Electrical Parameters of a Laser Beam Channel in the Atmosphere. II

Russian Physics Journal - Results of measurements of the conductivity and electric field strength in the laser radiation propagation channel and near it are presented. An experimental setup and...     

Electrical Parameters of a Laser Beam Channel in the Atmosphere. I

Russian Physics Journal - Results of measurements of the conductivity in the laser radiation propagation channel not only in laboratory, but also outdoors for laser radiation focused in the free...     

人工触发闪电通道的导电特性

用光学多道分析仪(OMA)获得了山东地区人工触发闪电回击过程的发射光谱.与以往的自然闪电光谱相比,除了氮、氧的中性原子及一次电离的离子谱和Hα谱线外,这次人工触发闪电的光谱还记录到了微量元素ArⅠ 602.5 nm及ArⅡ 666.5 nm的谱线.在局部热力学平衡近似下,根据光谱线的相对强度等参量,计算了闪电通道等离子体的温度;利用Hα线的Stark加宽、通过半经验方法获得了闪电通道的电子密度;首次结合等离子体理论得到了闪电通道的电导率,并由此讨论了通道的导电特性,分析了通道电导率与回击电流之间的相关性,为进一步计算回击电流提供了参考数据.结果分析得出:闪电通道是良导体,电子是通道电流的主要载体;一般情况下,人工触发闪电的通道亮度比自然闪电通道大,而通道回击电流小于自然闪电.     

Electrical Conductivity in General Relativity

The general relativistic kinetic theory including the effect of a stationary gravitational field is applied to the electromagnetic transport processes in conductors. Then it is applied to derive the general relativistic Ohm's law where the gravitomagnetic terms are incorporated. The total electric charge quantity and charge distribution inside conductors carrying conduction current in some relativistic cases are considered. The general relativistic Ohm's law is applied to predict new gravitomagnetic and gyroscopic effects which can, in principle, be used to detect the Lense-Thirring and rotational fields.     

Mechanism of Electrical Conductivity and Thermal Conductivity in AgSbSe2

Russian Physics Journal - Research was done on electrical conductivity and thermal conductivity of AgSbSe2 in the temperature range of 80–330 K. It was demonstrated that charge transfer in...     

Electrical Conductivity of a Single Electro-deposited CoZn Nanowire

CoZn nanowires are fabricated by the electrodeposition method at constant voltage mode with porous anodic aluminum oxide as templates. Scanning electron microscope and transmission electron microscope images show that the CoZn nanowires have a rather smooth surface. The nanowires have an average diameter of 50 nm,which coincides with the diameter of the used templates. The x-ray diffraction pattern reveals the polycrystalline structure of the CoZn nanowires. The electrical conductivity of a single CoZn nanowire is studied. The metallic behavior is observed at temperatures from 230 K to 30 K. Moreover, an abnormal behavior appears around 30 K.The resistance shows the slight upturn phenomenon below 30 K down to 2 K, which is due to the major conduction role of the oxidation layer on the surface of the CoZn nanowire.     

Electrical Conductivity of Nonideal Plasma

The electrical conductivity of fully ionized moderately nonideal plasmas with coulomb interaction parameters 0.1 < ? ? 1 where ? = Ze2n1/3/KT is the ratio of coulomb and thermal energies is calculated for displaced Maxwell and Fermi electron distributions, respectively. The electrons are scattered by an effective coulomb potential ?(r) = Zer-1 exp (-r/?) which considers binary (0 < r < ?) and many-body (? < r < ?) interactions. The shielding distance is given by ? = ?(4?n/3Z)-1/3 with ? = ?0?-N ~ 1 for classical plasmas and ? = ?(4?n/3Z)-1/3 with ? = ?0?-N?-M ~ 1 for quantum plasmas, where ? = Ze2n1/3/h2 m-1n2/3 is the ratio of coulomb interaction and quantum potential energies of the electrons. It is shown that the resulting conductivity formulas are applicable to densities up to four orders of magnitude higher than those of the ideal conductivity theory, which breaks down at higher densities because the Debye radius loses its physical meaning as a shielding length and upper impact parameter.     

Scanning a Silicon Photomultiplier with a Laser Beam

Physics of Particles and Nuclei Letters - The Silicon Photomultiplier (SiPM) is a novel semiconducting photodetector which can detect single photons. It consists of many microcells (pixels)...     

全电离氢等离子体的电导率

主要研究了全电离等离子体的散射相移、传输截面和电导率.相移应用WKB方法计算,且计算结果与使用精确计算方法得到的结果非常一致,证明了所用计算方法的正确性和准确性.在对传输截面的计算中,观察到了形状共振,这种共振是由于半束缚态的消失产生的.电导率的计算应用了Chapman-Enskog方法,并与其它理论和实验结果进行了比较.     

