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 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.     

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.     

Transient radiation of particles in dihedral and trihedral angles

The image method is used for determining the field of transient radiation emitted by a charged particle intersecting a dihedral angle formed by ideally conducting charged planes. The spectral-angular distributions of radiation intensity in a dihedral angle with different corner angles are calculated. The effect of the direction of motion of the particle and of the position of the point at which the particle intersects the plane on radiation parameters is considered. Transient radiation distributions in a trihedral angle are also obtained.     

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 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 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 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.     

Origin of complex fragments from32S+natAg reaction at 37.5 A·MeV

Fragment emission from collisions of³²S with^natAg at 37.5 A·MeV has been studied with the 4π multi-detector AMPHORA. Production of intermediate mass and heavy fragments as well as of light charged particles has been measured. The total charged particle multiplicity and polar angular distributions have been used to select various classes of collisions. Analysis of angular and energy distributions of fragments and light particles in central collisions indicates the formation of a hot source (excitation energy of≈4.4 A·MeV) with an additional contribution from a preequilibrium process at more forward angles. Azimuthal angle correlations of He-Li, Li-Li, B-B, and C-C pairs have been used as a tool to study the origin of complex fragments. Data at backward angles are well described by considering a thermalized emitter with an angular momentum around 70? and a fragment emission time of the order of 200 fm/c. A microscopic approach of BNV type confirms these emission times and angular momenta indicating the persistence of an incomplete fusion process responsible for the emission of complex fragments at backward angles.     

Role of highest occupied molecular orbitals in molecular field-free alignment by a femtosecond pulse

This paper studies the molecular rotational excitation and field-free spatial alignment in a nonresonant intense laser field numerically and analytically by using the time-dependent Schr?dinger equation. The broad rotational wave packets excited by the femtosecond pulse are defined in conjugate angle space, and their coefficients are obtained by solving a set of coupled linear equations. Both single molecule orientation angles and an ensemble of O₂ and CO molecule angular distributions are calculated in detail. The numerical results show that, for single molecule highest occupied molecular orbital (HOMO) symmetry σ tends to have a molecular orientation along the laser polarization direction and the permanent dipole moment diminishes the mean of the orientation angles; for an ensemble of molecules, angular distributions provide more complex and additional information at times where there are no revivals in the single molecule plot. In particular, at the revival peak instant, with the increase of temperature of the molecular ensemble, the anisotropic angular distributions with respect to the laser polarization direction of the π _g orbital gradually transform to the symmetrical distributions regarding the laser polarization vector and for two HOMO configurations angular distributions of all directions are confined within a smaller angle when the temperature of the molecular ensemble is higher.     

夸克喷注与胶子喷注角分布特性的研究

用蒙特卡洛模拟Jetset 7.4产生质心能量为91.2GeV的正负电子对撞事件. 在引入喷注的圆锥角后, 对不同味的夸克喷注和由不同味夸克发射的胶子产生的喷注的角分布特性进行了仔细研究. 结果发现, 在相同的能量下, 胶子喷注的角分布范围比夸克喷注的角分布范围要明显宽一些. 在带电粒子数、横动量相同的条件下, 胶子喷注的平均圆锥角比夸克喷注的平均圆锥角大很多. 喷注的平均圆锥角随带电多重数以及喷注的横动量的分布都呈线性正关联. 由不同味的夸克发射的胶子产生的喷注的圆锥角分布特性相同；而不同味的夸克喷注的圆锥角分布存在明显的差异.     

Transition radiation emitted by a particle moving along the axis of a perfectly conducting conical surface

The spatial field distribution is determined for the transition radiation emitted by a relativistic particle moving along the axis of a perfectly conducting circular conical surface with a fixed apex. Emission from particles moving away from and towards the apex is examined. Expressions are obtained that can be used to calculate the angular distribution of radiation intensity for various apex angles between 0 and π. Significant differences are demonstrated between the spatial distributions of radiation generated by outgoing and incoming particles.     

