Selectivity and Efficiency of Laser Isotope Separation Processes of Gadolinium

Isotopic selectivity and ionization efficiency are discussed in the isotope separation processes of Gd based on polarization selection rules and based on isotope shift. Enrichment of ¹⁵⁷Gd to 90% was experimentally demonstrated using both methods together. The features of the absorption spectra of Gd in yellow-red and blue regions were summarized. Absorption spectra that are suitable for separation process using isotope shift were examined and an obtainable selectivity and efficiency are quantitatively calculated.     

Researches on Laser Isotope Separation of Gadolinium and Boron

Laser isotope separation experiments of Gd and B by atomic and molecular methods, respectively, have been performed. Gadolinium-157 was selectively photoionized by means of three linearly polarized dye lasers, the excitation process of which is based on the polarization selection rules. The effect of magnetic field on isotopic selectivity was discussed. ¹⁰BCl₃ was selectively photodissociated through IR multiphoton dissociation by the irradiation of TEA CO₂ laser or free electron laser (FEL). Selectivity was improved by two-color laser irradiation.     

超短脉冲激光自生磁场同位素分离实验研究

通过超短脉冲激光与固体氮化硼（BN）靶相互作用过程中产生的自生磁场实现了对同位素硼的分离,采用二次离子质谱法（SIMS）对同位素分离效果进行了测量。研究表明,一级浓缩比达50.8%。     

基于光化学锂同位素分离条件的同位素比率测量

从光化学锂同位素分离实验研究的需求出发,基于其分离条件,提出了一种测量锂同位素比率的方法。该方法利用锂原子蒸气对探测光吸收峰的峰值来计算锂的同位素比率,避开了测量原子密度时所需的吸收信号频率定标与光强随频率变化积分中积分限的选择问题。该方法还根据锂同位素吸收谱的特殊性采用具有较强吸收效应的⁶Li的D₂线对应的吸收峰峰值,可在原子蒸气中⁶Li含量较低时提高对比率的测量精度。设计并搭建了实验装置,对该方法进行了测试。同一条件下所测得的同位素比率相对标准偏差小于1%,表明该方法对光化学分离方法中锂同位素比率相对变化是敏感的。这意味着该方法可作为以原子蒸气为分离介质的激光锂同位素分离研究的诊断手段。     

原子激发光化学同位素分离理论计算

简要介绍了原子激发光化学同位素分离方法的基本原理,应用速率方程建立了双能级原子在激光作用下与气体分子相互作用的数学模型,并利用该模型进行了模拟计算。在分析了该方法的选择性之后,重点讨论了激光功率和激光中心频率对分离效果的影响。结果表明,原子光化学分离方法具有很高的分离选择性;不同同位素原子在反应腔内的消耗速率差异很大,当采用单光子失谐激发时,随着失谐量绝对值的增大,浓缩系数先增大后减小。     

Near-Resonant Effects on Propagation of Frequency-Swept Laser Pulse in Atomic Vapor Laser Isotope Separation

The propagation characteristics of frequency-swept laser pulse in near-resonant medium were studied by the numerical calculation and the experiment. The characteristics of the frequency-swept laser pulse has been largely modified in comparison with the frequency-fixed laser pulse. These modifications were demonstrated also experimentally for Sm vapor. The results agreed well with the numerically calculated.     

