HL-2A 装置上动态斯塔克效应偏振仪研究

在HL-2A 装置上发展了两类动态斯塔克效应(MSE)偏振仪并应用于磁场倾斜角的测量。其中被称为比值法的MSE 系统误差可以被控制在±0.15°以内。在HL-2A 装置实验中,利用该方法成功获得7 个空间点、径向覆盖范围为24cm 的磁场倾斜角剖面分布,其时间分辨可达到40ms。应用平衡重建代码(EFIT)结合MSE 测量数据的限定,可以得到安全因子(q)的径向分布,其中q=1 面的位置与软X 射线测量得到锯齿振荡反转面的位置一致。调制法MSE 在标定实验中误差也可控制在±0.15°以内。实验结果表明偏振片透振方向与双光学弹性调制器 (dual PEM)快轴夹角平分线的偏差对系统的线性和误差均有较大的影响。目前,该系统已经建成一个空间通道,测得磁场倾斜角的时间分辨可以达到20ms。     

轴对称奇A核系统的强耦合临界点对称性

鉴于临界点对称性方法在描述原子核形状相变中的成功应用,在强耦合方案下对原有描述偶偶核球形到长椭形状相变的临界点对称性模型X（n）（n=3,4,5）进行扩展,据此建立描述轴对称奇A核系统的SX（n）临界点对称性。通过对X（n）模型与SX（n）模型的转动谱结构进行对比分析,揭示了SX（n）临界点模型的动力学结构受模型维数n的影响较小且更接近刚性转子的模型特征,这些模型特征进一步通过检验过渡区核素150,151,152,153Sm以及172,173,174,175Os中的相关转动带结构得到了初步证实。In view of the successful application of the methods based on critical point symmetries (CPSs) in nuclear shape phase transitions, the new CPSs named SX(n) are established in this work for axially-symmetric odd-A nuclei through extending the original X(n) CPSs with n=3,4,5, which were used to describe the spherical to prolate shape phase transitions in even-even nuclei, in the strong-coupling scheme. By comparing the spectral structures in between the X(n) and the SX(n) CPSs, it is revealed that the dynamical structures of SX(n) are closer to the rigid rotor and less changed with the model dimension in comparison with X(n). Moreover, these features of SX(n) are preliminarily verified by checking the rotational structures of 150,151,152,153Sm and 172,173,174,175Os nuclei.     

窄带紫外LED照射对大鼠骨代谢的影响

背景：紫外线是维持骨骼健康的关键条件之一，但由于传统的紫外线光谱较宽，在骨质疏松症领域并未引起足够的重视。材料与方法：在研究中，建立了一种新设计的窄带光谱LED器件，以研究紫外LED对骨质疏松大鼠骨代谢、骨形态和皮肤的影响。共设置了去卵巢大鼠（n=24）和去卵巢大鼠（n=36）。然后将去卵巢大鼠分为假手术组（Sham，n=12）和检测模型组（Sham，n=12)。将去卵巢大鼠分为LED照射组（LED，n=12）、未处理组（OVX，n=12）或检测模型组（OVX，n=12）。LED 辐照参数（0.8 mW·cm-2，1 000 s，每周两次）。结果：与假手术组相比，维生素D、mRNA、血清ALP、血清25(OH)D₃、血清P1NP的表达明显升高，血清PTH和血清TRAP的表达明显降低。大鼠皮肤照射前后p53基因未见明显变化。结论：研究结果表明，新型紫外 LED 器件照射可显着提高血液中 25(OH)D₃ 水平，促进骨形成，抑制骨吸收，且对大鼠皮肤无不良影响。     

