Showing papers by "Moscow Institute of Physics and Technology published in 1994"
TL;DR: In this article, a review of the state-of-the-art models of fast ionisation waves (FIWs) and their properties and properties is presented. But the focus of the review was not on the acceleration, but on the properties of the wave front.
Abstract: An analysis of experimental and theoretical investigations is the basis of this state-of-art review of models of fast ionisation waves (FIWs) and of characteristics and properties of these waves. The attention is concentrated on waves with the maximum possible velocities of 109–2×1010 cm s–1 when the amplitudes of voltage pulses are 20–300 kV. At low and moderate pressures the reduced intensity of the electric field in the front of a wave is so high that the front becomes a moving source of a beam of high-energy electrons in which the current can reach several kiloamperes. At moderate pressures the high-energy electrons in the wave front overtake the front and cause preliminary ionisation of the gas ahead of the front. At low pressures these electrons determine mainly the mechanism of the motion of the front. At high pressures (in excess of 200 torr) the main source of such preionisation is the radiation emitted by the front. The high rate of filling of the discharge volume with a plasma, high electric fields and high energies of the electrons in the front, and the slight heating of the gas make fast ionisation waves attractive for applications.
167 citations
TL;DR: In this paper, the authors classify different theories of self-intersecting random surfaces assigning special weights to intersections, and construct equivalent spin systems for this general case in two dimensions.
47 citations
28 citations
TL;DR: In this article, a dramatic cosmic event will take place: comet Shoemaker-Levi 9 will collide with Jupiter and an explosion will occur, and the energy released during the explosion will exceed by some thousandfold the total nuclear potential accumulated by mankind.
Abstract: In July 1994 a dramatic cosmic event will take place: comet Shoemaker–Levi 9 will collide with Jupiter. The entry of the comet into the atmosphere of Jupiter will be accompanied by a rapid energy release and an explosion will take place. The energy released during the explosion, of the order of 107 Mt, will exceed by some thousandfold the total nuclear potential accumulated by mankind. Some characteristics of the interaction of the comet with Jupiter are discussed and possible consequences of the collision are outlined.
23 citations
TL;DR: In this paper, the authors analyzed the North Korean missile program based on publicly available information and a technical understanding of missile systems and concluded that a 1,000 kilometer-range Nodong missile with a one tonne payload could be built using Scud technology and it appears feasible to extend the range to roughly 1,300 kilometers (with the same payload) if the missile body can be constructed out of high-strength aluminum rather than steel, although it is unclear whether North Korea has such a capability.
Abstract: In this paper, we analyze the North Korean missile program based on publicly available information and a technical understanding of missile systems. In particular, we present models for the 1,000 kilometer‐range Nodong missile and a 1,300 kilometer‐range variant, both based on Scud technology. These models are single‐stage missiles with four clustered Scud‐engines and would have a circular error probable (CEP) of two to four kilometers or larger. We conclude that a 1,000 kilometer‐range missile with a one tonne payload could be built using Scud technology. Moreover, it appears feasible to extend the range to roughly 1,300 kilometers (with the same payload) if the missile body can be constructed out of high‐strength aluminum rather than steel, although it is unclear whether North Korea has such a capability. If both missiles are based on Scud technology, their existence would not imply a breakthrough in North Korean missile technology. These missiles would then represent essentially the longest‐range missi...
20 citations
TL;DR: In this paper, the residual polarization of negative muons in p-type Si on temperature in the 4.2-270 K range was investigated, where the impurity concentration in the sample was 2 · 1013 cm−3.
Abstract: The dependence of the residual polarization of negative muons in p-type Si on temperature in the 4.2–270 K range has been investigated. Measurements were carried out in external magnetic field of 0.08 T transverse to the muon spin. The impurity concentration in the sample was 2 · 1013 cm−3. Muon spin relaxation was observed at temperatures below 30 K. The relaxation rate atT=30 K is equal to 0.18±0.08μs−1. The relaxation rate grows with the decrease of temperature and at 4.2 K exceeds 30μs−1. The value of the residual polarization at zero timeP(t=0) is constant within the investigated temperature range.
16 citations
TL;DR: In this paper, an asymptotic method with the angle of attack as a small parameter was used to solve the full viscous shock-layer (FVSL) equations in a body-oriented coordinate system.
12 citations
TL;DR: In this paper, changes in the management of the space program and the operational status of various systems in the former Soviet Union are examined with particular emphasis on defense-related space systems.
