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ABSTRACT: Proton-neutron, neutron-neutron and proton-proton momentum correlation
functions ($C_{pn}$, $C_{nn}$, $C_{pp}$) are systematically investigated for
$^{15}$C and other C isotopes induced collisions at different entrance channel
conditions within the framework of the isospin-dependent quantum molecular
dynamics (IDQMD) model complemented by the CRAB (correlation after burner)
computation code. $^{15}$C is a prime exotic nucleus candidate due to the
weakly bound valence neutron coupling with closed-neutron shell nucleus
$^{14}$C. In order to study density dependence of correlation function by
removing the isospin effect, the initialized $^{15}$C projectiles are sampled
from two kinds of density distribution from RMF model, in which the valence
neutron of $^{15}$C is populated on both 1$d$5/2 and 2$s$1/2 states,
respectively. The results show that the density distributions of valence
neutron significantly influence nucleon-nucleon momentum correlation function
at large impact parameter and high incident energy. The extended density
distribution of valence neutron largely weakens the strength of correlation
function. The size of emission source is extracted by fitting correlation
function using Gaussian source method. The emission source size as well as the
size of final state phase space is larger for projectiles sampling from more
extended density distribution of valence neutron corresponding 2$s$1/2 state in
RMF model. Therefore momentum correlation function can be considered as a
potential valuable tool to diagnose the exotic nuclear structure such as skin
and halo.
11/2012;
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ABSTRACT: The reaction dynamics of axisymmetric deformed $^{24}$Mg + $^{24}$Mg collisions have been investigated systematically by an isospin-dependent quantum molecular dynamics (IDQMD) model. It is found that different deformations and orientations result in apparently different properties of reaction dynamics. We revealed that some observables such as nuclear stopping power ($R$), multiplicity of fragments, and elliptic flow are very sensitive to the initial deformations and orientations. There exists an eccentricity scaling of elliptic flow in central body-body collisions with different deformations. In addition, the tip-tip and body-body configurations turn out to be two extreme cases in central reaction dynamical process. Comment: 5 pages, 7 figures, to appear in Physical Review C (Rapid Communication)
05/2010;
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Y. G. Ma,
D. Q. Fang,
P. Zhou,
X. Z. Cai, J. G. Chen,
W. Guo,
X. Y. Sun,
W. D. Tian,
H. W. Wang,
G. Q. Zhang, [......],
H. Sakurai,
S. Shimoura,
R. Shioda,
E. Takeshita,
S. Takeuchi,
K. Yamada,
Y. Yamada,
Y. Yasuda,
K. Yoneda,
T. Motobayashi
[show abstract]
[hide abstract]
ABSTRACT: We have measured two‐proton momentum and angular correlations for the 23Al excited states from the 23Al radioactive beam on a 12C target at an energy of 60∼70 A MeV at the projectile fragment separator beamline (RIPS) in the RIKEN Ring Cyclotron Facility. The decay products, namely 21Na+p+p from 23Al are clean identified. The relative momentum and opening angle between two protons in the rest frame of three body decay channels demonstrate that there are some diproton emission components from 2He cluster for the excited 23Al.
AIP Conference Proceedings. 05/2010; 1235(1):377-383.
