A. G. Yastremskii

Two-dimensional simulation of the development of an inhomogeneous volume discharge in a Ne/Xe/HCl gas mixture

The kinetic processes accompanying plasma column formation in an inhomogeneous discharge in a Ne/Xe/HCl gas mixture at a pressure of 4 atm were investigated by using a two-dimensional model. Two cathode spots spaced by 0.7 cm were initiated by distorting the cathode surface at local points, which resulted in an increase in the field strength in the cathode region. Three regimes differing in the charging voltage, electric circuit inductance, and electric field strength at the local cathode points were considered. The spatiotemporal distributions of the discharge current; the electron density; and the densities of excited xenon atoms, HCl(v = 0) molecules in the ground state, and HCl(v > 0) molecules in vibrational levels were calculated. The development of the discharge with increasing the electron density from 104 to 1016 cm−3 was analyzed, and three characteristic stages in the evolution of the current distribution were demonstrated. The width of the plasma column was found to depend on the energy deposited in the discharge. The width of the plasma column was found to decrease in inverse proportion to the deposited energy due to spatiotemporal variations in the rates of electron production and loss. The calculated dependences of the cross-sectional area of the plasma column on the energy deposited in the discharge agree with the experimental results.

Influence of the input radiation pulse characteristics on the parameters of a XeF(C – A) amplifier in a THL-100 laser system

We report the results of experimental and theoretical investigations on the influence of spatial and energy parameters of input radiation with a pulse duration of on output characteristics of a XeF(C – A) amplifier in a visible-range, multi-terawatt THL-100 laser system. Dynamics of the energy density radial distribution for laser radiation passing through the amplifier is studied. Results of numerical simulation are presented for amplification of laser beams with Gaussian and super-Gaussian radial energy density distributions. It is shown that the laser energy of obtained experimentally is not the limiting value. According to calculations, the output energy of the amplifier with such mirror configuration may reach , which in the case of a pulse compressed down to corresponds to the radiation power of .

Modeling of lasing possibility in XeF(C-A) amplifier of the THL-100 laser system

Results of experimental measurements and numerical simulations of the N2 and XeF2 gas pressure effects on the gain characteristics are presented in the paper. It is experimentally and theoretically is shown that maximum total gain (5-6)×104 achieved at a pump energy E = 240 J, 0.2 Torr XeF2 and 0.5 atm N2 pressure. Increasing and decreasing of N2 pressure leads to decrease of the gain. The possibility of the XeF(C-A) amplifier operation in a generator mode is discussed and the theoretical study results of generation are presented. It is shown that an annular laser radiation with energy up to 8.5 J can be obtained. The study results of the influence on the laser energy of N2 and XeF2 pressure and reflectance coefficient of output mirror are presented.

Kinetic processes in the electric discharge in SF6

The simulation of the kinetic processes in the spatially homogeneous and heterogeneous plasma of the gas discharge in SF6 is performed. The calculated time dependences of the rates of the most important processes and the concentrations of electrons, ions, and other particles that affect the plasma characteristics are presented. The calculated and experimental results are compared. The kinetic processes are analyzed and their effect on the plasma characteristics is demonstrated. The calculated data regarding the development of the plasma channel are presented. An increase in the conductivity inside the channel is discussed.

Conditions of the generation of subnanosecond pulses in a THL-100 laser system

The results from the generation and amplification of positively chirped pulses of 0.05 ns duration at a central wavelength of 475 nm in a THL-100 laser system are presented. It is found that the initial complex allows the generation of such radiation pulses with Gaussian intensity profiles and energies of up to 7 mJ. When such pulses with energies of 2–4 mJ are amplified in an XeF(C-A) amplifier, it is possible to achieve a saturation mode and obtain at the output laser beams with energies of up to 3.2 J. The possibility of compressing subnanosecond pulses at a wavelength of 475 nm in a compressor based on diffraction gratings is demonstrated.

High power laser system of a visible range with output XeF(C-A) amplifire

THL-100 hybrid femtosecond laser system operating in the visible spectral range and the experimental results obtained by now are presented.

Volume electrical discharge in Ne/SF6/C6H14 and pure SF6

The electrical and spatial characteristics of a volume electrical discharge are studied as functions of the ratio of partial pressures of the mixture components at varying initial voltage. Early in the discharge, hot (plasma) cathode spots are observed with diffusive plasma flares developing above them. Overlapping of the flares produces a volume plasma column. The column homogeneity depends on the diffusive-flare density, and the length of the volume-discharge stage is determined by the time it takes for one or more flares to transform and give rise to the channel stage. Estimates of the ionization, attachment, and ion recombination rates are used to show that the electron density in plasma channels is two orders of magnitude lower than that of positive and negative ions forming a stagnant stiff skeleton of the plasma.