L. X. Liu, H. W. Wang, Y. G. Ma, X. G. Cao, X. Z. Cai, J. G. Chen, G. L. Zhang, J. L. Han, J. F. Hu, X. H. Wang, H. J. Fu
The data acquisition system is based on ROOT and waveform digital technology, including neutron detector, waveform digitizer, PCI card, optical fiber, computer, reaction target device, stepper motor, data acquisition software and control target software. It achieves to acquire and record the waveform information of signal measured by the detector using a waveform digitizer. The specific target position is changed by the stepper motor which is remotely controlled by the data acquisition software and control target software. It is implemented by the exchange of information between the data acquisition software and the control target software. The system realizes to automatically open files and change targets at fixed intervals. It is capable of data compression by removing the data those are not signals, and automatic alarm when the beam is lost.
D. Q. Fang, C. W. Ma, Y. G. Ma, X. Z. Cai, J. G. Chen, J. H. Chen, W. Guo, W. D. Tian, K. Wang, Y. B. Wei, T. Z. Yan, C. Zhong, J. X. Zuo, W. Q. Shen
The Glauber theory has been used to investigate the reaction cross section of proton-rich nucleus $^{23}$Al. A core plus a proton structure is assumed for $^{23}$Al. HO-type density distribution is used for the core while the density distribution for the valence proton is calculated by solving the eigenvalue problem of Woods-Saxon potential. The transparency function in an analytical expression is obtained adopting multi-Gaussian expansion for the density distribution. Coulomb correction and finite-range interaction are introduced. This modified Glauber model is apt for halo nuclei. A dominate s-wave is suggested for the last proton in $^{23}$Al from our analysis which is possible in the RMF calculation.
Y. G. Ma, G. L. Ma, X. Z. Cai, J. G. Chen, J. H. Chen, D. Q. Fang, W. Guo, Z. J. He, H. Z. Huang, J. L. Long, C. W. Ma, B. H. Sa, W. Q. Shen, Q. M. Su, K. Wang, Y. B. Wei, T. Z. Yan, C. Zhong, J. X. Zuo
The $Δ$-scaling method has been applied to the total multiplicity distribution of the relativistic ion collisions of p+p, C+C and Pb+Pb which were simulated by a Monte Carlo package, LUCIAE 3.0. It is found that the $Δ$-scaling parameter decreases with the increasing of the system size. Moreover, the heat capacities of different mesons and baryons have been extracted from the event-by-event temperature fluctuation in the region of low transverse mass and they show the dropping trend with the increasing of impact parameter.
K. Wang, Y. G. Ma, Y. B. Wei, X. Z. Cai, J. G. Chen, D. Q. Fang, W. Guo, G. L. Ma, W. Q. Shen, W. D. Tian, C. Zhong, X. F. Zhou
Langevin equation is used to simulate the fission process of $^{112}$Sn + $^{112}$Sn and $^{116}$Sn + $^{116}$Sn. The mass distribution of the fission fragments are given by assuming the process of symmetric fission or asymmetric fission with the Gaussian probability sampling. Isoscaling behavior has been observed from the analysis of fission fragments of both reactions and the isoscaling parameter $α$ seems to be sensitive to the width of fission probability and the beam energy.
Y. G. Ma, D. D. Han, W. Q. Shen, X. Z. Cai, J. G. Chen, Z. J. He, J. L. Long, G. L. Ma, K. Wang, Y. B. Wei, L. P. Yu, H. Y. Zhang, C. Zhong, X. F. Zhou, Z. Y. Zhu
The emission of nuclear clusters is investigated within the framework of isospin dependent lattice gas model and classical molecular dynamics model. It is found that the emission of individual cluster which is heavier than proton is almost Poissonian except near the transition temperature at which the system is leaving the liquid-vapor phase coexistence and the thermal scaling is observed by the linear Arrhenius plots which is made from the average multiplicity of each cluster versus the inverse of temperature in the liquid vapor phase coexistence. The slopes of the Arrhenius plots, {\it i.e.} the "emission barriers", are extracted as a function of the mass or charge number and fitted by the formula embodied with the contributions of the surface energy and Coulomb interaction. The good agreements are obtained in comparison with the data for low energy conditional barriers. In addition, the possible influences of the source size, Coulomb interaction and "freeze-out" density and related physical implications are discussed.
