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Showing papers in "Technical Physics Letters in 2003"


Journal ArticleDOI
TL;DR: In this article, a new composite medium that possesses simultaneously negative permittivity and permeability in the microwave wavelength range is proposed, which is composed of evanescent waveguide structures responsible for the negative permitivity, with embedded cylindrical elements of a one-dimensional chiral medium accounting for negative permeability.
Abstract: A new composite medium that possesses simultaneously negative permittivity and permeability in the microwave wavelength range is proposed. The medium is composed of evanescent waveguide structures responsible for the negative permittivity, with embedded cylindrical elements of a one-dimensional chiral medium accounting for the negative permeability. The evanescent waveguide structures exhibit blooming and antiresonances in the reflection coefficient.

64 citations


Journal ArticleDOI
TL;DR: In this paper, a criterion that the polarizability tensor must obey if the scatterers possess no dissipative losses was derived for bianisotropic scattering inclusions, which can be applied to analytical modeling of periodic structures composed of such inclusions.
Abstract: In the dipole and local field approximations, electromagnetic scatterers are modeled in terms of the polarizability tensor. The matrix elements of this tensor, which are determined by the scatterer geometry, are complex even in the absence of losses in the material. There is a criterion that the polarizability tensor must obey if the scatterers possess no dissipative losses. This condition, derived here for bianisotropic scatterers, can be applied to analytical modeling of periodic structures composed of such scattering inclusions.

49 citations


Journal ArticleDOI
TL;DR: In this paper, the electron beam formation in a diode filled with a molecular gas at atmospheric pressure was studied and it was suggested that the main fraction of runaway electrons at low initial values of the parameter E/p (∼0.1 kV/(cm Torr)) is formed in the space between cathode plasma and anode.
Abstract: We have studied the electron beam formation in a diode filled with a molecular gas at atmospheric pressure. A beam current amplitude of up to ∼20 A at an electron energy of ∼70 keV was obtained in an air-filled diode. It is suggested that the main fraction of runaway electrons at low initial values of the parameter E/p (∼0.1 kV/(cm Torr)) is formed in the space between cathode plasma and anode. As the plasma spreads from cathode to anode, the electric field strength between the plasma front and anode increases and the E/p value reaches a critical level.

43 citations


Journal ArticleDOI
TL;DR: In this article, the optical properties of thin aluminum films with thickness from 1.7 to 15 nm were studied at a wavelength of 8 mm with allowance for a substrate material, and the experimental data were interpreted taking into account the dependence of electric conductivity on film thickness.
Abstract: Optical characteristics (R, T, A) of thin aluminum films with thicknesses from 1.7 to 15 nm were studied at a wavelength of 8 mm with allowance for a substrate material. The absorption exhibits a maximum for a film thickness of 2.5 nm. The experimental data are interpreted taking into account the dependence of electric conductivity on film thickness.

36 citations


Journal ArticleDOI
TL;DR: In this paper, the conditions for the formation of a pulsed beam of runaway electrons in a diode filled with air at atmospheric pressure were studied, whereby the current and voltage pulses in the system were measured with a subnanosecond time resolution.
Abstract: We have studied the conditions for the formation of a pulsed beam of runaway electrons in a diode filled with air at atmospheric pressure, whereby the current and voltage pulses in the system were measured with a subnanosecond time resolution. It is experimentally demonstrated for the first time that the electron beam appears on the leading front of the voltage pulse at a relatively small voltage on the discharge gap. At atmospheric pressure, a full width at half maximum of the current pulse does not exceed 0.3 ns.

