2008

Aksenov, V.P.^a, Izmailov, I.V.^b, Kanev, F.Yu.^a, Starikov, F.A.^c   Algorithms for the reconstruction of the singular wave front of laser radiation: Analysis and improvement of accuracy   // Quantum Electronics, 2008, Volume 38, Issue 7, Pages 673 - 677

^a  Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, prosp. Akademicheskii 1, 635055 Tomsk, Russian Federation
^b  Tomsk State University, prosp. Lenina 36, 634050 Tomsk, Russian Federation
^c RFNC - VNIIEF, Sarov, Russian Federation

The possibility of reconstructing a singular wave front of laser beams by the local tilts of the wave front measured with a Hartmann sensor is considered. The accuracy of the reconstruction algorithm described by Fried is estimated and its modification is proposed, which allows one to improve the reliability of the phase reconstruction. Based on the Fried algorithm and its modification, a combined algorithm is constructed whose advantages are demonstrated in numerical experiments.

Kanakov, V.A.^a, Lupov, S.Yu.^a, Orekhov, Yu.I.^b, Rodionov, A.V.^c   Techniques for retrieval of the boundary displacement data in gas - dynamic experiments using millimeter - waveband radio interferometers // Radiophysics and Quantum Electronics, 2008, Volume 51, Issue 3, Pages 210 - 221

^a  N. I. Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russian Federation
^b  Yu. E. Sedakov Institute of Measuring Systems, Nizhny Novgorod, Russian Federation
^c  RFNC - VNIIEF, Sarov, Russian Federation

We describe a radio - interferometry method for measuring movement parameters of objects in application to gas - dynamic experiments. The origins of biasing in calculation of these parameters from measured interferograms are discussed. Bias reduction algorithms for the interferometer signal processing are described. For experimental setups with a single moving boundary, this algorithm is optimal for estimating the instantaneous phase and frequency of a narrow - band signal with bandpass prefiltering and quadrature - channel signal orthonormalization. For experiments with several moving boundaries, it provides the interferogram curve fitting by parameters of the electrodynamic model of an experimental setup. The results of test experiments verifying the reliability of the obtained information are presented.

Piskarev, I.M.^a , Ushkanov, V.A.^a, Selemir, V.D.^b, Spirov, G.M.^b, Malevannaya, I.A.^b, Zuimach, E.A.^b   The formation of ozone and UV radiation from high - power pulsed electric discharges  // Russian Journal of Physical Chemistry A, 2008, Volume 82, Issue 9, Pages 1565 - 1569

^a  Skobel'Tsyn Institute of Nuclear Physics, Moscow State University, Moscow 119992, Russian Federation
^b  RFNC - VNIIEF, Sarov, Russian Federation

High - power electric discharges with pulse energies of from 0,15 J to 4 kJ   were studied. The yields of UV photons and ozone were found to be approximately equal, which led us to conclude that discharge conditions under which UV radiation and ozone fully destroyed each other were possible. If ozone formation was suppressed, as when a negative volume charge was created in the spark gap region, the flux of UV photons reached 3 Г - 10 ²³ photons / ( cm ² s ).

Popov, N.N.^a, Kaganova, I.I.^a, Polyakov, L.V.^a, Bragov, A.M.^b, Lomunov, A.K.^b    Effect of the strain rate and test temperature on the mechanical properties of a Ti - Ni - Fe shape memory alloy  // Russian Metallurgy ( Metally ), 2008, Issue 1, Pages 61 - 65

^a  RFNC - VNIIEF, Sarov, Russian Federation
^b  Research Institute of Mechanics, Nizhni Novgorod State University, pr. Gagarina 23, Nizhni Novgorod 630600, Russian Federation

The test temperature ( from - 196 to + 50°C  ) and the strain rate ( from 10 ^-4 to 10 ³ s ^-1 ) are found to affect the character of deformation of a shape memory alloy TN1K based on titanium nickelide and alloyed with iron. The shapes of the tensile and compressive curves are shown to depend on the position of the test temperature with respect to the characteristic phase - transition temperatures. The mechanical properties are extremal in the temperature ranges corresponding to the R phase region. As the strain rate increases in the quasi - static range, the strength characteristics of the material increase and the plastic characteristics decrease. As the strain rate increases in the quasi - static range, the yield strength changes analogously; in this case, a yield drop appears in the compressive and tensile stress - strain diagrams. The data obtained are used to optimize the technology of the thermomechanical joints of pipelines and construction elements.