Angular distribution of the terahertz radiation intensity from the plasma channel of a femtosecond filament

A phenomenological model of the terahertz radiation of the plasma channel of a femtosecond filament has been elaborated that satisfactorily describes the experimental results of the detection of low-frequency radiation in air. The angular distributions of the terahertz radiation intensity in the absence and presence of an external electrostatic field have been obtained. The dependence of the divergence angle of the terahertz radiation on the filament parameters has been determined.     

移相式干涉仪在锥体棱镜角度测试中的应用

为了实时、高精度地测试光学零件，对移相式数字波面干涉仪在锥体棱镜角度测试中的应用进行了研究。通过锥体棱镜二面角偏差计算方法得到了二面角偏差和干涉波面之间的关系，分析了干涉波面的形状与锥体棱镜综合误差的关系，编写了锥体棱镜角度和综合误差测试程序，并且在移相式数字波面干涉仪和ZYGO干涉仪上分别对锥体棱镜进行测试，给出了2者的比较测试结果。结果表明，移相式数字波面干涉仪测量锥体棱镜二面角偏差的误差在0.3″范围内，RMS值的测量误差在λ/50内；提出的方法可实现检测过程的自动化。     

Proton spin relaxation and self-diffusion in some ‘isotropic’ nematogens

Angular distributions of reactive scattering arising from a long-lived collision complex dissociating via a transition state that approximates to a linear rotator are predicted for H atom displacement occurring over a distribution of bending angles β with respect to the rotator axis. A conical angular distribution may be generated when only a narrow range of bending angles contributes to the reactive scattering. However, the angular distribution may take on quite different character as the distribution of bending angles becomes broader. Thus, an isotropic angular distribution is generated by a bending angle distribution which follows the spherical polar weighting P(β) ∝ sin β. Forward and backward scattering is generated by bending angle distributions favouring less strongly bent displacement, while sideways scattering is generated by a bending angle distribution favouring more strongly bent displacement. The experimental angular distribution for OH + CO reactive scattering which shows mild forward and backward peaking, corresponds to a range of bending angles for H atom displacement from the H-OCO transition state which is broadened about the nominal preferred direction β = 45° but avoids strongly bent directions with β ≈ 90°.     

Angular distributions of promptγ-rays in the light charged particle accompanied and binary fission of252Cf

Double-differential emission distributions W(B,E_x) in angle 8 and energy E_x of prompt x-rays released in binary and light charged particle (LCP) accompanied fission of 252-Cf have been measured. The x-ray anisotropies are rather similar for both fission modes but the shapes of the angular distributions differ considerably. The maxima of the angular distributions are shifted from zero degree in the binary mode to 8≈20.30 deg. in the LCPac. fission. This behaviour may be understood as an influence of the α-particle (predominantly emitted in equatorial direction) on the alignment of angular momenta produced in bending modes.     

Spatial coherence in transition radiation from short electron bunches

The characteristics of coherent transition radiation that is generated by a “disk-shaped” electron bunch inclined with respect to the direction of its propagation have been considered. It has been shown that the angular distribution of transition radiation becomes asymmetric because of spatial coherence. For angles of inclination much larger than the characteristic emission angle equal to the inverse Lorentz factor, the angular distribution for wavelengths comparable to the longitudinal size of the bunch has a single maximum. In this case, the maximum of the yield of coherent transition radiation coincides with the inclination angle of the bunch.     

Special features of the coherent transient radiation of an electron bunch accelerated in a microtron

The angular distribution of radiation generated by a relativistic electron bunch penetrating through a metal foil was experimentally measured at angles much greater than the characteristic angle γ^?1. The experiments showed that the emission at large angles exhibits an asymmetric angular distribution with a pronounced maximum. The results of numerical calculations of the transient radiation of an electron bunch accelerated in a microtron agree with the experimental data.