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ABSTRACT: Dynamical dipole $\gamma$-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 $\gamma$ rays are calculated and the centroid energy and dynamical dipole emission width of the $\gamma$ spectra are extracted to investigate the properties of $\gamma$ emission. In addition, sensitivities of dynamical dipole $\gamma$-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 $\gamma$ radiation can provide information on the equation of state and the symmetry energy around the normal nuclear density. Comment: 5 pages, 6 figures
04/2010;
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W Luo,
W Xu,
Q Y Pan,
X Z Cai, J G Chen,
Y Z Chen,
G T Fan,
G W Fan,
W Guo,
Y J Li, [......],
Y G Ma,
W Q Shen,
X C Shi,
B J Xu,
J Q Xu,
Y Xu,
H O Zhang,
Z Yan,
L F Yang,
M H Zhao
[show abstract]
[hide abstract]
ABSTRACT: As a prototype of the Shanghai Laser Electron Gamma Source in the Shanghai Synchrotron Radiation Facility, an x-ray source based on laser-Compton scattering (LCS) has been installed at the terminal of the 100 MeV linac of the Shanghai Institute of Applied Physics. LCS x-rays are generated by interactions between Q-switched Nd:yttrium aluminum garnet laser pulses [with wavelength of 1064 nm and pulse width of 21 ns (full width at half maximum)] and electron bunches [with energy of 108 MeV and pulse width of 0.95 ns (rms)] at an angle of 42 degrees between laser and electron beam. In order to measure the energy spectrum of LCS x-rays, a Si(Li) detector along the electron beam line axis is positioned at 9.8 m away from a LCS chamber. After background subtraction, the LCS x-ray spectrum with the peak energy of 29.1+/-4.4|(stat)+/-2.1|(syst) keV and the peak width (rms) of 7.8+/-2.8|(stat)+/-0.4|(syst) keV is observed. Normally the 100 MeV linac operates with the electron macropulse charge of 1.0 nC/pulse, and the electron and laser collision repetition rate of 20 Hz. Therefore, the total LCS x-ray flux of (5.2+/-2.0) x 10(2) Hz can be achieved.
The Review of scientific instruments 01/2010; 81(1):013304. · 1.52 Impact Factor
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ABSTRACT: The dependence between neutron-to-proton yield ratio ($R_{np}$) and neutron skin thickness ($\delta_{np}$) in neutron-rich projectile induced reactions is investigated within the framework of the Isospin-Dependent Quantum Molecular Dynamics (IQMD) model. The density distribution of the Droplet model is embedded in the initialization of the neutron and proton densities in the present IQMD model. By adjusting the diffuseness parameter of neutron density in the Droplet model for the projectile, the relationship between the neutron skin thickness and the corresponding $R_{np}$ in the collisions is obtained. The results show strong linear correlation between $R_{np}$ and $\delta_{np}$ for neutron-rich Ca and Ni isotopes. It is suggested that $R_{np}$ may be used as an experimental observable to extract $\delta_{np}$ for neutron-rich nuclei, which is very significant to the study of the nuclear structure of exotic nuclei and the equation of state (EOS) of asymmetric nuclear matter. Comment: 7 pages, 5 figures; accepted by Phys. Lett. B
06/2009;
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E. J. Ma,
Y. G. Ma, J. G. Chen,
X. Z. Cai,
D. Q. Fang,
W Guo,
G. H. Liu,
C. W. Ma,
W. Q. Shen,
Y Shi,
Q. M. Su,
W. D. Tian,
H W Wang,
K Wang,
T. Z. Yan
[show abstract]
[hide abstract]
ABSTRACT: We investigate the cross sections of the elastic electron or positron scattering from $^{208}$Pb, $^{12}$C, $^{12,16}$O and $^{28, 32}$S by the relativistic partial-wave expansion method using the static charge density distribution from the self-consistent relativistic mean field model and also calculate the charge form factor for $^{12, 16}$O and $^{28, 32}$S. The numerical results are compared with the available data. Calculations indicate that the extended charge density distributions of $^{12}$O and $^{28}$S have observable effects on the cross sections of the electron or positron scattering as well as the charge form factors.
10/2007;
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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, [......],
T. Ohnishi,
T. Ohtsubo,
A. Ozawa,
T. Suda,
K. Sugawara,
T. Suzuki,
A. Takisawa,
K. Tanaka,
T. Yamaguchi,
I. Tanihata
[show abstract]
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ABSTRACT: The longitudinal momentum distribution (P//) of fragments after one-proton removal from 23Al and reaction cross sections (σR) for 23,24Al on a carbon target at 74A MeV have been measured. The 23,24Al ions were produced through projectile fragmentation of 135A MeV 28Si primary beam using the RIPS fragment separator at RIKEN. P// is measured by a direct time-of-flight (TOF) technique, while σR is determined using a transmission method. An enhancement in σR is observed for 23Al compared with 24Al. The P// for 22Mg fragments from 23Al breakup has been obtained for the first time. FWHM of the distributions has been determined to be 232 ± 28 MeV/c. The experimental data are discussed by using the Few-Body Glauber model. Analysis of P// demonstrates a dominant d-wave configuration for the valence proton in ground state of 23Al, indicating that 23Al is not a proton halo nucleus.
