Collective bounce-off phenomenon in139La+Ag(Br) reaction at 1.1 A GeV energy

Out of a total statistics of 896¹³⁹La+Ag(Br) interactions, 128 interactions having multiplicity of target fragments (Z⩾1)⩾8 and projectile fragments (Z⩾2)⩾4 have been selected. They correspond to quasi-peripheral interactions. Azimuthal angle correlation between sources of target fragments (TFs) and projectile fragments (PFs) shows the existence of bounce-off effect. Using data of La+Ag(Br) and⁸⁴Kr+Ag(Br) reactions it is shown that individual helium [Z=2, PFs] and heavier fragment [Z⩾3, PFs] show different emission characteristics. Further, a two prong correlation functionT(Φ _ij ) plotted for heavier fragments and helium fragments separately, indicates the possibility of existence of different physical conditions. This observation is supported by the different momentum widths of helium fragments and heavier fragments. From the momentum width data of Kr+Ag(Br) reactions normalized density comes out to be ≈4.7. Using quasi-elastic kinematics for the bounce-off nuclei, the excitation energy has been computed from the experimental data of flow angles. The strength of bounce-off seems to decrease with the increase of excitation energy or temperature.     

HL—1装置汤姆逊散射测量空间两点电子温度

本文叙述用激光汤姆逊散射方法测量HL-1装置在不同放电条件下空间两点的电子温度。简要介绍了测量条件,空间两点测量的实验安排及数据获取系统等。对实验结果进行了初步分析。在适当改变等离子体边缘径向电场分布时,电子温度有明显增加。     

黑腔靶中超热电子特性研究

近几年来,在“神光”装置上进行了1.053μm激光与平面靶及一系列柱形黑腔靶相互作用实验。用一台多道滤波—荧光X光能谱仪(FFS)测得各种靶发射的超热X射线谱,由谱推导超热电子温度T_h和超热电子总能量E_h当照射靶单束激光能量E_(tar)为400～670J、脉宽τ=650～1150ps时,发现黑腔内明显存在两群服从Maxwell分布高能电子(T_h=35～45keV;T_(hh)=150～350kev),而且E_(he)占E_(tar)的份额为10％～12％。实验还表明:腔内的E_(he)与非线性过程特征量(SRS)有较好的线性关系,因此推断出腔内超热电子产生的主要机制是受激Raman散射。在相同照射条件下,黑腔靶产生的超热电子比平面靶严重。     

Effects of metal irises on the guided-mode properties in asymmetrical slab waveguides

The diffraction phenomenon caused by metal transverse irises placed into an asymmetrical slab waveguide is examined by using the integral equation method. We concentrate on the possibility of controlling the radiation characteristics of the structure by changing the irises positions and the slab waveguide asymmetry. The aperture electric-field distribution is expressed in terms of a finite series of Chebyshev polynomials. The dominant TE guided-mode reflection and transmission coefficients, the near-field distribution and the far-field radiation pattern are calculated, while numerical results are presented for several cases of asymmetrical slab waveguides and different irises’ positions.     

Measurements of diffuse backscattering Mueller matrices of turbid media

We report on the development of a method that records spatially dependent intensity patterns of polarized light that arise from illuminating a turbid media with a polarized laser beam and being diffusely backscattered. Our technique employs polarized light from a He-Ne laser () which is focused onto the surface of the scattering medium. A surface area of approximately 2×2 cm centered on the light input point is imaged through polarization analysis optics onto a CCD camera. The Mueller matrix is reconstructed by 49 intensity measurements with various orientations of polarizer and analyzer. The measured Mueller matrix of polystyrene spheres was compared with the theory result of incoherent scattering of light by spheres. The experimental and theory results are in excellent agreement. It appears that the azimuthal patterns of the Mueller matrix are determined by the symmetry of the turbid media.     

