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
Heavy-ion collisions(HICs)is a unique experimental tool for investigating the properties of nuclear matter under extreme conditions in the laboratory.At HIRFL-CSR energies,HICs can create nuclear matter with 2-3 times...Heavy-ion collisions(HICs)is a unique experimental tool for investigating the properties of nuclear matter under extreme conditions in the laboratory.At HIRFL-CSR energies,HICs can create nuclear matter with 2-3 times the saturation density(ρ_(0)).The HIRFL-CSR external-target experiment(CEE)is a large-acceptance spectrometer designed to explore frontier topics in high-energy nuclear physics,such as the QCD phase structure and nuclear matter equation of states.In this letter,we introduce simulation and analysis software for the CEE experiment(CeeROOT).Based on the CEE conceptual design and CeeROOT software,the configurations of its subdetectors were optimized by considering foreseeable physical constraints.The final detector layout of the CEE spectrometer and its acceptances were validated through simulations of U+U collisions at 500 MeV/u and pp collisions at 2.8 GeV,which demonstrated that the CEE experiment will serve as a detector with wide acceptance and multi-particle identification capabilities for studying high-energy nuclear physics topics at HIRFL-CSR energies with pp,pA,and A A collisions.展开更多
The neutron richness of the light charged particles emitted out of the fission plane in heavy ion reactions has been experimentally investigated via the production of A=3 mirror nuclei in ^(86)Kr+^(nat)Pb reactions at...The neutron richness of the light charged particles emitted out of the fission plane in heavy ion reactions has been experimentally investigated via the production of A=3 mirror nuclei in ^(86)Kr+^(nat)Pb reactions at 25 MeV/u.The energy spectra and angular distributions of triton(t)and ^(3)He in coincidence with two fission fragments are measured with the Compact Spectrometer for Heavy IoN Experiment(CSHINE).The energy spectrum of ^(3)He is observed harder than that of triton in the fission events,in accordance with the phenomena reported as“^(3)He-puzzle”in inclusive measurements.With a data-driven energy spectrum peak cut scenario,it is observed that the yield ratio R(t∕^(3)He)increases with the angle to the fission plane,showing an enhancement of neutron-rich particle emission from out-of-fission-plane.A qualitative comparison with the transport model calculations suggests that this observation may serve as a new probe for the nuclear symmetry energy.展开更多
The prompt fission neutron spectrum(PFNS)is a key nuclear data quantity that is of particular interest and plays a crucial role in understanding and modeling fission processes.An array comprising 48 liquid scintillati...The prompt fission neutron spectrum(PFNS)is a key nuclear data quantity that is of particular interest and plays a crucial role in understanding and modeling fission processes.An array comprising 48 liquid scintillation detectors and a parallelplate avalanche counter(PPAC)was developed at the China Institute of Atomic Energy(CIAE)to measure the PFNS of actinide nuclei.Efficiency and energy calibrations were performed for all the liquid scintillators,and their efficiencies were consistently found to be better than 5%.The time resolutions of the PPAC and liquid scintillators were measured to be 1.08 ns and 1.16 ns using~(252)Cf and~(207)Bi sources,respectively.The pulse shape discrimination of the liquid scintillator was utilized to identify neutron andγsignals on an event-by-event basis,and the figure of merit was deduced as 1.12 at a 200 ke Vee threshold.The contribution to the PFNS from multiple scattered neutrons was evaluated via Geant4 simulations,and those originating from the environment were found to be comparable to the crosstalk between the detectors.The neutron efficiency of the entire detection array was calibrated using a~(252)Cf spontaneous fission source and was demonstrated to be consistent with the Geant4 simulation results,which verified the reliability of the detection array.展开更多
The semicylindrical time projection chamber(scTPC)is designed to measure the angular distribution of the cross section for intermediate-energy(3He,t)charge-exchange reactions in inverse kinematics.The scTPC prototype ...The semicylindrical time projection chamber(scTPC)is designed to measure the angular distribution of the cross section for intermediate-energy(3He,t)charge-exchange reactions in inverse kinematics.The scTPC prototype comprises a cathode,field cage,drift region,amplification structure based on a multilayer thick gas electron multiplier(THGEM),and a readout plane with 886 zigzag-shaped pads.The gain uniformity of the THGEM and the drift velocity of electrons were calibrated.Track recognition based on the Hough transform was then developed to reconstruct cosmic ray tracks and determine their position resolution.The position resolution of secondary particle tracks resulting from collisions between the heavy-ion beam and the 3He target was measured,yielding an x-resolution of 0.71 mm and a z-resolution of 0.73 mm.The scTPC demonstrates sufficient energy and spatial resolution to support charge-exchange reaction experiments in inverse kinematics.展开更多
