2017年 第34卷 第3期
High Intensity heavy-ion Accelerator Facility (HIAF) and China initiative Accelerator Driven System (CiADS) are among 16 national research facilities built as a priority during China's Twelfth Five Year Plan. In this paper, the scientific feasibility, structures and the features of HIAF and CiADS are briefly summarized. Meanwhile, their present construction progresses are reported and their developments in the near future are outlined.
Nuclear astrophysics is an interdisciplinary research field. It composes of nuclear physics, which studies micro phenomena, and astrophysics which studies macroscopic phenomena in our world. The main research goals of nuclear astrophysics are:(1) how, when and where chemical elements are synthesized and what is their final abundance distribution in the universe; (2) how nuclear processes (reactions induced by charged particles, neutrons, photons and neutrinos, beta decays and electron capture processes) determine the evolution and the ultimate fate of stars. At present, nuclear astrophysics has been developed into a new prosperous stage with a huge number of experimental and theoretical progresses. This paper summarized the current progress of nuclear astrophysics in China, in the subfiels of direct and indirect measurement of key reactions, measurement of mass and decay, as well as the theoretical calculation and network simulation. In present paper, the prospects to solve the key scientific nuclear astrophysics problems are represented. These key problems include (1) direct measurement of important reactions at astrophysical energies in the laboratory on the earth surface and in the underground laboratory; (2)extrapolation of cross sections at higher energies for the reactions induced by charged particles; (3) indirect measurement of key reactions in the hydrostatic and explosive nuclear processes; (4) study of the mass, the properties of decay and resonant states for the nuclides far from the stability line in explosive astrophysical events; (5) establish and improve the database for nuclear astrophysics, and develop network simulation codes, and systematically study astrophysical sites and abundance distribution of nucleosynthesis; (6) origin of the elements heavier than iron in the universe.
PandaX是位于四川的中国锦屏地下实验室（CJPL）内的，利用氙作为工作物质，探测暗物质等其它极稀有事件的大型地下粒子探测实验计划。PandaX探测器中的氙工作在气液两相的模式。通过检测液相和气相中闪烁光强的比例，实现对目标粒子包括WIMP和Axion等疑似信号的鉴别。PandaX已顺利完成了有效区体积约为120 kg氙的一期计划，目前正在运行实施有效区体积约为500 kg氙的二期计划。在WIMP质量为45 GeV/c2附近，探测灵敏度达2.97×10-45 cm2（90%置信度），没有发现WIMP疑似信号。本工作介绍了PandaX一期和二期的进展，以及后续升级计划，其中包括升级PandaX的时间投影室至4吨，建造用于屏蔽岩石放射性本底的水屏蔽，以及136Xe双贝塔衰变的研究计划等。
PandaX is a xenon-based dark matter and other rare events searching project located at China JinPing underground Laboratory (CJPL), Sichuan province, China. Dual phases, liquid and gas phase of xenon are used in the detector. Particles, including Weak Interaction Massive Particles (WIMPs) or axions etc., may induce scintillating signals in both liquid (S1 signal) and gas (S2 signal) phases, and then are identified by analyzing the ratio of S1 and S2. The PandaX had completed its first stage, the 120 kg in fiducial volume, and now is running in its stage Ⅱ with fiducial volume of 500 kg. The running results show that the WIMP-matter cross section detecting sensitivity of about 2.97×10-45 cm2(90% C.L.) has been achieved at a WIMP mass of 44.7 GeV/c2, and no WIMP candidates are identified. The upgrading plan of the PandaX is discussed, which include to build a larger Time project chamber (TPC) of about 4 tons, a water tank for radiation shielding, and the plan of 136Xe double beta decay studies.
With undergoing researches on antimatter physics, it is crucial to understand what the interaction between antiprotons is. Is it the same as the interaction between protons? This measurement will definitely help us to understand the formation mechanism of antimatter nuclei as well as the symmetry of matter and antimatter. In this context, our STAR collaboration measured the correlation function of antiproton-antiproton pairs from 200 GeV/c Au+Au collisions. After substracting the residual correlation due to the secondary antiprotons that decayed from other particles, the primary antiproton-antiproton correlation function is extracted. By applying the quantum theory of multi-particle correlation, two key parameters that characterize the corresponding strong interaction:namely, the scattering length (f0) and effective range (d0) were obtained. Within error bars, it is found that the f0 and d0 for the antiproton-antiproton interaction are consistent with their antiparticle counterparts -the ones for the proton-proton interaction. Like the force that holds ordinary protons together within the nuclei of atoms, the force between antiprotons is attractive and strong, which overcomes the tendency of the like (negatively) charged particles to repel one another, and allows the antiprotons to bind to form antinucleus. The current measurement is for the first time to measure the interaction between antimatter, it offers a foundation to understanding the structure of more-complex antinuclei and their properties. Also our measurement offers a new way to test the CPT symmetry, which has an important impact for human beings to understand the law of motion in our world.
首先简要介绍第一代到先进的第四代核能系统的发展、与核能系统发展密切的抗辐照结构材料研发进展、第四代核能系统结构材料辐照性能研究新方法。第四代核能系统发展中，辐照引起材料性能退化是一个需要研究和解决的瓶颈问题。现有中子源都不能满足第四代核能系统结构材料高剂量中子辐照性能研究的要求。为此，发展了用于核能系统结构材料高剂量辐照性能快速检测加速器重离子辐照方法和第四代核能系统实际辐照工况模拟的重离子与氢和氦三束同时辐照新方法，文中进行了详细的介绍。最后介绍了中国原子能科学研究院核能系统结构材料辐照性能研究现状和近期发展计划。该院在HI-13串列加速器器上建立了多种不同用途的重离子辐照装置、三个独立加速器构成的重离子与氢和氦三束同时辐照实验平台，开展了一系列核能结构材料，例如国产改进型奥氏体钢、CLAM钢、1515钢、钽、钨等的辐照性能的系统测试和研究。为了更好地开展核能结构材料性能研究，从国外引进了一台超导直线加速器和一台可变能量重离子回旋加速器。结合现有2×13 MeV，2×1.7 MV串列加速器、30 MeV和100 MeV质子回旋加速器、高压倍加器，中国实验快堆、中国先进研究堆、微堆等，CIAE将建成一个比较完整和先进的核能系统结构材料辐照实验平台系统供国内外用户使用。
This paper introduces briefly the development of nuclear energy systems from the GEN I to the advanced GEN IV, the progress of manufacturing radiation resistant materials associated with the development of nuclear energy systems and the new methods of investigating radiation properties of the structural materials for the GEN IV nuclear energy systems at first. Irradiation induced deterioration of materials properties is a bottle neck problem, which must be investigated and solved for the development of the GEN IV nuclear energy systems. Unfortunately, all the currently available neutron sources cannot meet the requirements of investigating radiation properties of structural materials irradiated by high dose neutron irradiation in the GEN IV nuclear energy systems. Therefore, two new methods of the accelerator heavy ion irradiation that simulates the high-dose neutron irradiation and the triple beam irradiation that mimics the real neutron irradiation environment in the GEN IV nuclear energy systems have been developed. These two methods are introduced in this paper. The present status of the study on radiation properties of structural materials for nuclear energy systems of the new generation and the near future development plan at China Institute of Atomic Energy (CIAE) are described also. The accelerator heavy ion irradiation facilities for different applications and the simultaneous triple beam irradiation platform with three separate accelerators or implanters have been established at the HI-13 tandem accelerator of CIAE. A series of structural materials for nuclear energy systems, such as the home-made modified austenic steel, CLAM steel, 1515 steel, Tantalum, Tungsten, etc. have been tested and investigated systematically. A superconducting linear accelerator and a variable energy heavy ion cyclotron have been imported from abroad for a better performance of the study. Combined with the currently existing facilities of 2×13 MeV and 2×1.7 MV tandem accelerators, 30 and 100 MeV proton cyclotrons, China experimental fast reactor, China advance research reactor, Miniature neutron source reactor, etc. a comprehensive and advanced system of experimental irradiation platform for structural materials of nuclear energy systems will be established in the near future for both domestic and foreign users.
Symmetry and its breaking are basic scientific problems. Chiral symmetries are common in nature, for example, the macroscopic spiral arms of galaxies and the rotation of planets; the microscopic spirals of the mineral crystalline, the organic molecules and the elementary particles. The concept of chirality in atomic nuclei was first proposed in 1997. Since then many efforts have been made to understand chiral symmetry and its spontaneous breaking in atomic nuclei. Up to now, more than 30 candidates of chiral nuclei have been reported in the 80, 100, 130, and 190 mass regions. The concept of the chirality in atomic nuclei, the prediction, the signal, and the experimental verification of the chiral nuclei are briefly introduced; the recent theoretical and experimental progress are reviewed, in particular the existence of multiple chiral doublets (MχD), i.e., more than one pair of chiral doublet bands in one single nucleus; the simultaneous spontaneous breaking of chiral and reflection symmetry in the newly observed atomic nuclei is introduced, together with a prospect on the future study on nuclear chiral symmetry.
The exploration of charge and mass limits of atomic nuclei and the synthesis of long-lived or stable superheavy nuclei (SHN) are at the frontier of modern nuclear physics. In the 1960s, based on the stability originating from quantum shell effects, the possible existence of an island of stability around 298114 was predicted. This prediction advanced the construction of heavy ion accelerators and detectors and the development of heavy ion physics. So far, superheavy elements (SHE) with Z up to 118 have been synthesized via heavy ion fusion reactions in laboratories. Recently the IUPAC/IUPAP Joint Working Party (JWP) concluded that criteria for the discovery of new elements have been met for those with Z=113, 115, 117 and 118. Therefore the seventh period of the periodic table of elements is completed. To synthesize even heavier elements or more neutron-rich SHN by using heavy ion fusion reactions, one confronts many challenges. More efforts should be made to study the properties of SHN both experimentally and theoretically. In this short review on the study on SHN and SHE, we will first introduce the background and theoretical predictions of SHN, including the origin of the possible existence of SHN and the predicted island of stability of SHN, etc. Then we will present progresses made up to now concerning the synthesis of SHN and the naming of the four new elements. As for the challenges nuclear physicists confront in synthesizing even heavier SHEs, we will detail those connected with heavy ion fusion-evaporation reactions, namely, the tiny cross sections to produce SHN and the fact that only neutron-deficient SHNs can be synthesized. Finally we will discuss some theoretical progresses on the study of SHN, including the structure of SHN and proton and neutron magic numbers after 208Pb, the stability and the synthesis mechanism of SHN as well as what we should focus on in the future.
