Methods for Reconstructing Spatial Distributions of Radiation from Plasmas

Methods are discussed for reconstructing spatial distributions from two types of projection-in a direction tangential to a torus and in a cross-sectional plane. For a tangential projection the reconstruction is unambiguous. For cross-sectional projections one usually does not have enough information for an unambiguous reconstruction, unless strong simplifying assumptions are made. A method is given for fitting a spatial distribution to such projections. Tests of both methods are discussed. The fitting method for cross-sectional projections is compared with a Fourier-series method.     

Dielectric Function and Diffusivity of Nonideal Plasmas

The dielectric function for a two-component (hydrogen) plasma at arbitrary degeneracies is considered in the entire (k, w)-space. Collisions are treated in Born approximation leading to a (k, w)-dependent collision integral. Two possible limits are considered: (1) k → 0 (first), w → 0 (second) leading to the dc conductivity σ. (2) w → 0 (first), k → 0 (second) leading to the diffusivity D. The relation between σ and D is discussed.     

Escape statistics for systems driven by dichotomous noise. I. General theory

Previous results on first-passage-time statistics for systems driven by dichotomous noise are extended in order to cover the escape from regions including fixed points of the stochastic flow. For such regions a treatment splitting the escape through one or the other boundary is required. The obtained escape probabilities and mean exit times are relevant for the complete characterization of stochastic systems undergoing bifurcations.     

Linear Motion under Constant Force and Radiation Reaction

The classical relativistic equation of motion with radiation reaction is solved exactly when the motion is along the lines of force due to a constant electric field. For physically admissible solutions, there is no contribution due to the radiation reaction. The general motion without radiation reaction is not linear.     

Electrical Conductivity of Non-ideal Plasmas and the Ion Distribution Function

The theory of electrical conductivity of electron-ion-systems is developed for a density region which reaches from the region of non-ideal plasmas up to the region of liquid metals. The conductivity is expressed by quantum mechanical correlation functions. Different forms of the electron-ion pseudopotentials are considered. The ion distribution function is derived using the mean spherical approximation (MSA) theory or the nonlinear Debye-theory. Higher order scattering effects are treated by introducing scattering phase shifts for the statically screened electron-ion potential. The numerical results for the conductivity show a SPITZER-like behaviour in the low-density non-degenerate limit where higher order scattering is important, and a ZIMAN-like behaviour in the strongly degenerate high-density limit where the ion distribution functions and the form of the electron-ion pseudopotential become more important.     

Radiation from a Line Source Placed in Two-dimensional Photonic Crystals

A novel formulation of radiation from a localized line source placed in two-dimensional photonic crystals consisting of layered periodic arrays of parallel circular cylinders is presented. The method employs the spectral domain approach. The spectral response of the photonic crystals to the line source excitation is calculated using the lattice sums, the T-matrix of a circular cylinder, and the generalized reflection and transmission matrices of the layered system. The far-zone radiated field is obtained using the conventional asymptotic method to the spectral response. The radiation patterns of the localized line source sandwiched by two photonic crystals are numerically studied.     

放大率恒定的二元光学超光谱成像仪光学系统设计

二元光学元件具有多种应用。用作透镜，在原理上色差非常大，若不在设计上做出补偿，则会限制其在宽波段上的使用。从理论上简单阐述了利用具有独特色散特性的二元光学元件的新型超光谱成像仪的基本原理和应用前景。在此超光谱成像仪中，二元光学透镜焦距随波长的变化改变了系统的F数，因此改变了系统的放大率，既系统放大率是波长的函数，这将引起光谱图像的像元配准误差，得到并不精确的相对光谱信号强度，从而限制了光谱图像重建算法的精度，为了补偿这一缺点，通过光学二组元法设计的变焦系统成功地解决了这一问题，并给出了理论设计公式。     

LED阵列光源应用于几何光学实验

设计并制作了单色LED、高功率白光LED阵列光源及配套电源,将其应用于普通物理几何光学实验中。在透镜焦距测量实验中,实现了光源和物屏的结合,成像效果好,光源稳定、可调,相比于卤钨灯光源,成本低,且环保、节能,散热小。     

Radiation of a relativistic magneton. I

A derivation is given of the field intensities created in vacuum by a neutral, arbitrarily moving point particle possessing a proper magnetic moment. For brevity this particle is called a magneton. The field of the magneton is represented as the superposition of a convective field and a radiation field. It is shown that the radiation field possesses the characteristic properties of the field of an electromagnetic plane wave — orthogonality and transversality.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 12–16, May, 1978.The authors wish to thank Professor V. G. Bagrov for his interest in the work and for valuable remarks.     

Multiple-Scattering Contributions to the Electrical Conductivity of Non-Ideal Plasmas. I. Two Particle Scattering

On the basis of the Green's function formalism multiple scattering effects due to two-particle scattering are investigated with respect to their influence on the electrical conductivity of dense, non-ideal hydrogen plasmas. Both the linear response formalism and the rigorous kinetic treatment via the Kadanoff-Baym equation yield equivalent results for this case. A local lowering of the conductance isotherms for is found to be a consequence of the disappearence of the last bound state of the shielded electron-proton complex. Influences due to lowest order dynamical shielding effects are found to cause considerable lowering of the conductivity in this region due to photon polarization. We also discuss effects of multiple two-particle scattering on the photon-polarization itself.     