A half-size prototype of the multi wire drift chamber for the cooling storage ring external-target experiment(CEE)was assembled and tested in the 350 MeV/u Kr+Fe reactions at the heavy-ion research facility in Lanzhou...A half-size prototype of the multi wire drift chamber for the cooling storage ring external-target experiment(CEE)was assembled and tested in the 350 MeV/u Kr+Fe reactions at the heavy-ion research facility in Lanzhou.The prototype consists of six sense layers,where the sense wires are stretched in three directions X,U,and V;meeting 0?,30?,and-30?,respectively,with respect to the vertical axis.The sensitive area of the prototype is 76 cm×76 cm.The amplified and shaped signals from the anode wires were digitized in a serial capacity array.When operating at a high voltage of 1500 V on the anode wires,the efficiency for each layer is greater than 95%.The tracking residual is approximately 301±2μm.This performance satisfies the requirements of CEE.展开更多
A tracking system composed of three multiwires proportional chambers(MWPCs) for the external target facility of the Cooler Storage Ring is reported in this paper. The active areas of the MWPCs are 518 mm 9400 mm, 582 ...A tracking system composed of three multiwires proportional chambers(MWPCs) for the external target facility of the Cooler Storage Ring is reported in this paper. The active areas of the MWPCs are 518 mm 9400 mm, 582 mm 9 450 mm, and 710 mm 9 500 mm Each MWPC consists of a series of alternately placed cathode and anode wire planes and can measure position along the directions of-30°, 0°, and 30° relative to horizontal. The construction and operation of the detectors are described, and a method for track reconstruction is introduced. A track-finding efficiency of about 62% and a spatial resolution of 1.21 mm have been achieved. The pion and proton can be identified clearly with the tracking system combined with a time-of-flight system.展开更多
The compact spectrometer for heavy ion experiment(CSHINE)is under construction for the study of isospin chronology via the Hanbury Brown–Twiss(HBT)particle correlation function and the nuclear equation of state of as...The compact spectrometer for heavy ion experiment(CSHINE)is under construction for the study of isospin chronology via the Hanbury Brown–Twiss(HBT)particle correlation function and the nuclear equation of state of asymmetrical nuclear matter.The CSHINE consists of silicon strip detector(SSD)telescopes and large-area parallel-plate avalanche counters,which measure the light charged particles and fission fragments,respectively.In phase I,two SSD telescopes were used to observe 30 MeV/u 40Ar?197Au reactions.The results presented here demonstrate that hydrogen and helium were observed with high isotopic resolution,and the HBT correlation functions of light charged particles could be constructed from the obtained data.展开更多
We report a reconstruction method for fast-fission events in 25 MeV/u^(86)Kr +^(208)Pb reactions at the Compact Spectrometer for Heavy Ion Experiment(CSHINE). The fission fragments(FFs) are measured using three large-...We report a reconstruction method for fast-fission events in 25 MeV/u^(86)Kr +^(208)Pb reactions at the Compact Spectrometer for Heavy Ion Experiment(CSHINE). The fission fragments(FFs) are measured using three large-area parallel-plate avalanche counters, which can deliver the position and arrival timing information of the fragments. The start timing information is provided by the radio frequency of the cyclotron. Fission events were reconstructed using the velocities of the two FFs. The broadening of both the velocity distribution and azimuthal difference of the FFs decreases with the folding angle, in accordance with the picture that fast fission occurs. The anisotropic angular distribution of the fission axis also consistently reveals the dynamic features of fission events.展开更多
The cooling storage ring(CSR)external-target experiment(CEE)is a spectrometer used in construction to study the properties of nuclear matter in high-baryon density regions at the Heavy-Ion Research Facility in Lanzhou...The cooling storage ring(CSR)external-target experiment(CEE)is a spectrometer used in construction to study the properties of nuclear matter in high-baryon density regions at the Heavy-Ion Research Facility in Lanzhou(HIRFL).This study presents the design,simulation,manufacturing,and testing of a half-size prototype of a multi-wire drift chamber(MWDC)for the CEE.First,the performance of the MWDC connected to homemade electronics was simulated.The results demonstrated that an energy resolution of 18.5% for 5.9-keV X-rays and a position resolution of 194μm for protons can be achieved by the current design.Because the size of the largest MWDC reached 176 cm×314 cm,a set of 98 cm×98 cm prototypes was built using the new techniques.The positioning accuracy of the anode wires in this prototype is better than 20μm.After optimization,using commercially available electronics,the prototype can achieved an energy resolution of 19.7%for a^(55)Fe X-ray source.The CEE-MWDC detector and electronics were simultaneously tested.An energy resolution of 22%was achieved for the^(55)Fe source;the track residuals were approximately 330μm for the cosmic rays.The results demonstrate that the current design and techniques meet the requirements of the CEE-MWDC array.展开更多
