Low frequency radiation characteristics of a modulated electron beam immersed in a magnetized plasma

The possibility of using a modulated electron beam injected in a magnetized plasma as a low frequency antenna (frequency lower than the gyrofrequency) is explored. The physical mechanism proposed to insure this property is spontaneous coherent emission. Derivation of the power lost by the beam is done with emphasis on the particular conditions named "focalization condition" encountered in the whistler range of frequency. In conclusion the limits of the model are discussed together with the perspectives opened by this work.     

Measurements of electron density and plasma current distributions in Tokamak plasma

A submillimeter-wave, phase-modulated polarimeter/interferometer is used for simultaneous time-dependent measurement of line-averaged electron density and poloidal field-induced Faraday rotation along chords of the plasma column in ISX-B tokamak. Heterodyne detection and hollow dielectric waveguide are utilized to achieve the high sensitivity required for the multichord experiment. A data analysis code has been developed to reconstruct the asymmetric distributions of plasma density. The validity of the code is examined, and the result shows good agreement with density profiles measured by Thomson scattering.     

Transient analysis of a magnetized plasma in three-dimensionalspace

The time-domain formation, in terms of unified nodal equations, of a magnetized cold plasma in three-dimensional space using the Bergeron method is described. The validity of this treatment is shown by simulations of both transverse propagation and longitudinal propagation. In the formulation of the characteristic equation in the time domain, the authors introduce variables corresponding to the first and second derivates of the electric polarization. Thus the iterative computation can be performed by using only the values obtained at the previous time step. This procedure very closely matches the architecture for high-speed computation in the vector processor of a supercomputer. This property can render practical the simulation of three-dimensional fields involving gyroelectric anisotropic media and expand the generality of the numerical vector analysis method in the time domain     

太赫兹波在均匀磁化等离子体中的传播特性

研究了太赫兹波通过均匀磁化等离子体的传播特性,给出了太赫兹波衰减和相移随等离子体密度、碰撞频率、太赫兹波频率和磁感应强度的变化规律。等离子体电子密度越大,衰减和相移越大;随着碰撞频率的增大,电磁波的衰减先增加到峰值后逐渐减小,且随着磁感应强度的增加,衰减的峰值变大,峰值向碰撞频率减小的方向移动;当电子碰撞频率接近电磁波频率时等离子体对右旋极化波的衰减达到极大值。太赫兹波频率增大,衰减逐渐减小,而相移先增加后逐渐减小。     

Polarization of coherent synchrotron radiation from an electron beam rotating in a plasma

After eliminating reflections from the walls of the plasma container, we observed polarization of the coherent synchrotron radiation from a relativistic electron beam rotating in a plasma. Several features of the polarization agree well with calculations based on the single particle synchrotron radiation theory. A particular polarization ratio (Fig. 3) does not, however. We deduce from this direct diffraction of the radiation by the beam electrons. This is strong evidence for beam-particle bunches of size ～cm. Also, there must be some absorption of the extraordinary wave to account for the observations. We suggest a way to apply these results to measure the pitch angle of the beam.     

非均匀磁化等离子体中电磁波的反射

主要研究磁化、稳定、二维、非均匀等离子体中的电磁波反射,讨论各种等离子体参数对反射功率的影响,计算每一分层边界的反射系数,推导总反射功率,并得出反射功率取决于电子密度、碰撞频率以及入射波的传播角.其中非均匀等离子体用分层来模拟.假定每一分层的电子密度为常数,但总的电子密度服从抛物线分布.     

Piecewise linear current density recursive convolution FDTD implementation for anisotropic magnetized plasmas

The piecewise linear current density recursive convolution (PLCDRC) finite-difference time-domain (FDTD) method for isotropic dispersive media greatly improves accuracy over recursive convolution (RC) and current density recursive convolution (CDRC) FDTD approaches but retains its speed and efficiency advantages. This letter extends this approach to anisotropic magnetoactive plasmas which incorporates both anisotropy and frequency dispersion at the same time, enabling the transient solutions of electromagnetic wave propagation in anisotropic magnetoactive plasmas. The high efficiency and accuracy of the method are confirmed by computing the reflection and transmission through a magnetized plasma layer, with the direction of propagation parallel to the direction of the biasing field. A comparison to frequency-domain analytic results and CDRC FDTD results is included.     

SO-FDTD法计算磁化等离子体层的反射透射系数

从磁化等离子体的介电系数张量出发,推导出电磁波垂直入射磁化等离子体层且背景磁场沿入射方向情况时的移位算子(Shift operator,SO)FDTD迭代公式.应用该方法计算了磁化等离子体层的反射透射系数,其结果和应用传播矩阵(Propagation Matrices,PM)法及Appleton方程的计算结果符合得很好.最后,分析了背景磁场对磁化等离子体层中两个本征波即左旋和右旋波传播带的影响.     

