2020, Volume 37, Issue 3
Special Issue of the 17th Conference on Nuclear Physics in China(CNPC2019)
- Invited Plenary Presentations
- Reports from the Winners of the “Hu Jimin Award of Education and Science”
- Parallel Session Presentations-Nuclear structure
- Parallel Session Presentations-Nuclear reaction
- Parallel Session Presentations-Nuclear astrophysics
- Parallel Session Presentations-Intermediate and high energy nuclear physics
- Intermediate and high energy nuclear physics
- Parallel Session Presentations-Detector, electronics and application technology
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
We present a brief review of some topical issues in the study of QCD exotic hadrons. A special emphasis of the threshold phenomena is made by taking into account the implementation of the effective field theory study of hadronic molecules and the impact arising from the triangle singularity. A combined analysis may provide some clues towards a better understanding of the hadron spectroscopy.
The gravitational waves emitted from a binary neutron star merger, as predicted from general relativistic magneto-hydrodynamics calculations, are sensitive to the appearance of quark matter and the stiffness of the equation of state of QCD matter present in the inner cores of the stars. These astrophysically created extremes of thermodynamics do match, to within 20%, the values of densities and temperatures which are found in relativistic heavy ion collisions, if though at quite different rapidity windows, impact parameters and bombarding energies of the heavy nuclear systems. In this article we combine the results obtained in general relativistic simulations of binary neutron star systems with ones from heavy ion collisions in the lab to pin down the EOS and the phase structure of dense matter. We discuss that the postmerger gravitational wave emission of the neutron star merger remnant might give, in the near future, insides about the properties of the hadron quark transition.
A number of nuclear reactions such as
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.
In recent years, high-precision mass measurements of short-lived nuclides were conducted using isochronous mass spectrometry (IMS) based on the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou (HIRFL-CSR). The new data enable us to discuss some related physical problems in the realm of nuclear structure and astrophysics. In this contribution, details of the measurements and data analysis are described. The IMS with two Time-Of-Flight (TOF) detectors is mainly introduced. In order to improve the mass resolving power while preserving the acceptance of the storage ring, additional velocity information beside the revolution time in the ring is obtained for each of the stored ions by using the double TOF detector system. The IMS with two TOF detectors is a brand new concept, and relevant experimental techniques need to be developed. We have established a simulation platform based on CSRe, developed high-performance TOF detectors and installed them in a straight section of the CSRe, performed online beam testing, developed new ion optics and optimized them, and developed data analysis methods and optimized them. Furthermore, planned technical developments are outlined in this contribution.
All data related to nucleus are referred to as nuclear data, which include nuclear reaction data describing the interaction between incident particle and nucleus, nuclear structure data and radioactive decay data characterizing the properties of nucleus. Nuclear data are the basic data for nuclear physics fundamental research, nuclear energy utilization, nuclear facilities construction and nuclear technology application. Nuclear data are also widely applied in nuclear medicine, material analysis, resource exploration, environmental monitoring, aerospace technology and nuclear astrophysics research fields. This paper briefly introduces the types of nuclear data, the generation process and application of nuclear data, then reviews the development of international nuclear data and the current status of nuclear data research in China. Finally some suggestions for the future development of nuclear data in China are given.
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.
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.
Neutron research facilities have been built on the high flux neutron source China Advanced Research Reactor(CARR), of which different kinds of neutron techniques, including neutron scattering, neutron imaging and neutron activation analysis, are now available. The neutron scattering instruments, including neutron diffractometers, small-angle neutron scattering, neutron reflectometer, inelastic neutron scattering spectrometers, can be used to analyze the microstructure and dynamic properties of materials. The thermal neutron imaging and cold neutron imaging facilities can be used for the non-destructive testing of defects inside materials. And neutron activation analysis systems are powerful for the detection of different elements or isotopes. There are now 19 neutron instruments which have been built or under construction. Some sample environment devices are also available. These facilities provide important support for both fundamental scientific researches and industrial applications in the fields of physics, chemistry, material science, life science, energy, environment and so on. CARR neutron research facilities will continue to open to the users from outside the institute, to not only serve scientific frontier researches, but also meet the major national innovation needs.
