Peculiarities of the spectral-angular distribution of transition radiation from a relativistic particle in a dihedral angle

The spatial distributions of transition radiation from relativistic particles entering and exiting the edge of a dihedral angle formed by perfectly conducting flat surfaces have been investigated. The angular distributions of the radiation intensity in dihedral angles with various opening angles have been calculated. The angular distributions of forward radiation (when the particle exits the dihedral angle) and backward radiation (when the particle enters the dihedral angle) are shown to differ significantly.     

Transition radiation in a dihedral angle formed by perfectly conducting planes

The spatial distribution of the field of transition radiation generated by a relativistic particle flying into a dihedral angle formed by perfectly conducting plane surfaces is determined. The cases when particles are injected from the edge and from a plane of the dihedral angle are considered. The angular distributions of radiation intensity in dihedral angles of different values are calculated.     

Experimental study of coherent transition radiation from relativistic electrons in a dihedral angle

Angular intensity distributions for transition radiation excited by a beam of relativistic electrons in the emitter in the form of a dihedral angle are measured in the millimeter range. The angle is formed by the intersection of two conducting planes. The source of radiation is a microtron with an electron energy of 7.4 MeV. We analyze the effect of the magnitude of the dihedral angle of the emitter, the position of the electron transition point on the surface of the angle, and the direction of motion of electrons on the angular distribution of radiation intensity. It is shown that the spectral and angular distributions of radiation intensity in the dihedral angle substantially differ from analogous distributions for a particle intersecting a planar conducting surface. The possibility of using radiation to measure the energy, spatial position, and direction of motion of charges is considered.     

Experimental study of coherent transition radiation from relativistic electron bunches entering a dihedral angle

The angular distributions of the intensity of transition radiation from a bunch of relativistic electrons entering a dihedral angle between two conducting planes have been measured in a millimeter wavelength range. A microtron with a particle energy of 7.4 MeV is used as a source of electrons. The effect of the particle injection direction and the magnitude of the dihedral angle on the angular distribution of the radiation intensity has been analyzed. The measurements show that the character of the distribution of radiation from a charge entering the dihedral angle significantly differs from that for a charge escaping the angle. A comparatively small change in the magnitude of the dihedral angle can lead to qualitative changes in the angular distribution of radiation from a charge entering the dihedral angle.     

Spatial distribution of transition radiation of relativistic particles in the dihedral angle formed by perfectly conductive planes

Spatial distributions of transition radiation intensity of particles entering the dihedral angle and escaping from it are calculated. It was shown that radiation of escaping charge at any opening of the dihedral angle ?? is concentrated near the motion direction. If the particle enters the angle, the radiation distribution is defined by the opening angle. At opening angles ?? = ??/n, radiation is concentrated near the direction of actual charge motion when n is an even number and near the direction of image charge motion when n is an odd number. At other opening angles, the spatial distribution of entering particle radiation has two maxima whose positions are defined by the injection angle.     

Application of transition radiation in a small dihedral angle to detection of relativistic particles

The features of transition radiation excited by a relativistic particle in a dihedral angle with an opening comparable to the angular divergence of transition radiation are considered. It is shown that the radiation distribution in the dihedral angle is more sensitive to the direction of emitting particle motion and to the position of the surface intersection by the particle, than the radiation excited when a plane surface is intersected. It is indicated that the spectral radiation density in the small dihedral angle is higher than the density of radiation excited when a plane surface is intersected. These features offer additional opportunities to use transition radiation in systems for measuring particle parameters.     

Transition radiation detectors with a dihedral angle or a cone as a radiator

The spectral and angular distributions of the transition radiation produced by a charge crossing an interface shaped like a dihedral angle or a cone are considered. The effects of the variation in the dihedral angle and cone angle, the location of the crossing point on the interface, and the direction of the charge motion on the spatial distribution of the radiation are discussed. The radiation characteristics of the particles that are incident on the interface and those leaving it are given. The features of transition-radiation detectors with dihedral-angle or cone radiators and detectors with plane-surface radiators are compared.     

Transition radiation from relativistic electrons crossing a perfectly conducting conical surface: Calculation and experiment

The angular distributions of the transition radiation intensity when a charged particle passes through the vertex of a perfectly conducting conical surface have been calculated. The radiation generated both when the particle exits the conductor and when it falls on the conductor has been considered. The angular distributions of the intensity of the transition radiation generated by a bunch of relativistic electrons have been measured in the millimeter wavelength range. A microtron with a particle energy of 7.4 MeV was the source of electrons. The influence of the particle injection direction and the conical-surface opening angle on the angular distribution of the radiation intensity has been studied. The measurements have shown that the distribution of the radiation generated by a charge when it enters the horn differs significantly in pattern from the distribution when it exits the horn.     

Transition radiation generated by a particle passing through the apex of a conducting cone

The spatial field distribution is determined for the transition radiation generated by a particle passing through the apex of a cone along its axis. Expressions for the angular distribution of the radiation intensity are obtained for apex angles between 0 and π. Characteristics of transition radiation emitted into a “funnel” and a dihedral angle are compared.     