均匀聚焦磁场中束晕-混沌的孤子控制

采用粒子.束核模型,对均匀聚焦磁场中满足K-V分布的离子束进行模拟研究.观察到束晕.混沌现象,基于束晕.混沌的非线性控制策略,提出控制束晕.混沌的孤子函数控制器,并给出具体的实施方案.模拟研究表明,运用这种方法可以消除束晕及其再生现象,达到对束晕.混沌的有效控制.     

Electrical Conductivity of Nonideal Quasi-Metallic Plasmas

Electrical conductivity formulas are derived from first principles for fully ionized nonideal plasmas. The theory is applicable to an electron-ion system with a 1) Maxwell electron distribution with an arbitrary interaction parameter ? = Ze2n1/3/KT (ratio of the mean coulomb interaction and thermal energies) and 2) Fermi electron distribution with an interaction parameter ? = Ze2n1/3h?2m-1 n2/3 (ratio of the coulomb interaction and Fermi energies). The momentum relaxation time of the electrons in the plasma is calculated based on plane electron wave functions interacting with the continuum oscillations (plasma waves) through a shielded coulomb potential Us(r) = esee exp (-r/?s)/r, which takes into account both electron-ion interactions (s = i) and electron-electron interactions (s = e). It is shown that the resulting conductivity formulas are applicable to higher densities, for which the ideal plasma conductivity theory breaks down because the Debye radius loses its physical meaning as a shielding length and upper impact parameter. The conductivity obtained for classical plasma is of the form ?c = ?c*(KT)3/2/m1/2e2 and agrees with the ideal plasma conductivity formula with respect to the temperature and density dependence for ?/Z ? 0, but its magnitude is significantly reduced as ?/Z increases. For quantum plasmas, the conductivity obtained is of the form ?Q = ?Q*h3n/m2Ze2, which shows that the degenerate plasma behaves like a low-temperature metal.     

Radiation-Induced Electrical Conductivity of Nanocomposite Materials

The radiation-induced conductivity of a nanocomposite with the inclusion of spherical nanoparticles as a function of intensity and time of action of gamma-radiation and the concentration and size of inclusions has been studied using the Rose–Fowler–Weisberg model. The energy spectrum of localized states associated with the nanoparticle inclusion has been determined. The numerical experiments have been made for polymethyl methacrylate (PMMA) nanocomposites with inclusion of CdS and α-Al₂O₃ nanoparticles as well as SrO nanoparticles.     

Electrical Conductivity Oscillations in Laminated Charge-Ordered Crystals with a Monotonic Negative Reluctance

In the present paper, the Shubnikov–de Haas oscillation frequencies arising in laminated charge-ordered crystals with a monotonic negative reluctance due to scattering of current carriers on charged impurities with a short-range potential are calculated and classified. It is demonstrated that non-semiclassical oscillation frequencies can be a measure of charge ordering.     

Kinetic Approach to the Electrical Conductivity in a Partially Ionized Hydrogen Plasma

The electrical conductivity is investigated for a partially ionized hydrogen plasma, starting from a generalized quantum kinetic equation with three particle collision integrals. To take into account plasma effects, screened potentials are used. The transport cross sections of the considered two and three particle scattering processes are calculated by perturbative solution of the Lippmann-Schwinger equations for the T-matrices up to the second Born approximation. In connection with a mass action law the influence of the electron-electron and the elastic electron-atom scattering is discussed. The pressure ionization (Mott-effect) is described by a minimum-behaviour of the electrical conductivity.     

Lower-Threshold Ionization in Laser Channel Propagation

Russian Physics Journal - The paper considers the creation of long ionized channels in atmospheric aerosol based on the combustion and detonation processes. The literature review is performed in...     

Calculation of Momentum Coupled by a High-Power Laser Beam

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Forward Scattering Signature of a Spherical Particle Crossing a Laser Beam out of the Beam Waist

When a particle crosses a laser beam out of the focal plane, the light attenuation signal occuring on the beam axis contains some information regarding the particle size and trajectory. These attenuation signatures are analysed and predicted with a simplified model based on Fraunhofer diffraction. Numerical and experimental results are found to be in good agreement. A modified laser Doppler velocimeter using this sizing method is able to perform simulataneous measurement of size and velocity of spherical particle in the range 10 μm–500 μm.     

Optimal Truncation of Element Beam in a Coherent Fiber Laser Array

The beam quality of a coherent fiber laser array often suffers from the low fill factor of the Gaussian laser array. One simple and effective approach to improve the fill factor is to truncate the array element properly. An analytical expression for far-field intensity distribution of a truncated coherent fiber laser array is derived. Optimal truncation of the element beam in different coherent fiber laser arrays is obtained by using energy encircled in the far-field central-lobe as the beam quality criterion. By optimal truncation, energy encircled in the central-lobe can be 97% compared with the ideal case. The shift in optimal truncation parameter in the case of phase noise is also analyzed.