Exploring the evolution of shell closures and examining the magicity of extremely exotic nuclei are the main research interests of HKU (University of Hong Kong) experimental nuclear physics group. The group has employed in-beam gamma-ray spectroscopy technique to investigate the vanishing of N=20 magicity in 30Ne (N=20) and the strong magicity in nuclei around 78Ni (Z=28, N=50). The approved future's experiment on spectroscopy of 53,56Ca, proposed by HKU, will give quantitative information for the "magic index" of N=34 and shell evolution toward N=40. The next goal is to investigate the structure of 100Sn (N=Z=50), particularly the energy of the first 2+ state, and the low-lying states in the neighboring nuclei. 100Sn lies on the proton drip-line and on the astrophysical rp-process path. Characterizing the magicity of 100Sn and the nature of single-particle states in its neighboring nuclei is therefore essential to the fundamental understanding of nuclear forces and nucleo-synthesis. To significantly increase the data statistics for our physics goals, HKU group has prepared the upgrade of gamma-ray spectrometer DALI2 with 30% more NaI(Tl) detectors integrated into a new array configuration. On the other hand, next significant insights into the structure of nuclei would require new gamma-ray detection array capable for higher precision gamma-ray spectroscopy. HKU group in collaboration with IMP and CIAE therefore proposes to construct a new-generation gamma-ray detection array based on the novel scintillator LaBr3(Ce) to explore the new physics in nuclei far from the valley of stability. Utilizing the radioactive beams at the Chinese large-scale facilities such as the Heavy Ion Research Facility in Lanzhou (HIRFL) in IMP and the future's High Intensity heavy-ion Accelerator Facility (HIAF), this novel LaBr3(Ce) array would lead to a significant boost to the frontiers of exotic-nuclei research, which will guide scientists towards the comprehensive and even beyond-traditional understanding of nuclear forces and nucleosynthesis.
We introduce our recent works on the clustering effects in atomic nuclear systems. The clustering structures for 20Ne and 9,10Be isotopes are studied with the Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function. It is found that a single THSR wave function can provide good description for the cluster state. The nonlocalised aspect of cluster dynamics is discovered with the hybrid-THSR-Brink wave function. Extensions are made for the THSR wave function to enable studies of N≠Z nuclei. The nuclear molecular orbit structures in low lying states of 9,10Be isotopes are correctly reproduced with this wave function. We also discuss the α-decay processes for proton/neutron-rich nuclei. The effect of proton/neutron skin is found to be considerable on α-decay half-life.
Starting from chiral N3LO, we have applied many-body perturbation theory (MBPT) to the structure of spherical, doubly closed-shell nuclei. The two-body N3LO interaction is softened by a similarity renormalization group transformation. The MBPT calculations are performed within the Hartree-Fock (HF) bases. Higher-order corrections in the HF basis are small relative to the leading-order perturbative result. Corrections up to the third order in energy and up to the second order in wave function are evaluated. Using the anti-symmetrized Goldstone diagram expansions of the wave function, we directly correct the one-body density for the calculation of the radius. Our results are in very good agreement with experimental data.
There are always difficulties in the direct measurement of reactions induced by neutron, in order to obtain the neutron induced nuclear reaction data which are extremely important for nuclear power development, the surrogate reaction method, which uses charged particles instead of neutron, was proposed. The existing surrogate reaction method generally chooses peripheral reaction as the surrogate reaction, such as inelastic scattering excitation or transfer reaction. As a result, the angular momentum involved is always far larger than the neutron induced reaction, which causes difficulties in the theoretical calculation. Because of this, we proposed to use light-ion capture reaction as the surrogate reaction, the compound nuclei spin is similar with that of the neutron induced reaction, so that the difficulties in spin correction can be effectively avoided. Based on this idea, the 239Pu(n, f) and (n, 2n) reaction cross sections were successfully extracted using 236U(α,f) and (α,2n) reactions as the surrogate reaction. The results coincide well with the data of ENDFB7 within the error range, which shows that the surrogate reaction method has its own superiority, and it can be applied in the measurement of nuclear data.
Spontaneous symmetry breaking is a fundamental concept in nature. Chiral Symmetry Breaking and reflection-asymmetry in nuclei has been a subject of intensive experimental and theoretical investigation. Two pairs of positive-and negative-parity doublet bands together with eight strong electric dipole transitions linking their yrast positive-and negative-parity bands have been identified in 78Br by means of in-beam gamma-ray spectroscopy techniques. These four rotational bands are suggested as multiple chiral doublet bands with octupole correlations. This observation indicates that nuclear chirality can be robust against the octupole correlations. It is of highly scientific interest to search for the chirality-parity quartet bands in nucleus with both stable triaxial and octupole deformations.
The effect of neutron transfers on near-and sub-Coulomb-barrier fusion of heavy-ions is still a complicated and controversial problem. This paper reviews the recent experimental results of the fusion excitation functions of several typical systems, which have been measured by using an electrostatic deflector setup at the HI-13 tandem accelerator of CIAE. Both the neutron pickup and stripping effects were studied. Moreover, a self-consistent method to reliably isolate the transfer effect quantitatively based on the coupledchannels calculation is proposed. These studies give a further support for the neutron transfer effect on sub-barrier fusion of heavy-ions and its complexity. Further experimental and theoretical studies are needed for clarifying the relevant reaction mechanisms.
The experimental results from the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC) show that a nearly perfect fluid (i.e. strong-coupling Quark Gluon Plasma) has been created in relativistic heavy-ion collisions. I introduce our theoretical results based on a multi-phase transport (AMPT) model. Several important topics such as collective flow, jet quenching, chiral magnetic effect, are addressed. The simulation results indicate that the initial fluctuations of energy density of the QGP lead to all orders of harmonic flows of final particles via parton cascade, the strong interactions between jet and the QGP make jet lose much energy, and the final state interactions play an important role to affect the initial chiral magnetic effect in relativistic heavy-ion collisions.
Nuclei are quantum systems in the evolution from few-body to many-body systems, and can exhibit many amazing collective phenomena. With the development of several advanced radioactive-beam facilities, the study of structures and excitations of extreme unstable exotic nuclei has become a hot issue. In this work, we solve the self-consistent FAM-QRPA in large deformed coordinate-spaces to treat continuum effects. We study properties of structures and collective excitations in deformed drip-line nuclei. We found that in weakly bound nuclei 40Mg, the diffuse surface density and pairing density play an important role in low-lying resonance. Through analysis of deformation-induced K-splitting in isovector dipole modes, we see that pygmy resonances have very different mechanism compared to giant resonances. In addition, large-scale fittings are performed to develop highprecision effective interactions, which will provide more reliable theoretical model for related subjects, such as nuclear astrophysics and nuclear fission energy.
Mass is a fundamental property of the atomic nucleus. Nuclear mass data play an important role in nuclear physics and nuclear astrophysics. Thanks to the developments of novel mass spectrometers and radioactive nuclear beam facilities, the experimental knowledge of nuclear masses has been continuously expanding along two main directions, including:measurements aimed at high-precision mass values and at the most exotic nuclei far from the stability. The latest progress are reviewed in the paper. In the past few years, mass measurements of short-lived nuclides were performed using isochronous mass spectrometry based on the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou(HIRFL-CSR). The progresses on the frontiers of short half-life and high precision are introduced. The Atomic Mass Evaluation (AME) is the most reliable source for the comprehensive information related to the atomic (nuclear) masses. The latest version of the AME, i.e., AME2016, was published in March, 2017, serving the research community with the benchmark data.
Within Wigner-Seitz approximation, both the coexisting phases method and the self-consistent Thomas-Fermi approximation can be used to describe the nonuniform matter consisting of nuclei, neutrons, and electrons, which may coexist in the inner crust of neutron star. Since the neutron fraction is very large, nuclear symmetry energy may have an important impact on the properties of nonuniform matter. However, the density dependence of nuclear symmetry energy around saturation density is still rather uncertain. This paper focuses on the influence of nuclear symmetry energy on the density range of inner crust, pasta phase structure, and crust-core transition density of neutron star, where the relativistic mean field theory is adopted to describe the nucleon-nucleon interaction. It is turned out that the nuclear symmetry energy and its density dependence play an import role in determining the properties of nonuniform matter in the inner crust of neutron star, which is consistent with the former related studies.
In this paper, we report on two recent studies of relativistic nucleon-nucleon and hyperonnucleon interactions in covariant chiral perturbation theory, where they are constructed up to leading order. The relevant unknown low energy constants are fixed by fitting to the nucleon-nucleon and hyperon-nucleon scattering data. It is shown that these interactions can describe the scattering data with a quality similar to their next-to-leading order non-relativistic counterparts. These studies show that it is technically feasible to construct relativist baryon-baryon interactions, and in addition, after further refinements, these interactions may provide important inputs to ab initio relativistic nuclear structure and reaction studies and help improve our understanding of low energy strong interactions.
在低温核天体物理环境下，如静态核稳定燃烧阶段的核反应都发生较低的能区，其伽莫夫窗口内的核反应截面非常小，这就需要加速器提供较强束流才能完成核反应截面的直接测量。最近在中国科学院近代物理的320 kV高压平台上建立了低能核天体物理实验室以及相应的研究平台。驱动该平台的是一个14.5 GHz的永磁铁型ECR离子源，它能够提供非常强的束流离子。对于质子和氦离子，离子源出口的最大流强可以达到100 eμA，在实验终端上可以获得大约30 eμA的流强。基于此强流加速器装置，我们建立了核天体物理实验测量装置，包括靶室以及带电粒子和伽玛射线探测器等设备。利用已知的核反应对探测器性能和实验方法进行了一系列测试。同时，展示了近年来取得的一些主要实验结果。最后，对该平台上开展工作的前景进行了展望，并指出基于该地面装置的低能核反应研究所积累的技术及经验对于我国锦屏深地核天体物理JUNA项目的重要意义。
For the hydrostatic stable burning in stars, the Gamow window is well below the Coulomb barriers for the charged-particle-induced nuclear reaction involved. Such nuclear reaction occurs through the quantum-mechanics tunneling effect, and its cross section drops rapidly approaching the Gamow window. An accelerator which can provide intense beam current is thus required to directly measure the reactions at low energies. An experimental setup for low-energy nuclear astrophysics studies has been recently established at a 320 kV high-voltage platform of the Institute of Modern Physics (IMP), Lanzhou, China. The driver machine of this platform is a very strong ECR ion source employing all-permanent magnets, which can typically supply up to about 100 eμA proton, alpha and many other heavy ions, and ultimately about 30 eμA currents can be achieved at the experimental terminal. The experimental setup includes a target chamber, and the charged-particle and γ-ray HPGe detectors. This work describes the setup established, characteristics of detectors, methodologies, and test results of several reactions with known cross sections. Furthermore, some important results published are shown briefly. We believe that the experimental technologies developed and experiences accumulated at this above-ground platform will be extremely helpful for the Jinping Underground Nuclear Astrophysics laboratory (JUNA) project in China.
