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《Physics letters. A》1986,116(9):423-426
The excitation of a uniformly accelerated detector moving in a vacuum has been widely discussed in recent years. The aim of the present paper is to point out that such an excitation and the associated radiation are similar to those occuring in the region of anomalous Doppler effect which takes place when a detector is moving at a constant superlight velocity in a medium. 相似文献
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E. D. Gazazyan A. D. Ter-Poghosyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2009,44(5):231-237
It is shown that transition radiation arising at the boundary of two media is being emitted as a Cherenkov one, if the phase
velocity of transition radiation waves in the medium of transition radiation propagation becomes equal to the velocity of
the moving radiating particle (the necessary condition for the Cherenkov radiation). The proof of this statement is based
on the analysis of the transition radiation formation zone, which may become large enough and provide interference between
the field of transition radiation and the own Coulomb field of the moving particle, in case when the Cherenkov radiation condition
is fulfilled. As a result, the transition radiation field transforms into the Cherenkov field. The problem is considered for
cases of both a waveguide and free space. 相似文献
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A Cherenkov quartz detector possesses a high radiation resistance because of the radiation resistance of quartz fibers in which a light signal is formed and which are used to transfer signals to photodetectors. Owing to properties of Cherenkov radiation, such as the existence of a threshold with respect to the velocity of radiating charged particles and an instantaneous character of the radiation, this type of calorimeter is not sensitive to neutrons and the majority of radiative-decay products and generates a short signal within a narrow spatial region. In view of these special features of a Cherenkov quartz calorimeter, it is advantageous (with respect to other calorimetric methods) in detecting narrow jets of high-energy particles against the background of high-density energy fluxes, this being necessary, for example, in experiments at the Large Hadron Collider, which is presently under construction at CERN. The results obtained by measuring the radiation resistance of quartz fibers and the main features of a Cherenkov quartz calorimeter that were measured for prototypes are discussed in the present article. 相似文献
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The combined finite-element-boundary-element method is used to solve the problem on the radiation of a water-filled piezoceramic cylinder positioned near an infinite plane. For the case of a perfectly rigid plane, the frequency characteristics of the transmitting response of the piezoelectric cylinder are obtained along with the frequency characteristics of the acoustic power, the directional characteristics, and the velocity and pressure distributions over the radiating cylindrical surfaces. It is found that, when the distance between the plane and the piezoelectric cylinder is small relative to the wavelength, the frequency characteristics of the cylinder and the velocity and pressure distributions noticeably differ from those obtained for a piezoelectric cylinder in an infinite space. The effect of the antisymmetric mode, which appears at small wave distances between the cylinder and the plane, on the characteristics of a water-filled piezoelectric cylinder is considered. 相似文献
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A. S. Kubankin N. N. Nasonov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2008,2(2):317-320
Parametric X-ray radiation (PXR) of relativistic electrons moving in a mosaic crystal is considered. A strong dependence of the PXR angular spectral distribution on the mosaic structure is shown. The effect of mosaic structure on the PXR spectrum strongly increases in the longitudinal plane specified by the radiating electron velocity vector and the averaged reciprocal lattice vector and decreases in the transverse plane with a decrease in the angle of incidence of the radiating electron onto a crystal plane, which allows one to study the anisotropy of mosaic structure of crystal planes. 相似文献
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提出了一种求取轴对称结构任意边界条件下声辐射特性的边界元方法。采用Burton和Miller改进型公式将高阶奇异项转化为弱奇异项之和,保证声辐射参数的唯一性,且计算简单精确。将结构表面声压与振速按照旋转轴角度进行Fourier级数展开,利用级数的正交性建立各项待定系数的求解公式;然后转化格林函数的法向偏导为切向偏导,方便直接计算各项积分,并将面积分公式表示为沿结构边界的线积分和沿旋转角度的积分;进一步采用二次等参单元离散结构边界线,建立声压与振速的关系矩阵,从而确定结构声辐射参数。以脉动球源和横向振动球源为例计算,与解析解和传统边界元法结果作对比,说明该方法的有效精确性。 相似文献
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The dipole radiation of a charged particle moving along a closed fractal trajectory with constant velocity is studied. It is found that the spectrum intensity of the radiation is displaced to the high frequency region when reducing the spatial scale of the fractal trajectory and tends to zero if the trajectory is a true fractal. 相似文献
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Quan Li Chao Wu Xuan Liu Song Zhao Zhihui Zhang Xiaobing Shang Zeyong Wei Hongqiang Li 《Annalen der Physik》2019,531(12)
