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Accepted Manuscript  doi: 10.11804/NuclPhysRev.37.2019CNPC34
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Nuclear structure of unstable nuclei, in particularly the nuclei near the magic number, has been one of the hot topics of nuclear physics study. Near the neutron magic number N=40, 50, rich nuclear structure phonomania appeared in the nickel region, in particularly for the neutron-rich isotopes, have stimulated intensive investigation from both theoretical and experimental aspects. In order to gain a better understanding of the nuclear structure in the nickel region, we choose to study the properties of neutron-rich Zn(Z=30) isotopes. In this paper, after a simple introduction of the laser spectroscopy experiment of Zn isotopes at CERN-ISOLDE, we reviewed the nuclear spins, magnetic moment, electric quadrupole moment and root mean square charge radius of the ground and long-lived isomeric states of 62–80Zn isotopes. Based on these properties, together with shell-model calculation from different interactions, we discussed systematically the nuclear structure phenomena, such as the shell structure evolution, magicity, deformation and shape coexistence, and the cross-shell excitation of correlated nucleons. At the end, on the basis of the current experimental data and nuclear structure information, as well as the theoretical prediction of energy level evolution of N=51 isotones in nickel region, we propose to measure the basic properties of 81,82Zn nuclei at the collinear resonance ionization spectroscopy setup at ISOLDE-CERN.
Accepted Manuscript  doi: 10.11804/NuclPhysRev.37.2019CNPC22
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Spin-related physics are hot topics in various research fields. Nucleons and quarks are both spin-half fermions. They are affected by the spin-orbit interaction as well as the magnetic field in non-central heavy-ion collisions, leading to interesting spin dynamics, especially the spin polarization perpendicular to the reaction plane. In relativistic heavy-ion collisions, the produced quarks can be approximately considered as massless particles due to the extremely high temperatures and high densities reached there, and the spin dynamics turns to the chiral dynamics in this case. Under the external electromagnetic field and vortical field, a series chiral anomaly effects may appear once there are asymmetries of electric charges and/or chirality charges. This manuscript reviews a series of studies on the spin and chiral dynamics based on transport simulations from our research group, including particle spin polarizations in intermediate-energy heavy-ion collisions and relativistic heavy-ion collisions, as well as chiral magnetic waves in an ideal system and in relativistic heavy-ion collisions.
Accepted Manuscript  doi: 10.11804/NuclPhysRev.37.2019CNPC77
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This article reviews concisely the symmetries and their breaking of strong interaction system. To establish the bridge between the abstract symmetry concept and principle in mathematics and the application in physics to reveal the underlying principle of strong interaction, we describe not only the abstract concept but also the realization of the unitary and other symmetries with the microscopic particles. We then describe the evolution of the strong interaction matter in the early universe in view of the symmetries and their breaking, especially on the dynamical generation of the observable mass(i.e., DCSB) and those of the strong and other interactions (gauge symmetry and breaking). We make also a survey of the symmetries and their breaking of nucleus, with concentration on the general methods of studying the many-body system in the symmetry point of view, the multi-particle shell model and the interacting boson approximation (IBM), the modes of nuclear collective motion and their evolution (i.e., nuclear shape phase transition). The survey intends to link the fundamental approaches with the practical investigations in the related frontiers of research properly and promptly.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC63
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Heavy ion reactions provide an effective tool to study the nuclear equation of state (EOS) in terristial laborartory. When the number of neutrons differs largely with the number of protons in a nuclear system or nuclei, the main contribution to the nuclear EOS comes from the symmetry energy term. The nuclear symmetry energy, reflecting the isovector sector of the nucleon-nucleon potential, is closely relevant to the structural properties of dense object and the merging process in stellar environments, as well as to the exotic properties of nuclei and the location of the board of nuclear chart. However, the density dependence of the nuclear symmetry energy is the most unknown ingredient in the properties of nuclear matter so far. Thus the investigation of nuclear symmetry energy in wide density range becomes the main frontiers in many world-level nuclear laboratories and astrophyics observatories. In this article, we review briefly the experimental progress in this field. Particularly the experimental studies on the transport of the isospin degree of freedom in heavy ion reactions and the constraint of nuclear symmetry energy based on the Heavy Ion Research Facity at Lanzhou (HIRFL) are introduced. It has been shown that the isospin drift process persists to the late stage of the reaction, indicating that the isospin transport time scale may depend on the physics process under investigation. Due to the long-time accumulation of isospin effects, the angular distribution of the isospin concentration of the light particles in a wide range of angle is a sensitive probe of nuclear symmetry energy. With ${S}\!=\!28.3\,\mathrm{M}\mathrm{e}\mathrm{V}$ fixed at saturation point, the slope of the symmetry energy depending on density is contrained in the range of $L\!=\!33\!\sim\!61\,\mathrm{M}\mathrm{e}\mathrm{V}$ at $\mathrm{C}\mathrm{L}\!=\!95$%. Using a Compact Spectrometer for Havy Ion Experiment (CSHINE) with ability to achieve isotopic particle identification and fission event reconstruction, the small angle correlation function of the isotope-resolved light charged particles can be measured to derive the time scale of isospin relaxation in heavy ion reactions at Fermi energies. In the last section of the article, the isovector orientation effect of the polarized deuteron beam scattering off heavy target is introduced, which offers a novel means to constrain the nuclear symmetry energy below saturation density.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC21
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The improved quantum molecular dynamics(ImQMD) model plus the GEMINI statistical decay model are used to analyze the odd-even effect of fragmentation cross sections for reactions 36Ar beams on C, Al, Cu, Pb targets at 400 AMeV. The result shows that the odd–even effect is appeared in the de-excitation process of primary fragments, and the pairing energy plays an important role. The odd–even effect of fragmentation cross sections disappears when the pairing energy is removed from the de-excitation process. The odd–even effect in neutron of fragmentation cross section is significantly.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC72