The study on the nuclear structure and exotic decay property of neutron-rich nuclides is an important subject in nuclear physics research. In the ongoing big project HIAF (High Intensity heavy-ion Accelerator Facility), a general purpose spectrometer specific to the multinucleon transfer reactions is being designed and will be constructed. In this spectrometer, the researches will be concentrated on synthesis and identification of new neutron-rich nuclides, and on the study of their nuclear structure and decay properties. In this paper, the motivation, conceptual design and working principle of this spectrometer have been introduced, and the opportunities and challenges in the construction have been discussed briefly. Unlike the fusion evaporation and projectile fragmentation reaction products which are emitted in forward directions near 0° in laboratory frame, the outgoing angles of the products from multinucleon transfer reactions cover a wide range of 25° ~80°, thus it is very difficult to collect and separate those products of interest. The requirements of high beam rate, high transmission efficiency and high transport speed make the gas cell be very challenging in design and construction. The gas cell is the key component for the success of this spectrometer.
The decay of the fully stripped ion 94mRu44+ in the order of one hundred microseconds has been studied for the first time by using the Isochronous Mass Spectrometry (IMS) at the HIRFL-CSR facility in Lanzhou. 94mRu44+ was produced via projectile fragmentation of a 112Sn primary beam bombarding on a 9Be production target. After the in-flight separation with RIBLL2, the ions were injected into the experimental ring (CSRe) and then stored there. The revolution times of the stored ions were measured by a Time-of-Flight (TOF) detector. Due to the mass change of a 94mRu44+ ion caused by its de-excitation to the ground state, hence the revolution time change, the decay process of 94mRu44+ could be directly observed in the CSRe. The sensitive window for detection of the decay events and the measurement precision of the decay time have been determined in this work. At the same time, we measured the mass of short-lived 94mRu44+ with the half-life about one hundred microseconds, which is the shortest among nuclides that have been studied by using storage-ring mass-spectrometry.
95Zr（n，γ）96Zr是稳定燃烧的恒星中合成96Zr的唯一途径，对研究恒星演化和重元素合成具有重要的意义。由于95Zr半衰期为64 d，直接测量95Zr（n，γ）96Zr截面极为困难，因此，本工作采用替代比率法间接测量95Zr（n，γ）96Zr截面。本工作测量了94Zr（18O，16Oγ）96Zr和90Zr（18O，16Oγ）92Zr反应，得到了复合核96Zr*和90Zr*衰变到γ道的几率比，并利用截面已知的91Zr（n，γ）92Zr截面乘以实验所测比率，得到了En=0~8 MeV能区的95Zr（n，γ）96Zr中子俘获截面。
95Zr(n, γ)96Zr cross section is important for the study of stellar evolution and heavy elements nucleosynthesis because the reaction is the only way to produce the 96Zr in Asymptotic giant branch stars. The direct measurement of 95Zr(n, γ)96Zr is very difficult due to the short half-life of 95Zr, 64 days. The surrogate ratio method was carried out to measure 95Zr(n, γ)96Zr cross sections. We measured the 94Zr(18O, 16Oγ)96Zr and 90Zr(18O, 16Oγ)92Zr reactions and obtained the γ-decay probability ratio of compound nuclei 96Zr* and 92Zr*. The 95Zr(n, γ)96Zr cross section is determined by the obtained ratio multiplying the known 91Zr(n, γ)92Zr cross section at En=0~8 MeV.
分析了20 < A < 190范围内丰中子核β衰变的实验数据，根据半衰期随质子数、中子数以及衰变能变化所呈现的壳效应和对效应等特点，提出了一种有效估算丰中子核β衰变寿命的公式。新的计算公式形式简单包含了较少的参数、计算量小。用该公式能较为准确地再现丰中子核的β衰变半衰期。用RIKEN最新测量丰中子核半衰期检验了该公式的外推能力，本工作可以为r-过程研究提供可靠的输入数据。
Experimental data of the β--decay half-lives for the nuclei with atomic number between 20 and 190 are investigated. We have systematically studied the shell effects and pairing effects on β--decay half-lives versus the decay energy Q and nucleon numbers (Z, N). An empirical formula has been proposed to calculate the β--decay half-lives of neutron-rich nuclei. The empirical formula is simple and has relatively few parameters. Experimental β--decay half-lives of the neutron-rich nuclei are well reproduced by the new formula. In addition, the extrapolating capacity of this formula has been checked with the very recent experimental data from RIKEN. The predicted half-lives for r-process relevant nuclei with the current formula can be served as the reliable input of r-process model calculations.
15O（α，γ）19Ne（p，γ）20Na反应链是高温CNO循环向快速质子俘获过程突破的一条关键路径，相关的反应率输入量可通过20Mg的β衰变可布居19Ne共振态并测量其衰变性质来获得。通过高效率高精度地测量20Mg β衰变中产生的质子与γ射线得到了20Mg衰变的详细信息，并构建了完整的衰变纲图，还进行了19Ne 4 033 keV共振态衰变性质的探索，获得了该态在20Mg β衰变中被布居的分支比上限。通过比20Mg和20O镜像能级跃迁的结果确认了同位旋非对称性，为检验相关理论模型提供了精确的实验数据。对于突破路径中有重要影响的19Ne 4 033 keV共振态的性质，有待更高统计的实验进一步研究。
The breakout from the hot CNO cycle to the rapid proton capture process can occur via the 15O(α,γ)19Ne(p,γ)20Na reaction sequence, and the β decay of 20Mg can be used as an alternative method to characterize some specific resonances, which will provide detailed nuclear structure input for reaction rate calculations. The reliable information on the decay properties and structure of 20Mg was obtained by measuring the emitted particles and γ-rays in the β decay with high efficiency and high resolution. Attempt was also made to search for the decay channels associated with the 4 033 keV resonance in 19Ne. To test fundamental symmetries, the transitions in the mirror decays of 20Mg and 20O were compared. The precise experimental data presented here would be important to constrain the theoretical calculations. It is desirable to clarify the astrophysically relevant problem by further experiments with improved statistics on the basis of the present work.
恒星氦燃烧阶段3α反应和12C（α，γ）16O反应相互竞争，两者的反应率共同决定了氦燃烧结束后12C与16O的丰度比，该比值是大质量恒星后继演化以及伴随的元素核合成过程的初始条件。目前，氦燃烧12C（α，γ）16O反应起始T9=0.2处，天体物理模型要求的反应率的精确度要低于10%，然而尚未有实验或理论给出满足要求的结果。最为直接和可靠地获取12C（α，γ）16O反应率的方法，就是尽可能往低能区测量其天体物理S因子，然后通过理论外推到感兴趣的能区。为此基于经典的R-矩阵理论，建立了适用于低能核反应的多道、多能级的约化R-矩阵理论来拟合几乎所有可用的16O系统的实验数据。配合使用协方差统计和误差传播理论，拟合外推得到了客观的、内部自恰的和唯一性好的12C（α，γ）16O反应天体物理S因子。总的外推S因子STOT（0.3 MeV）=162.7±7.3 keV·b，理论上首次给出达到恒星演化与元素核合成模型的最低要求的S因子。基于计算给出的全能区的S因子，数值积分给出了温度位于0.04 6 T9 6 10的12C（α，γ）16O天体物理反应率。在T9=0.2处，推荐的反应率为（7.83 ±0.35）×10-15 cm3mol-1s-1。
During stellar helium burning, the rates of 3α and the 12C(α,γ)16O reaction, in competition with one another, determine the relative abundances of 12C and 16O in a massive star. The abundance ratio is the beginning condition of the following nucleosynthesis and star evolution of massive stars, which are extremely sensitive to the rate of 12C(α,γ)16O reaction at T9=0.2. The most direct and trustworthy way to obtain the reaction rate of the 12C(α,γ)16O reaction is to measure the S factor for that reaction to as low energy as possible, and to extrapolate to energies of astrophysical interest. Based on a new multilevel and multichannel reduced R-matrix theory for applications in nuclear astrophysics, we have obtained an accurate and self-consistent astrophysical S factor of 12C(α,γ)16O, by a global fitting for almost all available experimental data of 16O system, with the coordination of covariance statistics and error-propagation theory. The extrapolated S factor of 12C(α,γ)16O was obtained with a recommended value STOT (0.3 MeV)=162.7±7.3 keV·b. And the reaction rates of 12C(α,γ)16O for stellar temperatures between 0.04 6 T9 6 10 are provided. At T9=0.2, the reaction rate is (7.83 ±0.35)×10-15 cm3mol-1s-1, where stellar helium burning occurs.
Spectroscopic factor describes the overlap between the initial and final states and gives some information on the occupancy of a given single-particle orbiting around nuclear. It plays an important role in a variety of topics on nuclear structure and nuclear astrophysics. Nowadays, several experiments have been performed to study the neutron spectroscopic factor of 10Be, but the results have a big difference with each other. In order to clarify this discrepancy, new measurement is highly needed. In this work, the angular distribution of 13C(9Be,10Be)12C reaction was measured at the Q3D magnetic spectrometer of the HI-13 tandem accelerator, China Institute of Atomic Energy, Beijing. And then, the neutron spectroscopic factor of 10Be was derived by normalizing the calculational differential cross-sections with the distorted-wave Born approximation to the experimental data. The present value is in good agreement with that obtained by Tsang et al. and also in good agreement with that derived from translationary invariant shell model calculation. One can use this result to calculate the 9Be(n, γ)10Be reaction rates and calculate its influence to the production of 12C.