JEC-FDTD for 2-D conducting cylinder coated by anisotropic magnetized plasma

The JE convolution finite-difference-time-domain (JEC-FDTD) method is extended to the anisotropic magnetized plasma which incorporates both anisotropy and frequency dispersion at the same time, enabling the transient solution of the electromagnetic wave propagation in anisotropic magnetized plasmas. Two-dimensional JEC-FDTD formulations for magnetized plasma are derived. The back scattering radar cross section (RCS) of a perfectly conducting cylinder coated by a layer of magnetized plasmas is calculated.     

Modeling of frequency-dependent magnetized plasma in hybrid symmetrical condensed TLM method

In this paper, magnetized plasma media are modeled using the time-domain TLM method with hybrid symmetrical condensed node (HSCN). The proposed technique consists in adding voltage sources characterizing dispersive media in the HSCN. Numerical results are presented for reflection and transmission coefficients for a magnetized plasma wall, proving the efficiency of the proposed model.     

Solutions in elementary functions obtained for 3D and axisymmetric intense electron flows

Three-dimensional nonrelativistic electron flows in the presence of an arbitrarily oriented uniform magnetic field are considered. The flows are formed by elliptic or hyperbolic current tubes and have a spatial axis. For such flows, a series of new exact solutions in elementary functions are constructed. In the case of nonmonoenergetic beams, a new type of singularities corresponding to the zero-velocity injection is discovered.     

The effects of electron collisions on electric dipole radiation through a conical plasma sheath

The radiated power of an electric dipole antenna in a thin, dissipative, infinite conical plasma sheath is analyzed. The electromagnetic fields are represented by contour integrals, and the radiated power is calculated according to the method of Baños et al. The sheath is characterized by a single parameter, which is proportional to the integrated electron density and depends inversely on the electron collision frequency. The radiation pattern is distorted from the form of the free-space dipole pattern because of the interaction between the primary dipole fields and the fields induced on the surface of the plasma sheath. In most cases it is found that for small electron densities, electron collisions attenuate the induced surface fields so that the patterns approach their free-space form. For larger electron densities, the pattern has a characteristic heart shape for zero collision frequency. The pattern increases in magnitude, while retaining the same form, as the collision frequency increases from zero. As the collision frequency is further increased, the pattern approaches the free-space pattern in magnitude and form.     

Compton散射对磁化等离子体调制不稳定性的影响

基于多光子非线性Compton散射模型,研究了多光子非线性Compton散射对激光在磁化等离子体中调制不稳定性的影响.将入射光和多光子非线性Compton散射光作为形成调制不稳定性的新机制,对非线性色散方程和控制方程进行了修正,给出了由入射光和多光子非线性Compton散射光形成的耦合左旋椭圆偏振光调制不稳定性的时间增...     

温度、密度对磁化等离子体光子晶体的影响

为了研究温度、密度对磁化等离子体光子晶体禁带特性的影响,采用在等温近似的条件下,磁化等离子体的分段线形电流密度卷积时域有限差分算法研究了1维磁化等离子体光子晶体的禁带特性。以高斯脉冲为激励源,用算法公式得到的电磁波透射系数来讨论了温度、等离子体层密度对其禁带特性的影响。结果表明,改变温度和等离子体层密度分布可以实现对禁带的控制。     

等离子体显示电路原理

介绍了等离子体显示（ＰＤＰ）的主要性能指标，着重分析一种等离子体显示电路，并介绍ＰＤＰ显示屏的使用要点。     

The false image of a line current within a conducting half-space

We show that the fields from a current line source, within a conducting-half-space, are only inadequately characterized by a positive real image in the air region. Such an assumption or assertion, as employed in previous electromagnetic compatibility (EMC) studies, is called into question. Buried cables are mentioned in particular     

EM fields of a phased line current over a conducting half-space

The need often arises to predict the electromagnetic field of power and communication lines over the earth. A simple and explicit derivation is given for the electromagnetic fields of a travelling current line source located over a layered conducting half-space. Special attention is paid to the case of a homogeneous half-space where analytical closed-form expressions can be obtained. Of some interest is the radiation of a vertically polarized radio ground wave which would not be present if the line source was uniform     

Phase velocity of a transverse electric wave propagating in a magnetized electron beam

In this paper three-dimentional simulations are carried out to the phase velocity of a transverse electric wave which propagates in a relativistic electron beam magnetized by a wiggler field and an axial guide magnetic field. Results show that the phase velocities are quite different from each other as the axial guide magnetic field changes its direction.     

Three-dimensional FDTD simulation of electromagnetic wavetransformation in a dynamic inhomogeneous magnetized plasma

A three-dimensional (3-D) finite-difference time domain (FDTD) algorithm is developed to study the transformation of an electromagnetic wave by a dynamic (time-varying) inhomogeneous magnetized plasma medium. The current density vector is positioned at the center of the Yee cube to accommodate the anisotropy of the plasma medium due to the presence of a static magnetic field. An appropriate time-stepping algorithm is used to obtain accurate solutions for arbitrary values of the collision frequency and the electron cyclotron frequency. The technique is illustrated by calculating the frequency shifts in a cavity due to a switched magnetoplasma medium with a time varying and space-varying electron density profile