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In this paper, we review the recent key results on anisotropic flow in heavy ion collisions at RHIC-STAR experiment. It mainly includes the results of elliptic flow of multi-strange and charm hadrons in top energy heavy ion collisions, and the results of elliptic and directed flow from RHIC Beam Energy Scan Program I. The results of 54.4 and 27 GeV are brand-new. We find the new results of directed flow follow the energy dependence trend; the Number of Constituent Quark scaling of elliptic flow indicates the partonic collectivity has been built-up in Au+Au collisions at 54.4 and 27 GeV. We also introduce the future plans of Beam Energy Scan experiments and the research focus of the anisotropic flow.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC61
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For a long time, nuclear shell structure is an important issue of nuclear physics. In particular, with rapid development of new generation of nuclear radioactive ion beam facilities and detectors, new shell structures appearing in neutron-rich nuclei have largely attracted the interests of the field, including the mechanism behind and the evolutions. Under the frame of relativistic Hartree-Fock theory founded on the meson-exchange diagram of nuclear force, taking calcium isotopes, doubly magic nuclide 208Pb and the selected superheavy and exotic nuclei as examples, this paper reviews the occurrence of new sub-shells in neutron-rich nuclei, the pseudo-spin symmetry (PSS) restoration and the in-medium nuclear attraction-repulsion balance, the PSS restoration/violation and nuclear shell structure, novel phenomena, etc., in which the roles of the Fock terms are intensively discussed.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC02
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In the article, Zn thin films were deposited on the glass substrates at room temperature by magnetron sputtering from a zinc target. And ZnS thin films were prepared by annealing Zn thin films in sulfur vapor and Ar gas at 200 and 400 ℃. The microstructure defects, crystallizations, surface morphology and optical properties of the samples were analyzed by PAT(positron annihilation technique), XRD(X-ray diffraction), SEM(scanning electron microscopy) and UV-VIS spectrophotometer. The resultant ZnS thin films exhibited a high optical transmittance of about 80% in the visible region. With the increase of sulfidation time, the band-gap value was increased from 3.55 to 3.57 eV, and the S/Zn atomic ratio was enhanced from 0.54 to 0.89, implying an obvious improvement of ZnS film quality. This demonstrated that the excess-sulfur problem in the ZnS films was well solved compared with those samples prepared by sulfidation in the vacuum-sealed quartz-glass ampoules. Besides, the structural defects of the thin films before and after sulfidation were investigated by positron annihilation Doppler broadening measurements. It was found that the S parameter of the samples after sulfidaton was greater than that before sulfidation, implying the higher structural defect concentration for the former.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC54
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According to three different interactions of YSOX, WBT and WBP, the spectral structure of nuclei 14C, 14,15N, and 14-18O near double magic nucleus 16O are analyzed by shell model calculations. The good effects have been found in spectral structure of these nuclei after reconsidering shell interaction. The large data analysis between these different shell model interactions and experiment also revealed the limitations of these existing interactions in this nuclei region, for example the large difference between theory and experiment, the reversed order of states and so on, which brings the further motivations of modifying shell model Hamiltonians.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC57
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Nuclear β decay is one of the key nuclear processes that determine how the heavy elements from Fe to U in the universe were made. The dominant nuclear process in β-decay is the Gamow-Teller(GT) transition, so the key point for nuclear β-decay study is to describe nuclear GT transition accurately. One of the most widely used nuclear model is random phase approximation (RPA). However, since it only includes one-particle one-hole excitation configurations, this model cannot describe spreading width of GT resonance, and tends to overestimate the β-decay half-lives. To overcome these difficulties, based on Skyrme density functional, the random phase approximation with particle vibration coupling (RPA+PVC) model was developed. Compared to RPA model, it further includes the one-particle one-hole coupled with phonons in its configuration space, which includes many-body correlations beyond mean field approximation. To extend the study to open shell nuclei, the quasiparticle random phase approximation with quasiparticle vibration coupling model (QRPA+QPVC), which includes pairing correlations, was developed. Based on the above models, the GT excitation, β decay, β+/EC of magic nuclei and superfluid nuclei were studied. It is found that with the same Skyrme interaction SkM*, the experimental GT width and transition strength profile were well reproduced, the quenching phenomenon was partly explained, and the description of β-decay half-lives were improved at the same time. The recent progress of this study is reviewed, and in the meantime the perspectives for future developments are given.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC37
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Nucleon, the main building block to the visible matter in the universe, is an ideal laboratory to study the strong interaction. In the experimental study of nucleon structure, Electron Ion Collider(EIC) plays important role. EIC is a super electron-microscope being able to take clear image of the inner structure of the nucleon, and hence is an effective tool to gain insights into the fundamental constituents of matter, e.g., especially the structures of the nucleon and nuclei. The Electron-ion collider in China(EicC) project is proposed based on the HIAF facility by promoting its ion beam to an energy around 15~25 GeV, which is then enforced to collide with an electron beam of 3~5 GeV. Both beams are polarized and their center-of-mass energy is 10~20 GeV. The main physics motivations include the precision measurements to the nucleon internal structure in the sea-quark region, and the promotion of our understanding of the origin of proton spin and mass, the study of exotic states, etc. In the paper, a fast simulation package based on parametrisation is developed for EicC. With the simulation package, one EicC detector conceptual design is proposed based on the virous physics simulations.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC07