特种工程塑料太赫兹光学参数测量及误差分析

以聚苯硫醚(PPS)、聚醚酰亚胺(PEI)及其玻璃纤维增强材料(PPS-GF30,PEI-GF30)为样品,获得了在太赫兹频段的光谱特性。首先,利用太赫兹时域光谱系统,在透射模式下,测试了四种材料在自由空间的时域信号。然后,根据提取光学参数的物理模型及菲涅尔透射公式计算材料的折射率及消光系数,同时对物理模型和菲涅耳公式解析法仿真,保障了实验测试和算法的合理性与可靠性。最后,依据误差传输理论计算了由主要因素决定的光学参数误差。在样品各自的太赫兹有效频段,实验显示： PPS： n=1.889~1.945(误差0.003~0.012),κ=0.001~0.047、(误差0.000 1~0.002 6),PPS-GF30： n=1.654~1.672(误差0.003~0.004),κ=0.002~0.057(误差0.000 1~0.002 8),PEI： n=1.713~1.733(误差0.002~0.012),κ=0.005~0.035(误差0.000 1~0.003 0),PEI-GF30： n=1.688~1.732(误差0.003~0.004),κ=0.036~0.068(误差0.000 2~0.002 6)。结果表明： 作为太赫兹超材料器件的基底,PPS适合低频,PEI适合高频,玻璃纤维增强的PPS,PEI相比纯样品,不仅力学性能得到改善,并有利于信号探测,而且在有效频段的高频部分,探测灵敏度更强。研究提供了PPS,PEI及其玻璃纤维增强材料在太赫兹频段的基础参数,为太赫兹领域超材料器件的研究提供了重要参考。     

类氢离子的相对论康普顿轮廓（英文）

基于中心场近似得到Dirac径向轨道,并使用恰当的Fourier变换系统计算了类氢离子电子动量分布和康普顿轮廓。以H原子和Xe53+离子为例,探讨了相对论效应和原子核的有限体积效应对单电子康普顿轮廓的影响。同时,详细研究了单电子康普顿轮廓对主量子数n、轨道量子数l、单电子总角动量量子数j和核电荷数Z的依赖关系。结果表明,相对论效应可以扩展康普顿轮廓的分布,并且使给定nl的轨道随着Z的增加分裂得越来越明显。然而,相对论效应也会随着主量子数n和轨道量子数l的增加而减弱。同时,对于nl_j轨道,其康普顿轮廓还具有n-l个平台的结构。另外,原子核的有限体积几乎不会影响H原子和Xe53+离子的康普顿轮廓。The Compton profiles of the electron in the ground and excited states of H-like ions have been calculated systematically with one-electron Dirac radial orbitals by using the proper Fourier transformation. Taking the H atom and Xe53+ ion as examples, the effects of relativity and finite nuclear size on Compton profile have been discussed. Furthermore, the dependence of one-electron Compton profile on the principle quantum number n, orbital quantum number l, angular quantum number j and nuclear charge Z has also been discussed. It is found that the relativistic effect can expand the distribution of the Compton profile and split the orbital more and more obviously for given nl(l=0) as increasing Z. However, the relativistic effect can gradually weaken with the increase of the principal quantum number n and orbital quantum number l. Furthermore, the Compton profile of the orbital with quantum number nl_j has certain number of platforms that is n-l. In addition, the nuclear finite size hardly affects the Compton profile for H atom and Xe53+ ion.     

HmTiSin(m=1～2;n=2～8)团簇结构、电子性质和红外光谱的密度泛函理论研究

近些年,由于硅半导体材料在微电子工业中的潜在应用,其理论和实验研究备受人们广泛关注。尤其是过渡金属掺杂的硅团簇材料在物理化学性质方面表现了极好的稳定性。这些主要归因于过渡金属含有未填满的d轨道电子,可以填充硅团簇表面的空轨道,减少团簇表面的悬挂键,进而提高整个掺杂硅团簇的结构稳定性,同时产生各种特殊光学、磁性和超导等性质。采用密度泛函理论DFT-B3LYP方法对H_mTiSi_n(m=1～2; n=2～8)团簇的几何结构和电子性质进行了理论计算,讨论了Ti掺杂硅团簇TiSi_n(n=2～8)及其氢化团簇基态结构的变化规律、解离通道和HOMO-LUMO能隙等特征。结果表明,随着Si原子数目的增加,在TiSi_n(n=2～8)团簇中其掺杂Ti原子依次吸附在团簇的棱、面及结构内部。当在掺杂团簇表面吸附氢原子时,都优于吸附在团簇的硅原子上,而且绝大多数的氢化结构采纳了TiSi_n团簇的骨架构型。解离能和HOMO-LUMO能隙的分析结果表明在团簇表面吸附两个H原子时能够明显提高整个团簇的结构稳定性。二阶能量差分的研究发现TiSi₂和TiSi₆团簇相对其他团簇具有较高的稳定性,同时两个H₁TiSi₇和H₂TiSi₇氢化团簇的稳定性更高。此外,模拟了这些氢化团簇的红外振动特征峰,对主要特征峰进行了归属。这些研究将为过渡金属掺杂硅基团簇材料的实验制备和表征提供重要的理论参考。     

