Searcharxiv⌕ Search

arXiv subjects

I. N. Onishchenko

Publications and source records attributed to I. N. Onishchenko.

31 records · Page 2Linked to original sources
arXiv2020

Wake excitation of volume and surface polaritons by a relativistic electron bunch in an ion dielectric

The process of wake fields excitation by a relativistic electron bunch in ion dielectric media is considered. The space-time structure of the excited wakefield in an ion dielectric waveguide is investigated. It is shown that the wake field in the infrared (terahertz) ranges consists of the field of longitudinal polaritons and Cherenkov radiation, which is a set of electromagnetic eigen waves (transverse polaritons) of a dielectric waveguide. A branch of surface polaritons appears in a dielectric waveguide with an axial vacuum channel. The process of wakefield excitation of surface polaritons by a relativistic electron bunch is also considered.

physics.acc-ph↗
arXiv2020

Dynamics of self-injected electron bunches at their acceleration by laser pulse in plasma

Dynamics of self-injected electron bunches has been numerically simulated in blowout regime at self-consistent change of electron bunch acceleration by plasma wakefield, excited by a laser pulse, to additional their acceleration by wakefield, excited by self-injected bunch. Advantages of acceleration by pulse train and bunch self-cleaning have been considered.

physics.plasm-ph↗
arXiv2020

Control of Characteristics of Self-injected and Accelerated Electron Bunch in Plasma by Laser Pulse Shaping on Radius, Intensity and Shape

At the laser acceleration of self-injected electron bunch by plasma wakefield it is important to form bunch with small energy spread and small size. It has been shown that laser-pulse shaping on radius, intensity and shape controls characteristics of the self-injected electron bunch and provides at certain shaping small energy spread and small size of self-injected and accelerated electron bunch.

physics.plasm-ph↗
arXiv2020

Increase of amplitude of accelerating wakefield excited by sequence of short relativistic electron bunches in plasma at magnetic field use

Earlier, the authors found a mechanism for the sequence of short relativistic electron bunches, which leads to resonant excitation of the wakefield, even if the repetition frequency of bunches differs from the plasma frequency. In this case, the synchronization of frequencies is restored due to defocusing of the bunches which get into the bad phases with respect to the plasma wave. However, in this case, the bunches are lost, which as a result of this do not participate in the excitation of the wakefield. In this paper, numerical simulation was used to study the dynamics of electron bunches and the excitation of the wakefield in a magnetized plasma by a long sequence of short bunches of relativistic electrons. When a magnetic field is used, the defocussed bunches return to the region of interaction with the field after a certain time. In this case, the electrons of the bunches, returning to the necessary phases of the field, participate in the excitation of the wakefield. Also, the use of a magnetic field leads to an increase of the frequency of the excited wave relative to the repetition frequency of bunches. The latter increases the time for maintaining the resonance and, consequently, leads to an increase of the amplitude of the excited wakefield.

physics.plasm-ph↗
arXiv2020

Homogeneous Focusing Field for Short Relativistic Electron Bunches in Plasma

Plasma wake lens in which all short relativistic electron bunches of sequence are focused identically and uniformly is studied analytically and by numerical simulation. For two types of lenses necessary parameters of focused sequence of relativistic electron bunches are formulated. Verification of these parameters is performed by numerical simulation.

physics.plasm-ph↗
arXiv2020

Wakefield excitation by a short laser pulse in ion dielectrics

The process of excitation of Cherenkov electromagnetic radiation by a laser pulse in ion dielectrics is investigated. Nonlinear electric polarization in isotropic ion dielectric medium and, accordingly, polarization charges and currents induced by a ponderomotive force of a laser pulse are determined. Frequency spectra of the excited wakefields in the infrared and microwave frequency ranges are obtained. The spatiotemporal structure of the wakefield in ion dielectric waveguide is obtained and studied. It is shown that the excited field consists of a potential polarization electric field, as well as a set of eigen electromagnetic waves of ion dielectric waveguide.