Phys. Rev. C. 10/2007; 76(3).
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ABSTRACT: Perchlorate removal in a clean, cost-effective and publicly acceptable manner is of the utmost importance as far as drinking water treatment is concerned. An electrodialytically assisted catalytic membrane system was developed for the reduction of perchlorate in dilute aqueous solutions. The catalyst support (membrane) was a stainless steel mesh coated with specific monometallic catalysts. A total of 18 metals covering the first, the second and the third row of the periodical table were tested. Results indicated that the perchlorate reduction rate followed the order: Cd > Pt > Cr > Mo > Sc Rh > Ru ∼ Sn > Pd > V ∼ Ti > Zn > Mn > Ni > Zr > Co > Cu > Pb. Due to its environmental benignity and relatively low material cost, tin was selected for further evaluation in spite of its moderate reaction rate. Results indicated that perchlorate reduction took place rapidly in the concentration range of 2–100 ppm at room temperature and chloride was the major end product. The reaction followed the Langmuir–Hinshelwood rate expression. Based on the activation energy obtained, i.e., 49.8 kJ mol −1 K, it is clear that surface reaction, not mass transfer, was the rate-limiting step. SEM images showed the formation of metallic catalyst in the size of nano-scale over the stainless steel mesh support. X-ray photoelectron spectroscopy (XPS) survey of the metallic catalyst indicated the presence of metal oxide and elemental metals. X-ray diffraction (XRD) spectra showed the presence of amorphous metallic catalysts.
Separation and Purification Technology 01/2007; 58:129-137. · 2.92 Impact Factor
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J G Chen,
W Xu,
W Guo,
Y G Ma,
X Z Cai,
H W Wang,
G C Lu,
Y Xu,
C B Wang,
Q Y Pan,
R Y Yuan,
J Q Xu,
Z Y Wei,
Z Yan,
W Q Shen
[show abstract]
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ABSTRACT: The design of an X-ray source based on Compton backscattering of CO 2 laser and 100 MeV electron beam is introduced. This instrument can produce 8218 keV X-ray and will be installed as a prototype for the Shanghai Laser Electron Gamma Source (SLEGS) at the end of 2007. Some detailed descriptions for the related instruments are presented. The related simulation results are provided and discussed. The backgrounds from the dipole magnet of the 100 MeV LINAC and bremsstrahlung of the 100 MeV electrons are also estimated. Due to the large power of the employed CO 2 laser, the expected flux of X-ray will be able to achieve the order of 10 6 s À1 , and the corresponding signal–noise ratio is about 10 6 .
Nuclear Instruments and Methods in Physics Research A. 01/2007; 5807555(07).
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J. G. Chen,
W Xu,
W Guo,
Y. G. Ma,
X. Z. Cai,
H W Wang,
G. C. Lu,
Y Xu,
C. B. Wang,
Q. Y. Pan,
R. Y. Yuan,
J. Q. Xu,
Z. Y. Wei,
Z Yan,
W. Q. Shen
[show abstract]
[hide abstract]
ABSTRACT: The design for the proto type of the Shanghai Laser Electron Gamma Source (SLEGS) at the Shanghai Synchrotron Radiation Facility (SSRF) is introduced. Some detailed descriptions for design of related instruments are provided. The proto type can produce X-ray with energy of 10 keV order. A description of the kinematics of Compton backscattering mechanism and the related simulation results are presented and discussed. The backgrounds from dipole magnet and bremsstrahlung are estimated and the signal-noise ratio is also given.
11/2006;
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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
[show abstract]
[hide abstract]
ABSTRACT: 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.
11/2006;
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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
[show abstract]
[hide abstract]
ABSTRACT: Shanghai Laser Electron Gamma Source, a $\gamma$-ray beam line of 10MeV order was proposed recently. The beam line is expected to generate $\gamma$-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 $\gamma$-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.