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The study of halo phenomenon gives us a new understanding of nuclear structure, in which the continuum, especially the resonance in the continuum, plays an important role. The complex momentum representation (CMR) method can not only describe the bound state, resonant state and continuous spectrum uniformly, but also describe the narrow and wide resonance well. In this paper, the CMR method is introduced for the study of nuclear resonance. The single particle energy of bound state and resonance state of 31Ne and 19C with deformation parameter β2 is given. The physical mechanism of halo formation in 19C and 31Ne and the reason of energy level inversion near the neutron number N = 20 are analyzed. The halo phenomenon in nuclei heavier than 37Mg is predicted. The result of this prediction is helpful to find heavier halo nuclei in experiments. These studies show that the CMR method is suitable for describing not only stable nuclei, but also exotic nuclei with diffuse material distribution.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC68
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We apply the coupled-channel Gamow shell model to calculate the spectra of 17O and 17F, as well as 16O(p,p) elastic cross sections at low energies. It is shown that continuum coupling is necessary to account for the particle-emission width of the unbound eigenstates of 17O and 17F. The low-lying spectrum of 17O and 17F and 16O(p,p) excitations functions are in fair agreement with experimental data. Nevertheless, it is also shown that the use of a realistic nuclear Hamiltonian is needed to have an optimal reproduction of 16O(p,p) elastic cross sections in the low-energy region.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC53
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In this paper the time performance of a plastic scintillator detector with an area of 10 cm×10 cm and read out by multiple silicon photomultipliers (SiPMs) at both ends was studied. The results tested with a 239Pu source are shown as: (1) the time resolutions became better gradually with the increase of the quantities of SiPMs connected in series; (2) when the number of 12 SiPMs was fixed, the time resolutions got worse as the number of parallel branches were increased; (3) the detector time resolutions can be effectively improved by using a fast-time plastic scintillator and adding its thickness; (4) to improve the positional uniformity of the time resolution, the scintillator with larger dimensions than beam spots should be used; (5) a resolution less than 131 ps was achieved with a 0.1 cm thickness EJ232 scintillator detector read out on each side by 12 SiPMs conncted in series. This study has importance significance for the upgrading of the start detector at RIBLL2.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC65
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We review our recent studies on chiral crossover and chiral phase transition temperatures in this proceedings. We will firstly present a lattice QCD based determination of the chiral crossover transition temperature at zero and nonzero baryon chemical potential $\mu_{\rm{B}}$ which is $T_{\rm{pc}}\!=\!(156.5\pm1.5)$ MeV. At nonzero temperature the curvatures of the chiral crossover transition line are $\kappa^{\rm{B}}_2$=0.012(4) and $\kappa^{\rm{B}}_4$=0.000(4) for the 2nd and 4th order of $\mu_{\rm{B}}/T$. We will then present a first determination of chiral phase transition temperature in QCD with two degenerate, massless quarks and a physical strange quark. After thermodynamic, continuum and chiral extrapolations we find the chiral phase transition temperature $T_{\rm{c}}^0\!=\!132^{+3}_{-6}$ MeV.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC26
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According to several common lifetime calculation methods of radioactive nuclides, the scope of applicable of the four calculation methods, which are named Method of Direct Fitting, Method of Logarithmic Time, Method of Maximum Likelihood and Method of Maximum likelihood when observation time windows is limited, are studied based on the simulation data. As the observation time window is limited or not, the applicable range of the lifetime calculation methods in different observation time windows and different counts are discussed. In simulation, fully stripped ion 94mRu44+ was selected as the target nuclide, the lifetime and error in different counts and different observation time windows are obtained, and the applicable range of the four methods is given. The experimental data of 94mRu44+ was obtained from the lifetime measurement experiment which is performed by using the Isochronous Mass Spectrometry (IMS) at the HIRFL-CSR facility in Lanzhou. The simulation results are consistent with the experimental results within one error bar, thereby it is further verified the applicable range of the calculation method and the reliability of the simulation data. The simulation results provide theoretical basis and reference for the design of the future lifetime experiments.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC52
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The spectrum of hadrons is important for understanding the confinement of quantum chromodynamics. Many new puzzles arose since 2003 due to the abundance of experimental discoveries with the $XYZ$ structures in the heavy quarkonium mass region being the outstanding examples. Hadronic resonances correspond to poles of the $S$-matrix, which has other types of singularities such as the triangle singularity due to the simultaneous on-shellness of three intermediate particles. Here we briefly discuss a few possible manifestations of triangle singularities in the $XYZ$ physics, paying particular attention to the formalism that can be used to analyze the data for charged $Z_c$ structures in the $\psi\pi$ distributions of the reaction $e^+e^-\to \psi\pi^+\pi^-$.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC09
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Direct reaction, including elastic scattering, inelastic scattering and transfer reactions, is one of the commonly used methods to study the exotic structure of light neutron-rich nuclei. Taking for example the structure studies of 6,8He, 11Li, 11,12Be, 14,15B, and 15,16C, this paper reviewed how to use these reactions to study the exotic structure of neutron-rich nuclei experimentally. The effective interactions (optical potential) between the halo nuclei 6,8He/11Be and the p/d targets are obtained by fitting the elastic scattering angular distributions. The deformation parameter of 16C is extracted from the inelastic scattering data of 16C+p/d, which indicates that the deformation of 16C can not be ignored. The p-, s- and d-wave intensities of the ground state in 8He and 11,12Be are quantitatively studied by the single-nucleon transfer reaction. The results show that in the ground state of 8He, besides four valence neutrons filling the 0p3/2 orbital, other configurations, such as (0p3/2)2(0p1/2)2, may have some probability. The ground state of 12Be is dominated by the d-wave intruder, but its neighbour 11Be is predominated by the s-wave intruder.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC41
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Deep learning is the state-of-the-art pattern recognition method. It is expected to help scientists to discover most relevant features from big amount of complex data. Different categories of deep learning, the best deep neural network architectures for different data structures, the interpretability of black-box models and the uncertainties of model predictions are reviewed in this article. The applications of deep learning in nuclear equation of state, nuclear structure, mass, decay and fissions are also introduced. In the end, a simple neural network is trained to predict the mass of nucleus. We found that the artificial neural network trained on experimental data has low prediction error for experimental data that are held back. Trained with experimental data, the network predictions for light neutron-rich nuclei deviate from Macro-Micro Liquid model, which indicate that there might be new physics missing in the theoretical model and more data are needed to verify this.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC39