自动电位滴定硼浓度方法在MOFs对硼同位素分离效果测定中的应用

金属 有机骨架（MOFs）材料作为吸附剂具有吸附硼同位素的潜力,为系统研究硼同位素效应,本文建立测定硼酸溶液中硼浓度的自动电位滴定法,以三种MOFs为例测定其对硼同位素的分离效果。采用弱酸强化法,甘露醇用量为理论用量的4倍,硼酸标准物质的测量值与参考值之差最小（-0.000 13 g）,方法的测量不确定度为0.000 2~0.000 8,测量精度为0.10%~0.40%,方法有效、可靠。应用建立的自动电位滴定法测定吸附前、后硼酸溶液的硼浓度,用MC-ICP-MS测定吸附前、后硼酸溶液的硼同位素丰度比¹⁰B/¹¹B,以Cu-MOF-OCH₃、UiO-66-NH₂、MIL-101(Cr)-2,3-OH三种MOFs材料为例,测定其对硼同位素的静态分离效果。结果表明,Cu-MOF-OCH₃、UiO-66-NH₂和MIL-101(Cr)-2,3-OH对硼同位素的分离因子(S)分别为1.066、1.037和1.079,均大于商用树脂Amberlite IR743的S（1.027）,其中,Cu-MOF-OCH₃对¹⁰B的10/11S>1,UiO-66-NH₂、MIL-101(Cr)-2,3-OH对¹¹B的^11/10S>1。本结果可为系统研究MOFs材料对硼同位素的分离效果提供参考。     

气体离心机非线性流场计算与分离性能研究

为更好地分析挡板与取料器对分离性能的影响,计算并分析离心机内部非线性流场非常必要。本文使用有限差分法对离心机内部强旋流场进行计算,采用参数优化的下降牛顿法求解非线性稳态Navier-Stokes流体方程组,计算模型为Iguassu模型。得到离心机流场结果后,用非线性丰度方程组数值求解来分析离心机的分离性能。驱动参数对分离性能的影响分析及线性与非线性解的比较再次表明了非线性流场计算的必要性。从贫料挡板附近内部流场能明显看出线性解与非线性解的区别,而这也造成了分离性能的差距。     

Effect of Flow Rate on Height Equivalent to a Theoretical Plate for Lithium Isotope Separation with Displacement Chromatography

A series of experiments of Li isotope separation with displacement chromatography using a highly porous resin were performed under several flow rates from 0.1 to 20 cm³/min. The flow rates were equivalent to a speed of a moving boundary of 0.0012 to 0.26cm/s. In evaluating Height Equivalent to a Theoretical Plate, HETP, as well as separation factor which indicate separative performance of chromatographic system, we developed a new relationship between HETP and a profile of ⁶Li mole fraction in the effluent with a mathematical model taking account of a mixing in a free space at the column outlet and in the fractionated samples. The values of separation factor and HETP of each experiment were simultaneously determined by the developed relation. The obtained values of the separation factor agreed with those evaluated by the frontal analysis method within the range of the experimental error. The obtained value of HETP increased with the flow rate in the range of the present experiments. It was suggested that diffusion of Li ion in particles as well as convective mixing of the solution played a significant role on determination of HETP.     

Intensity and Pressure Effects in CO2 Laser Isotope Separation of Tritium Photolysis of CF3CTCIF with 2-ns Pulses

Albedo-Sn method was developed to predict the angular flux near the coupling boundary in the bootstrap method, using the energy-and-angle dependent double differential albedo boundary condition. In order to verify the applicability of the method to the reactor shielding design, two types of shielding problem have been analyzed. First, the neutron skyshine dose rates measured at the YAYOI reactor in University of Tokyo are predicted within an accuracy of 20%. It is also found that the neutron spectrum in the air-over-ground is much affected by albedo reflection from the ground and is reproduced well by the albedo-Sn method. Second, as for the neutron streaming through a sodium pipe chase-way, the albedo-Sn calculation saves a computer time and gives the results which agree with those by the reference Sn calculation.     

Influence of a Static Magnetic Field on Laser Induced Tungsten Plasma in Air

In this work,laser induced tungsten plasma has been investigated in the absence and presence of 0.6 T static transverse magnetic field at atmospheric pressure in air.The spectroscopic characterization of laser induced tungsten plasma was experimentally studied using space-resolved emission spectroscopy.The atomic emission lines of tungsten showed a significant enhancement in the presence of a magnetic field,while the ionic emission lines of tungsten presented little change.Temporal variation of the optical emission lines of tungsten indicated that the atomic emission time in the presence of a magnetic field was longer than that in the absence of a magnetic field,while no significant changes occurred for the ionic emission time.The spatial resolution of optical emission lines of tungsten demonstrated that the spatial distribution of atoms and ions were separated.The influence of a magnetic field on the spatial distribution of atoms was remarkable,whereas the spatial distribution of ions was little influenced by the magnetic field.The different behaviors between ions and atoms with and without magnetic field in air were related to the various atomic processes especially the electrons and ions recombination process during the plasma expansion and cooling process.     