J-TEXT托卡马克高速单色成像系统研制

在 J-TEXT 托卡马克上研制了一套高速单色成像系统用于研究等离子体杂质行为与磁流体力学(MHD) 不稳定性之间的关系。用 STRAH 代码模拟估算了碳杂质(CV227.09nm,CIII464.7nm)辐射强度。采用光纤耦合方 法设计了系统光路结构,光路覆盖高场侧区域 0.3a~0.95a(a 为小半径),其空间分辨率为 1.3cm。选用光电倍增管 (PMT)作为系统的探测器,结合跨阻电路与有源滤波器的电路方案,系统实现 5×10⁵VA^-1 电流增益,其电路带宽 为 100kHz,时间分辨率达到 10μs。初步实验结果表明,系统可以监测到 J-TEXT 中等离子体 MHD 不稳定性放电 中 CV 分布的变化。      

级联弧放电氦等离子体特性研究

采用另加偏压的单阴极弧氦放电直线等离子体装置对氦等离子体的基本特性进行了研究。对氦轴向输运规律做了描述并与光谱测量数据做了定性地比较。实验结果表明,氦等离子体的电子温度与电子密度均随放电电流、约束磁场的增加而增加。氦原子与氦离子的辐射光谱随放电电流、偏压、磁场的变化规律进行了测量分析,同时氦离子对钨靶积分辐照效应进行了观察。这些结果不但提供了氦等离子体的基本特性,对于研究氦离子与面向等离子材料相互作用导致产生气泡、肿胀、脆化损伤等的评估,特别是对将来伴有(n, α)反应时具有一定的参考价值。     

HT-7装置软X射线诊断系统及锯齿行为研究

利用HT-7装置上建立的多阵列软X射线诊断系统对等离子体放电中的锯齿不稳定性进行研究,发现锯齿的出现及其行为特点与等离子体电子密度N_e、电子温度T_e、边界安全因子q_α、壁条件等放电参数有密切关系。在低杂波电流驱动等离子体放电条件下,观察到m/n=1/1的中间模振荡出现在锯齿的上升阶段,并迅速发展、饱和、衰减,在锯齿塌陷或先兆振荡出现以前消失。分析和讨论了欧姆加热条件下和低杂波加热条件下的锯齿行为。     

EAST中n=4共振磁扰动下等离子体的环向旋转制动

在EAST中n=4的共振磁扰动下观察到明显的等离子体旋转制动效应，其分布具有全局性，且峰值靠近等离子体中心。利用模拟得到的新经典环向粘滞(NTV)力矩来反演等离子体环向角速度的变化，结果表明在大部分径向区域与实验测量的速度变化符合得较好，量值上相差约1~2倍。     

磁控条件下激波冲击三角形气柱过程的数值研究

本文基于磁流体动力学方程组,在保证磁场散度为零的条件下,采用CTU+CT（corner transport upwind+constrained transport）算法,对有无磁场控制下激波与重质或轻质三角形气柱相互作用过程进行数值研究.结果表明：无论有无磁场,两气柱在激波冲击下均具有完全不同的波系结构和射流现象.其中,入射激波与重气柱发生常规折射,形成介质射流,而与轻气柱作用则发生非常规折射,形成反相空气射流.无磁场时,气柱在激波冲击下,产生Richtmyer-Meshkov和Kelvin-Helmholtz不稳定性,界面出现次级涡序列,重气柱上下角卷起形成主涡对,轻气柱空气射流穿过下游界面后形成偶极子涡.施加横向磁场后,次级涡序列、主涡对以及偶极子涡均消失.进一步研究表明,在磁场作用下,洛伦兹力将不稳定性诱导产生的涡量向界面两侧的Alfvén波上输运,减少界面涡量沉积,抑制界面卷起失稳.最终,涡量沿界面两侧形成相互远离的涡层,界面不稳定性得到控制.此外,定量分析表明磁场能加快两气柱上游界面的运动,抑制下游界面的运动,且对轻气柱的控制效果更好.     