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We provide a short review on some recent developments in the soft and hard probes of quark-gluon plasma(QGP) in high-energy nuclear collisions. The main focus is on the theoretical and phenomenological studies of anisotropic collective flow and jet quenching related to the Relativistic Heavy-Ion Collider(RHIC) and the Large Hadron Collider(LHC). The origin of the collectivity in small collision systems is also briefly discussed. For soft probes, we discuss initial-state fluctuations and geometric anisotropy, the hydrodynamic evolution of the fireball, and final-state anisotropic flows, flow fluctuations, correlations and longitudinal decorrelations. Systematic comparison to experimental data may infer the evolution dynamics and various transport properties of the QGP produced in heavy-ion collisions. For hard probes, we focus on the flavor dependence of parton energy loss and jet quenching, the hadronization of heavy quarks in QGP, full jet evolution in nuclear medium and medium response. Detailed analysis of related observables can help us achieve more comprehensive understanding of jet-medium interaction and heavy flavor production in relativistic nuclear collisions. For small systems, we discuss how initial-state and final-state effects explain the observed collective flows of light and heavy flavor hadrons in proton-nucleus collisions, which is helpful in understanding the origin of the collectivity in large collision systems.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC44
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In contemporary nuclear research field, it is of special interest to synthesize the new isotopes far from the stability line and to explore the existing limit of nuclei. For the most proton-rich N≈126 isotones, which are located near the crossing point between the proton drip line and the N=126 closed shell, synthesizing and α-decay studies may shed new light on the structural evolution of the N=126 shell closure. Based on measurements at the gas-filled recoil separator SHANS, the most neutron-deficient new isotopes, 219,220,223,224Np, were synthesized via 36,40Ar+185,187Re fusion-evaporation reactions. The new experimental results allow us to establish the α-decay systematics for Np isotopes around N=126 for the first time, and to test the robustness of this shell closure in neptunium. The systematic analysis of single proton separation energies figures out the exact location of the proton drip line in Np isotopic chain. At the same time, the isotope 219Np was identified as the presently known heaviest nuclide beyond the proton drip line. In addition, the possibility of producing other new isotopes (218,221,222Np) in this region is discussed in terms of the measured cross sections and the theoretical predictions.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC29
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Relativistic heavy-ion collisions generate high-temperature quark gluon plasma with extremely strong electromagnetic and fluid vortical fields. The quark gluon plasma exhibits intriguing macroscopic quantum phenomena in the presence of strong electromagnetic and vortical fields, e.g., the chiral magnetic effect, chiral vortical effects, chiral separation effect, chiral electric separation effect, and spin polarization. These phenomena provide us a unique experimental means to study the nontrivial topological sector of the quantum chromodynamics, e.g., possible parity violation of strong interaction at high temperature, and subatomic spintronics of quark gluon plasma. They are also closely related to other subfields of physics, such as particle physics, condensed matter physics, astrophysics, and cold atomic physics, and thus form a new interdisciplinary research area. The goal of the present article is to give an introduction to these phenomena and to review the current status of their experimental search in heavy-ion collisions. In particular, we find that the magnetic fields generated in heavy-ion collisions can reach $10^{18}\sim 10^{20}$ G and the fluid vorticity can reach $10^{22}$ s–1; these are the known strongest magnetic fields and vorticity in the current universe. We quantitatively analyze the isobar collisions and find that, even if the background level is of 93%, the current isobar collisions can still test the occurrence of the chiral magnetic effect at $3\sigma$ significance level. We give the causal set of equations of spin hydrodynamics and give the collective modes in it; the spin hydrodynamics is useful to resolve the sign problem appearing in the comparison between theoretical calculations and experimental measurements of the spin polarization of hyperons.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC01
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Accelerator mass spectrometry(AMS) is the most sensitive analytical technique for measuring long-lived radionuclides, which is widely used in the fields of environment, geology, archaeology and physics. In recent years, the miniaturization of AMS device has been greatly developed in the world. In order to develop miniaturized AMS devices and their analysis technology, China institute of atomic energy has independently developed a single-stage AMS device with an acceleration voltage of 0.2 MV and a tandem AMS device with an terminal voltage of 0.3 MV, respectively. Based on the single-stage AMS device, the high efficiency transport technique and background eliminating method have been developed for 14C measurement, and realized the high sensitivity measurement of 14C. The measurement sensitivity reaches 14C/12C (atomic number ratio)=2×10–15. Using the 0.3 MV tandem AMS device, the gas stripping conditions, background eliminating and detection methods of 129I at low ion energy were systematically studied, and the high efficient transmission and high sensitive measurement methods of 129I were established, the sensitivity is 129I/127I=1×10–14. This is the first time to develop miniaturized AMS devices in China, which lays the foundation for the localization of AMS.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC19
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We have studied the relativistic Kelvin circulation theorem for ideal Magnetohydrodynamics. The relativistic Kelvin circulation theorem is a conservation equation for the called T-vorticity, We have briefly reviewed the ideal magnetohydrodynamics in relativistic heavy ion collisions. The highlight of this work is that we have obtained the general expression of relativistic Kelvin circulation theorem for ideal Magnetohydrodynamics. We have also applied the analytic solutions of ideal magnetohydrodynamics in Bjorken flow to check our results. Our main results can also be implemented to relativistic magnetohydrodynamics in relativistic heavy ion collisions.
