arXiv subjects

A. V. Korol

Publications and source records attributed to A. V. Korol.

At least 19 recordsLinked to original sources

arXiv2026

High-Intense Gamma-Ray Emission from a Crystalline Undulator with Realistic Bending Profiles

The development of compact and intense $γ$-ray sources in the MeV energy range remains a significant frontier in radiation physics, with profound implications for nuclear physics, medicine and applied science. In this work, we present a comprehensive numerical investigation of the photon emission probability and brilliance of a Crystalline Undulator (CU) based on a periodically bent Si(110) crystal. Our approach integrates realistic deformation profiles obtained via Finite Element Method simulations of a realistic sample, where bending is induced by patterned Si$_3$N$_4$ surface stressors. Relativistic molecular dynamics simulations, performed using the MBN Explorer software package, consider a 10 GeV positron beam consistent with the foreseen FACET-II facility specifications. Our results reveal a distinct undulator radiation peak in the 1.6-2.1 MeV range, well-separated from the broader channeling radiation background. We show that for an optimal aperture angle of $1/2γ$, the source reaches a maximum peak brilliance of about $5\times10^{22}$~photons/s/mm$^2$/mrad$^2$/0.1\%~BW. This performance is highly competitive with large-scale Gamma-Beam Systems and exceeds that of Inverse-Compton Scattering sources, confirming the potential of crystalline undulators as high-brilliance, compact light sources for the MeV domain.

physics.acc-ph↗

arXiv2025

Atomistic modeling of the channeling process with and without account for ionising collisions: A comparative study

This paper presents a quantitative analysis of the impact of inelastic collisions of ultra-relativistic electrons and positrons, passing through oriented crystalline targets, on the channeling efficiency and on the intensity of the channeling radiation. The analysis is based on the numerical simulations of the channeling process performed using the MBNExplorer software package. The ionising collisions, being random, fast and local events, are incorporated into the classical molecular dynamics framework according to their probabilities. This methodology is outlined in the paper. The case studies presented refer to electrons with energy $\E$ ranging from 270 to 1500 MeV and positrons with $\E=530$ MeV incident on thick (up to 1 mm) single diamond, silicon and germanium crystals oriented along the (110) and (111) planar directions. In order to elucidate the role of the ionising collisions, the simulations were performed with and without account for the ionising collisions. The case studies presented demonstrate that both approaches yield highly similar results for the electrons. For the positrons, the ionising collisions reduce significantly the channeling efficiency. However, it has been observed that this effect does not result in a corresponding change in the radiation intensity.

physics.acc-ph↗

arXiv2023

Atomistic modelling of electron propagation and radiation emission in oriented bent ultra-thin Si and Ge crystals

Computational modelling of passage of high-energy electrons through crystalline media is carried out by means of the relativistic molecular dynamics. The results obtained are compared with the experimental data for 855 MeV electron beam incident on oriented bent ultra-thin (15 microns) silicon and germanium crystals. The simulations have been performed for the geometries of the beam--crystal orientation that correspond (i) to the channeling regime and (ii) to the volume reflection. A comparison with the experiment is carried out in terms of angular distributions of the electrons deflected by the crystals bent with different curvature radii as well as of the spectra of the emitted radiation. For both crystals a good agreement between the simulated and experimentally measured data is reported. The origin of remaining minor discrepancies between theory and experiment is discussed.

physics.acc-ph↗

arXiv2021

MBN Explorer atomistic simulations of 855 MeV electron propagation and radiation emission in oriented silicon bent crystal: theory versus experiment

The method of relativistic molecular dynamics is applied for accurate computational modelling and numerical analysis of the channelling phenomena for 855 MeV electrons in bent oriented silicon (111) crystal. Special attention is devoted to the transition from the axial channelling regime to the planar one in the course of the crystal rotation with respect to the incident beam. Distribution in the deflection angle of electrons and spectral distribution of the radiation emitted are analysed in detail. The results of calculations are compared with the experimental data collected at the MAinzer MIctrotron (MAMI) facility.

physics.acc-ph↗

arXiv2020

Channeling of ultrarelativistic particles in a diamond crystal

The results of numerical simulation of the channeling of ultra-relativistic 270 MeV electrons and positrons in a diamond crystal are presented. Using the MBN Explorer package, the trajectories of the have been determined of the particles incident on a 20 microns thick crystal along (110) crystallographic plane. The channeling parameters and radiation spectra of electrons and positrons have been computed for the cases of straight and periodically bent diamond crystals.

physics.acc-ph↗

arXiv2013

Hybridization-related correction to the jellium model for fullerenes

We introduce a new type of correction for a more accurate description of fullerenes within the spherically symmetric jellium model. This correction represents a pseudopotential which originates from the comparison between an accurate ab initio calculation and the jellium model calculation. It is shown that such a correction to the jellium model allows one to account, at least partly, for the sp2-hybridization of carbon atomic orbitals. Therefore, it may be considered as a more physically meaningful correction as compared with a structureless square-well pseudopotential which has been widely used earlier.

physics.atm-clus↗

arXiv2011

Demodulation of a positron beam in a bent crystal channel

The evolution of a modulated positron beam in a planar crystal channel is investigated within the diffusion approach. A detailed description of the formalism is given. A new parameter, the demodulation length, is introduced, representing the quantitative measure of the depth at which the channelling beam preserves its modulation in the crystal. It is demonstrated that there exist crystal channels with the demodulation length sufficiently large for using the crystalline undulator as a coherent source of hard X rays. This finding is a crucial milestone in developing a new type of lasers radiating in the hard X ray and gamma ray range.

physics.acc-ph↗

arXiv2010

Stable propagation of a modulated positron beam in a bent crystal channel

The propagation of a modulated positron beam in a planar crystal channel is investigated. It is demonstrated that the beam preserves its modulation at sufficiently large penetration depths which opens the prospect of using a crystalline undulator as a coherent source of hard x-rays. This finding is a crucial milestone in developing a new type of lasers radiating in the hard x-ray and gamma-ray range.

physics.acc-ph↗

arXiv2009

Confinement resonances in photoionization of endohedral atoms: a myth or reality?

