G. N. Zvereva

Possible application of a volume avalanche discharge initiated by an electron beam for designing a krypton dimer laser

The emissive and amplifying properties of volume nanosecond discharge plasma formed at high pressures in krypton have been investigated theoretically and experimentally. It is theoretically shown that lasing can be obtained in this type of discharge at krypton pressures exceeding 6–7 atm. In the discharge gap with a cathode of small curvature radius, volume discharge without preliminary ionization is obtained at a high pressure and intense krypton dimer emission that peaks at a wavelength of 146 nm is detected. It is shown that, upon excitation by a volume avalanche discharge initiated by an electron beam, no less than 90% of the energy in the range 120–540 nm is emitted by krypton dimers. At a krypton pressure of 1.5 atm, an energy of ∼30 mJ of spontaneous emission into the total solid angle and a radiation pulse width at half maximum of ∼240 ns are obtained.

Numerical simulation of a barrier discharge in Xe

Components of plasma of a barrier discharge in xenon are calculated for various values of the parameter E/N. Features of excimer population are analyzed. Efficiencies of the VUV emission yield are calculated, and basic channels of energy loss determining the efficiency are established.

Investigation of water decomposition by vacuum ultraviolet radiation

The concentrations of products of liquid and gaseous water decomposition under the action of VUV (7n = 172 nm) radiation are calculated. It is shown that the VUV radiation causes efficient formation of highly reactive *OH radicals. The application the products of water photodecomposition is exemplified by the possibility of degradation of polychlorinated biphenyl upon interaction with these products.

Calculation of the parameters of vacuum-ultraviolet emission of excimers in the plasma of a barrier discharge in a krypton-xenon mixture

The intensities of vacuum-ultraviolet emission of excimers in a krypton-xenon mixture are calculated in terms of the homogeneous model of a barrier discharge. The mechanisms of the formation of excimer molecules are investigated at different xenon concentrations. The obtained dependences of the efficiency of vacuum-ultraviolet emission on the reduced electric field E/N (where E is the electric field strength and N is the particle concentration of the gas) and the xenon content exhibit a plateau and a subsequent steep decline. The efficiency of vacuum-ultraviolet emission reaches a maximum at the plateau when the xenon content δ is approximately equal to 40%. The concentrations of xenon excimers can be as high as 1014–1015 cm−3. This is comparable to the concentrations in a barrier discharge in pure xenon.

VUV spectrum of the barrier discharge in a krypton-xenon mixture

VUV spectra of a barrier discharge in a krypton-xenon mixture at the pressure P=400 hPa were experimentally studied. The xenon addition was varied in a range of 0.01–1%. The supply voltage frequency was 20 kHz. The form of spectra and their evolution at different xenon impurity concentrations were analyzed by solving the system of nonlinear differential equations simulating the main processes taking place in the active phase of a discharge and in the afterglow. The analysis supports the results obtained earlier and qualitatively describes the experimental spectra.

Investigation of the amplifying properties of a krypton gas discharge plasma

The characteristics of a gas discharge in krypton (at a pressure of several atmospheres), used as a medium for lasers based on excimer transitions in the VUV region, have been calculated. It is shown that, to achieve the threshold values of excimer concentration, a high preionization level and the shape of the applied voltage pulse are important factors. It has been found that the shape of the excimer emission pulse is determined, to a large extent, by stepwise processes with the participation of electrons and by the relaxation time of the electron energy.

Calculation of the parameters of excimer light sources on the basis of a positive column glow discharge

We calculate the concentration of plasma and gas-temperature components in a contracted filament of a glow capillary discharge (R = 0.75 mm) in xenon for pressures of P = 100 and 400 Torr and currents of I = 6–15 mA for cases of with and without cryogenic cooling of the discharge. We find that the gas temperature in the channel of the glow discharge has a value of 1000–2000 K, the concentration of xenon excimers attains a maximum at the boundary of the filament with a value of 1010–1011 cm−3, and the efficiency of electric energy transformation into excimer radiation energy has a value of 0.1–5%.

Excitation transfer in the plasma of a barrier discharge in a krypton-xenon mixture

Processes of excitation transfer in the plasma of a barrier discharge in a krypton-xenon mixture are studied. A kinetic diagram of energy transfer is proposed, and a system of coupled kinetic equations describing the dynamics of processes in the plasma of a barrier discharge of mixtures in pure xenon as well as in a krypton-xenon mixture is composed and solved. The effect of excitation transfer on the population distribution over vibrational levels of krypton excimers excited by a barrier discharge in a krypton-xenon mixture is studied. The deviation from the equilibrium distribution over vibrational levels is found. It can be interpreted as an indication of the activation of the mechanism of depopulation of the lowest vibrational levels of excimer states of krypton.