W. Guo, W. Xu, J. G. Chen, Y. G. Ma, X. Z. Cai, H. W. Wang, Y. Xu, C. B. Wang, G. C. Lu, R. Y. Yuan, J. Q. Xu, Z. Y. Wei, Z. Yan, W. Q. Shen
Shanghai Laser Electron Gamma Source, a $γ$-ray beam line of 10MeV order was proposed recently. The beam line is expected to generate $γ$-ray with maximum energy of 22MeV by backward Compton scattering between CO$_2$ laser and electron in the 3.5GeV storage ring of future Shanghai Synchrotron Radiation Facility. The flux of non-collimated $γ$-ray can be 10$^9$ $\sim$ 10$^{10}$s$^{-1}$ if a commercial CO$_2$ laser of 100W order output power is employed and injected with optimized settings.
Y. G. Ma, T. Z. Yan, X. Z. Cai, J. G. Chen, D. Q. Fang, W. Guo, G. H. Liu, C. W. Ma, E. J. Ma, W. Q. Shen, Y. Shi, Q. M. Su, W. D. Tian, H. W. Wang, K. Wang
Anisotropic flows ($v_1$, $v_2$ and $v_4$) of light nuclear clusters are studied by a nucleonic transport model in intermediate energy heavy ion collisions. The number-of-nucleon scalings of the directed flow ($v_1$) and elliptic flow ($v_2$) are demonstrated for light nuclear clusters. Moreover, the ratios of $v_4/v_2^2$ of nuclear clusters show a constant value of 1/2 regardless of the transverse momentum. The above phenomena can be understood by the coalescence mechanism in nucleonic level and are worthy to be explored in experiments.
Y. B. Wei, X. Z. Cai, W. Q. Shen, Y. G. Ma, H. Y. Zhang, C. Zhong, W. Guo, J. G. Chen, G. L. Ma, K. Wang
The isospin-dependent quantum molecular dynamics (IDQMD) model is used to study the total reaction cross section $σ_R$. The energy-dependent Pauli volumes of neutrons and protons have been discussed and introduced into the IDQMD calculation to replace the widely used energy-independent Pauli volumes. The modified IDQMD calculation can reproduce the experimental $σ_R$ well for both stable and exotic nuclei induced reactions. Comparisons of the calculated $σ_R$ induced by $^{11}Li$ with different initial density distributions have been performed. It is shown that the calculation by using the experimentally deduced density distribution with a long tail can fit the experimental excitation function better than that by using the Skyrme-Hartree-Fock calculated density without long tails. It is also found that $σ_R$ at high energy is sensitive to the long tail of density distribution.
H. L. Wu, W. D. Tian, Y. G. Ma, X. Z. Cai, J. G. Chen, D. Q. Fang, W. Guo, H. W. Wang
Dynamical dipole $γ$-ray emission in heavy-ion collisions is explored in the framework of the quantum molecular dynamics model. The studies are focused on systems of $^{40}$Ca bombarding $^{48}$Ca and its isotopes at different incident energies and impact parameters. Yields of $γ$ rays are calculated and the centroid energy and dynamical dipole emission width of the $γ$ spectra are extracted to investigate the properties of $γ$ emission. In addition, sensitivities of dynamical dipole $γ$-ray emission to the isospin and the symmetry energy coefficient of the equation of state are studied. The results show that detailed study of dynamical dipole $γ$ radiation can provide information on the equation of state and the symmetry energy around the normal nuclear density.
G. L. Ma, Y. G. Ma, K. Wang, B. H. Sa, W. Q. Shen, H. Z. Huang, X. Z. Cai, H. Y. Zhang, Z. H. Lu, C. Zhong, J. G. Chen, Y. B. Wei, X. F. Zhou
The $Δ$-scaling method has been applied to ultra-relativistic p+p, C+C and Pb+Pb collision data simulated using a high energy Monte Carlo package, LUCIAE 3.0. The $Δ$-scaling is found to be valid for some physical variables, such as charged particle multiplicity, strange particle multiplicity and number of binary nucleon-nucleon collisions from these simulated nucleus-nucleus collisions over an extended energy ranging from $E_{lab}$ = 20 to 200 A GeV. In addition we derived information entropy from the multiplicity distribution as a function of beam energy for these collisions.