Transition radiation in a system of two cascaded gratings

Transition radiation that arises when a charged particle passes through two consecutive plane gratings is considered. The gratings are made up of parallel metal wires. The planes of the gratings are parallel to each other and perpendicular to the direction of motion of the particle. The conductors of one of the gratings are perpendicular to the conductors of the other. It is shown that the generated transition radiation has elliptic polarization; the ellipticity and the sign of rotation depend on the angle of radiation, the distance between the gratings, and the velocity of the charged particle.     

光学渡越辐射电子束发散角二维拟合数值分析北大核心CSCD

光学渡越辐射具有良好的方向性,通过对光学渡越辐射空间分布曲线进行拟合可以对束流发散角进行计算。采用理论计算的方法,分析了电子入射到金属-介质界面时,入射角变化对光学渡越辐射二维空间分布的影响。计算分析表明,光学渡越辐射在特定偏振方向上的分布并不仅仅由电子束在该方向的发散角分量决定,同时还受到其他方向发散角分量的影响。计算对比了电子束散角一维分布和二维分布模型下光学渡越辐射空间分布的差异。结果表明,采用一维分布模型拟合计算的电子束均方根发散角存在偏差,较二维分布拟合结果偏小。     

正弦平方势与小振幅近似下的弯晶沟道辐射

在理想情况下和经典力学框架内,引入正弦平方势,把粒子在弯晶中的运动方程化为具有外力矩的摆方程。并对系统的相平面特征进行了数值分析。在小振幅近似下,把粒子运动方程化为具有硬特性的弹簧-振子系统,用Jacobian椭圆函数和椭圆积分解析地给出系统的解和粒子运动周期。讨论了弯晶沟道辐射频率、无量纲偏转角和辐射谱的一般特征。指出利用沟道辐射作为激光的可能性。以正电子在碳单晶中沟道辐射为例进行了具体计算,得到了与其他工作基本一致的结果。     

光学渡越辐射电子束发散角二维拟合数值分析

光学渡越辐射具有良好的方向性,通过对光学渡越辐射空间分布曲线进行拟合可以对束流发散角进行计算。采用理论计算的方法,分析了电子入射到金属-介质界面时,入射角变化对光学渡越辐射二维空间分布的影响。计算分析表明,光学渡越辐射在特定偏振方向上的分布并不仅仅由电子束在该方向的发散角分量决定,同时还受到其他方向发散角分量的影响。计算对比了电子束散角一维分布和二维分布模型下光学渡越辐射空间分布的差异。结果表明,采用一维分布模型拟合计算的电子束均方根发散角存在偏差,较二维分布拟合结果偏小。     

Diffraction radiation of a dielectric wedge at the resonance frequency

The diffraction radiation at the frequency that is close to the natural resonance of the medium is considered for a fast charged particle that passes in the vicinity of a dielectric wedge. The dependence of the angular distribution of the diffraction radiation on the angle between the wedge faces and on the energy of the ultrarelativistic particle is analyzed.     

Smith-Purcell radiation in the “pre-wave” zone

A model is proposed for calculating the angular distributions of the intensity of resonant diffraction radiation generated by a charged particle moving near a plane conducting periodic structure (Smith-Purcell radiation) with allowance for the effect of the so-called pre-wave zone. It is shown that the criterion of the location of a detector in the pre-wave zone for this kind of radiation in the relativistic case is determined by the geometric sizes of the grating and is almost independent of the Lorentz factor of the particle. The characteristics of the radiation in the pre-wave zone are calculated by numerical integration over the grating surface. It is shown that the line of Smith-Purcell radiation is broadened in this case, whereas the results of the calculations for the “wave” zone are in satisfactory agreement with the known analytical model of the resonant diffraction radiation.     

弯轨Čerenkov辐射计算中的稳相法

从介质中沿弯曲轨道运动的带电粒子辐射的频谱角分布公式出发, 分析了粒子速度大于介质中的光速时, 稳相点在?erenkov效应中所起的关键作用, 并给出了通过在稳相点附近做渐近展开来计算弯轨?erenkov辐射的稳相法. 运用稳相法, 计算了同步?erenkov辐射在粒子轨道平面附近以及在临界角附近的频谱角分布. 计算结果表明, 同步?erenkov辐射频谱的特征依赖于观测方向附近对应的稳相点性状, 特别是在较大的临界角附近的频谱与小角度近似时很不相同. 关键词： ?erenkov效应 稳相点 稳相法 同步?erenkov辐射     

The Kirchhoff method for transition radiation from flat and concave targets

Transition radiation (TR) emitted by a charged particle incident obliquely on a perfectly conducting surface is considered. A method is proposed that allows one to calculate the characteristics of backward radiation at a finite distance, including in the so-called pre-wave zone. Particular cases of a flat target, as well as a target in the form of a cylindrical surface whose axis is perpendicular to the trajectory of the particle are considered. In the first case, the radiation characteristics in the wave zone, calculated by the model proposed, are in complete agreement with available results. In the second case, when a detector is situated in the pre-wave zone, the radiation is focused. The properties of radiation are discussed as a function of the shape of the target surface, the angle of incidence of a particle, and the distance to the detector.