physics.acc-ph↗
arXiv2020

Suppression of vortical turbulence in plasma of mass-separator in crossed electrical and magnetic fields due to finite lifetime of electrons and ions and due to finite system length

The dispersion equation, describing the instability development of vortex turbulence excitation in cylindrical plasma in crossed radial electric and axial magnetic fields with taking into account the longitudinal inhomogeneity and finite time of leaving of plasma electrons and ions from the system, has been derived. It is shown that the finite length of system time and finite time of system leaving of plasma electrons and ions leads to the appearance of the instability threshold and to decrease of growth rate of its development.

physics.plasm-ph↗
arXiv2019

BBU instability in rectangular dielectric resonator

Studies were made into the arise and an evolution of the beam breakup (BBU) instability in a rectangular dielectric resonator under excitation by a sequence of relativistic electron bunches. The dielectric resonator is a metal rectangular waveguide $R_{26}$ $(45mm\times 90mm)$ with Teflon dielectric slabs $8.2mm$ thick (dielectric constant $\varepsilon=2.051$) located along the wide side of the resonator. The wavelength of the $LM_{21}$ operating mode having a symmetric profile of the longitudinal electric field component is $53.2mm$. The electron energy of bunches is $4.5MeV$ , the charge of each bunch is $6.4nC$, the bunch repetition period is equal to twice the wavelength of the $LM_{21}$ mode. By the use of numerical PIC simulations, the charge losses of electron bunches on the dielectric plates were investigated as the bunches were displaced relative to the cavity axis. It is found that the charge losses on the dielectric slabs due to the BBU instability do not exceed $5\%$. When the bunch repetition period is changed to a multiple of another eigenfrequency (e.g., the $LM_{11}$ mode), the charge losses of drive bunches do not change appreciably.

physics.acc-ph↗
arXiv2019

Focusing of Drive and Test Bunches in a Dielectric Waveguide Filled with Inhomogeneous Plasma

The paper presents the results of numerical PIC-simulation of accelerated and drive bunches dynamics in a dielectric waveguide filled with radially inhomogeneous plasma. The wakefield was excited by the electron bunch in a quartz (permittivity 3.75) dielectric tube with outer and inner diameters of 1.2 mm and 1.0 mm, respectively, which was nested into a cylindrical metallic waveguide. The drive bunch characteristics were chosen to be: 5 GeV for electron energy, 3 nC for the charge, 0.2 mm - the bunch length, 0.9 mm - the bunch diameter. The accelerated bunch had the same parameters, except for the charge, which was equal to 0.3 nC. The interior of the waveguide was filled with plasma having different transverse density profiles, viz., the density profile formed in the capillary discharge, and the radially nonuniform density profile with the vacuum channel along the waveguide axis. For all the cases under study the plasma density was low, so that the plasma frequency was lower than the fundamental dielectric mode frequency. The obtained PIC-simulation data have shown that the vacuum channel in the inhomogeneous plasma cylinder improves the accelerated bunch focusing. There is the optimum vacuum-channel size value, at which the focusing turns out to be the strongest. The improvement in the accelerated bunch focusing is accompanied by the decrease in the accelerating gradient as compared with the full plasma filling of the drift channel. The best acceleration takes place in the absence of plasma; however in that case the test bunch focusing does not occur.

physics.acc-ph↗
arXiv2015

Proceedings of the third French-Ukrainian workshop on the instrumentation developments for HEP

The reports collected in these proceedings have been presented in the third French-Ukrainian workshop on the instrumentation developments for high-energy physics held at LAL, Orsay on October 15-16. The workshop was conducted in the scope of the IDEATE International Associated Laboratory (LIA). Joint developments between French and Ukrainian laboratories and universities as well as new proposals have been discussed. The main topics of the papers presented in the Proceedings are developments for accelerator and beam monitoring, detector developments, joint developments for large-scale high-energy and astroparticle physics projects, medical applications.

physics.ins-det↗