Photonuclear reactions of calcium isotopes calculated with the nuclear shell model

Photoabsorption cross sections in calcium isotopes are investigated theoretically with the most advanced nuclear-structure calculations using the nuclear shell model. We show that the photoabsorption cross sections in ⁴⁸Ca dominated by a giant dipole resonance (GDR) are well reproduced with the shell model and predict that a pygmy dipole resonance (PDR) appears in ⁵²Ca in the low-energy tail of GDR. Excellent agreement with the experiment is achieved due to highly correlated many-body wave functions obtained by treating a huge matrix with the dimension of ∼10¹⁰.     

巨偶极共振参数子库（CENPL．GDP－1）的管理－检索程序系统

中国评价核参数库（ＣＥＮＰＬ）的ＧＤＰ－１子库存贮了用Ｌｏｒｅｎｔｚ曲线符合光核反应数据获取的巨偶极共振参数，建立了它的管理检索程序系统。由于库数据文件中仅存有从５１Ｖ到２３９Ｐｕ共１０２个核素的巨偶极共振参数，程序系统采用直接检索、替代、插值和系统学公式计算等方法可以补充库数据文件的不足。这里描述了它的特点、功能及使用方法。     

两种深空核爆炸辐射电磁脉冲模型的比较

深空核爆炸通过电偶极子和磁偶极子两种辐射机制产生电磁脉冲。本文具体分析了两种辐射模型产生电磁脉冲的物理机制,并估算了远处观察点的辐射电场。计算表明,电子以高斯波形出射时,百吨TNT当量爆炸在km量级范围内产生的电偶极子和磁偶极子辐射电场强度分别为kV/m和10 V/m量级。深空中地磁感应强度较弱,电子的角向运动相比初始方向运动是小量,因而磁偶极子的辐射强度远小于电偶极子的。     

Novel Dipole Trapped Spheromak Configuration

We report the observation and characterization of a spheromak formed in the Swarthmore Spheromak Experiment (SSX) and trapped in a simple dipole magnetic field. The spheromak is studied in the prolate (tilt unstable) 0.4 m diameter, L = 0.6 m length copper flux conserver in SSX. This configuration is stable to the tilt, despite the prolate flux conserver. The spheromak is characterized by a suite of magnetic probe arrays for magnetic structure B(r,t), ion Doppler spectroscopy for T _i and flow, interferometry for n _e , and soft X-ray analysis for T _e . Three dimensional MHD simulations of this configuration verify its gross stability.     

Asymmetry of Neoclassical Transport by Dipole Electric Field

Effects of dipole electric fields on neoclassical transport are studied. Large asymmetry in transport is created. The dipole fields, which are in a negative R-direction, reduce the ion drift, increase electron drift, and change the steps of excursion due to collisions. It is found that different levels of dipole field intensities have different types of transport, For the lowest level of the dipole field, the transport returns to the neoclassical one. For the highest level of the dipole field, the transport is turned to be the turbulence transport similar to the pseudo-classical transport. Experimental data may be corresponded to a large level of the dipole field intensity.     

Systematic study of dynamical dipole mode via the isospin-dependent Boltzmann-Uehling-Uhlenbeck model

Dynamical dipole mode in heavy-ion collisions has been studied by using an isospin-dependent BoltzmannUehling-Uhlenbeck(IBUU) model. We investigate the dependence of centroid energy and strength of the γspectrum on beam energy, N/Z ratio and mass asymmetry. The calculated yield and angular distribution of theγ-ray produced by dynamical dipole emission are consistent with the experimental data. The results show that the detailed study of dynamical dipole radiation can provide information on the isospin evolution of chargeasymmetric heavy-ion collisions around the normal nuclear density.     

Vibrational Mode in Two-Dimensional Dust Monolayer with Finite Size Dust Grains

Vibrational mode in a two-dimensional dust monolayer is investigated by considering the finite size of dust grains. Each dust grain is assumed to be a negative point charge and a dipole moment due to the inhomogeneous charge distribution on its surface. The dispersion relation of the vibrational mode is derived. Both the self-excited and externally excited cases are discussed. It is shown that the mode is sensitive to the direction of the dipole moment.     

Equilibrium Reconstruction of Anisotropic Pressure Profile in the Levitated Dipole Experiment

The Levitated Dipole Experiment (LDX) is an innovative confinement concept that uses an internal superconducting dipole field to confine plasma. Plasma equilibrium is calculated by a least-squares fit of an anisotropic pressure model to magnetic measurements constrained by X-ray images. Reconstructions have been done for different heating schemes using two-frequency electron cyclotron heating at 2.45 and 6.4 GHz. Results show that a maximum local β ∼ 20% has been achieved using two frequency heating at a combined full power of 5 kW. Analysis of the reconstruction results shows that the magnetic sensors are sensitive primarily to changes in the plasma dipole moment. This is partly due to the fact that the dipole current decreases as the plasma current increases (as required by flux conservation through the superconducting dipole) and the magnetic sensors detect the sum of these changes. This paper will present details of the reconstruction procedure and describe how new magnetic sensors will aid in resolving the pressure profile more accurately.     