Corrected proofs  doi: 10.11804/NuclPhysRev.37.2019CNPC13
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Heavy quarks (charm and beauty), especially beauty, with expectedly different properties from light quarks are considered as ideal probes for the Quark-Gluon Plasma (QGP). However, there are few measurements on beauty hadrons or on their decay leptons. With the most recent measurements on charmed hadrons and heavy flavor decay electrons (HFE) at mid-rapidity in Au+Au collisions at $\sqrt{s_{\rm NN}}=200\;{\rm{GeV}}$ at RHIC, a data-driven method is developed to separate charm and beauty components from the HFE measurements. From charmed hadron measurements, electrons from charm decays via semileptonic decay simulations are obtained, with which the beauty component can be extracted from the HFE spectrum. As preliminary results, the $p^{}_{\rm T}$ spectra, $R_{\rm AA}$ and $v_2$ distributions of electrons from charm and from beauty decays ($R_{\rm AA}^{\rm c\rightarrow e}$ and $v_2^{\rm c\rightarrow e}$, $R_{\rm AA}^{\rm b\rightarrow e}$ and $v_2^{\rm b\rightarrow e}$) in minimum bias Au+Au collisions are presented, respectively. Less suppression of $R_{\rm AA}^{\rm b\rightarrow e}$ is observed compared with that of $R_{\rm AA}^{\rm c\rightarrow e}$ at moderate-to-high $p_{\rm T}$, and $v_2^{\rm b\rightarrow e}$ shows smaller than $v_2^{\rm c\rightarrow e}$ at low-to-moderate $p_{\rm T}$.
Accepted Manuscript  doi: 10.11804/NuclPhysRev.37.2019CNPC03
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At present, study of the novel Compton telescope with high sensitivity has great scientific significance. The calorimeter, as one of the important components of the Compton telescope, is required to have excellent energy resolution and position resolution. For this purpose, a CsI(Tl) $\gamma$-ray detector of dual-ended readout based on silicon photomultipliers (SiPM) was designed as the basic detection unit of the calorimeter for the Compton telescope. Different wrapping materials (Teflon, Tyvek and ESR) and different crystal sizes (5 mm×5 mm×60 mm, 5 mm×5 mm×80 mm and 5 mm×5 mm×100 mm) were used to construct the detectors, and the detectors were tested with a 137Cs source. The influence of the wrapping materials was not significant to the energy resolution but quite pronounced to the light attenuation length and position resolution. Besides, the light attenuation length and position resolution showed strong correlation, i.e. the shorter light attenuation length corresponding to the better the position resolution; In addition, for the three detectors using different sizes of the crystals, they did not show significant differences in performance. Eventually, the CsI(Tl) crystal detector with the size of 5 mm×5 mm×80 mm and the wrapped with ESR was determined to construct the detector satisfied with the requirements of the calorimeter for the novel Compton telescope. The energy resolution can reach 5.2% and the position resolution is about 5.2 mm.
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2020, 37(2): 1-2.
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2020, 37(2): 119-135.   doi: 10.11804/NuclPhysRev.37.2019060
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Investigation of fusion reaction mechanism is one of important topics in recent years. In comparison with radioactive ion beam, the beam intensities of weakly bound nuclei are orders of magnitude higher. The study of the reaction mechanism induced weakly bound nuclei can further explore the coupling effect of breakup, transfer and other reaction channels on the fusion process. A lot of experimental data have shown that there are many interesting phenomena in the fusion reaction induced by weakly bound nuclei at energies near the Coulomb barrier, such as "enhancement below the Coulomb barrier'' and "suppression above the Coulomb barrier'' of the complete fusion cross section. In this paper, we mainly review the researches of the suppression phenomenon and discuss the possible reasons for the suppression. The main reason for the suppression phenomenon of the complete fusion cross section is that the weakly bound nuclei break up before entering the fusion barrier, thus reducing the incident flux of the complete fusion reaction channel. At the same time, the experimental results show that the degree of suppression may be related to the mass number and structure of target nuclei. There are three kinds of methods to measure the fusion reaction induced by weakly bound nuclei, which are $\gamma$ ray measurement, charged particle measurement and charged particle -$\gamma$ ray coincidence measurement. The charged particle -$\gamma$ ray coincidence measurement has obvious advantages in reaction channel identification. This paper introduces the three measurement methods and the researches using these three methods at home and abroad, including the researches of our groups. In addition, the recent theoretical research work on fusion reactions induced by weakly bound nuclei is also introduced.