C. Zhong, Y. G. Ma, D. Q. Fang, X. Z. Cai, J. G. Chen, W. Q. Shen, W. D. Tian, K. Wang, Y. B. Wei, J. H. Chen, W. Guo, C. W. Ma, G. L. Ma, Q. M. Su, T. Z. Yan, J. X. Zuo
The isotopic and isotonic distributions of the projectile fragmentation products have been simulated by a modified statistical abrasion-ablation (SAA) model and the isoscaling behavior of projectile-like fragments has been discussed. The isoscaling parameters $α$ and $β$ for hot fragments before evaporation and cold fragments after evaporation have been extracted, respectively. It looks that the evaporation has strong effect on $α$. For cold fragments, a monotonic increase of $α$ and $|β|$ with the increasing of $Z$ and $N$ is observed. The relation between isoscaling parameter and the change of isospin content is demonstrated. In addition, the disappearance of the isospin effect of projectile fragmentation is also discussed in the viewpoint of isoscaling parameter.
Y. G. Ma, Y. B. Wei, W. Q. Shen, X. Z. Cai, J. G. Chen, J. H. Chen, D. Q. Fang, W. Guo, C. W. Ma, G. L. Ma, Q. M. Su, W. D. Tian, K. Wang, T. Z. Yan, C. Zhong, J. X. Zuo
Momentum correlation functions of the nucleon-nucleon pairs are presented for reactions with C isotopes bombarding a $^{12} \rm C$ target within the framework of the isospin-dependent quantum molecular dynamics model. The binding-energy dependence of the momentum correlation functions is also explored, and other factors that have an influence on momentum correlation functions are investigated. These factors include momentum-dependent nuclear equation of state, in-medium nucleon-nucleon cross sections, impact parameters, total pair momenta, and beam energy. In particular, the rise and the fall of the strength of momentum correlation functions at lower relative momentum are shown with an increase in beam energy.
Y. G. Ma, X. Z. Cai, J. G. Chen, D. Q. Fang, W. Guo, G. H. Liu, C. W. Ma, E. J. Ma, W. Q. Shen, Y. Shi, Q. M. Su, W. D. Tian, H. W. Wang, K. Wang, Y. B. Wei, T. Z. Yan
Nucleon-nucleon momentum correlation function have been presented for nuclear reactions with neutron-rich or proton-rich projectiles using a nuclear transport theory, namely Isospin-Dependent Quantum Molecular Dynamics model. The relationship between the binding energy of projectiles and the strength of proton-neutron correlation function at small relative momentum has been explored, while proton-proton correlation function shows its sensitivity to the proton density distribution. Those results show that nucleon-nucleon correlation function is useful to reflect some features of the neutron- or proton-halo nuclei and therefore provide a potential tool for the studies of radioactive beam physics.
Y. G. Ma, K. Wang, Y. B. Wei, G. L. Ma, X. Z. Cai, J. G. Chen, D. Q. Fang, W. Guo, W. Q. Shen, W. D. Tian, C. Zhong
The isoscaling behavior is investigated using the isotopic/isobaric yields from the equilibrated thermal source which is prepared by the lattice gas model for lighter systems with A = 36. The isoscaling parameters $α$ and -$β$ are observed to drop with temperature. The difference of neutron and proton chemical potential shows a turning point around 5 MeV where the liquid gas phase transition occurs in the model. The relative free neutron or proton density shows a nearly linear relation with the N/Z (neutron to proton ratio) of system and the isospin fractionation is observed.
Y. B. Wei, Y. G. Ma, X. Z. Cai, C. Zhong, J. G. Chen, H. Y. Zhang, D. Q. Fang, K. Wang, G. L. Ma, W. Guo, W. D. Tian, W. Q. Shen, W. L. Zhan, G. Q. Xiao, H. S. Xu, Z. Y. Sun, J. X. Li, Z. Y. Guo, M. Wang, Z. Q. Chen, Z. G. Hu, L. X. Chen, C. Li, R. S. Mao, J. Bai
Distribution of the parallel momentum of $^{28}$Si fragments from the breakup of 30.7 MeV/nucleon $^{29}$P has been measured on C targets. The distribution has the FWHM with the value of 110.5 $\pm$ 23.5 MeV/c which is consistent quantitatively with Galuber model calculation assuming by a valence proton in $^{29}$P. The density distribution is also predicted by Skyrme-Hartree-Fock calculation. Results show that there might exist the proton-skin structure in $^{29}$P.
