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A. P. Potylitsyn

Publications and source records attributed to A. P. Potylitsyn.

At least 19 recordsLinked to original sources
arXiv2016

Transition radiation on a dynamical periodical interface

We investigate the transition radiation on a periodically deformed interface between two dielectric media. Under the assumption that the dielectric permittivities of the media are close, a formula is derived for the spectral-angular distribution of the radiated energy in the general case of non-static profile function for the separating boundary. In particular, the latter includes the case of surface waves propagating along the boundary. The numerical examples are given for triangular grating and for sinusoidal profile. We show that instead of a single peak in the backward transition radiation on a flat interface, for periodic interface one has a set of peaks. The number and the locations of the peaks depend on the incidence angle of the charge and on the period of the interface. The conditions are specified for their appearance.

physics.optics↗
arXiv2013

Metameterial refraction characteristics within the millimeter-wave range

Phase delays, spectral, orientation, and angular dependences of radiation refraction in metamaterial targets have been experimentally studied within the millimeter-wave range. It has been shown that angular and spectral dependences have a complicate structure, which demonstrated properties typical both for positive and negative refraction indexes. At this, a change of refraction nature occurs in radiation wavelength interval comparable with the sizes of metamaterial structural elements.

cond-mat.mtrl-sci↗
arXiv2010

The investigation of relativistic electron electromagnetic field features during interaction with matter

The features of electromagnetic field of relativistic electrons passing through a hole in an absorbing screen as a function of the distance from the screen in range of radiation formation length were investigated. The analysis of obtained results allows approving the existence of an unstable state of electron with a particularly deprived its coulomb field, which turns into a stable state of usual electron at a distance of a radiation formation length.

physics.acc-ph↗
arXiv2010

Comparison of coherent Smith-Purcell radiation generated by 6.1 MeV electron beam in metal and dielectric lamellar gratings

Coherent Smith-Purcell radiation generated by bunched electron beam in the lamellar metal and dielectric gratings in the millimeter wavelength range was compared theoretically and experimentally. For theoretical estimation a simple model suitable for both dielectric and metal gratings was developed. Experimental comparison was carried out using extracted bunched 6.1 MeV electron beam of the microtron at Nuclear Physics Institute (Tomsk Polytechnic University). Both theoretical estimations and experimental data showed the difference of the radiation characteristics from the lamellar metal and dielectric gratings. The radiation from the dielectric grating had peak structure not monotonic one and was more intense comparing with metal grating radiation in the wavelength less than coherent threshold. These differences may be useful for research and development of new compact monochromatic radiation sources in sub-THz and THz region.

physics.acc-ph↗
arXiv2010

Diffraction radiation from a screen of finite conductivity

An exact solution has been found for the problem of diffraction radiation appearing when a charged particle moves perpendicularly to a thin finite screen having arbitrary conductivity and frequency dispersion. Expressions describing the Diffraction and Cherenkov emission mechanisms have been obtained for the spectral-angular forward and backward radiation densities.

physics.optics↗
arXiv2010

Universal description for different types of polarization radiation

When a charged particle moves nearby a spatially inhomogeneous condensed medium or inside it, different types of radiation may arise: Diffraction radiation (DR), Smith-Purcell radiation (SPR), Transition radiation (TR), Cherenkov radiation (CR) etc. Along with transverse waves of radiation, the charged particle may also generate longitudinal oscillations. We show that all these phenomena may be described via quite simple and universal approach, where the source of the field is the polarization current density induced inside the medium by external field of the particle, that is direct proof of the physical equivalence of all these radiation processes. Exact solution for one of the basic radiation problems is found with this method: emission of a particle passing through a cylindrical channel in a screen of arbitrary width and permittivity $ε(ω) = ε^{\prime} + i ε^{\prime \prime}$. Depending on geometry, the formula for radiated energy obtained describes different types of polarization radiation: DR, TR and CR. The particular case of radiation produced by the particle crossing axially the sharp boundary between vacuum and a plasma cylinder of finite radius is also considered. The problem of SPR generated when the particle moves nearby a set of thin rectangular strips (grating) is solved for the arbitrary value of the grating's permittivity. An exact solution of Maxwell's equations for the fields of polarization current density suitable at the arbitrary distances (including the so-called pre-wave zone) is presented. This solution is shown to describe transverse fields of polarization radiation and the longitudinal fields connected with the zeros of permittivity.

