A. V. Serov

Application of the method of images in the problems of transition radiation in a dihedral angle

Application of the method of images to the description of transition radiation generated when a charged particle passes through a dihedral angle formed by perfectly conducting planes is considered. It is shown that the electromagnetic field generated when a charged particle passes through a dihedral angle of α = π/m is equivalent to the field generated when 2m charged particles (a given particle with charge q and 2m − 1 images with charges ± q of alternating signs) instantaneously start to move. Expressions are obtained that describe the field of transition radiation in the wave zone as a sum of the fields generated by the starting particles. The spectral-angular distributions of radiation in dihedral angles of α = 90°, 60°, 45°, 36°, and 30° are calculated. Specific features of this transition radiation are considered. It is suggested that this radiation can be used to diagnose the spatial distribution and the direction of motion of charged particles.

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.

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.

Experimental study of the scattering of 7.4-MeV electrons intersecting a foil at an angle of 10°–45° to its surface

Angular distributions of electrons intersecting 40- and 120-μm aluminum foils and a 60-μm copper foil have been measured. Electrons have been injected from a microtron with a particle energy of 7.4 MeV. The effect of the material and thickness of a foil, as well as of the direction of injection, on the spatial distribution of passed particles has been analyzed. The measurements have shown that the intersection of the foil at small angles to its surface not only increases the transverse dimensions of the beam but also changes the direction of its motion.

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.

Angular distributions of reflected and refracted relativistic electron beams crossing a thin planar target at a small angle to its surface

The scattering of electrons by aluminum, copper, and lead foils, as well as by bimetallic aluminum-lead and aluminum-copper foils, has been studied experimentally. A microtron with an energy of particles of 7.4 MeV has been used as a source of electrons. The beam of particles incident on a target at small angles is split into particles reflected from the foil, which constitute a reflected beam, and particles crossing the foil, which constitute a refracted beam. The effect of the material and thickness of the foil, as well as the angle between the initial trajectory of the beam and the plane of the target, on the direction of motion and the angular divergence of the beam crossing the foil and the beam reflected from the foil has been analyzed. Furthermore, the effect of the sequence of metal layers in bimetallic films on the angles of refraction and reflection of the beam has been examined.

Scattering of relativistic electrons by a thin bimetallic foil

Angles of refraction θd of electron beams passing through thin planar bimetallic foils and the angles of reflection φr of the beams reflected by these foils have been measured. The experiments were performed with a microtron with a particle energy of 7.4 MeV as the source of electrons and aluminum-lead and aluminum-copper foils. The thicknesses of aluminum, lead, and copper layers were 54 mg/cm2 (200 μm), 44 mg/cm2 (50 μm), and 79 mg/cm2 (70 μm), respectively. The particles were injected at the angles α = 5°−30° to the foil surface. The measurements were performed at various orientations of a bimetal with respect to the trajectory of the beam. In the first case, the particles moving through the foil first crossed the aluminum layer and then the layer of a higher density metal (copper or lead). In the opposite case, the particles were injected into the copper or lead layer and then crossed the aluminum layer. It has been found that changing the order of the metallic layers to the opposite one considerably affects the angles of reflection and refraction at some angles of incidence. Similar measurements have been carried out for electrons incident on scatterers made of homogeneous metals (aluminum, copper, and lead). Comparison with the experiments with bimetallic foils allows estimating the contribution of each layer to refraction and reflection of the injected beam.

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.

Experimental study of the spatial distributions of relativistic electron beams reflected and refracted by a thin foil

Photographs of cross sections of an electron beam scattered from thin foils have been obtained on a dosimetric film. The procession of images makes it possible to obtain the spatial distribution of particles both reflected from a foil and passed through it. The spatial distribution of electrons incident on aluminum, copper, and lead foils, as well as on bimetallic foils composed of aluminum and lead layers and of aluminum and copper layers, has been measured. The effect of the material and thickness of the foil, as well as of the angle between the initial beam trajectory and the target plane, on the spatial distribution of electrons has been studied. The effect of the sequence of the metal layers in bimetallic foils on the distribution of beams has been analyzed. A 7.4-MeV microtron has been used as a source of electrons.

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.