D. Q. Fang, W. Guo, C. W. Ma, K. Wang, T. Z. Yan, Y. G. Ma, X. Z. Cai, W. Q. Shen, Z. Z. Ren, Z. Y. Sun, J. G. Chen, W. D. Tian, C. Zhong, M. Hosoi, T. Izumikawa, R. Kanungo, S. Nakajima, T. Ohnishi, T. Ohtsubo, A. Ozawa, T. Suda, K. Sugawara, T. Suzuki, A. Takisawa, K. Tanaka, T. Yamaguchi, I. Tanihata
The longitudinal momentum distribution (P_{//}) of fragments after one-proton removal from ^{23} Al and reaction cross sections (σ_R) for ^{23,24} Al on carbon target at 74A MeV have been measured. The ^{23,24} Al ions were produced through projectile fragmentation of 135 A MeV ^{28} Si primary beam using RIPS fragment separator at RIKEN. P_{//} is measured by a direct time-of-flight (TOF) technique, while σ_R is determined using a transmission method. An enhancement in σ_R is observed for ^{23} Al compared with ^{24} Al. The P_{//} for ^{22} Mg fragments from ^{23} Al breakup has been obtained for the first time. FWHM of the distributions has been determined to be 232 \pm 28 MeV/c. The experimental data are discussed by using Few-Body Glauber model. Analysis of P_{//} demonstrates a dominant d-wave configuration for the valence proton in ground state of ^{23} Al, indicating that ^{23} Al is not a proton halo nucleus.
Y. B. Wei, Y. G. Ma, W. Q. Shen, G. L. Ma, K. Wang, X. Z. Cai, C. Zhong, W. Guo, J. G. Chen
Hanbury Brown-Twiss (HBT) results of the nucleon-nucleon correlation function have been presented for the nuclear reactions with neutron-rich projectiles (Be isotopes) using an event-generator, the Isospin-Dependent Quantum Molecular Dynamics model. We explore that the relationship between the binding energy per nucleon of the projectiles and the strength of the neutron-proton HBT at small relative momentum. Moreover, we reveal the relationship between the single neutron separation energy and the strength of the halo neutron-proton HBT. Results show that neutron-proton HBT results are sensitive to binding energy or separation energy.
K. Wang, Y. G. Ma, G. L. Ma, Y. B. Wei, X. Z. Cai, J. G. Chen, W. Guo, C. Zhong, W. Q. Shen
We apply a statistical-evaporation model (HIVAP) to calculate the cross sections of superheavy elements, mainly about actinide targets and compare with some available experimental data. A reaction channel $^{30}$Si + $^{243}$Am is proposed for the synthesis of the element Z = 109 and the cross section is estimated.
C. Zhong, X. Z. Cai, W. Q. Shen, H. Y. Zhang, Y. B. Wei, J. G. Chen, Y. G. Ma, W. Guo, D. Q. Fang
The Boltzmann-Uehling-Uhlenbeck (BUU) Model, which includes the Fermi motion, the mean field, individual nucleon-nucleon (N-N) interactions and the Pauli blocking effect etc., is used to calculate the total reaction cross section $σ_R$ induced by $α$-particles on different targets in the incident energy range from 17.4 to 48.1 MeV/u. The calculation result can reproduce the experimental data well. The nucleus-nucleus interaction radius parameter $r_0$ was extracted from experimental $σ_R$. It is found that $r_0$ becomes constant with increasing the mass number of target.
Y. B. Wei, Y. G. Ma, W. Q. Shen, G. L. Ma, K. Wang, X. Z. Cai, C. Zhong, W. Guo, J. G. Chen, D. Q. Fang, W. D. Tian, X. F. Zhou
Hanbury Brown-Twiss (HBT) results of the neutron-proton correlation function have been systematically investigated for a series nuclear reactions with light projectiles with help of Isospin-Dependent Quantum Molecular Dynamics model. The relationship between the binding energy per nucleon of the projectiles and the strength of the neutron-proton HBT at small relative momentum has been obtained. Results show that neutron-proton HBT results are sensitive to the binding energy per nucleon.