导电突扩管中磁流体管流的数值模拟

采用基于OpenFOAM环境自主开发的低磁雷诺数磁流体求解器,对45°和90°突扩矩形管中液态金属流体在受到垂直流向的外加磁场作用时的速度、感应电流、压力的分布及突扩位置处的MHD三维现象进行数值模拟.结果表明：磁场沿突扩方向时,由于无回流涡,45°比90°突扩管在肩部位置速度分布更优.哈特曼数增大,强射流和突扩结构,在突扩肩部位置引发流动的不稳定性.伴随感应电流的不稳定,流动不稳定发展到突扩位置上游.磁场沿垂直突扩方向时感应电流的三维效应显著.哈特曼数增大,MHD压降显著增大.同方向磁场和相同哈特曼数,不同突扩角度的三维无量纲压力梯度无明显差异.     

A consistent and conservative scheme for incompressible MHD flows at a low magnetic Reynolds number. Part III: On a staggered mesh

The consistent and conservative scheme developed on a rectangular collocated mesh [M.-J. Ni, R. Munipalli, N.B. Morley, P. Huang, M.A. Abdou, A current density conservative scheme for incompressible MHD flows at a low magnetic Reynolds number. Part I: on a rectangular collocated grid system, Journal of Computational Physics 227 (2007) 174–204] and on an arbitrary collocated mesh [M.-J. Ni, R. Munipalli, P. Huang, N.B. Morley, M.A. Abdou, A current density conservative scheme for incompressible MHD flows at a low magnetic Reynolds number. Part II: on an arbitrary collocated mesh, Journal of Computational Physics 227 (2007) 205–228] has been extended and specially designed for calculation of the Lorentz force on a staggered grid system (Part III) by solving the electrical potential equation for magnetohydrodynamics (MHD) at a low magnetic Reynolds number. In a staggered mesh, pressure (p) and electrical potential (φ) are located in the cell center, while velocities and current fluxes are located on the cell faces of a main control volume. The scheme numerically meets the physical conservation laws, charge conservation law and momentum conservation law. Physically, the Lorentz force conserves the momentum when the magnetic field is constant or spatial coordinate independent. The calculation of current density fluxes on cell faces is conducted using a scheme consistent with the discretization for solution of the electrical potential Poisson equation, which can ensure the calculated current density conserves the charge. A divergence formula of the Lorentz force is used to calculate the Lorentz force at the cell center of a main control volume, which can numerically conserve the momentum at constant or spatial coordinate independent magnetic field. The calculated cell-center Lorentz forces are then interpolated to the cell faces, which are used to obtain the corresponding velocity fluxes by solving the momentum equations. The “conservative” is an important property of the scheme, which can guarantee computational accuracy of MHD flows at high Hartmann number with a strongly non-uniform mesh employed to resolve the Hartmann layers and side layers. 2D fully developed MHD flows with analytical solutions available have been conducted to validate the scheme at a staggered mesh. 3D MHD flows, with the experimental data available, at a constant magnetic field in a rectangular duct with sudden expansion and at a varying magnetic field in a rectangular duct are conducted on a staggered mesh to verify the computational accuracy of the scheme. It is expected that the scheme for the Lorentz force can be employed together with a fully conservative scheme for the convective term and the pressure term [Y. Morinishi, T.S. Lund, O.V. Vasilyev, P. Moin, Fully conservative higher order finite difference schemes for incompressible flow, Journal of Computational Physics 143 (1998) 90–124] for direct simulation of MHD turbulence and MHD instability with good accuracy at a staggered mesh.     

高超声速飞行器磁控热防护系统建模分析

针对高超声速飞行器防热, 搭建了螺线管磁控热防护系统的物理模型. 采用低磁雷诺数磁流体数学模型, 分析了外加磁场强度及磁场形态对磁控热防护效果的影响. 对比了三种磁场类型(磁偶极子、螺线管、均布磁场)下磁控热防护效果的差异, 分析了螺线管几何参数对磁控热防护效果的影响. 研究表明, 磁场降低表面热流作用存在“饱和现象”; 三种磁场形态的磁控热防护能力从小到大依次为磁偶极子、螺线管、均布磁场; 相同驻点磁感应强度条件下, 增大螺线管半径有利于提高磁控热防护效果, 缩短螺线管与驻点距离不利于驻点和肩部防热, 螺线管长度对磁控热防护效果影响相对较小.     