physics.acc-ph↗
arXiv2009

Generalized surface current method in the macroscopic theory of diffraction radiation

The surface current method known in the theory of electromagnetic waves diffraction is generalized to be applied for the problems of diffraction radiation generated by a charged particle moving nearby an ideally-conducting screen in vacuum. An expression for induced surface current density leading to the exact results in the theory of transition radiation is derived, and by using this expression several exact solutions of diffraction radiation problems are found. Limits of applicability for the earlier known models based on the surface current conception are indicated. Properties of radiation from a semi-plane and from a slit in cylinder are investigated at the various distances to observer.

physics.acc-ph↗
arXiv2006

Forward Diffracted Parametric X Radiation From a Thick Tungsten Single Crystal at 855 MeV Electron Energy

Features of forward diffracted Parametric X-Radiation (PXR) were investigated at experiments with the 855 MeV electron beam of the Mainz Microtron MAMI employing a 410 micrometer thick tungsten single crystal. Virtual photons from the electron field are diffracted by the (10-1) plane at a Bragg angle of 3.977 degree. Forward emitted radiation was analyzed at an energy of 40 keV with the (111) lattice planes of a flat silicon single crystal in Bragg geometry. Clear peak structures were observed in an angular scan of the tungsten single crystal. The results were analyzed with a model which describes forward diffracted PXR under real experimental conditions. The experiments show that forward diffracted PXR may be employed to diagnose bending radii of lattice planes in large area single crystals.

physics.acc-ph↗
arXiv2005

Focusing of transition radiation and diffraction radiation from concave targets

In the article the transition radiation from a relativistic charge crossing a finite radius paraboloid target with taking into account the pre-wave zone effect is considered. It is shown that in this case the radiation cone narrowing occurs in contrast with the transition radiation from the flat target if the detector is situated at the distance, which is smaller than the focus distance (the focusing effect) from the target. At the charged particle passage through the central hole in a paraboloid target the diffraction radiation focusing (DR) occurs too. The focusing of coherent DR for the non-invasive measuring of the electron bunch length is proposed.

physics.acc-ph↗
arXiv2004

Image of optical diffraction radiation (ODR) source and spatial resolution of ODR beam profile monitor

The approach to obtain the image shape of an optical diffraction radiation (ODR) source focused by lens on a detector with taking into account the "pre-wave zone" effect has been developed. In full analogy with optical transition radiation source the characteristic size of ODR slit image doesn't depend on the Lorentz-factor and is defined by slit width, wavelength and lens aperture. If a beam is passed through a narrow slit the shape of a slit image depends on a beam size. ODR generated by extremely ultrarelativistic beam passing through a narrow slit may be used to determine the beam size from ODR slit image.

physics.acc-ph↗
arXiv2003

Is it possible to obtain polarized positrons during multiple Compton backscattering process?

If a beam of unpolarized positrons (which is considered as a sum of two fractions with opposite helicities) passes through an intense circular polarized laser radiation these fractions may be separated. For high laser flash intensity each positron will interact with $k_0\gg$1 laser photons subsequently (linear multiple compton scattering process). Due to difference in the compton cross-section for positrons polarized in opposite directions the mean final energy of each fraction will be different. It allows to get a polarized positron beam using the momentum selection (with some intensity loss). Estimations show the possibility to obtain a positron beam with 35% longitudinal polarization and 25% intensity from the initial one for focussed laser flash with total energy 5J and positron beam with energy 5 GeV.