Various theories have predicted the deep Dirac levels (DDLs) in atoms for many years. However, the existence of the DDL is still under debating, and need to be confirmed. With the development of high intensity lasers, nowadays, electrons can be accelerated to relativistic energies by high intensity lasers. Furthermore, electron-positron pairs can be created, and nuclear reactions can be ignited, which provide a new tool to explore the DDL related fields. In this paper, we propose a new experimental method to study the DDL levels by monitoring nuclei's orbital electron capture life time in plasma induced by high intensity lasers. The present study reveal that if a DDL exists, a nuclear electron capture rate could be enhanced by factor of over
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.
Aim of the high-energy nuclear physics experiments is to investigate the production and evolution properties of a new nuclear matter state − the Quark-Gluon Plasma under the extreme conditions of high temperature and energy density. This study brings the unique insight into understanding the deep structure of the current material world and the properties of the strong nuclear force in such ultra hot and dense multi-particle system. It also provides the important opportunity to explore new physics phenomenons under such extreme conditions. In this paper, the main international high-energy nuclear physics experimental projects that China has participated and their physics goals are briefly outlined. The recent highlights of the achievements on investigating the properties of the Quark-Gluon Plasma and on exploring the new physics phenomenons in high-energy heavy-ion collisions made by China are overviewed. The perspective on the experimental research projects for high-energy nuclear physics to the future is given as well.
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
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
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.
The β decays of atomic nuclei refer to the transformation that the nuclei emit a β particle or capture an electron. The accurate measurements of the β transition strength functions Sβ(E) are of great significance in exploring the structure of unstable nuclei, revealing the process of stellar nucleosynthesis and also verifying the β decay theories. Experimentally, one way to determine the β transition strength is to directly measure the beta decay product using β-γ coincidence technique and/or total absorption spectroscopy. This method can give the transition information within the Qβ window. Another method to obtain the β decay strength is via the charge exchange reactions performed at the intermediate energy region (100~400 MeV/u), such as (p, n) or (3He, t). This is done by a high-precision measurement of the differential cross section. This method allows to access the transition strength that beyond the Qβ window, however, it is restricted by the beam intensity, and as a consequence hard to perform a systematical study of unstable nucleus with low yields. In view of this, in this paper we proposes a systematic measurement of the total charge exchange reaction cross section of the unstable nuclei. Combined with the well developed nuclear reaction theory, this method may set a constrain to the summed strength of the Gamow-Teller transition of the unstable nuclei within the proton separation threshold. Moreover, we introduce briefly the relevant work that has been carried out and planned.
Recently, isomeric states are discovered for the first time in 101In, 123,125Ag, and 218Pa. The nuclear shell model is used to explain the underlying physics in these and related isomers in In, Ag isotopes, and the
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.
In tokamak plasmas, the confinement performance can be significantly improved in high confinement regime. Investigation on the plasma instabilities in this regime is important for the confinement control and steady state operation of tokamak. This paper mainly introduces the researches on the high confinement mode and underlying edge plasma instabilities. It emphasizes on the studies on high confinement mode transition, features of edge-localized mode and its control, pedestal instabilities and pedestal saturation mechanism. The study suggests that pedestal dynamics and edge-localized mode might be actively controlled by the pedestal turbulence, resulting in the steady state operation both with high confinement performance and low heat loads on plasma facing components.