27 citations


Journal ArticleDOI
TL;DR: In this article, the phase transformation of amorphous silicon dioxide (SiO2) into crystobalite (type B samples) has been studied and shown to be stable up to 1650°C.
Abstract: Thermal processing of a rice husk sol in air at T≥750°C leads to the phase transformation of amorphous silicon dioxide (SiO2) into crystobalite (type B samples). Thermal treatment of the same sol at T≈ 1400 °C in a closed graphite crucible leads to the formation of a mixture comprising hexagonal SiC phases and graphite (type A samples). Unannealed type A samples showed high refractory properties, being stable up to 1650°C. Using kaolin binder in silicon carbide articles leads to a decrease in the material refractoriness.

25 citations


Journal ArticleDOI
TL;DR: In this article, the authors studied the possibility of controlling the radiation spectrum of a high-power relativistic backward wave tube (BWT) by varying the period of its delay system.
Abstract: We have studied the possibility of controlling the radiation spectrum of a high-power relativistic backward wave tube (BWT) by varying the period of its delay system. For a BWT comprising several sections with different corrugation periods, two-and three-mode generation regimes with commensurate amplitudes of spectral components have been found, the separation of which can be controlled by changing the corrugation period. It is shown that, for a sufficiently large detuning, such a configuration of the interaction space makes possible the generation of noiselike chaotic signals with separated or overlapping spectra. In the latter case, the width of the radiation spectrum is almost twice that of a regular BWT of the same length.

21 citations


Journal ArticleDOI
TL;DR: The surface and subsurface layers of cast iron articles upon electrolyte-plasma treatment (EPT) were studied for the first time by a combination of methods, including Rutherford backscattering, elastic recoil detection analysis, X-ray diffraction, optical metallography, and microhardness measurements as mentioned in this paper.
Abstract: The surface and subsurface layers of cast iron articles upon electrolyte-plasma treatment (EPT) were studied for the first time by a combination of methods, including Rutherford backscattering, elastic recoil detection analysis, X-ray diffraction, optical metallography, and microhardness measurements. It was found that tungsten and copper ions are incorporated into the surface layers of the metal. Total thickness of an EPT-hardened layer is about 3 mm, the maximum hardness (up to 7000 MPa) being observed at a depth from 1 to 2.5 mm. The X-ray diffraction analysis (i) shows that the EPT-hardened layer comprises a mixture of α and γ phases, (ii) indicates the formation of a fine-grained martensite structure with high dislocation density (above 1012 cm−2) and an oxide (FeO) phase, and (iii) reveals mass transfer involving the doping elements (W and Cu).

19 citations


Journal ArticleDOI
TL;DR: In this article, the formation of a beam of runaway electrons in a diode filled with helium at a pressure from 0.1 to 760 Torr was studied under conditions of a pulsed ≈4 ns) high ≈200 kV) voltage applied to the discharge gap.
Abstract: The formation of a beam of runaway electrons in a diode filled with helium at a pressure from 0.1 to 760 Torr was studied under conditions of a pulsed ≈4 ns) high ≈200 kV) voltage applied to the discharge gap. Both theoretical results and experimental data indicate that the electron beam is generated both at a large strength of the electric field, when the fraction of runaway electrons is large, and in a field of low strength, where intensive electron multiplication takes place. In the latter case, a high current can be obtained despite a small fraction of runaway electrons relative to their total number. The electron beams obtained in the helium-filled diode had a current amplitude of up to 140 A (corresponding to a current density above 10 A/cm2) at an electron energy of ∼150 keV.

19 citations


Journal ArticleDOI
TL;DR: In this article, preliminary data on the synthesis and physical properties of polycrystalline Bi1.8Pb0.3 Sr2Ca2Cu3Ox high-temperature superconductors of low density with a foam-like microstructure are reported.
Abstract: Preliminary data on the synthesis and physical properties of polycrystalline Bi1.8Pb0.3 Sr2Ca2Cu3Ox high-temperature superconductors of low density with a foam-like microstructure are reported.