The cross section for the J^(π)(T)=3^(+)(0)state was measured to be enhanced in an isolated 6Li nucleus compared to the same reduced state in a ^(6)Li cluster.This difference demonstrates a nuclear medium modificatio...The cross section for the J^(π)(T)=3^(+)(0)state was measured to be enhanced in an isolated 6Li nucleus compared to the same reduced state in a ^(6)Li cluster.This difference demonstrates a nuclear medium modification of the tensor force,which is sensitively probed by the T=0 channel.In contrast,the J^(π)(T)=0^(+)(1)state(T=1)was found to have approximately equal excitation strength in both ^(6)Li systems.We interpret this tensor force modification as a consequence of density saturation within a many-body interaction framework.展开更多
A new inelastic excitation and cluster-decay experiment was conducted to investigate the negative-parity linear-chain structure in 16C.The helium and beryllium isotopes emitted from the highly excited states of 16C an...A new inelastic excitation and cluster-decay experiment was conducted to investigate the negative-parity linear-chain structure in 16C.The helium and beryllium isotopes emitted from the highly excited states of 16C and the recoil target deuteron were detected in coincidence.The 16C excitation-energy spectra associated with different decay paths were reconstructed using the invariant mass method.Owing to the newly reconfigured detector setup,the detection acceptance was extended to a higher excitation-energy range,allowing a number of new resonant states to be observed beyond the previously reportedπ^(2)σ^(2)-bond positive-parity linear-chain band.Based on comparison with the AMD calculations for both resonance energies and relative decay widths,these newly observed states can be tentatively assigned as the 1^(-),3^(-),5^(-)and 1^(-)members of the negative-parity linear-chain molecular rotational band.More experimental studies are expected to directly measure the spins of these states.展开更多
Experimental and theoretical investigation of the fragmentation reaction in the Fermi-energy domain is currently of particular importance for not only nuclear physics but also some interdisciplinary fields. In the pre...Experimental and theoretical investigation of the fragmentation reaction in the Fermi-energy domain is currently of particular importance for not only nuclear physics but also some interdisciplinary fields. In the present study, neutron-rich ^(14)C and ^(16)C ion beams at 27.5 MeV/nucleon were used to bombard carbon and polyethylene (CD_(2))_(n) targets. Energy and angular distributions of the produced fragments were measured. Background events originating from the carbon content in (CD_(2))_(n) target were efficiently excluded using an extended E-P plot method. Experimental results are systematically analyzed using the HIPSE-SIMON dynamic model. The comparison reveals that, for the carbon target, the HIPSE-SIMON calculation overestimates the yields of the beam-velocity component for fragments near the projectile and also the energy phase space for fragments far away from the projectile, suggesting that fine tuning of the overall interaction profile adopted in the model is required. In contrast, for reactions with the deuteron target, the model calculation can reasonably reproduce the experimental data. The implication of the fragmentation mechanism on the validity of the invariant mass method, as frequently used to reconstruct the clustering resonant structures in light nuclei, is also discussed.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 Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB34030000)the National Natural Science Foundation of China(Nos.11927901 and 12475133)+1 种基金the Youth Team Program in Basic Research Fields Stably Supported by the Chinese Academy of Sciences(No.YSBR-088)the Western Light Project of the Chinese Academy of Sciences。
文摘Heavy-ion collisions(HICs)is a unique experimental tool for investigating the properties of nuclear matter under extreme conditions in the laboratory.At HIRFL-CSR energies,HICs can create nuclear matter with 2-3 times the saturation density(ρ_(0)).The HIRFL-CSR external-target experiment(CEE)is a large-acceptance spectrometer designed to explore frontier topics in high-energy nuclear physics,such as the QCD phase structure and nuclear matter equation of states.In this letter,we introduce simulation and analysis software for the CEE experiment(CeeROOT).Based on the CEE conceptual design and CeeROOT software,the configurations of its subdetectors were optimized by considering foreseeable physical constraints.The final detector layout of the CEE spectrometer and its acceptances were validated through simulations of U+U collisions at 500 MeV/u and pp collisions at 2.8 GeV,which demonstrated that the CEE experiment will serve as a detector with wide acceptance and multi-particle identification capabilities for studying high-energy nuclear physics topics at HIRFL-CSR energies with pp,pA,and A A collisions.