We study the properties of the kaon through the light-front wave function(LFWF) obtained from the Basis Light-front Quantization(BLFQ) approach. Our Hamiltonian contains the kinetic energy terms, a transverse confining potential motivated by the light-front holographic quantum chromodynamics(LFHQCD) model, a complementary longitudinal confining potential, and the quark-gluon interactions based on quantum chromodynamics (QCD). Our basis space includes the lowest two Fock sectors. Based on the previous work, we tune the only additional strange quark mass parameter to match the resulting kaon mass with the experimental data. Based on the obtained leading Fock sector LFWF, we calculate the parton distribution amplitude(PDA) of the kaon which is in reasonable agreement with the one calculated from perturbative QCD in the massless quark limit. The obtained kaon form factor (FF) agrees with results from the Super Proton Synchrotron(SPS) experiment at the European Organization for Nuclear Research (CERN) and the Fermi National Accelerator Laboratory(FNAL) experiment. The electromagnetic radius (at the leading order Fock sector) is comparable to the one from the particle data group(PDG). In addition, the kaon parton distribution function(PDF), after QCD evolution, can be used to calculate the ratio of the kaon up quark PDF to that of the pion whose trend qualitatively agrees with that of the CERN-NA-003 experimental data. The obtained kaon PDF shows that the ratio between longitudinal momentum fractions of valence quarks,
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.
Structure of nucleus far from the β-stability line is a currently hot topic in the field of nuclear physics. The β-decay spectroscopy is an important method to study the nuclear structure, especially for the drip-line nuclei with low yield. This paper reviews the experimental studies of β-delayed decay spectroscopies for the extremely proton-rich nuclei in sd-shell recently carried out at the RIBLL1 facility. The precise data on half-lives, masses of decay daughter nuclei, energy spectra and branch ratios of β-delayed proton and two-proton decays as well as γ transitions for 15 nuclei have been obtained, which greatly enrich the spectroscopy information of the nuclei close to the proton drip-line in this region. In particular, the decay properties of some nuclei like 22Si and 20Mg as well as 27S and 26P are described in detail. Moreover, some hot topics related to the three-body force, the decay asymmetry of mirror nuclei, and the thermomuclear reaction rates related to the super-abundant issue of 26Al in the Milky Way are discussed.
This paper reviews the research and recent progress in the fields of nuclear spectroscopy, nuclear astrophysics, detector development, and high energy nuclear physics at Shandong University, Weihai. Specifically, we emphatically introduce the shape coexistence and delayed band crossing in
In this paper we study low-lying states of even-even nuclei in the sd and pf shells in the framework of the shell model with the phenomenological pairing plus quadrupole-quadrupole (P+Q) interaction. By adopting the single-particle energy and the monopole interaction from the USDB and GXPF1 interactions, the low-lying spectra of spherical nuclei and deformed nuclei are successfully reproduced by a unified set of parameters. We obtain a reasonably good result for binding energies by removing the monopole component from the pairing interactions. The isoscalar pairing interaction does not play an important role in the states. The monopole interaction provides contributions to the empirical proton-neutron interaction, the symmetry energy, and the Wigner energy.
We propose a pair-condensation variation approach to evaluate the importance of collective pairs and determine their structure in low-lying states. Based on such a variation, the Nucleon Pair Approximation(NPA) could avoid the collective-pair uncertainty, which the previous NPA calculations have suffered a lot. With the trial calculation for transitional 132Ba, we exemplify the ability of our variation approach. In detail, the variation can be adopted to calculate the quadrupole deformation parameters with non-axisymmetric deformation degree of freedom. It conclusively helps the NPA to decide which collective pair is essential for obtaining a lower yrast level scheme and reproducing the
The dominance of zero-spin ground state of even-even nuclei by two-body random ensemble(TBRE) is attributed to some of the two-body matrix elements(TBMEs). In this paper, we investigate the correlation between the probability of spin-zero ground state and TBMEs through enhance each TBME by changing the width of distribution and keep other TBMEs with standard gaussian distribution. We find that the probability of spin-zero ground state is insensitive to some TBMEs. Moreover, we further investigate the probability of spin-zero ground state through setting the centroid of TBME to realistic interaction, we find that the probability of spin-zero ground state is correlate with the centroid of TBME.
