I. N. Kartashov

Bio: I. N. Kartashov is an academic researcher from Moscow State University. The author has contributed to research in topics: Plasma & Cherenkov radiation. The author has an hindex of 6, co-authored 30 publications receiving 94 citations. Previous affiliations of I. N. Kartashov include Russian Academy of Sciences.

Influence of Plasma Unsteadiness on the Spectrum and Shape of Microwave Pulses in a Plasma Relativistic Microwave Amplifier

Abstract: Dependence of the shape of a microwave pulse in a plasma relativistic microwave amplifier (PRMA) on the initial plasma electron density in the system is detected experimentally. Depending on the plasma density, fast disruption of amplification, stable operation of the amplifier during the relativistic electron beam (REB) pulse, and its delayed actuation can take place. A reduction in the output signal frequency relative to the input frequency is observed experimentally. The change in the shape of the microwave signal and the reduction in its frequency are explained by a decrease in the plasma density in the system. The dynamics of the plasma density during the REB pulse is determined qualitatively from the experimental data by using the linear theory of a PRMA with a thin-wall hollow electron beam. The processes in a PRMA are analyzed by means of the KARAT particle-in-cell code. It is shown that REB injection is accompanied by an increase in the mean energy of plasma electrons and a significant decrease in their density.

Amplification of surface waves in a plasma waveguide by a straight relativistic electron beam in a finite magnetic field

Abstract: The problem of the excitation of electron waves in a thin-walled annular cold plasma in a cylindrical waveguide by a straight relativistic electron beam in a finite magnetic field is considered. The dispersion properties of a waveguide system with parameters close to the experimental ones are investigated. It is shown that the growth rate of the excited high-frequency plasma wave is comparable to that of the low-frequency wave, which is weakly sensitive to the strength of the longitudinal magnetic field.

Collective Cherenkov effect and anomalous Doppler effect in a bounded spatial region

Abstract: The problem of the development of instability in a bounded spatial region due to the collective Cherenkov effect or the anomalous Doppler effect is studied in the linear approximation. Threshold conditions for the onset of the convective and absolute instabilities of different longitudinal modes and their growth rates are determined with allowance for reflections from the boundaries of the system. The dynamics of the development of an initial perturbation during convective instability is simulated.

Electromagnetic beam-plasma interactions in a magnetic field

Abstract: The excitation of plasma oscillations in a thin-walled annular plasma by an annular electron beam in a cylindrical waveguide is considered in the linear approximation. The instability growth rates and spatial amplification coefficients in the beam-plasma system under the conditions of the Cherenkov and anomalous Doppler resonances are obtained and compared with those in a transversely homogeneous system. The contributions from different instability mechanisms are analyzed.

Dissipative surface waves in plasma

Abstract: Debatable aspects of the theory of nonpotential surface waves propagating along the boundary of a dissipative medium with frequency dispersion are discussed. On the basis of the known theoretical results and theoretical analysis carried out in this work, a theory of surface waves that is valid for any dissipation of the perturbation energy in the medium is developed. It is shown that, if dissipation is sufficiently strong, there can be surface waves the physical nature and dispersion law of which differ radically from those of ordinary surface waves. The damping rate of such waves is low even at large dissipation in the medium, and their group and phase velocities exceed the speed of light. In particular, surface waves on the interface between vacuum and cold collisional electron plasma are considered. The existence of such surface waves for different media of laboratory and natural origin is discussed.

Electron dynamics and acceleration study in a magnetized plasma-filled cylindrical waveguide

Abstract: In this article, EH01 field components are evaluated in a cylindrical waveguide filled with plasma in the presence of external static magnetic field applied along the direction of the mode propagation. The electron acceleration inside the plasma-filled cylindrical waveguide is investigated numerically for a single-electron model. It is found that the electron acceleration is very sensitive to the initial phase of mode-field components, external static magnetic field, plasma density, point of injection of the electron, and microwave power density. The maximum amplitude of the EH01 mode’s field components is approximately 100 times greater than the vacuum-waveguide case for operating microwave frequency f=7.64GHz, plasma density n0=1.08×1017m−3, initial phase angle ϕ0=60°, and microwave power ∼14MW in a cylindrical waveguide with a radius of 2.1cm. An electron with 100keV gets 27MeV energy gain in 2.5cm along the waveguide length in the presence of external power ∼14MW with a microwave frequency of 7.64GHz. The electron trajectory is also analyzed under the effects of magnetic field when the electron is injected in the waveguide at r=R∕2.

The development and interaction of instabilities in intense relativistic electron beams

Abstract: We report on the physical mechanisms of development, coexistence and interaction of Pierce-Bursian and diocotron instabilities in the non-neutral relativistic electron beam (REB) in the classic vircator. The analytical and numerical analysis is provided by means of 3D electromagnetic simulation. We conducted an extensive study of characteristic regimes of REB dynamics determined by the instabilities development. As a result, a regime map has been obtained. It demonstrates sequential switching of the REB dynamics from the regime with N=1 to the regime with N = 7 electron bunches in the azimuth direction with the beam current growth for the different external magnetic fields. The numerical analysis of bunch equilibrium states has identified the physical causes responsible for the REB regime switchings.

Terahertz electromagnetic wave generation and amplification by an electron beam in the elliptical plasma waveguides with dielectric rod

Abstract: The propagation of electromagnetic waves in an elliptical plasma waveguide including strongly magnetized plasma column and a dielectric rod is investigated. The dispersion relation of guided hybrid electromagnetic waves is obtained. Excitation of the waves by a thin annular relativistic elliptical electron beam will be studied. The time growth rate of electromagnetic waves is obtained. The effects of relative permittivity constant of dielectric rod, radius of dielectric rod, accelerating voltage, and current density of the annular elliptical beam on the growth rate and the frequency spectra are numerically presented.

Explosive boiling of metals upon irradiation by a nanosecond laser pulse

Abstract: A repeated effect of explosive boiling has been found in metals exposed to a nanosecond laser pulse in the framework of molecular dynamic simulations combined with a continuum description of a conduction band electrons system. This effect can be used, in particular, as a marker of approaching critical parameters of the region in the irradiated matter.

Excitation of electromagnetic surface waves by an annular electron beam in a plasma waveguide with a dielectric rod and a magnetized plasma column

Abstract: The dispersion relation for symmetrical TM electromagnetic surface waves propagating in a plasma waveguide with a strongly magnetized plasma column and a dielectric rod is investigated. The growth rate for excitation of these waves is obtained and its dependence on the radius of the annular beam, current intensity and accelerating voltage are investigated.