一种高稳定半导体激光器驱动电源的设计与分析

设计了一种高稳定半导体激光器驱动恒流电源,分析和讨论了集成运放负反馈型恒流源的负载、温度特性以及稳定精度。给出了LD注入电流稳定度的测量结果,LD注入电流稳定度可达10^-6,用稳定的激光器观察了充有约1．3kPa缓冲气体的自然铷的D2吸收谱线。此外,该电源还具有抗击浪涌击穿、断电保护和过流保护等多种功能。     

A Simple Configuration for Discontinuous Wavelength-tuning Optical Pulse Source

A simple configuration is proposed to perform wavelength switching in actively mode-locked fiber ring lasers, in which a sampled fiber Bragg grating and a tunable optical filter are cascaded in the ring cavity to exactly select the operating wavelength. The switching of four wavelengths with a spacing of 1.6 nm is obtained. The experimental results demonstrate that this technique is reliable and convenient.     

A Simple Configuration for Discontinuous Wavelength-tuning Optical Pulse Source

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Diagnostics of L.F. Plasma Fluctuations by Probes and Optical Line Radiation

Two wide spreaded methods for the measurement of plasma fluctuations are investigated both theoretically and experimentally. In limited regions of frequency and wave number, the fluctuation amplitudes obtained by probes and optical line radiation show sufficient good agreement; in general, however, different effects must be eliminated in order to obtain quantitative values. As an application, a transition from isothermal ion acoustic turbulence to a hybrid turbulent state including temperature fluctuations in a low pressure d.c. plasma has been discovered.     

Anisotropic fluid in a spherical spacetime: I. Radiation from a compact star

Generalizing work of Misner and Sharp, we develop the general relativistic theory of any spherically symmetric spacetime, allowing for shearing stresses (hence unequal principal pressures) in the matter. Assumptions specific to the system considered are required to determine the time-evolution of the principal pressures. For a gas of noninteracting massless particles, the necessary equations follow from relativistic kinetic theory. The equations for null radiation are solved in the steady-state case, neglecting both: (a) the mass loss of the central body, and (b) the effect of the radiation on the background (Schwarzschild) geometry. Once the velocity-field of the radiation is specified, its energy-momentum tensor follows by integration. The form of the velocity-field cannot be uniquely fixed by the theory because it varies from case to case. Asymptotically, at large distances R, the energy density and principal pressures of null radiation usually fall off as R^?4 while its proper speed increases as R. A one-parameter family of model stars emitting null radiation in flat spacetime is constructed. These differ in how narrow a cone the radiation is beamed into. Radiation emitted isotropically differs markedly from that which is emitted with sharp directionality.     

外围介质介电常数对金纳米棒光学性质影响的数值模拟

采用电化学方法制备出悬浮胶体金纳米棒。在室温下测得其紫外-可见吸收光谱和荧光发射光谱。结合准静电场理论与散射理论对金纳米棒的光学特性进行了数值模拟。计算结果表明,由于金纳米棒形状的各向异性,吸收截面与散射截面均出现两个共振峰,分别对应于横截方向与长轴方向的表面等离子共振。对于几何形状一定的金纳米棒,在外围介质介电常数从1.5增加到2.5的过程中,两个共振吸收峰均增强并非线性红移。然而对于散射光谱,短波方向的共振峰线性红移,强度变化微弱;长波方向的共振峰减弱并非线性红移。     

Extreme Ultraviolet Radiation Source Based on a Discharge Sustained by a Radiation Pulse from a Terahertz Free-Electron Laser

Journal of Experimental and Theoretical Physics - We consider the possibility of sustaining a discharge in xenon efficiently emitting light in a wavelength range of 11.2 nm ± 1% by a...     

Optical properties of 3d-ions doped RbCdF3. Radiation effects

Abstract

The optical properties of RbCdF₃ crystals doped with Cr³⁺, Mn²⁺ and Ni²⁺ have been studied. Absorption and photoluminescence spectra correspond to these ions in an octahedral environment. The lifetimes of the emitting levels have been measured at different temperatures. Single exponential decays are obtained for Mn²⁺ and Ni²⁺ while a non-exponential decay is found in the case of Cr³⁺. Radiation effects have also been studied. A new absorption band is produced in the 305 nm region by RT X-irradiation. Exciting with light in this band the 3d-ions emissions are observed.     

大芯径大数值孔径阶跃光纤传导模特征方程求解

导出了相邻阶第二类变型贝塞尔函数的比值在小宗量的逼近形式,利用Lentz—Thompson方法计算相邻阶第一类贝塞尔函数的比值在小宗量的值,计算精度为浮点数系统的最低有效位。从而解决了求解大芯径、大数值孔径阶跃光纤的特征方程时．贝塞尔函数溢出双精度浮点数表示范围的问题。分别对多模石英光纤和大芯径大数值孔径的聚合物光纤的传导模特征方程进行了求解,石英光纤的传导模特征值计算结果与Optiwave公司的软件一致;对于聚合物光纤,算法给出了所有模式的计算结果,其中模式角向序数小于70的计算结果与Optiwave公司的软件一致,而Optiwave公司的软件不能计算角向序数大于70的模式。