18 citations


Journal ArticleDOI
TL;DR: A prototype of the IR radiation modulator operating at T =303 K, using the giant magnetotransmission effect in a La 0.82Na 0.18MnO3+δ lanthanum manganite film, has been constructed and the optical characteristics of the setup have been measured.
Abstract: A prototype of the IR radiation modulator operating at T=303 K, using the giant magnetotransmission effect in a La0.82Na0.18MnO3+δ lanthanum manganite film, has been constructed and the optical characteristics of the setup have been measured. In a wavelength range from 1.4 to 11 μm, the IR modulation depth varies from 3.5 to 6.5%. The possibilities of increasing the modulation depth are considered.

Journal ArticleDOI
TL;DR: In this paper, the propagation of naturally polarized light through a Fabry-Perot resonator with a layer of cholesteric liquid crystal is considered, and it is shown that strongly non-reciprocal multilayer systems can be used as optical diodes or optical insulators (transmitting signals via an optical communication channel in one direction and blocking signals propagating in the opposite direction).
Abstract: The propagation of naturally polarized light through a Fabry-Perot resonator with a layer of cholesteric liquid crystal is considered. In the presence of absorption, this system exhibits nonreciprocity even for naturally polarized light, which implies the existence of a new type of nonreciprocal reflection. An analysis of the peculiarities of this nonreciprocity shows that strongly nonreciprocal multilayer systems can be used as optical diodes or optical insulators (transmitting signals via an optical communication channel in one direction and blocking signals propagating in the opposite direction) or as systems for the accumulation of light energy.

Journal ArticleDOI
TL;DR: In this paper, a simple bistable stochastic system with an overdamped Kramers oscillator featuring white noise and a periodic rectangular signal with a constant component was studied theoretically and using an analog model.
Abstract: The phenomenon of stochastic resonance in a simple bistable stochastic system, representing an overdamped Kramers oscillator featuring white noise and a periodic rectangular signal with a constant component, has been studied theoretically and using an analog model. An increase in the constant component, determining a static asymmetry of the potential, leads to a decrease in the signal to noise ratio as compared to the symmetric case.

Journal ArticleDOI
TL;DR: The results of simulations using a particle-in-cell technique showed that the phenomenon of electron runaway in a gas is determined by the condition that the interelectrode distance must be comparable with the Townsend electron multiplication length as discussed by the authors.
Abstract: The results of simulations using a particle-in-cell technique show that the phenomenon of electron runaway in a gas is determined by the condition that the interelectrode distance must be comparable with the Townsend electron multiplication length, rather than by local criteria commonly accepted at present. For a given gas, a critical voltage between the electrodes, for which the fraction of runaway electrons is relatively large, is a universal function of the product of the electrode spacing and the gas pressure. The same function determines a condition of the self-sustained discharge initiation in which the electron multiplication plays a significant role. This function has, besides the well-known Paschen branch, an additional upper branch describing breakage of the self-sustained discharge operation as a result of a sufficiently rapid application of a high voltage between the electrodes.

Journal ArticleDOI
TL;DR: In this article, the results of numerical modeling and experimental investigation of a high-power, resonance relativistic backward wave tube were presented by using the working TM01 mode reflections from the ends of the electrodynamic system, optimum conditions for the electron beam interaction with both the (−1)st harmonic of the backward electromagnetic wave and the main harmonic of concurrent wave are achieved.
Abstract: The results of numerical modeling and experimental investigation of a high-power, resonance relativistic backward wave tube are presented. By using the working TM01 mode reflections from the ends of the electrodynamic system, optimum conditions for the electron beam interaction with both the (−1)st harmonic of the backward electromagnetic wave and the main harmonic of the concurrent wave are achieved. A single mode generation with 5 GW output power and a 30% efficiency was obtained in experiments at a frequency of 3.6 GHz. The working frequency can be controlled within 15% (at the half maximum power level) by changing the slow-wave structure period at the constant electron beam parameters.