Kudasov, Yu.B.   Correlation mechanism of negative differential resistance for tunneling through a molecule   // Bulletin of the Russian Academy of Sciences: Physics, 2008, Volume 72, Issue 2, Pages 172 - 175

RFNC - VNIIEF, Sarov, Russian Federation

The microstructure of a current channel is experimentally found under the conditions when homogeneous air gaps are subjected to nanosecond voltage pulses in an electric field insufficient for streamer generation. As a possible mechanism of microstructure formation, instability of the ionization process at the avalanche stage leading to the formation of a self - similar spatial structure is considered. The fractal dimension of this structure is determined. In inhomogeneous gaps, the avalanche is shown to be unstable as well. The energy benefit of structuring is considered. It is demonstrated that the microstructure of streamer discharges in homogeneous gaps can also be treated in terms of the model suggested.

Drozhzhin, V.S.^a, Shpirt, M.Ya.^b, Danilin, L.D.^a, Kuvaev, M.D.^a, Pikulin, I.V.^a, Potemkin, G.A.^a, Redyushev, S.A.^a   Formation processes and main properties of hollow aluminosilicate microspheres in fly ash from thermal power stations  // Solid Fuel Chemistry, 2008, Volume 42, Issue 2, Pages 107 - 119

^a  RFNC - VNIIEF, Sarov, Russian Federation
^b  Institute for Fossil Fuels, Leninskii pr. 29, Moscow 119991, Russian Federation

The main parameters of aluminosilicate microspheres formed at thermal power stations in Russia were studied; these parameters are responsible for the prospective industrial application of these microspheres. A comparative analysis of the properties of mineral coal components, the conditions of coal combustion, and the effects of chemical and phase - mineralogical compositions of mineral impurities in coals from almost all of the main coal deposits on the formation of microspheres was performed. The effects of thermal treatment conditions on gas evolution processes in mineral particles and on the fraction of aluminosilicate microspheres in fly ash were considered. It was found that the yield of microspheres was higher in pulverized coal combustion in furnaces with liquid slag removal, all other factors being equal. The regularities of microsphere formation were analyzed, and the mechanism of microsphere formation in fly ash during the combustion of solid fuels was considered.

Dubinov, A.E.^a, Dubinova, A.A.^b   Exact integral - free expressions for the integral Debye functions  // Technical Physics Letters, 2008, Volume 34, Issue 12, Pages 999 - 1001

^a  RFNC - VNIIEF, Sarov, Russian Federation
^b  Advanced School of General and Applied Physics, Nizhni Novgorod State University, Nizhni Novgorod 603950, Russian Federation

Exact explicit integral - free expressions for the integral Debye functions and an integral - free expression for the heat capacity of the k - dimensional crystal lattice as a function of the temperature are obtained for the first time. The expressions involve polylogarithms and the Riemann zeta function.

Pikulev, A.A., Tsvetkov, V.M.    Efficiency of the barrier - discharge UV   Xe : SF₆  lamp  // Technical Physics, 2008, Volume 53, Issue 10, Pages 1332 - 1335

RFNC - VNIIEF, Sarov, Russian Federation

The efficiency of the barrier - discharge UV lamp filled with a  Xe / SF₆ = 50 : 1  mixture is studied as a function of the pressure in the mixture ( ranging from 40 to 180 Torr  ) and electrode distance ( 3 - 11 mm ). It is shown that, if the product pd is constant, the power of the discharge and the intensity of the UV radiation ( 354 nm ) decrease with increasing pressure and shrinking the electrode gap. The maximal efficiency of the lamp ( 6 - 8%  ) is reached in the pressure range 30 - 50 Torr.

Karelin, V.I., Tren'Kin, A.A.   Formation of the microscopic structure of high - voltage nanosecond diffuse discharges in sharply nonuniform geometry  // Technical Physics, 2008, Volume 53, Issue 9, Pages 1236 - 1239

RFNC - VNIIEF, Sarov, Russian Federation

The possibility of the development of ionization instability in the avalanche and plasma phases ( of the long - wave and short - wave type, respectively ) is demonstrated for high - voltage nanosecond discharges in sharply nonuniform geometry. Specific implementation is determined by the electric field distribution in the cathode region and by the emissivity of the cathode. The spatial structure of the discharge formed in both cases is self - similar.

RFNC - VNIIEF, Sarov, Russian Federation

It is shown experimentally that an increase in the lasing mixture residence time in the case of a laser module over 60 - 120 min prior to an experiment elevates the lasing threshold and deteriorates the energy parameter of the laser. The worsening of the energy parameters of the laser may be due to accumulation of impurity gases. It is shown that the presence of impurities affects the working characteristics of the laser media under investigation to various extents.