Abstract: Changes in the management of the space program and the operational status of various systems in the former Soviet Union are examined with particular emphasis on defense‐related space systems. After the break‐up of the Soviet Union, Russia assumed general responsibility for the entire scope of Soviet space activity. Space program management was re‐organized to separate military and civilian activities. Russia is committed to maintaining military space capabilities, however, its top priority is now the conversion of military space technology for civilian uses, including global environmental problems.
11 citations
TL;DR: Raman scattering in superconducting Tl2Ba2CuO6 crystals has been investigated in this article, where it has been shown that all the Raman peculiarities can be explained assuming finite-wavevector excitations which participate in Raman scattering.
Abstract: Raman scattering in superconducting Tl2Ba2CuO6 crystals has been investigated. Scattering in a forbidden polarization, the phonon-lineshape asymmetry depending on the scattering configuration, and electronic scattering in a wide energy range have been observed. It has been shown that all the Raman peculiarities can be explained assuming finite-wavevector excitations which participate in Raman scattering.
11 citations
TL;DR: In this paper, the capabilities of the currently deployed Russian space-based early warning system were analyzed and it was shown that the system could not be modified to adapt to new missions, such as detection of accidental or unauthorized launches or countering the emerging threat of ballistic missile launches from third-world countries.
Abstract: Early warning against ballistic missile attack has played a very important role in the military doctrines of the Unites States and Russia. Both countries have deployed systems of early warning satellites that could detect an attack almost immediately after the missiles were launched. These systems were vital for providing a launch on warning capability that was an important building block of their deterrence policies. With the end of the Cold War, the probability of a large‐scale nuclear conflict has practically disappeared and the mission of the early warning system has become more diversified. The new missions, such as detection of accidental or unauthorized launches or countering the emerging threat of ballistic missile launches from third‐world countries, becoming almost equally important, could require an early warning system of a different kind. This article analyzes the capabilities of the currently deployed Russian space based early warning system and shows that the system could not be modified to...
8 citations
TL;DR: In this paper, the spatial and frequency instability of an intense laser wave in sodium vapor at low-frequency laser detuning with respect to the D1 sodium transition is reported and it is shown that the observed picture of the scattering (cone radiation, generation of shifted sidebands, formation of filaments) in general is analogous to that at high-frequency detuning.
TL;DR: In this paper, it was shown that an arbitrary periodic flow of ideal incompressible fluids can be represented by three pairs of periodic Clebsch variables, which can be expressed as follows:
TL;DR: In this article, a new method for the determination of the CKM mixing matrix element Vtb has been proposed, and it has been shown that at future colliders one can measure the tb-mixing element with an accuracy of 12-28%.
TL;DR: In this paper, an approximate analytical solution for the kinetic equation for electrons in the field of a Coulomb center formed by a muon in the end of its track was obtained.
Abstract: An approximate analytical solution is obtained for the kinetic equation for electrons in the field of a Coulomb centre formed by a muon in the end of its track. It is shown that thermalization times and could differ by several orders of magnitude, depending on the behaviour of transport cross sections. The fraction of non-thermalized electrons returning to the muon and forming muonium (P Mu ) depends on pressure and temperature. Therefore,μSR experiments give us an opportunity to obtain information on the distribution function of track electrons.
TL;DR: Wehrl and Lieb as discussed by the authors extended the concept of entropy to spin-1/2 systems and compared the results and discussed the Wehrl-Lieb entropy as an alternative formulation to von Neumann's.
Abstract: Years ago, A. Wehrl (Rev. Mod. Phys.50, 221 (1978)) introduced the concept of classicallike entropy of quantum states when a two-label continuous representation is used; for instance, the harmonic oscillator coherent states. Subsequently, E. H. Lieb (Commun. Math. Phys.62, 35 (1978)) extended that concept of entropy to the Bloch coherent spin states. Here, we consider spin-1/2 systems and calculate both the Wehrl–Lieb and von Neumann entropies, and then we compare the results and discuss the Wehrl–Lieb entropy as an alternative formulation to von Neumann's. As illustration, three examples are worked out: (i) the decoherence of a quantum state in a measurement process, (ii) the conservation of coherence, and (iii) the recoherence phenomena that appear in the solutions of a specific master equation that originates from a nonlinear Schrodinger equation.
TL;DR: In this paper, the three-dimensional supersonic viscous flow over a blunted body flying horizontally through a cloud of hot gas (a thermal) is studied numerically.
TL;DR: In this article, the authors considered the deflection and focusing of atoms in a quantized light field and proposed a method to create narrow atomic wave packets by focusing atoms in the light field.