Several Tin isotopes are on the path of slow neutron capture (s-) process, and the direct components of (n, γ) reactions can be derived from their neutron spectroscopic factors. In the present work, the angular distributions of 122,124Sn(p, d) and (d, p) reactions are obtained using the high-precision Q3D magnetic spectrograph in Beijing HI-13 tandem accelerator in China Institute of Atomic Energy. The distorted-wave Born approximation (DWBA) calculations are performed to extract the neutron spectroscopic factors of the ground state of 122-125Sn and the first excited state of 123,125Sn. The neutron spectroscopic factors of the ground state of 122Sn and 124Sn are firstly obtained in this work. As the events of the ground state and first excited state of 123,125Sn can be distinguished clearly by our experiment, the neutron spectroscopic factories of 123,125Sn are more reliable.
中国锦屏地下实验室（CJPL）坐落于四川省锦屏山中，利用水电站修建的隧道建成。由于其本底环境极低，非常适合开展低本底实验测量。一台基于ECR源的400 kV强流加速器将安装在CJPL中，其可以为核天体物理实验提供流强为12 emA的质子束流，6 emA的He+束流和2.5 emA的He2+束流。拟通过非共振反应12C（p，γ）13N以及一系列的共振反应27Al（p，γ）28Si等，对加速器的束流能量进行精确刻度，对束流的能量展宽以及长期稳定性进行测量。由于该加速器正在中国原子能科学研究院进行地面调试，我们利用中国科学院近代物理研究所的320 kV研究平台，进行了12C（p，γ）13N和27Al（p，γ）28Si反应的测试实验。测量结果表明，在质子束流能量为224 keV时，束流的能量展宽约为1.0 keV，束流能量在连续4小时的测量期间，其晃动幅度远小于±200 eV。
China JinPing underground Laboratory (CJPL) was established inside the tunnels piercing Jinping Mountain in Sichuan Province, China, which can provide an ideal environment for low background experiment. A new 400 kV accelerator, with high current based on an ECR source, will be placed at this underground laboratory for nuclear astrophysics experiment. The beam characteristics of this accelerator, like absolute energy, energy spread, and long-term energy stability, will be determined by several wellknown resonance and non-resonance reactions. Due to the new accelerator still being under construction, the resonance reaction of 27Al(p, γ)28Si and non-resonance 12C(p, γ)13N were studied at the 320 kV highvoltage platform in Institute Modern Physics of CAS in Lanzhou. The energy spread of proton beam is about 1.0 keV at proton energy Ep=224 keV and the long-term energy stability of proton beam is much better than 200 eV during 4 hours measurement.
通过70As的放射性衰变研究了70Ge的激发态，新发现能量为1 036.99，1 196.66，1 539.29和2 531.7 keV的四条新γ射线，重新确认了2 219.34 keV γ射线的跃迁位置，新确认496.74，1 295.24和1 417.24 keV这三条γ射线首次放入衰变纲图，本工作证实了1 881.67，2 325.42和2 424.41 keV γ射线的跃迁位置，建议了能量为4 243.10和5 265.81 keV的两个新能级，建立了新的衰变纲图，基于比较半衰期和γ跃迁分支比建议了一些能级的自旋-宇称。
The excited states of the 70Ge nucleus are investigated in radioactive decay of the 70As. Four new transitions with 1 036.99, 1 196.66, 1 539.29 and 2 531.7 keV are found for the first time. The position of 2 219.34 keV transition are reassigned, the transition positions of 496.74, 1 295.24 and 1 417.24 keV γ-rays are assigned for the first time, and the placements of 1 881.67, 2 325.42 and 2 424.41 keV γ-rays are confirmed in the present work. Two new levels, at 4 243.10 and 5 265.81 keV excitation energy, respectively, are proposed. The decay scheme is established and for a number of levels spin-parity assignments are suggested on the basis of logft values and γ-branching ratios.
High spin states of 192Tl were populated by the 181Ta(16O, 5n)192Tl heavy ion fusion evaporation reaction at 97 MeV beam energy. A new level scheme with 8 new levels was constructed and the level spins were tentatively assigned. The negative yrast band was extended up to 23-ħ. Systematics of signature of inversion were also discussed for the negative yrast band of odd-odd Tl istopes. Signature inversion has been found in 196,198Tl with neutron number increasing in these four Tl isotopes, and it is explained by the competition between the strength of n-p interaction and Coriolis force.
The nuclear ground state properties of Ca, Ni, Sn and Pb isotopes, such as the binding energies, the charge radii, are studied systematically by 4 sets of new Skyrme parametrizations SKC, SKD, SkOP1 and SkOP2 in the framework of the Skyrme-Hartree-Fock-Bogoliubov (SHFB) method. The new magic numbers of neutronrich Ca isotopes and the isotopic shift of Pb isotopes are discussed emphatically. By the comparisons between the calculations and the experimental data and results from the SLy5 interaction parametrization, it is found that the experimental binding energies can be reproduced accurately by all parametrizations. The calculated accuracies of SKC, SKD SkOP1 and SkOP2 parametrizations are higher than the ones of SLy5 parametrization. For the neutron-rich Ca nuclei, the shell effect of N=28 can be reproduced by the SKC and SKD parametrizations, but the magic numbers at N=32 and 34 are not found by the calculations of all the parametrizations. For the charge radii, the experimental evolution tendency of Ca isotopes and isotopic shift of Pb isotopes can not be reproduced by all the parametrizations. In addition, all Skyrme parametrizations are extended to study the structure of the nuclei far from the β stability line, it is shown that the single-particle energy evolutions with the isospin are not suitable for being studied by these parametrizations. Thus the tensor force component should be considered besides the isospin dependence in spin-orbit coupling term when the Skyrme interaction parametrizations are fitted.
The β-decay half-lives of N ~ 80 and 126 isotonic chains are calculated with HFB+QRPA models based on Skyrme force. In the calculations, the well constrained Skyrme tensor interaction and isoscalar spin-triplet (IS) pairing interaction are included so that to study their effects on the half-lives. The effects of tensor interaction and IS pairing interaction on the half-lives are compared. The IS pairing interaction with strength similar to that of isovector (IV) one produces only a trivial effect in N ~82 nuclei, and N ~126 nuclei with big neutron excess. While the tensor interaction with presently constrained strengths produces an obvious effect.
基于（β2，γ，β4）形变空间下对-形变自洽的原子核能量面计算方法，系统研究分析了50 < Z < 82区偶偶核的形状及硬度演化特征。计算的平衡形变与其它理论预言及存在的实验值进行了对比。从相应的形变势能曲线提取了与β2及γ相关的硬度参数Cβ，Cγ，这与实验观测到的低位β及γ振动带信息相符。还简要讨论了转动情况下的硬度演化，例如基于蜈蚣型E-GOS曲线，表明存在不可忽略的振动效应。
Nuclear shape and stiffness evolutions in even-even nuclei with 50 < Z < 82 are systematically analyzed in terms of the pairing-deformation self-consistent nuclear-energy-surface calculation in (β2,γ,β4) deformation space. Calculated equilibrium deformations are presented and compared with other theoretical predictions and available experimental data. The stiffness parameters Cβ and Cγ respectively related to quadrupole deformations β2 and γ are determined from the deformation energy curves, which are consistent with the observed low-lying β and/or γ bands. The stiffness evolution under rotation along the yrast line is briefly discussed, e.g., on the basis of the centipidelike E-GOS curves, showing an unnegligible vibration effect.
With two different truncations, i.e., neutron core-excitation truncation and orbital particle-number truncation, the research is studied at the truncation effects in shell-model calculations by the hole nuclei of 130Sn, 131Sn, 130In, 130In and 130Cd. We found that the right ground state of 130In needs proton core-excitation in shell model space, and allowing two neutron core-excitations will promote the low-lying states in 132Sn. The neutron core-excitations will also slightly affect the low-lying levels of hole-nuclei close to 132Sn, and the values of BE2 between the corresponded low-lying states reflect more obviously to the neutron core-excitations.
The basic properties of nuclear structure are studied within the quark mean field (QMF) model by taking the effects of pions and gluons into account. In QMF, the nucleon is made up of three constituent quarks confined by a harmonic oscillator potential. The quantum chromodynamics describing the strong interaction must satisfy the chiral symmetry and quarks interact with each other through exchange of gluons. Therefore pion correction and gluon correction are included in the nucleon mass obtained by using quark confinement potential in quark mean field model. We determine the unknown parameters in the model by fitting the experimental data of the binding energies and radii of several stable finite nuclei and obtain a set of parameters of quark mean field interaction, named QMF-NK. The charge density distributions of 40Ca and 208Pb are calculated, which are in good agreement with the experimental data. Later the saturation properties of symmetric nuclear matter which are consistent with the empirical data are obtained. With the pion and gluon corrections, the QMF model could treat finite nuclei and nuclear matter better.
We revisit the cluster emission from trans-lead nuclei within the density dependent cluster model. According to the refined density distribution of daughter and cluster via the available experimental data on nuclear charge radii and neutron skin thickness, the crucial cluster-core potential is constructed by the double-folding model. Then the Schrödinger equation of the cluster-core relative motion is solved along the outgoing Coulomb wave function boundary condition to obtain the decay width. The present decay width of cluster radioactivity is clearly augmented as compared to our previous results without the specific concern of the density distribution of daughter and cluster. Moreover, the computed decay width reduces along with the increasingly depressed density in the cluster center.
The relativistic effect in nuclear matter is investigated with the latest lattice nucleon-nucleon (NN) potential. A one-boson-exchange potential (OBEP) including three mesons, pion, σ meson and ω meson was constructed based on the lattice NN potential. The meson-nucleon coupling constants and cutoff momentums are determined by fitting the phase shifts of NN scattering from lattice NN potential. The properties of nuclear matter with this OBEP from lattice potential are calculated by one very successful ab initio many-body method, Brueckner-Hartree-Fock model. The equations of state and saturation properties of symmetric nuclear matter present very obvious different behaviors in non-relativistic and relativistic frameworks. The relativistic effect plays attractive contributions with the components of S and D waves in lattice NN potential, which is opposite comparing to the relativistic effect from the conventional NN potential.