基金the National Natural Science Foundation of China(Nos.12205160,11961131010,11961141004,and 11965004)by the Ministry of Science and Technology of China(Nos.2022YFE0103400 and 2020YFE0202001)+2 种基金by the Polish National Science Center(No.2023/49/B/ST2/01294)This work is also supported by Initiative Scientific Research Program and the Center of High Performance Computing of Tsinghua Universitythe Heavy Ion Research Facility at Lanzhou(HIRFL).
文摘The neutron richness of the light charged particles emitted out of the fission plane in heavy ion reactions has been experimentally investigated via the production of A=3 mirror nuclei in ^(86)Kr+^(nat)Pb reactions at 25 MeV/u.The energy spectra and angular distributions of triton(t)and ^(3)He in coincidence with two fission fragments are measured with the Compact Spectrometer for Heavy IoN Experiment(CSHINE).The energy spectrum of ^(3)He is observed harder than that of triton in the fission events,in accordance with the phenomena reported as“^(3)He-puzzle”in inclusive measurements.With a data-driven energy spectrum peak cut scenario,it is observed that the yield ratio R(t∕^(3)He)increases with the angle to the fission plane,showing an enhancement of neutron-rich particle emission from out-of-fission-plane.A qualitative comparison with the transport model calculations suggests that this observation may serve as a new probe for the nuclear symmetry energy.
基金supported by Continuous-Support Basic Scientific Research Project(No.BJ010261223282)the National Natural Science Foundation of China(Nos.U2167201,11975318)+2 种基金the State Key Laboratory of Nuclear Physics and TechnologyPeking University(No.NPT2023KFY01)the Research and Development Project of China National Nuclear Corporation。
文摘The prompt fission neutron spectrum(PFNS)is a key nuclear data quantity that is of particular interest and plays a crucial role in understanding and modeling fission processes.An array comprising 48 liquid scintillation detectors and a parallelplate avalanche counter(PPAC)was developed at the China Institute of Atomic Energy(CIAE)to measure the PFNS of actinide nuclei.Efficiency and energy calibrations were performed for all the liquid scintillators,and their efficiencies were consistently found to be better than 5%.The time resolutions of the PPAC and liquid scintillators were measured to be 1.08 ns and 1.16 ns using~(252)Cf and~(207)Bi sources,respectively.The pulse shape discrimination of the liquid scintillator was utilized to identify neutron andγsignals on an event-by-event basis,and the figure of merit was deduced as 1.12 at a 200 ke Vee threshold.The contribution to the PFNS from multiple scattered neutrons was evaluated via Geant4 simulations,and those originating from the environment were found to be comparable to the crosstalk between the detectors.The neutron efficiency of the entire detection array was calibrated using a~(252)Cf spontaneous fission source and was demonstrated to be consistent with the Geant4 simulation results,which verified the reliability of the detection array.