Abstract: We consider the deflection and focusing of atoms in a quantized light field We study the influence of spontaneous emission on the deflection pattern and propose a method to create narrow atomic wave packets A possible experiment is suggested
TL;DR: In this paper, a two-pass laser amplifier with a phase-conjugating mirror operating on the basis of forward scattering of intersecting optical beams in a layer of a nematic liquid crystal on the mirror was made.
Abstract: A study was made of a two-pass laser amplifier with a phase-conjugating mirror operating on the basis of forward scattering of intersecting optical beams in a layer of a nematic liquid crystal on the mirror. The reflection coefficient of the mirror was optimised by the selection of the liquid-crystal cell temperature and of the absorption coefficient of the nematic mixture. A study was made of the compensation of the thermal aberrations in the amplifier rod during a return trip of the phase-conjugated scattered beam through the amplifier.
TL;DR: In this article, the renormalization of the electron-phonon interaction by impurity scattering for phonons of different symmetry has been analyzed and the analysis has been extended so as to take into consideration the finite wavevector phonons.
Abstract: Raman scattering in high-temperature superconductors is considered, assuming the presence of a random potential caused by either crystal non-stoichiometry or oxygen disorder. The renormalization of the electron-phonon interaction by impurity scattering for phonons of different symmetry has been analyzed. The analysis has been extended so as to take into consideration the finite wavevector phonons. On the basis of the theory developed, unusual properties of phonon Raman scattering in the high-temperature superconductors are qualitatively considered. They include the phonon line-shape and its dependence on the scattering polarizations and resonant conditions, and non-Bose temperature dependence of a number of Raman active phonons.
26 Oct 1994
TL;DR: In this paper, the spectral models of the diffuse attenuation coefficient Kd((lambda) ) developed by Austin, Petzold, 1984 and by Volynsky, Sud'bin, 1992 correspond with each other.
Abstract: The goal of this work is to verify different spectral models of the diffuse attenuation and absorption coefficients of sea water and to work out a recommendation for their use. It is shown that the spectral models of the diffuse attenuation coefficient Kd((lambda) ) developed by Austin, Petzold, 1984 and by Volynsky, Sud'bin, 1992 correspond with each other, as well the models of Ivanov, Shemshura, 1973 and of Kopelevich, Shemshura, 1988 for calculation of the spectral absorption coefficient a((lambda) ) on the values of Kd((lambda) ). Theoretical foundation of the relation between a((lambda) ) and Kd((lambda) ) is given. The up-to-date physical model of the sea water light absorption is considered and checked by means of comparison with measured values of the attenuation coefficient at the ultraviolet and visible spectral ranges.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, the influence of natural and induced optical activity on the resulting photoacoustic (PA) response is analyzed and a method of controlling the amplitude of PA signal is proposed based on the possibility to affect the interference energy dissipation by an external magnetic field.
Abstract: The process of thermo-optical excitation of sound by opposing light waves is studied in the magnetically active medium The influence of natural and induced optical activity on the resulting photoacoustic (PA) response is analyzed A method of controlling the amplitude of PA signal is proposed The method is based on the possibility to affect the interference energy dissipation by an external magnetic field
13 Sep 1994
TL;DR: In this paper, a new type of fiber optic sensor of electrostatic field was considered and the sensitivity of about 0.2 (V/m)/(root)Hz was achieved.
Abstract: New type of fiber optic sensor of electrostatic field is considered. Using the interferometric detection technique the sensitivity of about 0.2 (V/m)/(root)Hz was achieved. Theoretical evaluation yields the thermal fluctuation limit of sensitivity of about 2.5 X 10-4 (V/m)/(root)Hz.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
01 Jan 1994
TL;DR: In this article, the nonlinear evolution of boundary layer eigen modes is considered in terms of unsteady three-dimensional triple-deck theory, where nonlinear effects come into play far downstream from the lower branch of the linear stability neutral curve.
Abstract: Nonlinear evolution of boundary layer eigen modes is considered in terms of unsteady three-dimensional triple-deck theory. It is taken that nonlinear effects come into play far downstream from the lower branch of the linear stability neutral curve. Such an assumption leads to clear separation of the critical layer and provides the basis for successive application of the asymptotic expansion technique. As a result, the equations governing the evolution of resonant triads are obtained and the growth rates of unstable subharmonics are calculated.
TL;DR: In this paper, the energy of the forced harmonic oscillator, distribution function and the squeezing coefficients as well as some other values are calculated for the models of δ-pulses, rectangular steps and some others types of time-dependence of the frequency of the oscillator.
