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Dive into the research topics where A. N. Tkachev is active.

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Featured researches published by A. N. Tkachev.


Technical Physics | 2006

X-ray radiation due to nanosecond volume discharges in air under atmospheric pressure

I. D. Kostyrya; V. F. Tarasenko; A. N. Tkachev; S. I. Yakovlenko

The formation of nanosecond discharges in atmospheric-pressure air versus the applied pulse polarity and discharge gap geometry is studied. It is shown that the polarity of high-voltage nanosecond pulses and the electrode configuration have a minor effect on the volume discharges under a variety of experimental conditions. When the spacing between needle-like electrodes is large, the discharge is asymmetric and its glow is weakly dependent on the sign of the potential applied to the electrode. Negative voltage pulses applied to the potential electrode generate X-ray radiation from both the surface and volume. For a subnanosecond rise time of the voltage pulse and diffusion character of the discharge, the X-ray radiation comes from the brightly glowing region of a corona discharge. The average values of the fast electron velocity and energy in nitrogen are calculated. At field strengths E/p < 170 kV/cm atm, the average velocity of a fast electron bunch is constant because of central collisions. At field strengths E/p > 170 kV/cm atm, fast electrons run away. Central collisions are the reason for X-ray radiation from the volume.


Jetp Letters | 2003

Production of powerful electron beams in dense gases

V. F. Tarasenko; S. I. Yakovlenko; V. M. Orlovskii; A. N. Tkachev; S. A. Shunailov

Subnanosecond electron beams with the record current amplitude (∼70 A in air and ∼200 A in helium) were produced at atmospheric pressure. The optimal generator open-circuit voltage was found for which the electron-beam current amplitude produced in a gas diode was maximal behind a foil. It was established that the electron beam was produced at the stage when the cathode plasma closely approaches the anode. It was shown that a high-current beam can be produced at high pressures because of the presence of the upper branches in the curves characterizing the electron-escape (runaway) criterion and the discharge-ignition criterion (Paschen curve).


Physica Scripta | 1995

Metastable State of Supercooled Plasma

S. A. Maiorov; A. N. Tkachev; S. I. Yakovlenko

The computer ab initio simulation and analytical theory, that revealed unexpected non-ergodic properties of a classical Coulomb plasma, is overviewed. The results of a many-charged-particles system simulation predict the possible existence of a real metastable plasma, supercooled with respect to its ionization degree. The three-body recombination at this state is suppressed. The existence of such a plasma state is a consequence of the entropy conservation in isolated Hamiltonian systems free from any stochastic action from the outside (external stochastic disturbance). The occurrence of a metastable supercooled plasma (rather similar to a supercooled vapor or superheated liquid) depends on two conditions: First, all the charged particles should behave exactly according to the laws of classical mechanics (hence, most negatively-charged particles should preferably be heavy ions). Second, the plasma ionization degree should be sufficiently high (> 10−3). It is shown from thermodynamic consideration that a mixture of supercooled plasma with a perfect (ideal) gas might form a plasmoid of the ball-lightning type.


Jetp Letters | 2003

On the Mechanism of the Runaway of Electrons in a Gas: The Upper Branch of the Self-Sustained Discharge Ignition Curve

A. N. Tkachev; S. I. Yakovlenko

Based on the results of simulation by the method of particles, it is shown that the Townsend mechanism of electron multiplication in a gas at a sufficiently large electrode spacing is valid at least up to such large values of E/p at which relativistic electrons are generated. On the other hand, the phenomenon of electron runaway in a gas is determined by the electrode spacing, which must be either comparable with or smaller than the characteristic electron multiplication length, rather than the local criteria accepted presently. It is shown that, for a particular gas, the critical voltage across the electrodes at which the runaway electrons comprise a significant fraction is a universal function of the product of the electrode spacing by the gas pressure. This function also determines the condition of self-sustained discharge ignition. It not only incorporates the known Paschen curve but also additionally contains the upper branch, which describes the absence of a self-sustained discharge at a high voltage sufficiently rapidly supplied across the electrodes.


Laser Physics | 2006

On the mechanism of subnanosecond electron beam formation in gas-filled diodes

V. F. Tarasenko; S. I. Yakovlenko; S. A. Shunailov; I. D. Kostyrya; A. N. Tkachev

Subnanosecond electron beams formed in diodes filled in with a gas at atmospheric pressure and X-rays emitted from nanosecond-discharge plasmas are studied. Both phenomena hold promise for lasing technology. A three-group separation of fast electrons in a gas-filled diode is proposed. It is found that the duration of the beam current in a diode filled with air at atmospheric pressure does not exceed 0.1 ns. It is also shown that the amplitude of the beam current attains maximum with a certain delay after the application of voltage to the discharge gap. A current of ∼400 A is detected behind the foil of a diode filled with air at atmospheric pressure. At a subnanosecond duration of the voltage pulse and the diffuse discharge, X-ray radiation is observed from the brightly glowing area of corona discharge. The mean steady-state velocities and energies of fast electrons in nitrogen are calculated. Head-on collisions are shown to control the constancy of the mean velocity of fast electrons for the field strengths E/p < 170 kV/(cm atm). At E/p > 170 kV/(cm atm), the escape of fast electrons takes place. It is particularly the head-on collisions that are decided to be responsible for the emission of X-rays from the bulk.