We demonstrate that the structure of confinement resonances in the photoionization cross section of an endohedral atom is very sensitive to the mean displacement of the atom from the cage center. The resonances are strongly suppressed if 2 exceeds the photoelectron half-wavelength. We explain the results of recent experiments which contradict the earlier theoretical predictions on the existence of confinement resonances in particular endohedral systems.

physics.atm-clus↗

arXiv2008

Photoionization of a strongly polarizable target

We demonstrate that the angular distribution of photoelectrons from a strongly polarizable target exposed to a laser field can deviate noticeably from the prediction of conventional theory. Even within the dipole-photon approximation the profile of distribution is modified due to the action of the field of alternating dipole moment induced at the residue by the laser field. This effect, being quite sensitive to the dynamic polarizability of the residue and to its geometry, depends also on the intensity and frequency of the laser field. Numerical results, presented for sodium cluster anions, demonstrate that dramatic changes to the profile occur for the photon energies in vicinities of the plasmon resonances, where the effect is enhanced due to the increase in the residue polarizability. Strong modifications of the characteristics of a single-photon ionization process can be achieved by applying laser fields of comparatively low intensities $I_0 \sim10^{10}-10^{11}$ W/cm$^2$.

physics.atm-clus↗

arXiv2007

The influence of the structure imperfectness of a crystalline undulator on the emission spectrum

We study the influence of an imperfect structure of a crystalline undulator on the spectrum of the undulator radiation. The main attention is paid to the undulators in which the periodic bending in the bulk appears as a result of a regular (periodic) surface deformations. We demonstrate that this method of preparation of a crystalline undulator inevitably leads to a variation of the bending amplitude over the crystal thickness and to the presence of the subharmonics with smaller bending period. Both of these features noticeably influence the monochromatic pattern of the undulator radiation.

physics.acc-ph↗

arXiv2007

Dynamical Screening of Atom Confined by Finite-Width Fullerene

This is an investigation on the dynamical screening of an atom confined within a fullerene of finite width. The two surfaces of the fullerene lead to the presence of two surface plasmon eigenmodes. It is shown that, in the vicinity of these two eigenfrequencies, there is a large enhancement of the confined atom's photoabsorption rate.

physics.atm-clus↗

arXiv2007

Electron-based crystalline undulator

We discuss the features of a crystalline undulator of the novel type based on the effect of a planar channeling of ultra-relativistic electrons in a periodically bent crystals. It is demonstrated that an electron-based undulator is feasible in the tens of GeV range of the beam energies, which is noticeably higher than the energy interval allowed in a positron-based undulator. Numerical analysis of the main parameters of the undulator as well as the characteristics of the emitted undulator radiation is carried out for 20 and 50 GeV electrons channeling in diamond and silicon crystals along the (111) crystallographic planes.

physics.acc-ph↗

arXiv2006

Parameters of the crystalline undulator and its radiation for particular experimental conditions

We report the results of theoretical and numerical analysis of the crystalline undulators planned to be used in the experiments which are the part of the ongoing PECU project [1]. The goal of such an analysis was to define the parameters (different from those pre-set by the experimental setup) of the undulators which ensure the highest yield of photons of specified energies. The calculations were performed for 0.6 and 10 GeV positrons channeling through periodically bent Si and Si$_{1-x}$Ge$_x$ crystals.

physics.acc-ph↗

arXiv2006

Feasibility of an electron-based crystalline undulator

The feasibility to generate powerful monochromatic radiation of the undulator type in the gamma region of the spectrum by means of planar channeling of ultra-relativistic electrons in a periodically bent crystal is proven. It is shown that an electron-based crystalline undulator operates in the regime of higher beam energies than a positron-based one does. A numerical analysis is performed for a 50 GeV electron channeling in Si along the (111) crystallographic planes.

physics.acc-ph↗

arXiv2005

Relativistic two-photon bremsstrahlung

An approximate approach for the description of the two-photon bremsstrahlung emitted by a relativistic projectile scattered in a spherically-symmetric field is developed. It based on the accurate treatment of the analytical structure of the singularities in relativistic one-photon free-free matrix elements. For the case of a Coulomb field the analytical expressions for the amplitude and cross section of process are presented. Numerical results obtained within the framework of the proposed approach are compared with the available experimental data and with the results of simpler theories.

physics.atom-ph↗

arXiv2004

Polarizational bremsstrahlung in non-relativistic collision

We review the developments made during the last decade in the theory of polarization bremsstrahlung in the non-relativistic domain. A literature survey covering the latest history of the phenomenon is given. The main features which distinguish the polarization bremsstrahlung from other mechanisms of radiation are discussed and illustrated by the results of numerical calculations.

physics.atom-ph↗

arXiv2004

Relativistic effects in polarizational bremsstrahlung

We review the achievements of the theory of polarization bremsstrahlung of relativistic particles, including the case when both colliders have internal structure. The main features which the relativistic effects bring into the problem are discussed and illustrated by the results of numerical calculations.

physics.atom-ph↗