The Study of Heat Pulse Propagation on HT—7 Tokamak

The propagation of heat pulses originating from sawtooth activity has been studied on the HT-7 tokamak.Two theoretical models are used for determining electron heat diffusivity from the experimental data measured by a diagnostic system of soft x-ray diode-array.The results show that one model caaled dipole model is more suitable for HT-7 tokamak.In order to improve the signal-to-noise(S/N) ratio of the original signals,over a few tens of sawteeth are averaged to generatc nicc wavcforms.The apace-time evolution is found to be diffusive in character,which is consistent with the theoretical model.The electron heat diffusivity determined from heat pulse propagation is larger than determined from background plasma power balance.The variation of Xe in different discharge phases has been also discussed.     

Conceptual design of Dipole Research Experiment (DREX)

A new terrella-like device for laboratory simulation of inner magnetosphere plasmas,Dipole Research Experiment,is scheduled to be built at the Harbin Institute of Technology (HIT),China,as a major state scientific research facility for space physics studies.It is designed to provide a ground experimental platform to reproduce the inner magnetosphere to simulate the processes of trapping,acceleration,and transport of energetic charged particles restrained in a dipole magnetic field configuration.The scaling relation of hydromagnetism between the laboratory plasma of the device and the geomagnetosphere plasma is applied to resemble geospace processes in the Dipole Research Experiment plasma.Multiple plasma sources,different kinds of coils with specific functions,and advanced diagnostics are designed to be equipped in the facility for multi-functions.The motivation,design criteria for the Dipole Research Experiment experiments and the means applied to generate the plasma of desired parameters in the laboratory are also described.     

HPuO分子激发态的外场效应

采用密度泛函(DFT)方法B3LYP/Gen,在Pu为相对论有效原子实势(RECP)基组水平上,优化计算得到了分子轴方向不同电偶极场（－0.005～0.005a.u.）作用下的HPuO的基态几何结构、偶极矩和分子总能量。在优化构型下,用同样的基组,采用含时密度泛函(TDDFT)方法(TD-B3LYP),研究了同样外电场条件下对HPuO的激发能的影响。计算结果表明,在外场作用下,对HPuO的前5个激发态电子跃迁光谱属于红外 远红外光谱,波长为1046.0～3038.7nm,这是钚原子的奇异特征。激发能与外电场的关系近似满足Grozema等提出的关系。     

Magnetic rotation in Rubidium-84

High-spin states in 84 Rb have been studied by using the 70Zn(18O, p3n)84Rb reaction at beam energy of 75MeV. Three regular magnetic dipole bands including strong M1 and weak E2 transitions have been observed in this nucleus which shows the characteristic feature of magnetic rotation. These bands are interpreted in the projected shell model for the first time on the basis of the four-quasiparticle configuration of the type π(fp)π(g29/2)v(g9/2). It is shown that the calculated sequence lies roughly in the same energy range as the experimental one but the interval between neighboring levels is larger than the corresponding experimental value. We believe that a 4-quasiparticle band crossing with the 2-quasiparticle band will depress the energies of the states.     

铯在钨(110)表面吸附行为的第一性原理研究

通过基于密度泛函理论的第一性原理计算方法，研究了铯原子在钨(110)表面上的吸附行为。计算结果表明，通过原子数之比定义的最大单层铯原子吸附率为0.4，铯原子的吸附位置随吸附率的增加而变化。铯原子吸附率为0.25时，最可能的吸附位置是长桥，而铯原子吸附率达0.4时，铯原子在钨(110)表面形成完整的单原子层，并呈现-ABA′B′-结构形式。随铯原子吸附率的增加，表面功函数先减小后增大，最终稳定在2.134 eV，其中最小值1.524 eV出现在吸附率为0.25时，该最小值低于纯铯(110)表面的功函数。偶极子模型和分态密度计算结果表明，铯原子向钨基体表面的电子转移机制和铯原子电子能量分布的变化是造成表面功函数降低的原因。     

Evaluation of Photonuclear Reaction Data on Tantalum-181 up to 140MeV

Photonuclear cross sections of ¹⁸¹Ta are evaluated up to an incident photon energy of 140MeV which is the threshold energy for pion production. Re-analyses were performed on the (γ, n) and (γ, 2n) data measured at Saclay and Livermore, and reference data were reconstructed. The absorption cross sections were evaluated with the giant electric dipole resonance (GDR) model below 40MeV. The calculation by the statistical model with preequilibrium correction reproduced the reference data of all the photoneutron cross sections consistently. From 40 to 140 MeV, the quasideuteron model (QDM) was adopted to evaluate photoabsorption cross sections and the results are compared with the measurements. The decaying processes including n, p, d, t, ³He, and α particle emission up to 140MeV were theoretically evaluated by the ALICE-F code.     