The light actinide nuclei 219U and 216Ac were produced in fusion-evaporation reaction using a 183W target and 40Ar beam. After recoiling from thin target, the fusion-evaporation residues were separated by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure) and transported into the focal plane detector systems, where their impantations and decays were measured. The method of searching for
The present work aims at the structural investigation of the
The excited states in 63,65,67Mn have been studied via in-beam
In this paper, the Gamow-like model is improved by introducing centrifugal potential and electrostatic shielding, and it is used in the study of α decay and proton radioactivity. It is found that our calculations can well reproduce the experimental data. In addition, the modified Gamow-like model is used to predict the proton radioactivity half-lives of 116 proton-rich nuclei and α decay half-lives of seven even-even nuclei with
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.
An independent theoretical analysis is presented for the 2– band in 248Cf, which has been identified to spin
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.
In antisymmetrized molecular dynamics(AMD) model, the binding energies and root mean square (RMS) radii of 4He, 6Li, 12C, 20Ne, 40Ca and 60Ni in their own mean field were studied by three sets of Gogny interactions (g0, g0as and g0ass). The binding energies of isotopes with atomic numbers from 1 to 18 were studied systematically. Comparing with the experimental data, it is found that the result of g0 is the best. These investigations would provide clues to the study of the nuclear reaction mechanism such as fusion in low energy region and multi fragmentation in medium energy region by AMD.
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.
With the application of the notch technique, the radial sensitive regions for the tightly bound system 16O+208Pb, and weakly bound system 9Be+208Pb were investigated. It is the first time that the shape and resonant scattering can be identified from the sensitivity functions. Moreover, strong energy dependence of sensitive regions were found for both the tightly and stable weakly bound systems: in the above barrier region, the sensitive region varies around the strong absorption radius; while below the barrier, the behavior of sensitive region is close to that of the closest approach in the Coulomb field.
The stochastic Langevin model is applied to calculate the evolution of postsaddle emitted neutrons, protons and
Recent measurements by CREMA Collaboration in Paul Scherrer Institute (Switzerland) determined the proton radius in Lamb shift spectroscopy of muonic hydrogen with a significantly improved precision. However, they discovered that this determination differs from the well-accepted CODATA value by 5.6 standard deviation. This discovery is named the “proton radius puzzle”, and attracted interests of many physicists. Inspired by this work, the CREMA Collaboration extended their experiments in muonic hydrogen to a series of light muonic atoms/ions, including
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.
The study of secondary neutrons produced by light charged particles induced reaction is of great significance to the design and optimization of accelerator shielding. The neutron double differential yields from 33 MeV-d, 65 MeV-3He and 65 MeV-4He bombarding thick carbon, copper and lead targets in the directions of
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.
The Trojan Horse Method(THM) is an important indirect method in experimental nuclear astrophysics. The S(E) factor of a two-body reaction in Gammow energy range related to astrophysics can be extracted from an appropriate three-body reaction measurement above the Coulomb barrier, under the quasi-free reaction condition. The method can overcome the difficulties caused by the Coulomb barrier suppression and the electron screening effect in direct measurement. While no extrapolation is needed, the method can also avoid the uncertainty in the extrapolation process. THM has a wide application in the experimental nuclear astrophysical study, low-energy fusion data measurement, neutron-induced reaction, electron screening effect and other important research fields. After a short introduction of the THM, this paper will focus on some of the most important experimental results in nuclear astrophysics measured by THM recently and the prospect of its future applications. The following key reactions will mainly be discussed: the indirect measurement of the key neutron source reaction
The fusion reaction of neutron-rich nuclei occurring in the neutron star crust is considered to be the important heating process in neutron stars and X-ray super burst. Limited by the intensity of radioactive beams and the complexity of reaction mechanism, experimental data so far are rare and can not constrain relevant theoretical model effectively. The time projection chamber (TPC) based on the active target technique works with the detection gas as the target, which can record all the tracks including the incident particle and charged particles from the reaction occurring in the detection gas. TPC has approximately 4
The reaction of 74,76Ge(n,
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.
Utilizing ultra-relativistic quantum molecular dynamics (UrQMD) model, the elliptic flow
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.
We review our recent studies on chiral crossover and chiral phase transition temperatures in this special issue. We will firstly present a lattice QCD based determination of the chiral crossover transition temperature at zero and nonzero baryon chemical potential
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.
