Breakup reactions of the double borromean nucleus ^(8)He were measured at 82.3 MeV/u on CH2 and C targets.The coincident detection of two decaying neutrons and the high performance for neutron cross talk rejection are...Breakup reactions of the double borromean nucleus ^(8)He were measured at 82.3 MeV/u on CH2 and C targets.The coincident detection of two decaying neutrons and the high performance for neutron cross talk rejection are realized in this experiment.The relative energy spectrum for ^(8)He was reconstructed with good statistics.The spectrum exhibits a structure of two resonant peaks,one at an excitation energy of about 3.0 and the other at about 4.14 MeV,respectively.Substantially larger cross section for the first resonance is observed in comparison to the results reported previously.展开更多
Energy losses of 0.63-1.03MeV/atom Sin(n≤3)clusters in thin carbon films(2-12μg/cm^(2))have been measured by using a special experimental setup with Rutherford backscattering(RBS)technique.The experimental results s...Energy losses of 0.63-1.03MeV/atom Sin(n≤3)clusters in thin carbon films(2-12μg/cm^(2))have been measured by using a special experimental setup with Rutherford backscattering(RBS)technique.The experimental results show that for a given energy per atom,the energy loss of Si^(+)_(2) ions,as well as Si^(+)_(3) ions,is significantly larger than that of Si+ions.This is the first observation of energy loss enhancement in the measurements with RBS technique.The enhancement in energy loss(i.e.the cluster effect)is evident when the effective thickness of the carbon target is thin enough,but not evident when it is thick.The effect will not be obvious until the energy of the projectile is over a certain limit for a special target.This suggests that the cluster effect only occurs in the first layers of the target film,and that the energy of the projectile must be large enough for the effect to be seen.展开更多
Correlation measurements of neutrons and fragments have been performed in a reaction of 33.4MeV/u ^(17)N on a ^(9)Be target.Energy spectra of n and nitrogen fragments were obtained at different angles.Based on the nuc...Correlation measurements of neutrons and fragments have been performed in a reaction of 33.4MeV/u ^(17)N on a ^(9)Be target.Energy spectra of n and nitrogen fragments were obtained at different angles.Based on the nuclear diffraction dissociation model,the measured energy spectra and the neutron angular distributions were reproduced quite well assuming that ^(17)N was composed of ^(16)N and n or ^(15)N and 2n interacting with the nonlocal separable potential.The satisfactory agreement between the theoretical calculations and the experimental data shows that the contribution of Coulomb dissociation is negligible in the reaction concerned.展开更多
Correlated fission fragments from the reaction of 25MeV/u ^(40)Ar+^(209)Bi and their further correlation with a par-tides have been studied for peripheral and central collisions simultaneously.The excitation energy at...Correlated fission fragments from the reaction of 25MeV/u ^(40)Ar+^(209)Bi and their further correlation with a par-tides have been studied for peripheral and central collisions simultaneously.The excitation energy at scission deduced from postscission multiplicity is about 1725 MeV.The fission timescale deduced from prescission multiplicity is about 4×10^(21)s.Systematic analysis of the mass and energy distributions of Hssion fragments as a function of the initial temperature of hot fissioning nuclei reveals the existence of different fission behavior of hot nuclei formed in central and peripheral collisions.Experimental data demonstrate the change of Hssion behavior at T~4MeV.展开更多
Reaction time of the deeply inelastic reaction in 8.5MeV/u ^(84)Kr+^(27)A1 was estimated to be 8×10^(-21)s by extracting pre-scissionαand proton multiplicities and by statistical model(PACE4)calculations.By usin...Reaction time of the deeply inelastic reaction in 8.5MeV/u ^(84)Kr+^(27)A1 was estimated to be 8×10^(-21)s by extracting pre-scissionαand proton multiplicities and by statistical model(PACE4)calculations.By using this reaction time value,the diffusion model calculations for the charge number distribution of fragments nicely explained the experimental results for the reactions at three incident energies 5.8,8.5 and 10.6MeV/u.It is indicated that a considerable fission-like component has contributed to the symmetric splitting fragments in the reactions,especially at 8.5 and 10.6 MeV/u.展开更多
In order to clarify whether statistical or dynamical treatments for emission of intermediate mass fragments(IMFs)will be needed in the intermediate energy heavy ion collisions,the measured angular and energy distribut...In order to clarify whether statistical or dynamical treatments for emission of intermediate mass fragments(IMFs)will be needed in the intermediate energy heavy ion collisions,the measured angular and energy distributions of IMF(3≤Z≤6)in 25 MeV/n ^(40)Ar+^(nat)Ag were analyzed by means of statistical calculation code GEMINI and quantum molecular dynamics code(QMD).While the angular distribution calculations with GEMINI code are not compatible with the experimental ones,the QMD calculations for inclusive angular distributions and energy spectra of IMF are in good agreement with the measured ones.展开更多
In-plane angular correlations between light charged particles and fragments with different charge number were measured in a ^(84)Kr+^(27)Al reaction at 8.5 MeV/n.An asymmetry in the angular correlation relative to the...In-plane angular correlations between light charged particles and fragments with different charge number were measured in a ^(84)Kr+^(27)Al reaction at 8.5 MeV/n.An asymmetry in the angular correlation relative to the beam direction was found which cannot be explained in the fusion-fission reaction mechanism framework.This may imply the domination of deeply inelastic collisions over the complete fusion in the reaction.展开更多
Stopping powers for Ge ions (3.5 MeV～8.0 MeV) in Al foil were mea-sured with RBS (Rutherford backscattering) technique and determmed with a new method. Our results are much smaller than the walues predicted by the TR...Stopping powers for Ge ions (3.5 MeV～8.0 MeV) in Al foil were mea-sured with RBS (Rutherford backscattering) technique and determmed with a new method. Our results are much smaller than the walues predicted by the TRIM code and LSS theory.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11035001,10975006 and J1103206the National Basic Research Program of China under Grant No 2007CB815002.