2020, 37(2): 136-150.   doi: 10.11804/NuclPhysRev.37.2019068
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The nuclear symmetry energy, which describes the energy difference of per proton and neutron in nuclear matter, has been extensively studied within the last two decades. Around saturation density, both the value and the slope of the nuclear symmetry energy have been roughly constrained, its high-density behavior is now still in argument. Probing high-density symmetry energy at terrestrial laboratories is being carried out at facilities that offer radioactive beams worldwide. While relevant experiments are being conducted, we theoretically developed more advanced isospin-dependent transport model including new physics such as nucleon-nucleon short-range correlations and in-medium isospin-dependent baryon-baryon scattering cross section. New sensitive probes of the high-density symmetry energy are provided, such as squeezed-out neutron to proton ratio, photon and light cluster as well as the production of mesons with strangeness or hidden strangeness. The blind spots of probing the high-density symmetry energy by sensitive observable are demonstrated. Model dependences of frequently used sensitive probes of the symmetry energy have been studied thoroughly based on different transport models. A qualitative observable of neutron to proton ratio at high kinetic energy is proposed to probe the high-density symmetry energy qualitatively. The probed density regions of the symmetry energy by some observables are first studied and usually lower probed density regions comparing with maximum compression density are obtained. Nucleon-nucleon short-range correlations usually reduce values of sensitive observables of the symmetry energy. Probing the curvature of the symmetry energy by involving the slope information of the symmetry energy at saturation point in the transport model is proposed. Besides constraining the high-density symmetry energy by using heavy-ion collisions, a lot of neutron-star related observations from heaven may also be used to constrain the high-density symmetry energy.
2020, 37(2): 151-159.   doi: 10.11804/NuclPhysRev.37.2020005
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Abstract:
In this paper, the calculated results of elements $Z\leqslant$118 based on the dinuclear system model and other models are compared with the experimental data. It is proved that different models are reliable in predicting the production cross sections of superheavy nuclei. The prediction results of superheavy nuclei $Z=119$ and $Z=120$ by different models are compared and analyzed. It is found that the optimal projectile-target combinations to synthesize superheavy nuclei $Z$=119 and $Z$=120 are $^{48}{\rm{Ca}}+ ^{{\rm{252}}}{\rm{Es}}$ and $^{40}{\rm{Ca}}+^{{\rm{257}}}{\rm{Fm}}$, respectively, and it is likely that the new isotopes $Z$=119 will be synthesized in the experiment before the new isotopes $Z$=120. Because of the lack of target with $Z>$100 in the laboratory, attempts are being made to find heavier projectiles than 48Ca to synthesize superheavy nuclei $Z$=121 and $Z$=122. The superheavy nuclei $Z$=121 can be synthesized by reactions V+Cf. However, the production cross sections of superheavy nuclei $Z$=122 are very small, which requires us to improve the detection and identification techniques in the future. We hope that the discussion in this paper can provide some guidances for experimental and theoretical nuclear physicists in the future.
2020, 37(2): 160-165.   doi: 10.11804/NuclPhysRev.37.2020022
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Abstract:
Multinucleon transfer reaction 136Xe+208Pb at $E_{\rm{c.m.}}$=617 MeV is simulated by improved quantum molecular dynamics (ImQMD) model with and without considering the effect of $Q$-value. The calculation results of ImQMD including the effect of $Q$-value (ImQMD+$Q$) generally better reproduce the experimental mass distribution and distribution of total kinetic energy lost (TKEL). $Q$-value effect is found to drive the transfer of less than ten nucleons and suppress more nucleons transfer. It also decreases the average lifetime of composite systems in the events at lower impact parameters. In the production of more neutron-rich isotopes with neutron number $N$=126, $Q$-value effect enhances the cross sections for these isotopes in the comparison between the results of ImQMD and ImQMD+$Q$.
2020, 37(2): 166-171.   doi: 10.11804/NuclPhysRev.37.2020008
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Abstract:
We study the large transverse momentum dilepton produced by the photon-nucleon interactions in the peripheral Au-Au collisions at RHIC and Pb-Pb collisions at LHC. We calculate the dilepton production yield by using the perturbative QCD factorization approach and the Weizsäcker-Williams approximation. The numerical results indicate that the photon-nucleon collision processes is negligible by comparing with the conventional large transverse momentum dilepton production at RHIC energies. However, in the large transverse momentum region, the photon-nucleon collision could be an important large transverse momentum dilepton source in the peripheral heavy ion collisions at LHC.
2020, 37(2): 172-179.   doi: 10.11804/NuclPhysRev.37.2020007
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Abstract:
Our article introduces a method to construct the squeeze operator in quantum field theory: consider two free Hamiltonians for the same scalar field with two different masses, through Bogoliubov transformation, we derive a generalized squeeze operator which maps the ground state of one to the other. The efficiency of its operation is verified in both the Dirac representation and also the Schrodinger wavefunctional representation in quantum field theory. We believe that the squeeze operators can be found similarly in any real scalar field theory as long as there are two sets of creation and annihilation operators connected by linear transformations.