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
This paper present a review on the dynamically generated sea quark and gluon distributions in the free nucleon and the cold nuclear medium. In the dynamical parton model, all the sea quarks and gluons come purely from the QCD fluctuations with DGLAP equations, where the small components of intrinsic sea quarks are neglected. The three valence quark distributions from maximum entropy method are taken as the nonperturbative input at
The critical exponents at the Critical end Point(CEP) and the spinodal boundaries are investigated in the Poyakov-Nambu--Jona-Lasinio(PNJL) model. The numerical results show that the four standard critical exponents,
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.
A novel algebraic approach recently proposed is presented in this paper for investigating the
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.
A Large Ion Collider Experiment(ALICE) at the Large Hadron Collider(LHC) at CERN will undergo a major upgrade during the 2nd LHC Long Shutdown(LS2) scheduled in 2019~2021 that will allow to study in detail of strong interaction matter Quark-Gluon Plasma(QGP) properties. To collecting more Pb-Pb events during the Run 3 and Run 4, the replacement of the existing Inner Tracking System(ITS) with a completely new ultra-light high resolution detector based on Monolithic Active Pixel Sensors(MAPS) technique is one of the cornerstones within this upgrade program. The new ITS will consist of seven detection layers: 3 inner layers, 2 middle layers and 2 outer layers. The upgraded ITS will be realized using more than twenty-four thousand pixel chips (called ALPIDE) covering a total active surface of about ten square meters. The thickness of ALPIDE is 50 μm, also with a pixel pitch of 27 μm × 29 μm. The main features of the ALPIDE are of low power consumption, high resolution and high speed readout. ITS2 will enable the ALICE detector to have excellent detection efficiency and impact parameter resolution when measuring extremely low transverse momentum particles, and also make the ALICE detector suitable for LHC high luminosity environment. At present, the production and test of the detector module of ITS2 project have been completed, and the integration of 7-layer barrel been completed at CERN clean room, and the on-surface commissioning has been completed in the end of 2020. The installation plan of ITS2 at the ALICE detector has been started in Jan. 2021, and is scheduled to be finished in end of May 2021. This talk will focus on the design and the physics performance of the new ITS, as well as the advanced techniques adopted in detector assembly and integration will be introduced. The status and commissioning of the ITS upgrade project will be reported.
ANAETF, a large data analysis framework for the External Target Facility (ETF) of HIRFL-CSR, has been developed and successfully used for data analysis in radioactive ion beam experiments. This paper covers the flow of data processing in the program, the general tracking algorithm for the drift chambers, the particle identification (PID) approach, and the techniques for extraction of reaction cross sections. The program achieves total detecting efficiencies of around ~90% and gives clear PID spectrum for carbon and beryllium fragments produced from the reaction of 240 MeV/u 12C secondary beams on a carbon target. The obtained cross sections are consistent with the previously reported experimental results.
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.
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)
The Gas Electron Multiplier (GEM) has attracted wide attention due to its better position resolution and isotropic two-dimensional structure, GEM is also planned to be used as the TPC readout detector in CSR External-target Experiment (CEE) under construction. The transmission characteristics of GEM under different electric field conditions have great influence on the effective gain and energy resolution of the detector. In this paper the effects of the electric field in the drift region and the induction region on the transmission characteristics of the detector are performed on single GEM, and the effects of voltage distribution and electric field in induction region on the transmission characteristics of double-layer GEM detector were studied. The results show that in single and multi-layer GEM detectors, electric fields in the different region affect the transmission characteristics of the detector mainly by changing the electron transmittance and changing the avalanche field intensity and distribution of GEM, which will affect the effective gain and energy resolution of the detector finally. The above experimental results indicate that GEM detector is a good candidate for CEE-TPC readout detector and they also provide a reference for the selection of the working point of multi-layer GEM in TPC.