文摘Breakup reactions of the double borromean nucleus ^(8)He were measured at 82.3 MeV/u on CH2 and C targets.The coincident detection of two decaying neutrons and the high performance for neutron cross talk rejection are realized in this experiment.The relative energy spectrum for ^(8)He was reconstructed with good statistics.The spectrum exhibits a structure of two resonant peaks,one at an excitation energy of about 3.0 and the other at about 4.14 MeV,respectively.Substantially larger cross section for the first resonance is observed in comparison to the results reported previously.
基金Supported by the National Natural Science Foundation of China under Grant No.19775006.
文摘Energy losses of 0.63-1.03MeV/atom Sin(n≤3)clusters in thin carbon films(2-12μg/cm^(2))have been measured by using a special experimental setup with Rutherford backscattering(RBS)technique.The experimental results show that for a given energy per atom,the energy loss of Si^(+)_(2) ions,as well as Si^(+)_(3) ions,is significantly larger than that of Si+ions.This is the first observation of energy loss enhancement in the measurements with RBS technique.The enhancement in energy loss(i.e.the cluster effect)is evident when the effective thickness of the carbon target is thin enough,but not evident when it is thick.The effect will not be obvious until the energy of the projectile is over a certain limit for a special target.This suggests that the cluster effect only occurs in the first layers of the target film,and that the energy of the projectile must be large enough for the effect to be seen.
基金Supported by the National Natural Science Foundation of China under Grant No.19575003。
文摘Correlation measurements of neutrons and fragments have been performed in a reaction of 33.4MeV/u ^(17)N on a ^(9)Be target.Energy spectra of n and nitrogen fragments were obtained at different angles.Based on the nuclear diffraction dissociation model,the measured energy spectra and the neutron angular distributions were reproduced quite well assuming that ^(17)N was composed of ^(16)N and n or ^(15)N and 2n interacting with the nonlocal separable potential.The satisfactory agreement between the theoretical calculations and the experimental data shows that the contribution of Coulomb dissociation is negligible in the reaction concerned.
基金Supported by the National Natural Science Foundation of China under Grant No.19235011.
文摘Correlated fission fragments from the reaction of 25MeV/u ^(40)Ar+^(209)Bi and their further correlation with a par-tides have been studied for peripheral and central collisions simultaneously.The excitation energy at scission deduced from postscission multiplicity is about 1725 MeV.The fission timescale deduced from prescission multiplicity is about 4×10^(21)s.Systematic analysis of the mass and energy distributions of Hssion fragments as a function of the initial temperature of hot fissioning nuclei reveals the existence of different fission behavior of hot nuclei formed in central and peripheral collisions.Experimental data demonstrate the change of Hssion behavior at T~4MeV.
文摘Reaction time of the deeply inelastic reaction in 8.5MeV/u ^(84)Kr+^(27)A1 was estimated to be 8×10^(-21)s by extracting pre-scissionαand proton multiplicities and by statistical model(PACE4)calculations.By using this reaction time value,the diffusion model calculations for the charge number distribution of fragments nicely explained the experimental results for the reactions at three incident energies 5.8,8.5 and 10.6MeV/u.It is indicated that a considerable fission-like component has contributed to the symmetric splitting fragments in the reactions,especially at 8.5 and 10.6 MeV/u.
基金Supported by the National Natural Science Foundation of China under Grant No.19235011。
文摘In order to clarify whether statistical or dynamical treatments for emission of intermediate mass fragments(IMFs)will be needed in the intermediate energy heavy ion collisions,the measured angular and energy distributions of IMF(3≤Z≤6)in 25 MeV/n ^(40)Ar+^(nat)Ag were analyzed by means of statistical calculation code GEMINI and quantum molecular dynamics code(QMD).While the angular distribution calculations with GEMINI code are not compatible with the experimental ones,the QMD calculations for inclusive angular distributions and energy spectra of IMF are in good agreement with the measured ones.
文摘In-plane angular correlations between light charged particles and fragments with different charge number were measured in a ^(84)Kr+^(27)Al reaction at 8.5 MeV/n.An asymmetry in the angular correlation relative to the beam direction was found which cannot be explained in the fusion-fission reaction mechanism framework.This may imply the domination of deeply inelastic collisions over the complete fusion in the reaction.
文摘Stopping powers for Ge ions (3.5 MeV～8.0 MeV) in Al foil were mea-sured with RBS (Rutherford backscattering) technique and determmed with a new method. Our results are much smaller than the walues predicted by the TRIM code and LSS theory.