相关分析法确定HL-1M装置磁流体的扰动模式

采用相关分析法模拟分析了HL-1M装置的磁扰动模式,模拟的结果同预期的结果一致。在具有磁流体不稳定性的典型放电中,探测到独立模m=2、3、4,耦合模m=2、3,以及同时出现的耦合模m=4、5和独立模m=5,给出了用扰动幅度的极向截面图分析磁扰动模式的结果,讨论了相关分析法在实验分析中的优点和局限性。     

HT-6A托卡马克平衡系统的实验

本文叙述了HT-6A托卡马克平衡系统及第一期平衡实验结果.讨论了HT-6A上铜壳对平衡的贡献;观察到改变垂直场形态因子n而产生的水平位移及垂直位移不稳定现象;介绍了正常放电时的平衡实验,观察到等离子体位移与MHD扰动是紧密相连的;用沙弗拉诺夫薄壳理论计算了对多大的等离子体电流应施加多大的垂直场,结果与实验完全符合。     

The instability conditions of a gas trapped in weak weakly interacting Fermi magnetic field

In this paper the analytical expression of free energy expressed by small parameter r of a weakly interacting Fermi gas trapped in weak magnetic field is derived by using `the maximum approximation' method and the ensemble theory. Based on the derived expression, the exact instability conditions of a weakly interacting Fermi gas trapped in weak magnetic field at both high and low temperatures are given. From the instability conditions we get the following two results. (1) At the whole low-temperature extent, whether the interactions are repulsive or attractive with (ɑn + 4\varepsilon_F/3) (n and \varepsilon _F denote the particle-number density and the Fermi energy respectively, ɑ= 4π a\hbar_F/ m, and a is s-wave scattering length) positive, there is a lower-limit magnetic field of instability; in addition, there is an upper-limit magnetic field for the system of attractive interactions with (ɑ n + \varepsilon_F/3) negative. (2) At the whole high-temperature extent, the system with repulsive interactions is always stable, but for the system with attractive interactions, the greater the scattering length of attractive interactions | a | is, the stronger the magnetic field is and the larger the particle-number density is, the bigger the possibility of instability in the system will be.     

A Complete 2D Stability Analysis of Fast MHD Shocks in an Ideal Gas

 An algorithm of numerical testing of the uniform Lopatinski condition for linearized stability problems for 1-shocks is suggested. The algorithm is used for finding the domains of uniform stability, neutral stability, and instability of planar fast MHD shocks. A complete stability analysis of fast MHD shock waves is first carried out in two space dimensions for the case of an ideal gas. Main results are given for the adiabatic constant γ=5/3 (mono-atomic gas), that is most natural for the MHD model. The cases γ=7/5 (two-atomic gas) and γ>5/3 are briefly discussed. Not only the domains of instability and linear (in the usual sense) stability, but also the domains of uniform stability, for which a corresponding linearized stability problem satisfies the uniform Lopatinski condition, are numerically found for different given angles of inclination of the magnetic field behind the shock to the planar shock front. As is known, uniform linearized stability implies the nonlinear stability, that is local existence of discontinuous shock front solutions of a quasilinear system of hyperbolic conservation laws. Received: 12 March 2002 / Accepted: 8 November 2002 Published online: 10 February 2003 Communicated by P. Constantin     

Magneto-Rayleigh-Taylor instability in compressible Z-pinch liner plasmas

In this paper, the characteristics of magneto-Rayleigh-Taylor(MRT) instability of liner plasmas in Mag LIF is theoretically investigated. A three-region slab model, based on ideal MHD equations, is used to derive the dispersion relation of MRT instability. The effect of compressibility on the development of MRT instability is specially examined. It is shown that the growth rate of MRT instability in compressible condition is generally lower than that in incompressible condition in the presence of magnetic field. In the case of zero magnetic field, the growth rate in compressible assumption is approximately the same as that in incompressible assumption. Generally, MRT instability in(x, y) plane can be remarkably mitigated due to the presence of magnetic field especially for short-wavelength perturbations. Perturbations may be nearly completely mitigated when the magnetic field is increased to over 1000 T during liner implosions. The feedthrough of MRT instability in liner outer surface on inner surface is also discussed.