The Influence of Magnetic Permeability on the Configuration of magnetic Field in Helimak Device

The Helimak of USA is a plasma physics experimental device designed and built by CASIPP.Its configuration of magnetic field is of very importance during the operation of this device.In this paper,the influence of magnetic permeability on configuration of magnetic field will be discussed due to the effect of weld metal in the vacuum vessel of Helimak,and some conclusion is useful for some engineering designs of the fusion experimental device.     

Magnetic Field Improvement in End Region of Rectangular Planar DC Magnetron Based on Particle Simulation

For a rectangular planar direct current （DC） magnetron, anomalous target erosion may occur in the curve-out region and inner side of the curved region. One key factor is that the magnetic field in the end region is weaker than that in the straight region, and another important factor may be that there is a circumferential component of the magnetic field in the curved region. Through a calculation of three-dimensional magnetic field for the rectangular magnetron, a magnet structure shimmed by permanent magnet bars and ferromagnetic bars is proposed to solve the above problems. Through a three-dimensional non-self-consistent particle simulation and the Yamamura/Tawara formula, the target erosion profile could be predicted. The simulation results show that for an improved uniformity in magnetic field, the entire target utilization could be much enhanced.     

Measurement of Dipole-Moment in Atomic Transitions under Strong External Magnetic Field

Obtaining an accurate value of the electric dipole moment μ is essential in the fields of laser application technologies. A direct way of measuring the electric dipole moment μ is to observe the Rabi-oscillation which manifests itself in the coherent photo-excitation behavior of atoms. In the case of the elements which have large angular momenta, identifying the Rabi-oscillation in their excitation behavior becomes rather difficult. We proposed an accurate and straightforward method of determining the electric-dipole moment μ between multifold degenerate levels. The point is to remove the degeneracy by applying an external magnetic field with the aid of the Zeeman effect and, then, to realize a degeneration free coherent excitation. As a result, we can observe the Rabi-oscillations explicitly in the excitation vs. laser-fluence curves. The present method provides a reliable basis of experimental determination of μ. As an example, we applied the present method to a transition to 0–17,362 cm^?1 level in uranium and obtained the value μ=0.86±0.06 (Debye).     

Effect of Changes in Feed Rate and Cut on Circulating Flow within Thermal Diffusion Column for Isotope Separation

A two-dimensional axisymmetric convectional flow field of an isotope separating thermal diffusion column with continuous feed and draw-offs is analyzed through the Newton iterative numerical solution of the equations of change without the Boussinesq approximation. Computations are performed for Ar gas within an inner hot radius of 0.2 mm and an outer cold radius of 5 mm, between which the temperature differs by 300 K. The rate of feed F, supplied into the middle point of the column, is varied from 1 to 5 cm³/s, while the cut θ, or the ratio of the upper drawing-off to feeding rates, from 0.1 to 0.9. Comparison of flow vectors, temperature and density profiles among various sets of (F, θ) makes it clear that the flow fields agree with one another for the same value of the total transport; that is, θF_pc (pc: feed gas density) in the upper section and -(1-θ)pc in the lower section of the column. Observations on the mass flow vectors near the feed slit lead to the finding that the multiplicative effect of separation cannot be expected in the column with the inner radius r_c of 5 mm at the feed rate F exceeding 2 cm³/s(i.e F/ΔTr_c ⁴ )>0.1 [1/(s·K·cm)]), because the feed flow interrupts the whole-length circulation of the natural convection.