Technical Physics | 2007

X-ray radiation from the volume discharge in atmospheric-pressure air

V. B. Bratchikov; K. A. Gagarinov; I. D. Kostyrya; V. F. Tarasenko; A. N. Tkachev; S. I. Yakovlenko

X-ray radiation from the volume discharge in atmospheric-pressure air is studied under the conditions when the voltage pulse rise time varies from 0.5 to 100 ns and the open-circuit voltage amplitude of the generator varies from 20 to 750 kV. It is shown that a volume discharge from a needle-like cathode forms at a relatively wide voltage pulse (to ≈60 ns in this work). The volume character of the discharge is due to preionization by fast electrons, which arise when the electric field concentrates at the cathode and in the discharge gap. As the voltage pulse rise time grows, X-ray radiation comes largely from the discharge gap in accordance with previous experiments. Propagation of fast avalanche electrons in nitrogen subjected to a nonuniform unsteady electric field is simulated. It is demonstrated that the amount of hard X-ray photons grows not only with increasing voltage amplitude but also with shortening pulse rise time.


Technical Physics | 2004

Formation of coniform microdischarges in KrCl and Xecl excimer lamps

Mikhail I. Lomaev; V. F. Tarasenko; A. N. Tkachev; D. V. Shitts; S. I. Yakovlenko

The dynamics of formation of the steady-state regime in KrCl and XeCl double-barrier excimer lamps excited by a pulsed-periodic discharge is studied. Diffusive microdischarges in the form of two cones with joint vertices are shown to appear for about 1 s. Over this time interval, the initially volume exciting discharge (within several early pulses) transforms into a spark (immediately before the formation of the coniform microdischarges). It is demonstrated that the spark-diffusive discharge transition may be associated with fast electron generation.


Technical Physics Letters | 2003

Electron beam formation in helium at elevated pressures

Sergey B. Alekseev; V. M. Orlovskii; V. F. Tarasenko; A. N. Tkachev; S. I. Yakovlenko

The formation of a beam of runaway electrons in a diode filled with helium at a pressure from 0.1 to 760 Torr was studied under conditions of a pulsed ≈4 ns) high ≈200 kV) voltage applied to the discharge gap. Both theoretical results and experimental data indicate that the electron beam is generated both at a large strength of the electric field, when the fraction of runaway electrons is large, and in a field of low strength, where intensive electron multiplication takes place. In the latter case, a high current can be obtained despite a small fraction of runaway electrons relative to their total number. The electron beams obtained in the helium-filled diode had a current amplitude of up to 140 A (corresponding to a current density above 10 A/cm2) at an electron energy of ∼150 keV.


Laser Physics | 2007

Generation regimes for the runaway-electron beam in gas

E. Kh. Baksht; V. F. Tarasenko; Mikhail I. Lomaev; D. V. Rybka; A. N. Tkachev; S. I. Yakovlenko

The generation of the runaway-electron beam in nitrogen and helium is studied at an oscillator voltage of about 25 kV. Various regimes of the electron beam generation with a pulse duration ranging from 200 ps to several nanoseconds are realized depending on the pressure in the gas diode. An ultrashort avalanche electron beam (UAEB) with a low (10–20%) variation in the voltage across the gap is obtained at a relatively high pressure in the gas diode. The UAEB generation can be delayed relative to the leading edge of the voltage pulse by tens of nanoseconds at low oscillator voltages.


Technical Physics | 2005

Electron beam formation in a gas diode at high pressures

Sergey B. Alekseev; V. M. Orlovskii; V. F. Tarasenko; A. N. Tkachev; S. I. Yakovlenko

Electron beam formation in krypton, neon, helium, and nitrogen at elevated pressures are experimentally investigated. It is shown that, when the krypton, neon, and helium pressures are varied, respectively, from 70 to 760 Torr, from 150 to 760 Torr, and from 300 to 4560 Torr, runaway electrons are beamed at the instant the plasma in the discharge gap approaches the anode and the nonlocal criterion for electron runaway is fulfilled. The fast-electron simulation of discharge gap preionization is performed. The simulation data demonstrate that preionization in the discharge gap is provided if the voltage pulse rise time is shorter than a nanosecond under atmospheric pressure.

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S. I. Yakovlenko

Russian Academy of Sciences

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V. F. Tarasenko

Russian Academy of Sciences

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I. D. Kostyrya

Russian Academy of Sciences

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V. I. Derzhiev

Russian Academy of Sciences

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L A Mikhal'tsov

Russian Academy of Sciences

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S A Chaushanskii

Russian Academy of Sciences

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V. M. Orlovskii

Russian Academy of Sciences

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A Yu Sapozhkov

Russian Academy of Sciences

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A. M. Boichenko

Russian Academy of Sciences

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Mikhail I. Lomaev

Russian Academy of Sciences

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