It is generally considered that hadron matter may undergo a deconfinement phase transition becoming quark matter at very high density in massive neutron stars. This hadron-quark phase transition has important impact on neutron stars, which has received much attention. We consider finite-size effect in this phase transition process, which contains the impact of Coulomb energy and surface energy. By including this effect, the mixed phase forms the pasta structures. The equilibrium conditions for coexisting hadronic and quark phases are derived by minimizing the total energy including the surface and Coulomb contributions. We employ the relativistic mean-field(RMF) model to describe the hadronic phase, while the Nambu-Jona-Lasinio(NJL) model is used for the quark phase. We conclude that the finite-size effect will raise the stiffness of EOS, and then increase the maximum mass of neutron stars, which depend on the value of surface tension. Our results show that finite-size effects can significantly reduce the region of the mixed phase, and the results lie between those from the Gibbs and Maxwell constructions. We show that a massive star may contain a mixed phase core and its size depends on the surface tension of the hadron-quark interface.
Knowledge about the inelastic scattering cross section of 56Fe is very important in neutron transportation calculation. However there are great discrepancies not only between experimental data but also between evaluated data. More detail analysis was performed for inelastic scattering cross section in the fast range up to 20 MeV where there are significant differences among the main evaluated libraries, mainly caused by the different inelastic scattering cross section measurements. The large discrepancies on 56Fe(n, n1'γ) cross section which could fill the neutron energy blank of the 56Fe(n,inl) were clarified and were converted to the inelastic scattering cross section of 56Fe. And the high-quality results were evaluated by using the unitarity constrain among total cross section, noelastic reaction and other reactions. The integral experiment result indicates that the new evaluated result of inelastic cross section brings greater improvement than that of CENDL-3.1.
在重离子碰撞（HICs）的实验数据和动力学模拟的反应中发现了丰中子余核产额的标度现象。在这种标度现象中，两个同位旋不同的炮弹碎裂反应产生的余核中，不同中子丰度差的余核的信息熵不确定度的差具有一致的分布。利用反对称化分子动力学模型（AMD）模拟并联合退激发模型（GEMINI）模拟了140 AMeV 58，64Ni+9Be碰撞体系中余核的产额，并展示了实验测量的余核已经理论模拟得到的余核的标度现象。由于信息熵方法对反应系统是否处于平衡状态没有要求，不仅可以用于处于平衡态系统的核物质研究，也可以用于动力学变化过程中的核物质性质研究。信息熵方法将为HICs中的核物质演化研究提供新的理论分析方法。
A scaling phenomena has been discovered for fragments produced in heavy-ion collisions both in the measured experiments and in the simulated reactions by transport model. In this scaling phenomena, the information entropy uncertainty difference between isobars with different neutron-excess has a uniform distribution between two reactions. The simulated reactions of 140 AMeV 58,64Ni+9Be by using the asymmetric molecular dynamics(AMD) model plus the sequential decay code GEMINI are analyzed to show the scaling phenomena of fragments. Since the application of information entropy theory does not require the system to be in equilibrium, it can be used both in the analysis of transport model and thermodynamics models. The advantage of the information entropy theory provides a new method to study the dynamical evolution of nuclear matter inheavy-ion collisions.
利用反对称化的分子动力学（AMD）模型模拟140 AMeV 58，64Ni+9Be反应，并利用同位旋标度法研究两相似反应系统的△μn（p）/T随时间演化趋势。分析比较不同碰撞参数和不同反应系统间的△μn（p）/T随时间演化结果，结果表明碰撞参数对重核的对称能影响大，系统不对称度越大对对称能的影响越大，为间接研究激发核体系对称能系数的能量依赖提供了帮助。
We have simulated the reactions 140 AMeV 58,64Ni+9Be by antisymmetric molecular dynamics model (AMD) and studied the evolution of △μn(p)/T with collision time from 20 fm/c to 1 000 fm/c. To study nuclear symmetry energy influencing factors, a comparative analysis has been proceed among theses results with different impact parameters and the difference reactions system. The results show that the impact parameters have a great influence on the symmetry energy of the heavy nucleus, and the greater the asymmerty degree of the system, the greater the influence on the symmetry energy. These results are helpful for the indirect study of the energy dependence of the symmetry energy coefficient of the excited nuclear system.
Langevin models that are coupled with particle emission are applied to calculate the drop of fission cross section caused by friction over its standard statistical-model value, σfdrop, as a function of excitation energy for three Bi nuclei with different isospins. We find that σfdrop become larger for 209Bi than for 202Bi and 195Bi, indicating a greater sensitivity of fission cross section to friction for high-isospin 209Bi. These results suggest that, to more accurately determine the presaddle dissipation strength by measuring fission excitation functions, it is best to populate those compound systems with a high isospin. Furthermore, we analyze the data of fission excitation functions measured in p + 209Bi and p + 208Pb reactions, which yield high-isospin 210Po and 209Bi systems, and extract a presaddle friction strength of (3-5)×1021 s-1 by comparing Langevin simulations with these experimental data.
In order to study the fission mechanism, the mass distributions and mass-angle distributions of the fission fragments for 28Si+174Yb were measured near the Coulomb barrier. The mass-angle correlations do not indicate any possible quasi-fission events in this bombarding energy range. The mass distributions were fitted by the single Gaussian distribution and then the mass widths were extracted. At above-barrier energies, the mass widths were found to increase with the energy. However, the mass widths show slight increase with decreasing energy below the barrier. Additionally, the mass widths can not be reproduced in the framework of the saddle statistic model with the given parameter, so further study is still needed.
The heavy-ion capture and fusion processes at energies near the Coulomb barrier can be treated as a multi-dimensional barrier penetration problem. In the eigenchannel framework, the couplings to other channels split the single potential barrier into a set of discrete barriers. Based on the concept of the barrier distribution, we have developed an empirical coupled-channel (ECC) model and performed a systematic study of capture excitation functions for 220 reaction systems. Recently, an experiment was reported in which the capture excitation functions of reactions 46,50Ti+124Sn were measured. In this work, we review the ECC model briefly and use this model together with the universal fusion function (UFF) prescription to study the coupled-channel effects in fusion reactions 46,50Ti+124Sn. The reduced fusion functions show that the sub-barrier capture cross sections of 46Ti+124Sn exhibit an extra enhancement as compared with those of 50Ti+124Sn. The results from the ECC model reproduce the experimental capture excitation functions successfully and show that this extra enhancement of the sub-barrier cross sections for 46Ti+124Sn can be ascribed to the positive Q value neutron transfer effect.
介绍了利用CR-39探测器对28Si与不同靶作用的电荷变化总截面和分截面的研究进展，给出723AMeV 28Si与碳靶作用电荷变化总截面和分截面的最新实验结果。对28Si与靶核反应电荷变化总截面和分截面与束流能量和靶核质量的关系进行了讨论，发现束流能量大于200 AMeV时，中高能28Si与不同靶核反应电荷变化总截面与束流能量无关，分截面表现出明显的奇偶效应，且随靶核质量数的增加而增加。
In this paper, the development of the total and partial charge changing cross sections of 28Si ions beam in different targets using the CR-39 detectors are reviewed. The newest experimental results of the total and partial charge changing cross sections of 28Si in carbon target at 723 AMeV are presented. The dependence of the target mass and the cross sections of 28Si including the total and the partial charge changing cross sections are discussed. It is found that the total charge changing cross sections of 28Si are independent of the energy when the energy of the ions beam is greater than 200 AMeV. The partial charge changing cross sections show an obviously odd-even effect, and increase with the increasing of the mass number of the target.
国家重大科技基础设施"强流重离子加速器装置"（High Intensity heavy-ion Accelerator Facility，HIAF）已由国家发改委批准立项并开始建设。建成之后，HIAF将为微观物质结构和重离子应用等研究提供很好的实验平台。HIAF的加速储存环（Booster Ring，BRing）设计可以加速最高动量为11.9 GeV/c的高流强质子束流。因此，HIAF-BRing将为GeV能区的核物理和强子物理研究带来新的机遇。另一方面，极化实验是研究微观物质及其相互作用的有力工具。我们提议启动相关物理和极化技术的预研工作，为在HIAF-BRing上开展自旋物理研究打下基础。
The construction of the future scientific facility High Intensity heavy-ion Accelerator Facility (HIAF) in China has started. Once established, HIAF will provide excellent conditions for fundamental investigations on both matter structure and heavy-ion applications. The booster ring (BRing) of HIAF is designed to accelerate high-intensity protons with the maximum momentum of 11.9 GeV/c. Therefore it will bring new opportunities for the nuclear and hadron physics in the GeV region. Polarized experiments have been proved as a powerful tool in the explorations of the building blocks of matter. We propose to initiate a pre-investigation for the related physics and polarization techniques, which will lay the foundation of the spin physics at the HIAF-BRing.
The topological charge interactions in relativistic heavy ion collisions cause quark chirality imbalance, resulting in charge separation under the strong magnetic field and local P and CP violation. In this paper, the chiral charge separation at RHIC and LHC energies is systematically analyzed as functions of the collision centrality, the collision energy and the nuclear shielding factor. It is found that there is not a very close dependence of the chiral charge separation effect on the collision energies, but that has an important dependence on nuclear shielding factor. Compared with the non-shielding effect, the shielding effect can reduce the chiral separation effect obviously. Due to the shielding effect, the distribution of a++(a--) and the distribution of a+-(a-+) are asymmetric. One also finds that chiral separation effect, which is almost negligible when more close to the central collision, occurs mainly in the peripheral collision for larger impact parameter.
We have established a quark-interchange model and have proposed a quark-antiquark annihilation model to study meson-meson scattering. From QCD we obtain a temperature-dependent quark potential. The transition potential corresponding to quark-antiquark annihilation and creation is derived in perturbative QCD. The experimental ground-state meson masses are reproduced and the experimental data of elastic phase shifts for ππ scattering near the threshold energy in vacuum can be accounted for in the Born approximation. Starting from S-matrix element, we derive the transition amplitude and the cross section for the scattering. Unpolarised cross sections for reactions involving π, ρ, K and K* are calculated. Remarkable temperature dependence of the cross sections is found.