physics.acc-ph↗
arXiv2002

Low-Energy Electron-Beam Diagnostics Based on the Optical Transition Radiation

A possibility of a few MeV electron beam diagnostics (Lorentz factor ~ 10) using polarization characteristics of the optical transition radiation (OTR) have been considered. Determinaton of the electron beam divergence have been performed with technique based on the OTR measurements. The technique is based on measuring the ratio R=Imin/Imax, where Imin(Imax) is the photon yield in the minimum (maximum) of OTR angular distribution. It is shown that the value of R can be obtained also from the measurement of the so-called psi-scan of the OTR yield registered by a fixed detector with the aperture < gamma^(-1) by varying the target tilt angle with respect to the electron-beam. The experiment curried out at 6.1 MeV Tomsk microtron has demonstrated the feasibility of the technique proposed.

physics.acc-ph↗
arXiv2002

Investigation of resonant polarization radiation of relativistic electrons in gratings at small angles

The Resonant Optical Polarization Radiation (ROPR) in the Smith-Purcell geometry and the one from the inclined grating at the Tomsk synchrotron and 6-MeV microtron have been investigated. The polarization radiation was observed at 4.2o from the 200 MeV electron beam and at 5o from the 6.2 MeV electron beam. Two methods of measurement of ROPR maxima in these two cases have been used. In the first case (the experiment on synchrotron) we have fixed the wavelength of radiation using an optical filter; the orientation dependence of this radiation was measured. In this dependence we have observed two peaks of radiation from electrons in gold foil grating of 0.1 mm period. The first large peak is a zeroth order peak in direction of specular reflection, and the second one is the 1-st order peak of resonant polarization radiation. In the experiment on microtron the spectra of ROPR from aluminum foil strip grating of 0.2 mm period in the Smith-Purcell geometry were measured, and the peak of the 1-st order Smith-Purcell radiation in these spectra was observed. The comparison of data obtained with the simulation results has been performed.

physics.acc-ph↗
arXiv2002

Polarized triplet production by circularly polarized photons

A process of the pair production by a circularly polarized photon in the field of unpolarized atomic electron has been considered in the Weizaecker-Williams approximation. The degree of longitudinal polarization of positron and electron has been calculated. An exclusive cross-section as well as a spectral distribution are obtained. We estimate the accuracy of our calculations at the level of a few percent. We show the identity of the positron polarization for considered process and for process of pair production in the screened Coulomb field of nucleus.

hep-ph↗
arXiv2002

Laser polarization of positron beam

For a number of physical studies which are planned to be made with the next generation colliders, it is necessary to use polarized beams of both electrons and positrons. The problem of producing and acceleration of polarized electrons may be considered to be solved, but the existing approaches to create polarized positron beams do not ensure the parameters required. This work proposes a new approach to produce polarized positron beams, which is based on the process of multiple Compton backscattering of unpolarized ultrarelativistic positrons in the field of intense circularly polarized laser wave.

physics.acc-ph↗
arXiv2001

Determination of Circular Polarization of gamma-quanta with Energy > 10 MeV using Compton Polarimeter

The circularly polarized gamma-quanta with energy > 10 MeV are formed during Compton backscattering of circularly polarized laser photons on an electron beam with energy 1.26 GeV. The contribution of nonlinear processes for planned parameters of a laser flash[T. Okugi, Y. Kurihara and M. Chiba, Jpn. J. Appl. Phys. 35, p. 3677 (1996).] can be rather significant, that leads to deterioration of polarization of a resulting gamma-beam. The direct method of measurement of gamma-beam circular polarization will allow not only to estimate a correctness of the theoretical calculations, but also to use the obtained information for simulation of polarization parameters of positrons.

physics.acc-ph↗
arXiv2000

Resonant Diffraction Radiation from an Ultrarelativistic Particle Moving Close to a Tilted Grating

A simple model for calculating the diffraction radiation characteristics from an ultrarelativistic charged particle moving close to a tilted ideally conducting strip is developed. Resonant diffraction radiation (RDR) is treated as a superposition of the radiation fields for periodically spaced strips. The RDR characteristics have been calculated as a function of the number of grating elements, tilted angle, and initial particle energy. An analogy with both the resonant transition radiation in absorbing medium and the parametric X-ray radiation is noted.

physics.acc-ph↗