11/2006;
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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
[show abstract]
[hide abstract]
ABSTRACT: 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.
11/2006;
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T. Z. Yan,
Y. G. Ma,
X. Z. Cai, J. G. Chen,
D. Q. Fang,
W Guo,
C. W. Ma,
E. J. Ma,
W. Q. Shen,
W. D. Tian,
K Wang
[show abstract]
[hide abstract]
ABSTRACT: Anisotropic flows ($v_2$ and $v_4$) of light nuclear clusters are studied by Isospin-Dependent Quantum Molecular Dynamics model for the system of $^{86}$Kr + $^{124}$Sn at intermediate energy and large impact parameters. Number-of-nucleon scaling of the elliptic flow ($v_2$) are demonstrated for the light fragments up to $A$ = 4, and the ratio of $v_4/v_2^2$ shows a constant value of 1/2. In addition, the momentum-space densities of different clusters are also surveyed as functions of transverse momentum, in-plane transverse momentum and azimuth angle relative to the reaction plane. The results can be essentially described by momentum-space power law. All the above phenomena indicate that there exists a number-of-nucleon scaling for both anisotropic flow and momentum-space densities for light clusters, which can be understood by the coalescence mechanism in nucleonic degree of freedom for the cluster formation.
06/2006;
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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
[show abstract]
[hide abstract]
ABSTRACT: 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.
02/2006;
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D. Q. Fang,
Y. G. Ma,
C. Zhong,
C. W. Ma,
X. Z. Cai, J. G. Chen,
W Guo,
Q. M. Su,
W. D. Tian,
K Wang,
T. Z. Yan,
W. Q. Shen
[show abstract]
[hide abstract]
ABSTRACT: The isospin effect and isoscaling behavior in projectile fragmentation have been systematically investigated by a modified statistical abrasion-ablation (SAA) model. The normalized peak differences and reduced isoscaling parameters are found to decrease with ($Z_{proj}-Z$)/$Z_{proj}$ or the excitation energy per nucleon and have no significant dependence on the size of reaction systems. Assuming a Fermi-gas behavior, the excitation energy dependence of the symmetry energy coefficients are tentatively extracted from $\alpha$ and $\beta$ which looks consistent with the experimental data. It is pointed out that the reduced isoscaling parameters can be used as an observable to study excitation extent of system and asymmetric nuclear equation of state in heavy ion collisions.
02/2006;
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G. L. Ma,
Y. G. Ma,
B. H. Sa,
X. Z. Cai,
J H Chen,
Z. J. He,
J. L. Long,
W. Q. Shen,
C. Zhong,
J. X. Zuo, J. G. Chen,
D. Q. Fang,
W Guo,
C. W. Ma,
Q. M. Su,
W. D. Tian,
K Wang,
Y. B. Wei
[show abstract]
[hide abstract]
ABSTRACT: The effect of hadronic rescattering on the elliptic flow has been investigated by the Cooper-Frye hadronization model from hydrodynamic evolution following by the afterburner hadronic rescattering model for 200 GeV/c Au + Au at 20-40% centrality. It is found that the hadronic rescattering can suppress elliptic flow $v_2$ in momentum space especially in lower transverse momentum region. In addition, the hadronic rescattering effects on transverse momentum spectra and anisotropy coordinate space of hadrons are studied.
06/2005;
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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
[show abstract]
[hide abstract]
ABSTRACT: 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 increasing 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 shows the dropping trend with increasing impact parameter.
Journal of Physics G Nuclear and Particle Physics 05/2005; 31(6):S1179. · 4.18 Impact Factor
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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
[show abstract]
[hide abstract]
ABSTRACT: 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 $\alpha$ and $\beta$ for hot fragments before evaporation and cold fragments after evaporation have been extracted, respectively. It looks that the evaporation has strong effect on $\alpha$. For cold fragments, a monotonic increase of $\alpha$ and $|\beta|$ 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. Comment: 4 pages, 4 figures
05/2005;
