A heavy-ion time-of-flight spectrometer called HiToF,with magnet focusing accomplished by a quadrupole triplet lens,was constructed at the Beijing Tandem Accelerator National Laboratory,mainly for studies of multi-nuc...A heavy-ion time-of-flight spectrometer called HiToF,with magnet focusing accomplished by a quadrupole triplet lens,was constructed at the Beijing Tandem Accelerator National Laboratory,mainly for studies of multi-nucleon transfer reactions at energies near the Coulomb barrier.The spectrometer was equipped with a rotating chamber with a diameter of 40 cm and could be rotated over a large angular range from−40◦to 160◦.The length from the target to the focal plane is 2.7 m,enabling high-precision time-of-flight measurements using two microchannel plate detectors with a 1.9 m apart and a typical time resolution of 120 ps.A multisampling position-sensitive ionization chamber forΔE−E measurement is placed on the focal plane,which offers aΔZ∕Z resolution of 1/50.The setup provided a maximum solid angleΔΩ=20 msr.An experiment on^(32)S+^(90,94)Zr at a beam energy of 135 MeV was performed to test the performance.The projectile-like ions were identified with a mass resolution ofσ=0.2 amu.The results showed that the HiToF spectrometer is a powerful setup for studying heavy-ion reaction mechanisms at low energies.展开更多
The nuclear potential is a cornerstone in the study of nuclear structures and reactions. Research on the real part of nuclear potential has been well described using various models;however, that on the imaginary part ...The nuclear potential is a cornerstone in the study of nuclear structures and reactions. Research on the real part of nuclear potential has been well described using various models;however, that on the imaginary part of nuclear potential remains insufficient. This study proposes a novel method to extract the imaginary nuclear potential from the high-precision excitation function of backward quasi-elastic scattering. The typical systems^(16)O+^(152,154)Sm,^(184,186)W with deformed target nuclei were analyzed. Nuclear imaginary potentials were obtained successfully by fitting the excitation functions within the single-channel and coupled-channel frameworks, respectively. A good reproduction at the energy range between sub-and above-barrier energy regions was achieved. Results show long-range imaginary-part potential at a wide energy region covering the Coulomb barrier, consistent with the strong absorption for well-deformed systems. This work is a preliminary attempt to bridge the gap between fusion and scattering and extract the deformation parameters in the whole energy range. The subsequent systematic analysis needs to be further improved.展开更多
Due to their high capacity,the P2-type layered oxide cathodes containing oxygen redox reaction processes have attracted wide attention for sodium-ion batteries.However,these materials usually exhibit poor electro-chem...Due to their high capacity,the P2-type layered oxide cathodes containing oxygen redox reaction processes have attracted wide attention for sodium-ion batteries.However,these materials usually exhibit poor electro-chemical properties,resulting from irreversible oxygen redox reactions and phase transition processes at high voltages,and thus hinder their large-scale application.This work reveals the mechanism for the significantly improved cycle stability and rate performance of Co/Ni-free Na_(0.7)5Li_(0.25-2/3x)CuxMn_(0.75-1/3x)O_(2)via Cu doping.Ex-situ XPS demonstrates that Cu doping reduces the amount of Mn^(3+)that triggers the Jahn-Teller effect during the cycling.In addition,the electron enrichment of oxygen around Cu can alleviate the irreversible oxidation of oxygen,and thus suppressing the phase transition originates from the rapid weakening of the electrostatic repulsion between O-O.Meanwhile,in-situ XRD results verify that the Na_(0.7)5Li_(0.19)Cu_(0.09)Mn_(0.7)2O_(2)maintains the P2 phase structure during charging and discharging,resulting in a near-zero strain characteristic of 1.9%.Therefore,the optimized cathode delivers a high reversible capacity of 194.9 mAh g−1 at 0.1 C and excellent capacity retention of 88.6%after 100 cycles at 5 C.The full cell paired with commercial hard carbon anode delivers energy density of 240 Wh kg−1.Our research provides an idea for designing a new type of intercalated cathode for sodium-ion batteries with low cost and high energy density.展开更多
基金supported by the National Key R&D Program of China(No.2022YFA1602302)the National Natural Science Foundation of China(Nos.U2167204,12175314,and 12235020)the Continuous-Support Basic Scientific Research Project.