We revisit the Regge-like spectra of light mesons in the relativistic string model and the simirelativistic quark model. An analytical mass formula is proposed for light mesons based on the auxiliary field technique, and a quasi-linear Regge-Chew-Frautschi plot with flavor dependence is derived and verified with the experimental data(PDG) for light mesons.The results show that the quark model predictions for meson masses agree with those of the string model, but are slightly better when the angular momentum is relatively large as compared with the observed data.
Polyakov-Nambu-Jona-Lasinio (PNJL) model is one of the most popular effective quark models to investigate the properties of strongly interacting matter. Based on the PNJL model, we consider the entanglement interactions between the chiral condensate and Polyakov-loop, as well as the chemical potential modification of Polyakov-loop potential simultaneously, which is named μEPNJL model. Compared with the original PNJL model, the calculations in the mean field approximation show that the critical end point (CEP) given in the μEPNJL model moves towards higher temperature and smaller chemical potential in the T-μ phase diagram. Besides, the chiral symmetry restoration and deconfinement phase transition coincide well in a wide range of chemical potential. Comparing our calculations with the measurement of the moments of net-proton multiplicity distributions at Relativistic Heavy-Ion Collider (RHIC) by STAR Collaboration, we find that the CEP given by μEPNJL model can be closer to the range predicted by the experiment through appropriate parameter adjustment.
The ZF-400 Intense Neutron Generator, which is designed by Lanzhou University with an expected neutron yield of 6×1012 n/s, is consist of ECR ion source, low energy beam transport (LEBT) line, accelerating tube and rotating target. The beam extracted from ECR source is analyzed and focused through LEBT, then, the beam is introduced into the accelerating tube. The focus and analysis ability of LEBT is very important for the beam loss, neutron yield and target's life. A LEBT line for intense neutron generator is designed in this paper, the project consisted of a solenoid, a bend magnet and three quadrupole lens. The qualified LEBT and its parameters have been got through the simulation with TRACK code. Then TraceWin program was employed to check this simulation and the result satisfied our requirement. Besides, the loss position of impurity ions was known through the simulation, and a project of beam line's cooling system was designed according to this result. Through the simulation, we find the optimal lens combination plan which can obtain lower beam loss and higher beam purity at low running power of LEBT.
利用标准放射伽玛源（22Na，137Cs）测量了尺寸为Φ5.08 cm×2.54 cm的BC501A中子探测器的脉冲幅度谱，并利用MCNP软件进行了模拟，详细考虑了探测器的几何尺寸、材料、以及能量分辨函数，计算结果很好地再现了实验数据，精确地确定了康普顿边缘的位置，完成了BC501A中子探测器的能量刻度。并采用14.8 MeV的T（d，n）4He中子源对聚乙烯样品开展了中子学积分实验，结果表明，BC501 A中子探测器的能量刻度过程以及聚乙烯中子学积分实验数据的处理过程是完全合理并且可靠的。
The pulse-height spectra of the BC501A scintillator (Φ5.08 cm×2.54 cm) were measured using 22Na, 137Cs γ-ray source, in which MCNP simulation was applied. The simulated pulse-height spectra show a good agreement with the measured data considering the geometry, material and energy resolution function of the scintillator. The position of the Compton edge has been precisely determined and an accurate energy calibration of BC501A scintillator was also achieved. An neutronics integral experiment of polythene with 14.8 MeV T(d, n)4He neutron source was carried out. The results indicate that the procedures of the energy calibration experiment of BC501A scintillator and the data analyzing in the polythene integral experiment are reasonable and reliable.
描述了为兰州放射性粒子束流线（RIBLL Ⅱ）上测量束流径迹而研制的一种基于LC延迟电路的双层多丝正比室（MWPC）。该探测器的探测灵敏面积为100 mm×80 mm，位置信号由阴极丝引出并通过LC延迟电路读出。探测器由两套完整的多丝正比室组成，每套的阳极丝夹在两层平行的阴极丝之间，阳极丝和阴极丝相互垂直。两套阴极丝相互垂直给出入射粒子的二维位置信息。为了增大感应信号以提高探测效率，将每套位置对应的阴极丝合并成一路接入LC延迟电路。用55Fe-5.9 keV X射线源均匀照射探测器的灵敏区域，测试表明其具有良好的位置灵敏一致性。用X射线源通过准直狭缝扫描整个探测器的灵敏区域，得到X，Y层的位置线性度均好于0.999；其位置分辨（σ）分别为199.9 μm和154.0 μm，目前，该探测器已成功用于RIBLL Ⅱ的实验中。
A double-layer Multi-Wire Proportional Chamber (MWPC) with 100 mm×80 mm active area has been developed for Radioactive Ion Beam Line in Lanzhou(RIBLL Ⅱ). The position information has been obtained by a LC delay circuit readout method. Being called of double-layer MWPC, it is composed of two full MWPCs, each consists of an anode plane sandwiched between two parallel cathode planes, anode wires and cathode wires are perpendicular to each other. In order to improve the detection efficiency, the cathode wires of corresponding position are combined to enhance inductive signal. The cathode wires of two full MWPCs are orthogonally placed to give two coordinates of the incident particles. The sensitivity uniformity is also found to be relatively good and the position resolution of X, Y direction are measured to be 199.9 and 154.0 μm using a 55Fe-5.9 keV X ray, respectively. The position linearity of X, Y direction are as good as 0.999 for whole sensitive area of the detector. The detector has been used successfully on the experiment at RIBLL Ⅱ.
On the base of the generalized perturbation theory and SN method, the theoretical model for calculating the sensitivity and uncertainty of reaction rates ratio (RRR) versus nuclear data is developed. Taking Jezebel-Pu239 critical benchmarking facility as an example, the sensitivity of F49/F25 ratio versus important nuclear data is calculated, as well as the uncertainty arising from the nuclear data. Basing on the sensitivity and uncertainty analysis as well as the covariance information of input evaluated data, refined evaluation of the inelastic data of Pu-239 is considered as a feasible measure to reduce the uncertainty of reaction rates ratios.
为测量中国锦屏地下实验室（China JinPing underground Laboratory，CJPL）极低通量的中子本底，需要建造大型快中子液体闪烁体探测器。建造探测器需要选用低放射性本底材料，并且化学性质稳定，不与液体闪烁体发生反应而影响液体闪烁体（EJ-335）的性能。为此，建造了小型液闪探测器，在其中分别放入聚四氟乙烯、无氧铜、氟橡胶、全氟醚橡胶这4种材料进行长期浸泡，并分别进行了如下测试：液闪长时间浸泡各种材料前后液闪的吸收光谱测试；用60Co γ源检测小型液闪探测器光产额随时间的变化情况；用Am-Be中子源检验探测器在浸泡前后的n-γ甄别性能。最终实验结果表明，聚四氟乙烯和全氟醚这2种材料与液闪有很好的兼容性，可作为大型快中子液闪探测器的容器和密封圈的备选材料。
In order to measure the flux and spectrum of neutron background which is extremely low in China JinPing underground Laboratory (CJPL), liquid scintillator detector with large scale used to detect fast neutron need to be fabricated. Surrounding materials used in detector require the excellent performance, such as low radioactivity as well as stable chemical properties, which do not react with liquid scintillator, so as to avoid affecting the performance of detector. Polytetrafluoroethylene(PTFE), highly purified no-oxygen copper, fluororubber and perfluoroelastomer had been put in a small detector and soaked for a long time. The change of absorption spectrum and light yield along with time as well as the performance of n-γ discrimination after soaked were tested. The results show that PTFE and Perfluoroelastomer are compatible with liquid scintillator, which offers a reference for the selection of material used in container and seal of liquid scintillator detector used to detect fast neutron.
准确定量铀氧化物样品中238U的含量对于裂变产额测量等工作具有重要意义，其定量方法的研究对于涉及238U的绝对测量的诸多实验都具有参考价值。利用四川大学2.5 MeV质子静电加速器产生的准单能中子对八氧化三铀样品进行中子活化，用高纯锗探测器测量活化产物的β衰变子体239Np的277.6 keV特征γ射线，利用已知的活化截面，算出样品中238U的质量占比为79.1%，不确定度为6.2%。利用电感耦合等离子体质谱法对样品中238U的含量进行了测量，其质量占比为59.2%。此外，基于EA3000元素分析仪、卡尔费休电位滴定仪和TGA-DSC2同步热分析质谱联用仪，测知样品中不含N元素，含水量在2.2%以下。并利用PIXE方法排除了样品中含有Al元素以上杂质，利用EPBS方法测知样品中U/O原子数比为1：3.6，误差约2%，推知样品中238U质量占比为80%，验证了活化法测得的238U含量。最终测得样品中238U的质量占比为79.1%，不确定度6.2%。对照按U3O8分子式折算的84.5%，考虑到水分含量等，此结果合理。
The accurate quantification of 238U in uranium oxides is of great importance for measurements of fission yield. The study for the method of 238U quantification has significance to lots of experiments involving absolute measurement of 238U. The reaction (n, γ) in the triuranium octoxide samples was induced by T(p,n)3He quasi-monoenergetic neutrons provided by the 2.5 MeV proton electrostatic accelerator in Sichuan University. The 277.6 keV characteristic γ ray of 239Np that comes from β-decay of the activation product 239U was detected by a HPGe detector. With the known (n, γ) cross section, the mass percentage of 238U in samples was determined to be 79.1%, with the uncertainty of 6.2%. ICP-MS was also used in the quantification of 238U in samples, its result was 59.2%. Meanwhile, the samples were analyzed by other several methods and the results showed that less than 2.2% H2O, no nitrogen, and no other impurity elements above Al were contained in the samples. EPBS was used to measure the atomic ratio of U and O and it was found that the mass percentage of 238U in samples was about 80%, verifying the result 79.1% of INAA.
The white porcelain samples of the four periods of Huangye kiln were studied in this paper, and the samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the material phase is basically the same of the white porcelain bodies from Huangye kiln, and mainly mullite, alpha quartz and cristobalite, unmelted quartz and a small amount of clay phase; There are some round bubbles in HuangYe kiln white porcelain, glazes, so are some feldspathic crystals with micro-level needles or columnar. It is evident to observe phase separation structure, which is accompanied by the birth. Apart from some pores, unfused quartz particles, larger Ti particles, mullite crystals and quartz crystals can also be found in the embryo of Huangye kiln white porcelain.