基金was supported by National Key R&D Program of China(No.2022YFE0103900)the National Natural Science Foundation of China(Nos.11875301,11875302,U1867214,U1832105,U2032166 and U1832167)+2 种基金the Fundamental Research Funds for the Central Universities(No.lzujbky-2022-sp06)the CAS“Light of West China”Programthe Heavy Ion Research Facility in Lanzhou。
文摘The semicylindrical time projection chamber(scTPC)is designed to measure the angular distribution of the cross section for intermediate-energy(3He,t)charge-exchange reactions in inverse kinematics.The scTPC prototype comprises a cathode,field cage,drift region,amplification structure based on a multilayer thick gas electron multiplier(THGEM),and a readout plane with 886 zigzag-shaped pads.The gain uniformity of the THGEM and the drift velocity of electrons were calibrated.Track recognition based on the Hough transform was then developed to reconstruct cosmic ray tracks and determine their position resolution.The position resolution of secondary particle tracks resulting from collisions between the heavy-ion beam and the 3He target was measured,yielding an x-resolution of 0.71 mm and a z-resolution of 0.73 mm.The scTPC demonstrates sufficient energy and spatial resolution to support charge-exchange reaction experiments in inverse kinematics.
基金supported by the National Natural Science Foundation of China(Nos.11927901,11875301,11875302,U1867214,U1832105,U1832167)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB34000000)+2 种基金the National Key R&D Program of China(No.2018YFE0205200)the CAS"Light of West China"Programthe Tsinghua University Initiative Scientific Research Program。
文摘A half-size prototype of the multi wire drift chamber for the cooling storage ring external-target experiment(CEE)was assembled and tested in the 350 MeV/u Kr+Fe reactions at the heavy-ion research facility in Lanzhou.The prototype consists of six sense layers,where the sense wires are stretched in three directions X,U,and V;meeting 0?,30?,and-30?,respectively,with respect to the vertical axis.The sensitive area of the prototype is 76 cm×76 cm.The amplified and shaped signals from the anode wires were digitized in a serial capacity array.When operating at a high voltage of 1500 V on the anode wires,the efficiency for each layer is greater than 95%.The tracking residual is approximately 301±2μm.This performance satisfies the requirements of CEE.
基金supported by the National Natural Science Foundation of China(Nos.U1332207,11222550,11405242 and 11305222)
文摘A tracking system composed of three multiwires proportional chambers(MWPCs) for the external target facility of the Cooler Storage Ring is reported in this paper. The active areas of the MWPCs are 518 mm 9400 mm, 582 mm 9 450 mm, and 710 mm 9 500 mm Each MWPC consists of a series of alternately placed cathode and anode wire planes and can measure position along the directions of-30°, 0°, and 30° relative to horizontal. The construction and operation of the detectors are described, and a method for track reconstruction is introduced. A track-finding efficiency of about 62% and a spatial resolution of 1.21 mm have been achieved. The pion and proton can be identified clearly with the tracking system combined with a time-of-flight system.
基金This work was supported by the National Natural Science Foundation of China(Nos.11875174 and 11961131010)。
文摘The compact spectrometer for heavy ion experiment(CSHINE)is under construction for the study of isospin chronology via the Hanbury Brown–Twiss(HBT)particle correlation function and the nuclear equation of state of asymmetrical nuclear matter.The CSHINE consists of silicon strip detector(SSD)telescopes and large-area parallel-plate avalanche counters,which measure the light charged particles and fission fragments,respectively.In phase I,two SSD telescopes were used to observe 30 MeV/u 40Ar?197Au reactions.The results presented here demonstrate that hydrogen and helium were observed with high isotopic resolution,and the HBT correlation functions of light charged particles could be constructed from the obtained data.
基金supported by the National Natural Science Foundation of China(Nos.11875174,11961131010,and 11961141004)the Polish National Science Center(No.2018/30/Q/ST2/00185)。
文摘We report a reconstruction method for fast-fission events in 25 MeV/u^(86)Kr +^(208)Pb reactions at the Compact Spectrometer for Heavy Ion Experiment(CSHINE). The fission fragments(FFs) are measured using three large-area parallel-plate avalanche counters, which can deliver the position and arrival timing information of the fragments. The start timing information is provided by the radio frequency of the cyclotron. Fission events were reconstructed using the velocities of the two FFs. The broadening of both the velocity distribution and azimuthal difference of the FFs decreases with the folding angle, in accordance with the picture that fast fission occurs. The anisotropic angular distribution of the fission axis also consistently reveals the dynamic features of fission events.
