arXiv subjects

K. V. Khishchenko

Publications and source records attributed to K. V. Khishchenko.

5 recordsLinked to original sources

arXiv2012

Amplification of a surface electromagnetic wave by running over plasma surface ultrarelativistic electron bunch as a new scheme for generation of Teraherz radiation

The amplification of a surface electromagnetic wave by means of ultrarelativistic monoenergetic electron bunch running over the flat plasma surface in absence of a magnetic field is studied theoretically. It is shown that when the ratio of electron bunch number density to plasma electron number density multiplied by a powered to 5 relativity factor is much higher than 1, i.e $γ^5 n_b/n_p>> 1$, the saturation field of the surface electromagnetic wave induced by trapping of bunch electrons gains the magnitude: $E_x=B_y\approx 0.16 \frac{ω_p m c}{e} (\frac{2n_b}{γ^2 n_p})^{1/7}$ and does not approache the surface electromagnetic wave front breakdown threshold in plasma. The surface electromagnetic wave saturation energy density in plasma can exceed the electron bunch energy density. Here, we discuss the possibility of generation of superpower Teraherz radiation on a basis of such scheme.

physics.plasm-ph↗

arXiv2010

Suppression of ablation in femtosecond double pulse experiments

We report the physical reasons of a curious decrease in the crater depth observed for long delays in experiments with femtosecond double pulses. Detailed hydrodynamic modeling demonstrates that the ablation mechanism is dumped when the delay between the pulses exceeds the electron-ion relaxation time. In this case, the interaction of the second laser pulse with the expanding target material leads to the formation of the second shock wave suppressing the rarefaction wave created by the first pulse. The evidence of this effect follows from the pressure and density profiles obtained at different delays after the first laser pulse.

physics.comp-ph↗

arXiv2007

Material decomposition mechanisms in femtosecond laser interactions with metals

A numerical hydrodynamic study of femtosecond laser ablation is presented. A detailed analysis of material decomposition is performed using a thermodynamically complete equation of state with separate stable and metastable phase states and phase boundaries. The lifetime of the metastable liquid state is estimated based on the classical theory of homogeneous nucleation. In addition, mechanical fragmentation of the target material is controlled based on available criteria. As a result, several ablation mechanisms are observed. A major fraction of the ablated material, however, is found to originate from the metastable liquid region, which is decomposed either thermally in the vicinity of the critical point into a liquid-gas mixture, or mechanically at high strain rate and negative pressure into liquid droplets and chunks. The calculation results explain available experimental findings.

physics.comp-ph↗

arXiv2006

The Effects of Preheating of a Fine Tungsten Wire and the Polarity of a High-Voltage Electrode on the Energy Characteristics of an Electrically Exploded Wire in Vacuum

Results obtained from experimental and numerical studies of tungsten wires electrical explosion in vacuum are presented. The experiments were performed both with and without preheating of the wires, using positive or negative polarity of a high-voltage electrode. Preheating is shown to increase energy deposition in the wire core due to a longer resistive heating stage. The effect was observed both in single wire and wire array experiments. The evolution of the phase state of the wire material during explosion was examined by means of one-dimensional numerical simulation using a semiempirical wide-range equation of state describing the properties of tungsten with allowance made for melting and vaporization.

physics.plasm-ph↗

arXiv2006

Influence of equation of state on interpretation of electrical conductivity measurements in strongly coupled tungsten plasma

We study the influence of equation-of-state (EOS) model on the interpretation of electrical conductivity measurements in strongly coupled plasma of tungsten by Korobenko et al. (2002 Plasma Physics Reports 28(12) 1008--1016). Three different semiempirical EOS models for tungsten are used. Discrepancies in obtained thermodynamic parameters and specific resistivity values as compared with calculation results of Korobenko et al. are analysed.

physics.plasm-ph↗