VUV spectra of krypton-xenon mixtures in a cooled DC-excited discharge

An experimental study was made of VUV spectra of a gas-discharge krypton plasma with a xenon impurity. The mixture pressure, the xenon impurity concentration, and the current were varied in ranges of 40–1000 hPa, 0.001–1%, and 10–50 mA, respectively. The heteronuclear XeKr dimers were shown to play a crucial role in the quenching of excitation energy of krypton dimers. The mechanism of transformation of the energy of excited krypton dimers in a low-temperature plasma of a binary krypton-xenon mixture is discussed.     

Parameters of VUV radiation from a DC capillary discharge in a mixture of krypton with xenon

This paper describes the technique and the results of measurement of the power and geometry of the VUV radiation beam from a dc capillary discharge in a mixture of krypton and xenon. The angular divergence of narrowband VUV radiation of the heteronuclear KrXe* molecule is shown to be narrower as compared to that of the discharge radiation in the range 200–1000 nm. The power of VUV radiation from a discharge tube 80 cm long is found to exceed 10 mW.     

Dynamics of the plasma column of a capillary discharge soft X-raylaser

A sequence of time-resolved soft X-ray pinhole images shows the rapid plasma compression in a fast high-power capillary discharge. The compressed plasma column has a length-to-diameter ratio >500 and a good axial uniformity, characteristics that have allowed for the first demonstration of large soft X-ray amplification in a discharge-created plasma     

VUV spectra from the krypton-fluoride ionic excimer

New continuous VUV radiation near 148 nm was observed from Kr/NF₃/He and Kr/F₂/He mixtures under X-ray excitation from a laser-produced plasma. Theoretical and experimental analysis shows that the continuum can be attributed to the transition of the ionic excimer Kr²⁺F^–.     

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.     

Guiding of intense laser beams in highly ionized plasma columns generated by a fast capillary discharge

We have demonstrated the guiding of laser pulses with peak intensities up to 2.2 x 10(17) W/cm(2) in a 5.5 cm long plasma column containing highly charged Ar ions generated by a fast capillary discharge. A rapid discharge-driven hydrodynamic compression guides progressively lower order modes through a plasma with increasing density and degree of ionization, until the guide collapses on axis. The lowest order mode (FWHM approximately 50 microm) is guided with 75% transmission efficiency shortly before the plasma reaches the conditions for lasing in Ne-like Ar. The subsequent rapid plasma expansion forms a significantly leakier and more absorbent guide.     

Polymer photoablation under windowless VUV hydrogen or helium discharge lamp

In this work, the photoablation of PolyPhenyl-Quinoxaline (PPQ) films is investigated by using the vacuum ultraviolet (VUV) incoherent emission (λ<160nm) from a novel windowless hydrogen (or helium) discharge lamp. A tentative explanation of the film etching process is given through the photochemical reactions which take place in the polymer under VUV illumination.     

Dynamics of capillary drying in water

We use atomistic simulations to address the question when capillary evaporation of water confined in a hydrocarbonlike slit is kinetically viable. Activation barriers and absolute rates of evaporation are estimated using open ensemble Monte Carlo-umbrella sampling and molecular dynamics simulations. At ambient conditions, the evaporation rate in a water film four molecular diameters thick is found to be of the order 10(5)(nm(2) s)(-1), meaning that water readily evaporates. Films more than a few nanometers thick will persist in a metastable liquid state. Dissolved atmospheric gas molecules do not significantly decrease the activation barrier.     

Optical guidance of terrawatt laser pulses by the implosion phase of a fast Z-pinch discharge in a gas-filled capillary

A new method of optical guidance by the implosion phase of a fast Z-pinch discharge in a gas-filled capillary is proposed. An imploding plasma column has a concave electron-density profile in the radial direction, just before a stagnation phase driven by a converging current sheet and a shock wave. The feasibility of optical guidance of a high-intensity (>1 x 10(17) W/cm(2)) Ti:sapphire laser pulse by use of this method over a distance of 2 cm, corresponding to 12.5 times the Rayleigh length, has been experimentally demonstrated. The guiding-channel formation process was directly probed with a He-Ne laser beam. The electron density in the fully ionized channel was estimated to be 2.0 x 10(17) cm(-3) on the axis and 7.0 x 10(17) cm(-3) on the peaks of the channel edge, with a diameter of 70 mum, as indicated by the experimental results, which were corroborated by a magnetohydrodynamics simulation.     

Dynamics of a capillary inflow

In the present paper, the process of liquid inflow in a capillary tilted at a certain angle is examined. An approximate equation is suggested that has an analytical solution, approximates satisfactorily an exact numerical solution of the nonlinear equation of motion, and provides agreement with the available experimental data. The nonuniformity of the inflow rate is estimated. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 69–72, May, 2007.     