The first gamma total absorption facility (GTAF) in China has been constructed in China Institute of Atomic Energy, which will be used to accurately measure the neutron capture cross section by prompt gamma method. A neutron source is established by 7Li(p, n)7Be reaction using pulsed proton beams generated by HI-13 tandem accelerator of CIAE. In order to effectively reduce the scattering neutron background produced by surrounding materials and detectors, and restrain the shape of neutron beam, neutron shield with boron-containing polyethylene (5% of B4C) coated with 5 cm lead and collimator of parallel hole are designed by MCNP program. The design makes spot of neutron beam flat and uniform, the diameter is about 2 cm, the flux of neutron outside the beam spot is reduced by 5 orders of magnitude, and the flux of gamma is reduced by 3 orders of magnitude. At the same time, neutron absorber (the outer radius is 10 cm, the thickness is 7 cm) is designed, which is used to absorb the scattered neutrons produced by the sample to be measured. The simulation results of MCNP and GEANT4 show that the boron containing polyethylene (10B4C mass fraction is 10%) is selected as the processing material of neutron absorber, in which the rate of neutron absorption reaches 80%, and the threshold of sum energy is set to 1 MeV, which meets the requirement of on-line experiment about the measurement of neutron capture cross section.
In order to meet the nuclear data requirement of Thorium Molten Salt Reactor (TMSR), a compact photoneutron source (PNS) driven by a 15 MeV electron LINAC was designed and built up by Shanghai Institute of Applied Physics. All devices including the LINAC, the neutron production target and the detector systems were all arranged in a shared hall, causing high backgrounds of neutron and γ-ray. The existing shields could not meet the requirements of low neutron background for the measurement in the thermal neutron energy regions. Therefore, more shields are needed to further reduce the neutron and γ-ray backgrounds. According to the analysis of neutron background source terms and the simulation of shielding effects of lead, concrete and boron polyethylene, the new local shields was designed. The MCNP5 simulation results show that, the new local shields can reduce the thermal neutron background by three orders of magnitude and the γ-ray background by two orders of magnitude. The experimental results with the new local shields show that, the ratio of effective thermal neutron to background thermal neutron is up to 100:1, which is of great significance for launching the foreseen physics program in the thermal neutron energy regions.
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.
Huangye kiln has rich culture connotation. It originated in the Sui Dynasty, flourished in the mid Tang Dynasty and declined in the late Tang Dynasty. To discuss whether the raw material sources and glaze formulations of the white porcelain from Huangye kiln are the same in different periods, 80 white porcelain samples from Huangye kiln in four periods, namely the Sui Dynasty, the early Tang Dynasty, the middle Tang Dynasty, and the late Tang Dynasty, were selected. The content of 9 chemical components (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, and Fe2O3) of the body and glaze of each sample was measured by proton induced X-ray emission (PIXE). Then the data were analyzed with Fisher discriminant analysis. The types of white porcelain glazes of Huangye kiln were classified by calculating the b value of the glazes. The results show that the bodies of the white porcelain from Huangye kiln in four periods may have been made of local raw materials taken from the same or nearby locations, that the glaze formulations in four periods are similar, and that the glaze formulation in the fourth period is the most stable and the most similar to that in the second period, but obviously different from that in the first period. They also show that most of the glazes of the white porcelain from Huangye kiln belong to the category of calcium glaze, and that a small quantity of glazes belongs to the categories of calcium-alkali glaze and alkali-calcium glaze.
The reactor core phenomena can be simulated and predicted with the high-fidelity neutronics coupled with thermal-hydraulics analysis, and the economic and safety of nuclear reactor could be further improved by using this new simulation tools. This work studied the methods of precise geometry modeling, accurate neutronics calculations and coupling with the pin-by-pin subchannel thermal-hydraulics, and a new high-fidelity neutronics and thermal hydraulics coupling code ENCP-X/CTF are developed. Some sensitivity analysis of the fuel rod heat conductance model, gap conductance model to the coupling results is performed, and the coupling system is applied for the large pressurized-water reactors. The results demonstrate that not only accurate macro parameters could be obtained, but also the detailed pin-level power distribution and temperature distribution could be analyzed.
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.