2020, 37(2): 180-185.   doi: 10.11804/NuclPhysRev.37.2019058
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Abstract:
In the booster ring (BRing) of the High Intensity heavy-ion Accelerator Facility (HIAF), the multi-bunch should be merged into single bunch after the acceleration. To study the influence of the beam loading effects during the bunch merging, the simulations of particle tracking with 238U35+ beam are carried out. According to the simulation results, during the bunching merging, the beam loading effects can result in the growth of the momentum spread and the bunch length as well as the oscillation of the bunch length and the bunch center. The potential well distortion induced by the wake voltage and wake field coupling during the bunch merging are the reasons why the bunch center oscillates and the emittance of the beam grows. To reduce the influence of the beam loading effects, the multi-harmonic feed-forward system is employed to compensate the wake voltage. With the feed-forward system, the beam loading effects can be compensated during the bunching merging. The feed-forward system is able to guarantee the high quality of the beam for extraction in the BRing. The frequency range to be covered and the largest wake voltage to be compensated by the feed-forward system are determined according to the simulation results.
2020, 37(2): 186-190.   doi: 10.11804/NuclPhysRev.37.2020013
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Abstract:
China Spallation Neutron Source(CSNS) beam power will upgrade to 500 kW(CSNS-II), energy gain of H- linac will up to 300 MeV from 80 MeV, and the 648 MHz βg=0.6 5-cell superconducting elliptical cavity will be adopted to accelerate the H- from 150 to 300 MeV. Accompanied with the advantage of high accelerating gradient, simple structure, easy post-processing, weak stiffeness and detuning is the shortcoming of elliptical cavity, this study analysis detuning characteristic of the elliptical cavity. With code COMSOL Multiphysics, helium pressure sensitivity coefficient KP and lorentz force detuning factor KL of bare cavity was calculated under two end fixed conditions, KP=–45.705 Hz/mbar(1 mbar=100 Pa) and KL=1.574 Hz/(MV/m)2. Stiffener ring was designed and optimized to reduce the Helium pressure sensitivity coefficient and lorentz force detuning factor, and double ring was chosen to improve the detuning of elliptical cavity at last by vast calculation and analysis, the position of stiffener ring was optimized at 75 and 120 mm under two end fixed boundary, Helium pressure sensitivity coefficient drop down to KP=6 Hz/mbar, lorentz force detuning factor drop down to KL=0.43 Hz/(MV/m)2. Moreover, elastic boundary was used to analyze helium pressure sensitivity coefficient and lorentz force detuning factor, more realistic results were got under tuner end 30 kN/mm boundary and the other end fixed condition, KP=4.8 Hz/mbar and KL=1.99 Hz/(MV/m)2, meet engineering requirements. In addition, dynamic lorentz force detuning was analyzed qualitatively with code CST. And natural frequency of cavity was calculated by code Workbench, results show that nature frequency is far from RF pulse repetition rate and ambient vibration frequency, no resonance happen.
2020, 37(2): 191-198.   doi: 10.11804/NuclPhysRev.37.2020024
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Abstract:
In the readout electronics for the Water Cerenkov Detector Array(WCDA) of the Large High Altitude Air Shower Observatory(LHAASO), both high precision time and charge measurement are required. A front-end readout chip PASC(Pre-Amplifier and Shaping Circuit) ASIC(Application Specific Integrated Circuit)is designed, and will be actually applied in the third water pond of the WCDA. In order to evaluate the performance of the chips after massive production, it is important to design an automatic test system. This paper presents the design of the ASIC test system, which is used to achieve automatic testing of the time and charge measurement performance of the chips. After a brief introduction of the chip under test, the design scheme and structure of the test system is presented, including the hardware circuits and test software. This system has been applied in batch test of the LHAASO project, and 100 chips have been successfully tested. It can communicate with multiple instruments through the central control software to perform instrument control and complete automated testing and data recording. This automated test method is more suitable for performance testing and evaluation of high precision readout chips under a large dynamic range, which greatly simplifies the test process and can greatly improve the work efficiency of a large number of repetitive test steps in batch test. The test results show that the performance of these chips meet the application requirements of the third pond of the WCDA in LHAASO.
2020, 37(2): 199-208.   doi: 10.11804/NuclPhysRev.37.2020020
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Abstract:
The high accuracy and reliability of the T0 signals is one of the most important prerequisites for Chinese Spallation Neutron Source(CSNS) target station spectrometer. Based on the CPLD(Complex Programmable Logic Device) and PMC(Peripheral Mezzanine Card) mother-daughter structure, T0 signal fan-out instruments were designed with a distributed architecture, including a special trigger signal receiver for the neutron chopper with 24 V level trigger. Before the first 1.6 GeV proton beam hits the target, the delay of all T0 signals have been adjusted correctly. These T0 signal fan-out instruments have superior flexibility, maintainability, scalability, which have been working for more than three years, and the whole T0 timing system has run smoothly and achieved high reliability. It has accumulated valuable experience for the higher demand of T0 signal fan-out instruments at the second phase spectrometer in the future.