VUV and Eu-L3 edge XANES spectra of europium-doped strontium tetraborate prepared in air

VUV-UV and Eu-L₃ edge XANES spectra were measured for europium-doped strontium tetraborate prepared by solid state reaction at high temperature in air. The VUV-UV spectra show that the host absorption band of SrB₄O₇ appears below 170 nm. The charge transfer band of Eu³⁺ doped in SrB₄O₇ is peaked at 272 nm. The 4f–5d transitions of Eu²⁺ consist of a band peaked at 310 nm with a shoulder at 280 nm and also include the bands peaked at 238 (weak) and 203 (strong) nm. The result of XANES spectrum at Eu-L₃ edge of the synthesized sample indicates that Eu³⁺ and Eu²⁺ coexist in SrB₄O₇:Eu prepared in air, which is consistent with the results of the VUV-UV spectra.     

Excitation of metal spectra in combined glow discharge

Consideration is given to the special features of the excitation of spectra of metals (Ag, Au, Fe, Hg, Pt, and Sb) that manifest themselves in investigating spectral sources with combined glow discharge (glow discharge and capillary discharge). It is established that the proposed method for introducing a substance into a plasma makes it possible to realize two fundamentally different regimes: without evaporation and with complete evaporation and matrix atomization. It is shown that a spectral source of combined glow discharge with a nonequilibrium plasma has significant advantages for the most important analytical characteristics over quasi-equilibrium combined discharge at atmospheric pressure. The gold and platinum sensitivity in combined glow discharge is 10⁻⁷%, and the reproducibility of spectral determinations is 0.001–0.100, depending on the measurement range. A fractional separation of elements that makes it possible to analyze the phase composition of substances, particularly metals, with high sensitivity is revealed in glow discharge. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 143–147, March–April, 1997.     

毛细管放电Z箍缩等离子体X射线激光

毛细管放电Z箍缩等离子体软X射线激光器近几年发展非常迅速，已经获得了在46．9nm的波长上近毫焦量级的激光输出，重复频率达到了4Hz．利用这种软X射线激光在等离子诊断、物质烧熔等方面已开展了初步的应用实验研究．文章介绍了毛细管放电泵浦的两种物理机制，阐述了类氖氩离子2p^53p^1S0-2p^53s^1P1能级间粒子数反转的形成及毛细管放电等离子体柱的演变过程．深入理解这些物理过程，对发展毛细管放电软X射线激光将起到积极作用。     

LSO-Ce fluorescence spectra and kinetics for UV,VUV and X-ray excitation

Abstract

LSO-Ce fluorescence emission and excitation spectra and decay kinetics have been measured for UV, VUV and X-ray excitation at RT and 80 K. The features of the fluorescence excitation spectra of two types of cerium centres in the region 3 to 6 eV are analysed in the assumption of competitative absorption between them. It is shown that the centres can have similar absorption bands. Forbidden energy bandgap for LSO is evaluated to be not less than 6.5 eV.     

Investigation of the breakdown temperature in capillary discharge plasmas

We developed a simple way to estimate the breakdown temperature Tb of plasma electrons in a capillary, which is based on measurement of the electrical breakdown voltage Vb. The result shows that the breakdown temperature Tb decreases with increasing pressure. The thermal equilibrium electron temperature Te in the capillary plasma after the electrical discharge is also measured by using the optical emission spectroscopy method.     

Dynamics of a radiating surface discharge

We have elaborated a code for numerical treatment of two-dimensional problems of the dynamics of a surface discharge with inclusion of radiative energy transfer. The gas dynamic, electric, and radiative properties of a surface discharge in atmospheric air have been studied experimentally for a total energy input of 100 J/cm in the input power range 3–6 MW/cm. A new technique involving a discharge sliding along a conducting surface is applied to initiate an extended surface discharge. The calculations agree satisfactorily with the experiments. The method elaborated here makes it possible to calculate a broad class of linear discharges with an eye to produce a radiation source with problem-oriented spectral power characteristics.     

Dynamics of electron-cascade formation in a pulsed discharge

The dynamics of the velocity distribution function of the electrons in a pulsed discharge is analyzed, taking account of the initial stage of electron heating within the framework of the BGK model integral. It is assumed that the basic contribution to the relaxation of the electron distribution function comes from elastic collisions with neutral particles. The dynamic distribution function obtained is used to determine the ionization coefficient and study the dynamics of electron-cascade development.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 70–75, May, 1984.In conclusion, Prof. V. B. Krasovitskit must be thanked for fruitful discussion and constant interest in the work.