A geometric phase model for electromagnetic radiating elements is proposed. By rotation of the radiating element, a frequency‐independent geometric phase occurs for circularly polarized components of radiation field along every direction in far field. In addition, the geometric phase is equal to the rotation angle for a circularly polarized source, which enables phase modulation ranging from 0 to 2π. In contrast, the Pancharatnam–Berry phase for circular polarization conversion components brought by optical element rotation is twice the rotation angle and is applicable only for the scattering waves propagating along the rotation axis. As a proof of principle, an antenna array is designed and fabricated in microwave regime to verify the phase modulation approach. Both the calculated and measured results verify that three different orbital angular momentum modes are generated simultaneously at 8.5 GHz and 11.5 GHz. 相似文献
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A. V. Serov 《Technical Physics》2006,51(7):902-906
The coherent radiation of relativistic electrons that are accelerated in a microtrone and move through a beam-deflecting magnet is measured. Experiments show that the radiation intensity depends not only on the number of electrons but also on which region of the bunch the radiating electrons are extracted from. The measurements provide information on how the phase extent of the electron bunch varies over the cross section. Numerical calculations of the radiation intensity versus number of particles passing through the beam-deflecting magnet and of the bunch coherence factor versus transverse coordinate are in good agreement with the experiment. 相似文献
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Nonstationary radiative-convective heat transfer was simulated at turbulent streamlining of a semitransparent film of melt
on a flat plate by the gas mixture and solid particles. The moving film is subjected to intensive radiation heating by an
external source radiating within a limited spectral range. The temperature and velocity fields are calculated in the boundary
layer and in the film. Calculation results allow determination of the effect of source temperature and film initial heating
on dynamics of temperature and velocity fields of the medium in the boundary layer-film system. 相似文献
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小型超宽谱高功率微波辐射系统由Tesla型100 kV级ns脉冲源、Peaking-Chopping型亚纳秒气体开关及TEM喇叭天线构成。系统重复运行频率100 Hz,辐射因子rEp值75 kV,主轴辐射场中心频率520 MHz,-3 dB频谱范围230~810 MHz。系统集成于一便携箱内,体积为80 cm50 cm26 cm,质量约45 kg。该系统结构紧凑,能够快速展开和撤收,可方便用于超宽谱高功率微波应用技术研究。 相似文献
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S. I. Yakovlenko 《Laser Physics》2006,16(3):474-476
A simple mechanism for the formation of a chain of voids (cavities) behind the spot of the laser optical discharge in an optical fiber is proposed. This mechanism is related to the motion of liquid in the opposite direction with respect to the propagation direction of the laser radiation between the isotherms that bound the charge-separation region and low-viscosity region. The motion is caused by the extrusion of the low-viscosity layer owing to the excessive pressure induced by the charge repulsion. The void shape (a bullet moving along the laser radiation) is determined by the isotherm sharpness. The bridge formation temperature (about 5000 K) is estimated based on the comparison of the extrusion velocity of the low-viscosity layer and the velocity of the bright spot. 相似文献
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Optics of tunneling from adiabatic nanotapers 总被引:1,自引:0,他引:1
Sumetsky M 《Optics letters》2006,31(23):3420-3422
A theory of light propagation along adiabatic photonic nanowire tapers (nanotapers) having diameters significantly less than the radiation wavelength lambda approximately 1 microm is developed. The fundamental mode of a nanotaper primarily consists of an evanescent field, which propagates in the ambient medium and is very sensitive to the nanotaper shape. General analytical expressions for the evanescent field and the radiation loss of adiabatic nanotapers are obtained and applied to the investigation of the optics of tunneling from a nanotaper of a characteristic shape. The radiation loss of this nanotaper occurs locally near a focal circumference of the evanescent field, representing an intersection of a complex caustic surface with real space, where the fundamental mode splits into the radiating and guiding components. The interference of these components gives rise to a sequence of circumferences with zero electromagnetic field. 相似文献
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从电子束一维稳态传输的电势非线性Poisson方程出发,推导了圆柱波导内实心束和环形束空间极限电流与电子入射电势的依赖关系,给出了数值求解方法和解的特征,分析比较了数值计算与现有解析公式及粒子模拟的结果.考虑电子的横向运动,对数值方法进行了二维修正,计算结果与粒子模拟结果具有很好的一致性.说明利用数值方法计算电子电势非线性微分方程能够得到更精确的电子束在圆柱波导内的空间极限电流;另外,对其他形状的波导,尤其是难以得到解析式的情况,根据实际几何结构设置边界条件,数值方法可以方便地给出束流传输特性,对设计新型结构的高功率微波器件提供理论指导.
关键词:
相对论电子束
圆柱波导
空间极限电流
束流传输 相似文献
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It is well established that fluid flow can have significant effects on structural acoustic behavior, as is the fact that induced coupling between discrete modes of vibration becomes significant as flow velocity increases. To date, work in this area has been confined to subsonic flows, with the effects on sound radiation efficiency and sound power radiation quantified and compared for various subsonic flow speeds. The purpose of this work is to study the effects that supersonic flow has on these structural acoustic phenomena, along with an investigation of the uncoupled behavior of single modes in the transonic region. Theoretical development of the equations governing the vibration of a simply supported plate in an infinite baffle and an aerodynamic system that models a semi infinite flowing medium along with the method for coupling these systems is included. Computational results are presented illustrating the behavior of the uncoupled modes in the transonic region and the uncoupled and coupled effects on the structural response and sound power radiation as well as a study of the radiation efficiency of the coupled system. 相似文献