2020, 37(2): 209-216.   doi: 10.11804/NuclPhysRev.37.2020015
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Abstract:
In order to provide a basic understanding on the effect of H on He behaviors in the structural materials for the future nuclear systems, the effect of H on He thermal desorption and retention behaviors in SIMP steels was studied using thermal desorption spectroscopy(TDS), scanning electron microscope(SEM), and transmission electron microscopy(TEM) by comparing the results of the alone irradiation of 130 keV He+ and the sequential irradiation of 130 keV He+ and 160 keV H2+. The TDS results show that a major peak of He release occurred in the temperature of 1 198~1 222 K via the mechanism of bubble migration. The peak temperature of He release was lower and the release amount was larger under the sequential irradiation of He+ and H2+ than that under the He+-alone irradiation. This indicates that He desorption was enhanced by the additional H irradiation. In addition, the enhancement effect of H on He thermal desorption depends on the dose of H irradiation. When the peak concentration of H increased from 5% to 50% (atom fraction), this enhancement effect was weakened. Combined with TEM and SEM results, it was found that the presence of H promoted the surface blistering during TDS heating, thus accelerating the release of He by the mechanism of bubble migration.
2020, 37(2): 217-224.   doi: 10.11804/NuclPhysRev.37.2019050
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Abstract:
In carbon ion radiotherapy, secondary particles produced through the interaction of carbon ion beam with the treatment head devices and the patient's body can reach many areas in the patient's body. Among the secondary particles, the yield of neutrons and $\gamma$-rays is largest. Without affecting the beam delivery function, reducing secondary neutrons and $\gamma$-rays produced in carbon ion radiotherapy is very important to decrease the normal tissue complications and secondary cancer risk after radiotherapy. In the present work, the Monte Carlo method was used to calculate the dose and spatial distributions of secondary neutrons and $\gamma$-rays deposited in water when multi-leaf collimators (MLC) made from different material leaves were adopted to form a typical 10 cm×10 cm square irradiation field for 400 MeV/u carbon ion beam. The simulation results showed that the secondary neutrons produced were mainly distributed at the incident end in the water phantom when the carbon ion beam passed through the MLC, while the secondary $\gamma$-rays were uniformly distributed in the entire water phantom and more dose of the secondary $\gamma$-rays appeared in the plateau when the irradiation field with spread-out Bragg peak (SOBP) travelled in the water phantom. The selection of MLC leaves should be determined according to the actual conditions of MLC leaves thickness and secondary particle equivalent dose requirements. The simulation study presented in this paper provides scientific evidence for the material selection of MLC leaves and other components in carbon ion radiotherapy using passive beam delivery system.
2020, 37(2): 225-232.   doi: 10.11804/NuclPhysRev.37.2019065
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Abstract:
Ultrafast laser system based on High Harmonic Generation (HHG) technology can not only accurately make atoms and molecules to the target quantum state, but also control the target quantum state by controlling the pulse time accurately. The reaction microscope can accurately measure the differential cross section in 4π solid angle in the quantum few-body collision, which greatly improves the measurement accuracy and the efficiency of experimental study on quantum few-body collision dynamics. The combination of these two advanced technologies will greatly expand the field of quantum few-body dynamics. At present, a single frequency selection of HHG is very important, and the resolution of the reaction microscope is mainly affected by the vacuum degree and the dispersion degree of the cold target. The Institute of Modern Physics (IMP) of Chinese Academy of Sciences(CAS) adopts the design of multistage differential system and titanium vacuum target chamber, which makes the vacuum degree of the spectrometer reach 10–11 mbar. This design greatly reduces the influence of background noise. Moreover, the supersonic cold target system is upgraded to realize the free control of the target thickness, which improves the accuracy of event recorded by the detector. Meanwhile, the XUV ultrafast laser system and the reaction microscope were successfully combined by using the multi-order XUV pulse monochromatic technology of HHG. The XUV pulse energy generated by this experimental platform ranges from 20 to 100 eV, so atomic and molecular dynamics processes with ionization or dissociation energy below 100 eV can be studied.
2020, 37(2): 233-239.   doi: 10.11804/NuclPhysRev.37.2020003
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Abstract:
By analyzing the experimental data of ${\rm{\gamma }}+^{50,52}$Cr, the divergence between the absorption cross section and measurements of neutron and proton emission cross sections was clarified, the correction of neutron emission cross section of 52Cr was given. The EGLO model of photon strength function was selected to describe the absorption cross section. Combined with the quasideuteron contribution, the evaluation of photon absorption cross section was given. MEND-G code has been newly developed for calculating gamma induced medium heavy nuclear reactions. By optimizing the theoretical parameters, the cross sections of n, p, ${\rm{\alpha }}$, etc. in the range of 200 MeV were given. The results of this work were in good agreement with the main measurement of neutron and proton emission below 30 MeV. All data of ${\rm{\gamma }}+^{50,52,53,54}$Cr have been output in ENDF/B-6 format, which was convenient for nuclear engineering.
2020, 37(2): 240-248.   doi: 10.11804/NuclPhysRev.37.2020010
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Abstract:
This paper presented a study of flowability of the inclined dense granular-flow target for a neutron irradiation facility, which is capable of providing high-energy neutrons suitable to advance fusion reactor material research. The results from simulations and theoretical analysis described the constancy and stability of the flow, which was rarely mentioned before. It was found that 25° was acceptable for a steady and stable accelerating flow and all the results supported the availability of this granular flow for a potential choice of the heat medium.