文摘A heavy-ion time-of-flight spectrometer called HiToF,with magnet focusing accomplished by a quadrupole triplet lens,was constructed at the Beijing Tandem Accelerator National Laboratory,mainly for studies of multi-nucleon transfer reactions at energies near the Coulomb barrier.The spectrometer was equipped with a rotating chamber with a diameter of 40 cm and could be rotated over a large angular range from−40◦to 160◦.The length from the target to the focal plane is 2.7 m,enabling high-precision time-of-flight measurements using two microchannel plate detectors with a 1.9 m apart and a typical time resolution of 120 ps.A multisampling position-sensitive ionization chamber forΔE−E measurement is placed on the focal plane,which offers aΔZ∕Z resolution of 1/50.The setup provided a maximum solid angleΔΩ=20 msr.An experiment on^(32)S+^(90,94)Zr at a beam energy of 135 MeV was performed to test the performance.The projectile-like ions were identified with a mass resolution ofσ=0.2 amu.The results showed that the HiToF spectrometer is a powerful setup for studying heavy-ion reaction mechanisms at low energies.
基金Supported by the National Key R&D Program of China (2022YFA1602302, 2023YFA1606402, 2024YFE0109804)the National Natural Science Foundation of China (U2167204, 12175313, 12175314, 12235020, 12275360, 12375130)the Continuous-Support Basic Scientific Research Project。
文摘The nuclear potential is a cornerstone in the study of nuclear structures and reactions. Research on the real part of nuclear potential has been well described using various models;however, that on the imaginary part of nuclear potential remains insufficient. This study proposes a novel method to extract the imaginary nuclear potential from the high-precision excitation function of backward quasi-elastic scattering. The typical systems^(16)O+^(152,154)Sm,^(184,186)W with deformed target nuclei were analyzed. Nuclear imaginary potentials were obtained successfully by fitting the excitation functions within the single-channel and coupled-channel frameworks, respectively. A good reproduction at the energy range between sub-and above-barrier energy regions was achieved. Results show long-range imaginary-part potential at a wide energy region covering the Coulomb barrier, consistent with the strong absorption for well-deformed systems. This work is a preliminary attempt to bridge the gap between fusion and scattering and extract the deformation parameters in the whole energy range. The subsequent systematic analysis needs to be further improved.
基金financially supported by the National Natural Science Foundation of China(22271211)the Natural Science Foundation of Shanxi Province(20210302123107 and 202202060301018)。
文摘Due to their high capacity,the P2-type layered oxide cathodes containing oxygen redox reaction processes have attracted wide attention for sodium-ion batteries.However,these materials usually exhibit poor electro-chemical properties,resulting from irreversible oxygen redox reactions and phase transition processes at high voltages,and thus hinder their large-scale application.This work reveals the mechanism for the significantly improved cycle stability and rate performance of Co/Ni-free Na_(0.7)5Li_(0.25-2/3x)CuxMn_(0.75-1/3x)O_(2)via Cu doping.Ex-situ XPS demonstrates that Cu doping reduces the amount of Mn^(3+)that triggers the Jahn-Teller effect during the cycling.In addition,the electron enrichment of oxygen around Cu can alleviate the irreversible oxidation of oxygen,and thus suppressing the phase transition originates from the rapid weakening of the electrostatic repulsion between O-O.Meanwhile,in-situ XRD results verify that the Na_(0.7)5Li_(0.19)Cu_(0.09)Mn_(0.7)2O_(2)maintains the P2 phase structure during charging and discharging,resulting in a near-zero strain characteristic of 1.9%.Therefore,the optimized cathode delivers a high reversible capacity of 194.9 mAh g−1 at 0.1 C and excellent capacity retention of 88.6%after 100 cycles at 5 C.The full cell paired with commercial hard carbon anode delivers energy density of 240 Wh kg−1.Our research provides an idea for designing a new type of intercalated cathode for sodium-ion batteries with low cost and high energy density.