Abstract: Squeezing phenomenon is analysed for the non-stationary forced harmonic oscillator which is perturbed parametrically by very short pulses. The energy of the oscillator, distribution function and the squeezing coefficients as well as some other values are calculated for the models of δ-pulses, rectangular steps and some others types of time-dependence of the frequency of the oscillator.
01 Jan 1994
TL;DR: In this article, a review of the literature devoted to the dynamics of an atom in a superintense radiation field is presented, where the atomic field strength was defined in Sect. 9.1.
Abstract: In this chapter we review works devoted to the dynamics of an atom in a superintense radiation field. The atomic field strength was defined in Sect. 9.1. A superintense field, according to this definition, is stronger than an atomic field. However, the different definitions given in Sect. 9.1 are intended only for low-frequency electromagnetic fields. For example, F a = 5.14 x 109 V/cm for ground state hydrogen atom if the radiation frequency is equal to zero. Similarly, for hydrogen atom excited states with principal quantum number n the atomic field strength is F a(n) = F a/n 4 only in the case of a constant electric field. Also, these definitions are valid only for small orbital momenta of the considered states. Increased radiation frequency and higher orbital momenta stabilize an atom. Let us first consider this stabilization qualitatively.
TL;DR: In this article, the authors examined changes in the organization of the ex-Soviet space program, current program status and priorities, and analyzed the impact of these changes on world space activities.
TL;DR: In this article, the detection of phonon damping due to electron -phonon interaction in high-temperature superconductors by Raman spectroscopy is more favorable in dirty metal than in pure because phonon decay into electronic continuum has no threshold there.
Abstract: Detection of phonon damping due to electron - phonon interaction in high-temperature superconductors by Raman spectroscopy is more favorable in dirty metal than in pure because phonon decay into electronic continuum has no threshold there.
29 Aug 1994
TL;DR: In this article, the authors reported the first experimental observation of many-component resonance fluorescence spectra of three-level atomic system in the intense laser field caused by the Rabi splitting of the ground 35 and two exited 3P states of sodium atom on six quasi-energy levels.
Abstract: The study of fluorescence spectra under the action of resonant laser wave plays a fundamental role in the understanding of processes of radiation interaction with matter. It is well known (see, e.g., Ref. I) that in the case of a two-level medium at low density the shape of such spectrum looks as a symmetrical triplet with sidebands separated from a central component by the generalized Rabi frequency. However, in the case of a strong laser field, the two-level approximation of real atomic systems very often is not adequate, since it is necessary to take into account the influence of the nearest levels. In the alkali metal vapors it implies that the Rabi frequency is order of doublet splitting value. In the present paper, as far as we known, we report on the first experimental observation of many-component resonance fluorescence spectra of three-level atomic system in the intense laser field caused by the Rabi splitting of the ground 35 and two exited 3P states of sodium atom on six quasi-energy levels (see Fig. 1). It follows from Fig. 1 that in the fluorescence spectra of the threelevel medium must be observed up to six sidebands at the frequencies w,? = wL + Cl; (0,' are the generalized Rabi frequencies of the three-level system,' wL is the laser frequency) and three degenerated components at The experimental arrangement consisted of a pulse tunable dye laser with pulse duration 20 ns and linewidth 0.01 nm, heat-pipe oven with the sodium vapor in density range + 10l6 and diagnostic systems that allowed us to investigate the fluorescence spectra perpendicularly to laser beam with a spectral resolution of 0.02 nm and temporal one 4
01 Jan 1994
TL;DR: In this article, the authors refer to fields of strength slightly less than or on the order of an atomic field strength F a as "subatomic fields" and show that such fields can produce extremely large perturbations of the atomic spectrum, i.e., extremely large changes in the energies and widths of the atoms.
Abstract: We will refer to fields of strength slightly less than or on the order of an atomic field strength F a as „subatomic fields“. Such fields can produce extremely large perturbations of an atomic spectrum, i.e., extremely large changes in the energies and widths of the atomic states. Extremely large field strengths are generated by decreasing the laser pulse duration which also spreads the atomic levels. The condition of F ~ F a corresponds to adiabaticity parameters γ on the order of unity in the visible frequency range. Thus, under these conditions the intermediate region between the tunneling and multiphoton limits is realized.
TL;DR: In this paper, the spectral distribution of magnetic moment fluctuations can be modulated with the oscillating function depending on frequency with gaps adjacent to even harmonics, which can be connected with the magnetic moment change correlation on different exciting field cycles and should become most apparent in samples with near-to-rectangular hysteresis loops.