKYS2021212009)Hengyang Municipal Science and Technology Project (202150054076)。
文摘A reasonable prediction of photofission observables plays a paramount role in understanding the photofission process and guiding various photofission-induced applications,such as short-lived isotope production,nuclear waste disposal,and nuclear safeguards.However,the available experimental data for photofission observables are limited,and the existing models and programs have mainly been developed for neutron-induced fission processes.In this study,a general framework is proposed for characterizing the photofission observables of actinides,including the mass yield distributions(MYD) and isobaric charge distributions(ICD) of fission fragments and the multiplicity and energy distributions of prompt neutrons(n_(p)) and prompt γ rays(γ_(p)).The framework encompasses various systematic neutron models and empirical models considering the Bohr hypothesis and does not rely on the experimental data as input.These models are then validated individually against experimental data at an average excitation energy below 30 MeV,which shows the reliability and robustness of the general framework.Finally,we employ this framework to predict the characteristics of photofission fragments and the emissions of prompt particles for typical actinides including ^(232)Th,^(235,238)U and ^(240)Pu.It is found that the ^(238)U(γ,f) reaction is more suitable for producing neutron-rich nuclei compared to the ^(232)Th(γ,f) reaction.In addition,the average multiplicity number of both n_(p) and yp increases with the average excitation energy.