MRTOF-MS是最近几年发展起来的新型质谱仪，较传统的飞行时间质谱仪而言，MRTOF-MS质量分辨本领更高。开发了一种用于MRTOF-MS设计的新方法，该方法由参数设置部分和离子运动计算部分共同组成；分全局搜索和局部细化两个步骤，可用于优化MRTOF-MS的几何构型、计算不同条件下的最佳电压设置组合。基于这种方法，设计了一种机械结构与国际上同类设备不同的MRTOF-MS，该设备可用于高精度原子核质量测量，也可用于快速质量选择，为LPT提供纯净的目标核。通过优化，确定了其几何参数和电压参数，讨论了不同电极上的电压偏差对质量分辨本领的影响，定量地分析了电源的精度要求。优化结果表明：MRTOF-MS的最佳漂移长度约为400 mm；在最佳电压设置下，当40Ar1+的总飞行时间为6.5 ms时，其质量分辨本领可达1.3×105；要求电源精度好于50 ppm，最好达到20 ppm。
Multi-reflection time-of-flight mass spectrometer (MRTOF-MS) has been developed as a new device which has a higher mass resolving power than traditional mass spectrometers in recent years. A new method including two sub-procedures, global search and local refinement, has been developed and applied to design a MRTOF-MS. It consists of two components, parameter configuration and ion motion simulation, and can be used to optimize the geometries of the spectrometer and the potentials applied on the electrodes to achieve the optimum in different conditions. By using this method, a different type of MRTOF mass analyzer has been designed for mass measurements and isobaric separation for Lanzhou Penning Trap (LPT). The geometry of this analyzer and potentials at different electrodes have been optimized, and the relations between resolving power and potentials and the power accuracy requirements have been analyzed and discussed quantitatively. The simulation shows that the optimal length of the drift-tube is about 400 mm; the maximal resolving power of 1.3×105 has been achieved with a total time-of-flight of 6.5 ms under the optimal potentials for an ion species of 40Ar1+; and the inaccuracy of the potentials applied to the mirror electrodes must be less than 50 ppm or preferably 20 ppm.
国产ZIRLO合金是CAP1400重要的燃料包壳管候选材料之一，因此需要在使用前对该材料进行辐照性能考验。研究了国产ZIRLO合金的辐照性能随辐照温度和损伤剂量的变化。辐照实验在中国原子能科学研究院HI-13串列加速器上，采用80 MeV的Ni离子进行，辐照产生的损伤采用透射电子显微镜、能量色散谱和纳米压痕法等方法表征。国产ZIRLO合金在300℃经10 dpa损伤剂量辐照后观察到均匀分布的析出颗粒，同样剂量在700℃辐照析出颗粒数目减少，析出相的主要成分为Nb。辐照后出现硬化现象，辐照损伤剂量越大，硬化程度越高；随着辐照温度升高，辐照硬化呈减小趋势。
The domestic ZIRLO is a promising candidate of cladding materials for CAP1400. It is necessary to test its radiation properties before its use. In this paper, the radiation properties of the domestic ZIRLO have been studied as functions of irradiation temperature and dose respectively. The experiment was performed at the HI-13 tandem accelerator of China Institute of Atomic Energy by using 80 MeV Ni ions at different temperature and different dose. The transmission electron microscopy, electron dispersive spectroscopy and nano-indentation were used to characterize the radiation damage. The experimental results show that the precipitates are uniformly distributed at 10 dpa and 300℃, while at 700℃ the number of precipitates is reduced. Among all the precipitates, Nbisthe dominant element. Hardening phenomenon was also observed after irradiation, the higher the radiation dose, the higher the degree of hardening, and it illustrates a decreasing tendency with the increasing of the irradiation temperature.
连续碳纤维增强碳化硅材料除了具有碳化硅材料固有的低中子活化性能，低衰变热性能和低氚渗透性能等优点以外，还具有密度低、线性膨胀系数小、高比强度、高比模量、耐高温、抗氧化、抗蠕变、抗热震、耐化学腐蚀、耐盐雾、优良的电磁波吸收特性等一系列优异性能，是各类核工程重要的潜在候选材料。在核聚变工程应用领域，连续碳纤维增强碳化硅材料作为第一壁材料不可避免地会受到各种辐射粒子的影响。研究清楚这些辐射粒子对它的辐照效应对其在核工程领域的安全使用至关重要。采用蒙特卡罗方法与分子动力学方法进行模拟计算，研究了氕、氘、氚和氦四种粒子对连续碳纤维增强碳化硅的辐照效应。SRIM和LAMMPS计算结果表明：当入射原子能量为100 eV，连续碳纤维增强碳化硅中碳的浓度在80%~85%时，氕、氘、氚和氦原子的溅射率存在最小值；入射粒子的种类对溅射率的影响显著，氦原子的溅射率大于氘原子和氚原子，而氘原子和氚原子的溅射率相差不大但均显著大于氕原子；溅射率随入射能量的增加先迅速增加后逐渐减小，氕、氘、氚和氦原子入射能量分别在200，400，600和800 eV时存在溅射率最大值；当氦原子入射能量为100 eV时，溅射率随入射角度的增加而逐渐减少。这些结果对连续碳纤维增强碳化硅材料在核工程上的应用具有一定的参考意义。
Continuous carbon fiber reinforced silicon carbide material has the low neutron activation, low decay heat performance and tritium permeability, which are inherent performance of silicon carbide materials. It also has other advantages such as low density, small linear expansion coefficient, specific strength and specific modulus, high temperature resistance, oxidation resistance, creep resistance, thermal shock, resistance to chemical corrosion, salt fog resistance, excellent electromagnetic wave absorption properties, etc. It is an important potential candidate material in various field of nuclear engineering. In the field of nuclear fusion engineering applications, continuous carbon fiber reinforced silicon carbide as the first wall material will inevitably be bombarded by a variety of radiation particles. The radiation effect is critical to its safe use in nuclear engineering. The Monte Carlo method and the molecular dynamics method were used to study the radiation effect of protium, deuterium, tritium and helium on continuous carbon fiber reinforced silicon carbide. The SRIM and LAMMPS simulation results show that when the incident energy is 100 eV and the concentration of carbon in the continuous carbon fiber reinforced silicon carbide is about 80% ~ 85%, the sputtering yield of protium, deuterium, tritium and helium atoms have the minimum values. The kind of incident particle has a significant effect on the sputtering yield. The sputtering yield of helium atoms is larger than that of tritium atoms and deuterium atoms. There is not much difference between the sputtering yield of deuterium atoms and tritium atoms, and both the sputtering yield of deuterium atoms and tritium atoms are larger than that of protium atoms. The sputtering yield initially increases rapidly with the increase of the incident energy and then decreases gradually. The incident energy of the protium, deuterium, tritium and helium atoms has the maximum value of the sputtering yield at 200, 400, 600 and 800 eV, respectively. When the incident energy of helium atoms is 100 eV, the sputtering yield decreases while the increase of the incident angle. These results can provide a certain reference for the application of continuous carbon fiber reinforced silicon carbide materials in nuclear engineering.
Vitrification is one kind of silicates which is used for immobilization of high-level waste (HLW). As the first engineered barrier of HLW disposition, its anti-irradiation characteristic is particularly noticeable. Vitrification is replaced by borosilicate glass to investigate radiation effect, and the irradiation damage generated by natural radioactivity in vitrification is simulated by different doses gamma rays on borosilicate glass. By measuring and analyzing the absorption spectrum of irradiated borosilicate glasses, it is confirmed that E'defect, non-bridging oxygen hole center, peroxy dangling bond and bridge oxygen link, etc. are induced in borosilicate glass after irradiation. Furthermore, the relations between the defects and absorbed doses are shown. For the concentrations of these defects induced by irradiation, all of them increase with absorbed dose. Meanwhile, absorption band gap in borosilicate glass after irradiation decreases with absorbed dose and the band gap becomes saturated when absorbed dose is equal to or greater than 105 Gy.
采用常用冷轧设备对铁进行冷轧引入形变缺陷。研究形变量和温度对形变缺陷的影响。形变样品中的微观缺陷、物相结构和形貌分别使用正电子湮没技术（PAT）、X射线衍射仪（XRD）和透射电子显微镜（TEM）进行表征分析。对经过673 K热处理的形变样品前后进行XRD测试，结果显示，随着形变量的增加，样品中晶面方向（200）具有择优生长趋势，673 K热处理后，择优趋势更加明显，同时晶粒的尺寸也增大。利用正电子湮没寿命谱和多普勒展宽能谱对样品中形变缺陷的热力学稳定性进行研究，发现形变引入的空位型缺陷约在673 K回复完毕，723 K后位错缺陷开始回复。
The pure iron was cold rolled with the thickness reduction from 0% to 75%. The microstructure defects, crystallographic structure and morphology of deformed specimens were characterized by positron annihilation technique (PAT), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD results show that the intensity of (200) increased with increasing deformation, 673 K heat-treatment promote the preference of (200) and the grain size of (200) was increased. The PAT results show that the vacancy type defect was annihilated at 673 K and the dislocation type defects start to annihilate at 723 K.
ZnS thin films have been prepared by sulfurizing zinc thin films deposited on glass substrate by magnetron sputtering for two hours. The microstructure defects, crystallizations and surface morphology of zinc films sulfurized at different temperature were analyzed by PAT (positron annihilation technique), XRD(X-ray diffraction) and SEM (Scanning electron microscopy), respectively. For analyzing the structure defect of four samples with different sulfurization temperature, PAT has been used to obtain the relative concentration of defects. With the positron energy range of 1.5~4.5 keV, the S parameter of ZnS films is minimum. It demonstrates that ZnS films produced at 445℃ have the minimum structural defect concentration and the highest density. XRD results show that films are blende structure with the preference of (111) orientation above 445℃. And from the result of SEM, because of ZnS films recrystallization, the crystal grains obviously become large and dense at 445℃.