共振能量转移分子显像在生物医学中的应用

共振能量转移分子显像(RETI)能显著改善光信号强度和组织穿透性,可用于活体深度组织光学显像。共振能量转移(RET)是指发生在近距离的供体与受体之间的能量转移,包括非放射共振能量转移和放射共振能量转移。RETI是基于共振能量转移的光学成像技术,主要包括荧光共振能量转移显像(FRETI)、生物发光共振能量转移显像(BRETI)、化学发光共振能量转移显像(CRETI)和放射共振能量转移显像(RRETI)。目前,RETI是分子显像研究的热门领域,已用于生物医药学研究各领域。本文对RETI技术原理及其在生物医学中的应用进行综述。     

Ab initio Calculations of Electron-Impact Excitation Cross Sections for N_2 Molecule

One of the great difficulties in understanding nitrogen plasma elementary processes is the lack of an available database of the cross-sections of electron-impact excitations and radiations. Ab initio calculations of vibrational excitation cross sections for electron collisions with nitrogen molecules in low-lying states using similarity function approach, such as a-a＇, a-w, B-B＇ and B-W transition systems, are reported here for the first time. In the meantime, the average excitation energies of neighboring levels of these systems have been calculated. In order to obtain the cross sections, accurate spectroscopic constants and transition dipole moments have been investigated. Potential energy curves and other electronic transition dipole moments for the low-lying states of N2 have been re-evaluated using complete active space self-consistent field （CASSCF） approach with aug-cc-pVqZ basis set. The calculated cross-sections could provide a database for studying the elementary processes and the properties in N2 plasma.     

Generalized analysis method for neutron resonance transmission analysis

Neutron resonance densitometry (NRD) is a non-destructive analysis method, which can be applied to quantify special nuclear materials (SNM) in small particle-like debris of melted fuel that are formed in severe accidents of nuclear reactors such as the Fukushima Daiichi nuclear power plants. NRD uses neutron resonance transmission analysis (NRTA) to quantify SNM and neutron resonance capture analysis (NRCA) to identify matrix materials and impurities. To apply NRD for the characterization of arbitrary-shaped thick materials, a generalized method for the analysis of NRTA data has been developed. The method has been applied on data resulting from transmission through thick samples with an irregular shape and an areal density of SNM up to 0.253 at/b (≈100 g/cm²). The investigation shows that NRD can be used to quantify SNM with a high accuracy not only in inhomogeneous samples made of particle-like debris but also in samples made of large rocks with an irregular shape by applying the generalized analysis method for NRTA.     

Resonance self-shielding method using resonance interference factor library for practical lattice physics computations of LWRs

This paper presents a new method of resonance interference effect treatment using resonance interference factor for high fidelity analysis of light water reactors (LWRs). Although there have been significant improvements in the lattice physics calculations over the several decades, there exist still relatively large errors in the resonance interference treatment, in the order of ～300 pcm in the reactivity prediction of LWRs. In the newly developed method, the impact of resonance interference to the multi-group cross-sections has been quantified and tabulated in a library which can be used in lattice physics calculation as adjustment factors of multi-group cross-sections. The verification of the new method has been performed with Mosteller benchmark, UO₂ and MOX pin-cell depletion problems, and a 17×17 fuel assembly loaded with gadolinia burnable poison, and significant improvements were demonstrated in the accuracy of reactivity and pin power predictions, with reactivity errors down to the order of ～100 pcm.     

金属离子对冠醚体系卤素标记速度的影响

本文利用冠醚作为催化剂进行了无溶剂条件下卤代烷烃与卤化钠的卤素交换反应。示踪元素为~(125)I、~(82)Br。考察了不同冠醚(12C4,15C5,18C6和24C8)的催化效率与络合物稳定化能的定量关系。根据晶体测定资料和AIC模型推算的分子几何学结果,计算了这些络合物的离子-偶极作用能量,所得次序与实验结果完全吻合。初步确认这些络合物中的配位键主要来自静电作用的贡献。离子与冠醚环的相对大小(孔径效应)不是决定络合物稳定性的唯一重要的因素;溶剂效应与络合比效应均有较大的贡献。本文列出了锂、钠和钾三种金属离子与12C4、15C5、18C6和24C8形成的络合物稳定化能,较好地解释了本文和国毓智等人发表的实验结果。     

235UF6和238UF6同位素分子共振能量转移研究

本文利用长程力碰撞理论计算了²³⁵UF₆和²³⁸UF₆同位素分子间ν₃振动能量的近共振碰撞转移过程,得到了不同温度下共振函数随能量差变化的曲线,发现共振函数的宽度随温度的升高而增大。计算了不同温度下共振转移几率和共振转移速率,发现它们随温度的升高而减小。可见,²³⁵UF₆和²³⁸UF₆同位素分子的平动会降低其共振转移几率和共振转移速率,这为激光光化学法分离铀同位素提供了理论依据。