基金supported by the Research Program of the National Major Research Instruments(No.11927901)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB34000000)+3 种基金the Function Development Project of Chinese Academy of Sciences(No.2022G101)National Key R&D Program of China(No.2018YFE0205200)Natural Science Foundation of China(Nos.11875301,11875302,U1867214,U1832105,U1832167)CAS"Light of West China"Program。
文摘The cooling storage ring(CSR)external-target experiment(CEE)is a spectrometer used in construction to study the properties of nuclear matter in high-baryon density regions at the Heavy-Ion Research Facility in Lanzhou(HIRFL).This study presents the design,simulation,manufacturing,and testing of a half-size prototype of a multi-wire drift chamber(MWDC)for the CEE.First,the performance of the MWDC connected to homemade electronics was simulated.The results demonstrated that an energy resolution of 18.5% for 5.9-keV X-rays and a position resolution of 194μm for protons can be achieved by the current design.Because the size of the largest MWDC reached 176 cm×314 cm,a set of 98 cm×98 cm prototypes was built using the new techniques.The positioning accuracy of the anode wires in this prototype is better than 20μm.After optimization,using commercially available electronics,the prototype can achieved an energy resolution of 19.7%for a^(55)Fe X-ray source.The CEE-MWDC detector and electronics were simultaneously tested.An energy resolution of 22%was achieved for the^(55)Fe source;the track residuals were approximately 330μm for the cosmic rays.The results demonstrate that the current design and techniques meet the requirements of the CEE-MWDC array.
基金supported by the National Natural Science Foundation of China(10175091,11305007)。
文摘The cross section for the J^(π)(T)=3^(+)(0)state was measured to be enhanced in an isolated 6Li nucleus compared to the same reduced state in a ^(6)Li cluster.This difference demonstrates a nuclear medium modification of the tensor force,which is sensitively probed by the T=0 channel.In contrast,the J^(π)(T)=0^(+)(1)state(T=1)was found to have approximately equal excitation strength in both ^(6)Li systems.We interpret this tensor force modification as a consequence of density saturation within a many-body interaction framework.
基金Supported by the National Key R&D Program of China(2023YFA1606403,2023YFE0101600,2022YFA1605100)the National Natural Science Foundation of China(12350007,12275007,12027809)。
文摘A new inelastic excitation and cluster-decay experiment was conducted to investigate the negative-parity linear-chain structure in 16C.The helium and beryllium isotopes emitted from the highly excited states of 16C and the recoil target deuteron were detected in coincidence.The 16C excitation-energy spectra associated with different decay paths were reconstructed using the invariant mass method.Owing to the newly reconfigured detector setup,the detection acceptance was extended to a higher excitation-energy range,allowing a number of new resonant states to be observed beyond the previously reportedπ^(2)σ^(2)-bond positive-parity linear-chain band.Based on comparison with the AMD calculations for both resonance energies and relative decay widths,these newly observed states can be tentatively assigned as the 1^(-),3^(-),5^(-)and 1^(-)members of the negative-parity linear-chain molecular rotational band.More experimental studies are expected to directly measure the spins of these states.
基金Supported by the National Key R&D Program of China(2023YFA1606403,2023YFE0101600,2022YFA1605100)the National Natural Science Foundation of China(12350007,12275006,12275007,12027809)。
文摘Experimental and theoretical investigation of the fragmentation reaction in the Fermi-energy domain is currently of particular importance for not only nuclear physics but also some interdisciplinary fields. In the present study, neutron-rich ^(14)C and ^(16)C ion beams at 27.5 MeV/nucleon were used to bombard carbon and polyethylene (CD_(2))_(n) targets. Energy and angular distributions of the produced fragments were measured. Background events originating from the carbon content in (CD_(2))_(n) target were efficiently excluded using an extended E-P plot method. Experimental results are systematically analyzed using the HIPSE-SIMON dynamic model. The comparison reveals that, for the carbon target, the HIPSE-SIMON calculation overestimates the yields of the beam-velocity component for fragments near the projectile and also the energy phase space for fragments far away from the projectile, suggesting that fine tuning of the overall interaction profile adopted in the model is required. In contrast, for reactions with the deuteron target, the model calculation can reasonably reproduce the experimental data. The implication of the fragmentation mechanism on the validity of the invariant mass method, as frequently used to reconstruct the clustering resonant structures in light nuclei, is also discussed.