弹性反冲探测分析技术（ERDA）对轻元素的测定具有灵敏度高、包含深度信息的优势，因此在材料氦行为研究中发挥着重要作用。镍基哈氏N合金被认为是未来熔盐堆的结构材料，氦脆是其服役性能下降的主要因素之一。利用掠入射模式的ERDA，解析了哈氏N合金样品中的氦原子浓度及其分布，但仅局限于0~175 nm深度范围内。结果表明：在800℃的退火条件下，距离样品辐照表面~33 nm深度区域内，出现了氦原子逃逸现象。更高温度的退火（1 050℃）可加剧氦原子的逃逸，但样品中仍有氦原子滞留。另外，采用透射式的ERDA，极大地扩大了对氦原子分析的深度范围，得到了纯镍薄膜在0~950 nm深度区域内的氦原子浓度分布。这表明将块体材料制备成薄膜样品，利用透射模式的ERDA，将可以得到氦原子在更大范围内的扩散、逃逸行为。
Since the elastic recoil detection analysis (ERDA) technique has the advantages of high sensitivity and deep information in analyzing the light elements, it plays an important role in the study of helium behavior in materials. Helium embrittlement is one of the main reasons for the degradation of the Hastelloy N alloy, which has been considered as the promising candidate structural material for the further molten salt reactor. In this work, the profile of helium concentrationin sample of Hastelloy N alloy was analyzed by ERDA experiments applying grazing-incidence geometry. However, the result was limited within the depth range of 0~175 nm, and it shown that helium atoms escaped in the range from the irradiated surface of the sample to the depth of ~33 nm when annealing the sample at 800℃ The annealing at higher temperature (1 050℃) increased the escape of helium atoms, but a small fraction of helium atoms still trapped in the sample. In addition, the profile of helium concentration was obtained in the helium-irradiated pure nickel film in the depth range of 0~950 nm, using the ERDA experiments in transmission geometry. This indicates that the diffusion behavior of helium atoms in bulk samples can be completely obtained using the ERDA experiments in tranmission geometry if the bulk material can be prepared into a thin film sample.
钨被广泛地认为是最具潜力的面向等离子体材料。钨在聚变堆中的服役过程中，会受到强束低能的氢氦粒子流的影响，其结果是钨的性能下降。本工作通过第一性原理计算的方法研究了过渡金属锆铁对钨中氢氦行为的影响。研究结果表明，锆或铁的掺入会使钨的机械强度降低，延展性增加；锆铁的掺入不会改变氢氦在钨中的最佳占位，但是它们对氢氦在钨中的稳定性有一定影响；锆和铁对钨中氢氦的捕获作用存在一个最佳作用半径；铁原子在短距离（< 3.626 Å）时对氦有捕获作用，在长距离（> 3.626 Å）时存在排斥作用，而锆对钨中氢氦均具有捕获作用；钨中氢表现为亲电子的性质，而氦表现出疏电子的特性。总体上讲，锆对钨中氢氦的捕获作用要强于铁对钨中氢氦的捕获作用。本研究工作能够为钨基面向等离子体材料制备提供理论指导。
Tungsten was widely considered as a highly promising candidate of plasma facing material, while the presence of hydrogen and helium has an adverse effect on the performance of the tungsten. The effects of transition metals (zirconium, iron) on the behavior of hydrogen and helium in tungsten were investigated by using the first-principles calculation method. The results show that doping of zirconium and iron decreases the mechanical strength of tungsten a little, but they increase the ductility of tungsten; zirconium and iron can't change the best occupied site of hydrogen and helium in tungsten, but they have some effect on the stability of the point defects formed by hydrogen and helium in tungsten; there is the best attraction radius between the transition metals (zirconium, iron) and hydrogen or helium in tungsten; there is an attractive interaction between iron and helium in a short distance (<3.626 Å), but a repulsion interaction in a long distance (>3.626 Å). An attractive interaction exists between zirconium and helium or hydrogen in tungsten whatever the distance is; the hydrogen that in tungsten has an electrophilic nature, while the helium has opposite features. The attraction interaction between zirconium and hydrogen or helium in tungsten is stronger than that of iron. Our works in this paper might provide a theory guide for the selection and preparation of the tungsten based alloy that is used as the plasma facing materials.
应用基于量子力学的密度泛函计算和过渡态搜寻的CI-NEB方法，研究了锆掺杂前后二氧化铀晶格中氧空位和氧间隙本征缺陷的扩散机理，计算了扩散路径和扩散能垒。计算结果表明，锆掺杂使得氧空位缺陷<100>方向的扩散能垒降低了0.40 eV，氧间隙交换机制的扩散能垒降低了0.07 eV。锆掺杂后，氧空位远低于氧间隙缺陷的扩散能垒。最后分析了扩散过程中氧原子和金属原子之间的键长，说明锆掺杂导致点缺陷扩散能垒降低与晶格畸变密切相关。
Oxygen vacancy and interstitial diffusion mechanisms in uranium dioxide doped with zirconium are investigated by the density functional theory calculations. The migration pathways and barriers are identified using the climbing-image nudge elastic band (CI-NEB) method. It is found that the vacancy migration barrier along the <100> direction decreases by about 0.40 eV, while the indirect interstitial migration barrier decreases by about 0.07 eV in the zirconium doped uranium dioxide. The oxygen vacancy migration barrier is far lower than the oxygen interstitial migration barrier in the uranium dioxide doped with zirconium. Based on the analysis of bond length of local structures during the migration of oxygen atoms, it is concluded that the lattice distortion may be responsible for the reduction of oxygen migration barrier.
钍基熔盐堆（Thorium Molten Salt Reactor，TMSR）核能系统先导专项的研究目标是研发第四代裂变反应堆核能系统（即钍基熔盐堆）。为充分利用液态燃料熔盐堆的在线添料与在线燃料处理的优势，同时考虑熔盐堆的快速部署，TMSR先导专项部署了小型模块化熔盐堆。考虑燃料处理技术现状及其可能的发展方向，小型模块化熔盐堆钍利用方案采用"三步走"战略。第一阶段采用在线加料与离线处理，实现钍的成规模利用；第二阶段采用在线加料和在线处理（U）与离线处理（MA）的结合，实现钍的高效利用；第三阶段采用在线加料及在线处理全部重金属，实现钍的自持增殖利用。随着"三步走"战略的逐步实施，钍铀燃料循环模式及后处理性能稳步提高，重金属利用率得到明显改善，同时有效降低了卸料毒性。考虑燃料许可容易度和建堆时间，首先为钍利用方案第一阶段布置了三种可能的启堆燃料，分别为低富集铀、低富集铀加钍和233U加钍。计算结果显示：以低富集铀启堆时，燃料循环性能与水堆相当；以233U启堆时，燃料利用率明显高于水堆，且其放射性毒性比水堆低约2个数量级。
The missions of the Thorium Molten Salt Reactor (TMSR) Nuclear Energy System are to research and develop the thorium based molten salt reactors (MSR) belonging to the fourth generation of nuclear fission reactor system. A Small modular Molten Salt Reactor (SmMSR) is deployed to make full use of the advantages of online refueling and online reprocessing and to consider the rapid deployment of MSR. An innovative "three-stage" strategy of thorium utilization based on SmMSR is proposed to take the current condition of fuel reprocessing and its future evolution. The first stage can realize the thorium utilization at a large scale with online refueling and off-line processing. The second stage can obtain efficient thorium utilization with online refueling, online processing of uranium and off-line processing of minor actinides (MAs). The third stage is implemented with self-sustaining or breeding mode with online refueling and online processing of all heavy metals. Along with the development of three stages, the utilization of heavy metals will be obviously improved and the radio-toxicity will be significantly reduced. A SmMSR is designed to achieve the goals of the first stage of thorium utilization. And three kinds of nuclear fuel cycles with different startup fuel types (i.e., low enriched uranium (LEU), thorium mixed with LEU (LEU+Th) and thorium mixed with 233U (233U+Th)) are implemented. The results show that the performance for fuel cycle containing LEU is comparable to the pressurized-water reactor (PWR). Meanwhile, the nuclear utilization for that containing 233U is much higher than PWR, and the radio-toxicity for which is lower by ~2 magnitudes than that for PWR.
The finite element method based on unstructured mesh has good geometry adaptability. It has been used to solve reactor physics problems, manual description of geometric modeling and meshing makes the current finite element code very complicated. It greatly restricts the application of this method in the numerical calculation of reactor physics. Using the CAD pre-processing software ICEM-CFD, tetrahedral or hexahedral mesh subdivision of 3D core geometry is performed, triangular or quadrilateral mesh subdivision of 2D core geometry is performed, the main code of neutron calculation for nuclear noise analysis based on finite element method is developed. The steady state parameters such as flux, adjoint flux and keff/keff* are calculated and tested through benchmark problem, the test results show that the calculation results of the steady state parameters of this code are credible. Finally, the neutron noise spectrum is calculated for the 3D PWR benchmark problem published by IAEA, and the noise distribution under given frequency is given.
OKTAVIAN pulsed sphere experiment was used for Shielding Benchmarks of the AMPX formatted multi-group (238n-48γ) coupled neutron-gamma cross-section library for Thorium Molten Salt Reactor, of which the following isotopes/elements were checked-F, Li, Be, C, Al, Si, Cr, Ni, Zr, Co, Cu, Mn, Mo, Nb, Ti, W. One dimension shielding problem was calculated using XSDRN-PM program of SCALE 5.1 code system and results were compared with experiment results and MCNP calculated results, which shows that neutron leakage spectra agree well. Calculated results of photon leakage spectra of most facilities compared with MCNP results and experiment data are over-rated. MILER-4 code which is used for converting GENDF files produced by NJOY to the AMPX master library format is revised to solve this problem. The shielding benchmark verifications confirm the reliability of this new library.
With the unceasing enhancement of the calculation accuracy requirement on the new generation of lattice code, higher requirements on multi-group constants library were put forward. For example, fine energy group structures are required, more types of data are need for the resonance processing, more accuracy burn-up data is required. To meet this series of demand, a multi-group constants production system NPLC-3 was developed. The NPLC-3 system which mainly based on the NJOY program contains an input parameter database and a series of functional codes such as driver code, main library production code, energy group collapsing code, work library production code and so on. Recently, different methods were adopted to validate these codes respectively according to their functions. Compared to the traditional methods in multi-group constants production, NPLC-3 system adopts several new methods in the design of burn up chain, calculation of burn up data and resonance parameters. What's more, the NPLC-3 system has an independent I/O interface, and can fully automatic generate input cards from the input parameters database. Relative to the past means of production library, NPLC-3 system has great improvement.