Journal ArticleDOI
TL;DR: In this paper, experimental data on the low-frequency noise in vanadium dioxide-based sandwich and planar structures possessing negative differential resistance was presented, and it was established that the noise spectrum obeys the 1/fα law and the values of coefficient α for the sandwich structure were experimentally determined for the first time.
Abstract: We present experimental data on the low-frequency noise in vanadium dioxide based sandwich and planar structures possessing negative differential resistance. It is established that the noise spectrum obeys the 1/f α law and the values of coefficient α for the sandwich structure are experimentally determined for the first time. The regions of switching in the current-voltage characteristics of structures of both types exhibit a noise possessing the character of deterministic chaos.

Journal ArticleDOI
TL;DR: In this article, it was shown that the main diffusion mechanism consists in correlated jumps of atoms over the vacancies near misfit dislocation cores in a two-dimensional Ni-Al system.
Abstract: Mutual diffusion at the interface in a two-dimensional Ni-Al system has been studied by the method of molecular dynamics. It is established that the main diffusion mechanism consists in correlated jumps of atoms over the vacancies near misfit dislocation cores.

Journal ArticleDOI
TL;DR: The formation of thin organic films of copper phthalocyanine (CuPc) deposited onto the surface of gold-coated quartz crystal resonator was studied in situ under ultrahigh vacuum conditions by means of total electron-beam-induced current spectroscopy in combination with deposit thickness determination by piezocrystal microbalance technique as discussed by the authors.
Abstract: The formation of thin organic films of copper phthalocyanine (CuPc) deposited onto the surface of gold-coated quartz crystal resonator was studied in situ under ultrahigh vacuum conditions by means of total electron-beam-induced current spectroscopy in combination with deposit thickness determination by piezocrystal microbalance technique. Variations in the fine structure of the total current spectra of CuPc layers of var-ious thicknesses in the 0–8 nm interval have been analyzed and the electron mean free path in thin CuPc films was determined as a function of the electron energy. For electron energies of 5.0, 7.2, 14.4, and 18.0 eV above the Fermi level, the mean free path is 6.4, 3.9, 2.6, and 2.3 nm.

Journal ArticleDOI
TL;DR: In this article, the electric conductivity and dielectric properties of composites comprising iron nanoparticles dispersed in a low-density polyethylene matrix were studied. And the regions of applicability, in which the percolation model provides adequate description of the electrical conductivity of the nanocomposites, were determined.
Abstract: We have studied the electric conductivity and dielectric properties of composites comprising iron nanoparticles dispersed in a low-density polyethylene matrix. The specific conductivity and dielectric constant as functions of the differential mass fraction of iron nanoparticles in such composites occurring in the semiconductor state are described by power relations with the average exponents (critical indices) t=s=1.5±0.3. The regions of applicability, in which the percolation model provides adequate description of the electric conductivity and dielectric properties of the nanocomposites, are determined.

Journal ArticleDOI
TL;DR: A simple analytical model of flow in the first barrel of a plane overexpanded jet is proposed in this article, which is used to solve the problem of determining the Mach disk height in a jet.
Abstract: A simple analytical model of flow in the first barrel of a plane overexpanded jet is proposed. The adequacy of the model is confirmed by comparison with the results of numerical calculations. The proposed model is used to solve the problem of determining the Mach disk height in a jet.

Journal ArticleDOI
TL;DR: In this article, an external axial magnetic field is applied to a vacuum arc, and the radial expansion of plasma from cathode spots transforms into a plasma flow along the magnetic field, provided that the electron-ion collision frequency is smaller than the Larmor frequency.
Abstract: When an external axial magnetic field is applied to a vacuum arc, the radial expansion of plasma from cathode spots transforms into a plasma flow along the magnetic field, provided that the electron-ion collision frequency is smaller than the Larmor frequency. As the magnetic field strength increases, the diameter of the resulting cylindrical channel decreases. This leads to an increase in the electron temperature and the ion charge due to enhanced Joule heating of the plasma. Unlike the intrinsic azimuthal magnetic field, the external axial field only restricts expansion of the plasma, rather than compressing the plasma jet.