Spin–orbit stiffness of the spin‐polarized electron gas

In a spin‐polarized electron gas, Coulomb interaction couples the spin and motion degrees of freedom to build propagating spin waves. The spin wave stiffness S_sw quantifies the energy cost to trigger such excitation by perturbing the kinetic energy of the electron gas (i.e. putting it in motion). Here we introduce the concept of spin–orbit stiffness, S_so, as the energy necessary to excite a spin wave with a spin polarization induced by spin–orbit coupling. This quantity governs the Coulombic enhancement of the spin–orbit field acting of the spin wave. First‐principles calculations and electronic Raman scattering experiments carried out on a model spin‐polarized electron gas, embedded in a CdMnTe quantum well, demonstrate that S_so = S_sw. Through optical gating of the structure, we demonstrate the reproducible tuning of S_so by a factor of 3, highlighting the great potential of spin–orbit control of spin waves in view of spintronics applications. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

一种基于多准则决策和PSO-LM混合优化算法的多峰Brillouin散射谱的特征提取方法

采用传统方法对多峰Brillouin散射谱进行拟合的过程中,通常是以谱线最大功率点为基准的,却忽略了其他比该点小但却是极值的功率点。这样获得的拟合曲线通常只有一个峰值,相当于把除最高峰之外还有多个小峰的多峰Brillouin散射谱进行了简化,导致大量有用信息的丢失。为了提高Brillouin散射谱的特征提取精度,提出了一种基于MCDM和PSO-LM混合优化算法的多峰Brillouin散射谱特征提取方法(MCDM-PSO-LM)。MCDM可以识别和准确定位多峰Brillouin散射谱的各个波峰和波谷;PSO-LM混合优化算法可以实现分别对各个波峰和波谷的曲线进行拟合并找到每一个波峰的中心频率,该算法既克服了PSO算法过早收敛于局部极值和LM算法依赖初值的问题,又可以将PSO算法的全局搜索能力和LM算法的局部收敛能力结合在一起。较传统算法而言,MCDM-PSO-LM算法保证了对最优值求解的速度和精度,提高了运算能力,使解析解最大限度地接近最优值。分别在不同信噪比和不同线宽条件下进行仿真验证,频移和温度误差分析结果表明,MCDM-PSO-LM方法可以对多峰Brillouin散射谱的各个波峰与波谷进行准确定位,可用于多峰Brillouin散射谱的特征提取,识别效果明显强于传统算法,提高了信息分析的准确性。     

Compton散射下横等离激元与对等离子体作用特性

应用多光子非线性Compton散射模型、横等离激元色散方程和Karpman方法,研究了Compton散射对横等离激元与对等离子体作用特性的影响,提出了将入射超强激光和Compton散射作为横等离激元与对离子等离子体非线性作用新机制,给出了横等离激元非线性控制方程、等离激元数和能量公式。结果表明:与散射前相比,Compton散射使等离子体密度发生剧烈扰动,高频横等离激元与低密度扰动耦合非线性增强,导致横等离激元落入低密度区的几率增大。等离子体非线性频移和高密度区能量增加,低密度区能量减小,导致横等离激元电场包络迅速坍塌,等离激元数增加,场强度更强。     

Raman spectroscopy of the BC3 phase obtained under high pressure and high temperature

A direct transformation of the g‐BC₃ phase to a new diamond‐like d‐BC₃ phase was observed in a diamond‐anvil cell (DAC) at high temperature, 2033 ± 241 K, and high pressure, 50 GPa. Analysis of the peak positions of the d‐BC₃, B₄C, α‐boron, and the boron‐doped diamond leads to the conclusion that the positions of the peaks of the d‐BC₃ are more similar to the peak pattern of the boron‐doped diamond rather than that of boron carbide, α‐boron. Copyright © 2007 John Wiley & Sons, Ltd.     

带光纤环的分布式光纤拉曼温度系统

 为了抑制分布式光纤拉曼温度系统的温漂和瑞利散射光窜扰反斯托克斯散射光,在传感光纤前端盲区后放置光纤取样环,用瑞利散射光解调反斯托克斯散射光及用光纤取样环的温度计算光纤线上其它点的温度,提高了系统的测温精度和稳定性。采用功率100 mW,波长1.55 μm,脉宽10 ns脉冲激光器和15 dB前置光纤放大器,100M14bitA/D转换卡及DSP作数字平均构建光纤拉曼温度系统的实验,实现了测温误差在±0.03 ℃内。