Journal ArticleDOI
TL;DR: In this article, the interaction of a nanoparticle occurring in a carrying condensed medium with fluctuations of the medium momentum caused by the particle motion was studied, and the space-time velocity correlation functions of the nanoparticle and surrounding molecules were determined by the molecular dynamics method.
Abstract: The interaction of a nanoparticle occurring in a carrying condensed medium with fluctuations of the medium momentum caused by the particle motion have been studied. The space-time velocity correlation functions of the nanoparticle and surrounding molecules were determined by the molecular dynamics method. These functions exhibit one or two maxima, depending on the system parameters. The first maximum is related to an acoustic wave propagating in the medium, and the second, to multiple collisions between the nanoparticle and nearest neighbor molecules. It is established that collective effects significantly influence both the velocity autocorrelation function and the diffusion coefficient of the nanoparticle.

Journal ArticleDOI
TL;DR: In this article, photoelectric converters based on InAsSbP and GaInAsSBP solid solutions were obtained by liquid phase epitaxy. The new devices are promising elements for thermophotovoltaic generators operating at a reduced emitter temperature (∼1000°C).
Abstract: Photoelectric converters based on InAsSbP and GaInAsSbP solid solutions were obtained by liquid phase epitaxy. The new devices are promising elements for thermophotovoltaic generators operating at a reduced emitter temperature (∼1000°C).

Journal ArticleDOI
TL;DR: In this paper, the physicochemical processes developed in pentaerythritol tetranitrate (PETN) under the action of a pulsed electron beam in a broad range of the beam power densities were studied.
Abstract: We have studied for the first time the physicochemical processes developed in pentaerythritol tetranitrate (PETN) under the action of a pulsed electron beam in a broad range of the beam power densities. Data on the pulsed cathodoluminescence spectrum and kinetics, explosive optical emission kinetics, and thresholds of the mechanical fracture and explosive decomposition of PETN are presented.

Journal ArticleDOI
TL;DR: In this article, the phase diagram of hexagonal oxide ferrimagnets is transformed to a nanocrystalline state (ultradisperse powder), followed by sintering, leading to significant changes in phase diagram, the temperature of synthesis, and the magnetic properties.
Abstract: Mechanical activation and fine comminution of hexagonal oxide ferrimagnets by milling to a nanocrystalline state (ultradisperse powder), followed by sintering, leads to significant changes in the phase diagram, the temperature of synthesis, and the magnetic properties as compared to those of the materials obtained by traditional ceramic technology. The final material structure is formed through “chemical assembly”—sequential consolidation of nanodimensional particles (structure-forming blocks)—rather than through the formation of low-temperature phases and their decomposition with increasing temperature.

Journal ArticleDOI
TL;DR: In this paper, the effect of the ion beam current density on the formation of metal nanoparticles in a subsurface layer of SiO2 substrates implanted with 30-keV Ag+ ions to a dose of 5×10 16 cm−2 was studied by optical spectroscopy and atomic force microscopy techniques.
Abstract: The effect of the ion beam current density, varied within 4–15 μA/cm2, on the formation of metal nanoparticles in a subsurface layer of SiO2 substrates implanted with 30-keV Ag+ ions to a dose of 5×10 16 cm−2 was studied by optical spectroscopy and atomic force microscopy techniques. An increase in the ion beam current density leads to the formation of nanoparticles of a greater size as a result of the glass substrate heating and due to an increase in the diffusion mobility of implanted silver atoms. These results suggest the possibility of controlling the dimensions of implanted nanoparticles in dielectrics by means of variation of the ion beam current density during the process.

Journal ArticleDOI
TL;DR: In this article, the authors estimate the requirements and consumptions for creating DW clouds capable of quenching large-scale fires, which are used for estimating the requirements of DW clouds.
Abstract: The electric explosion of a wire in a thin-walled cylindrical glass ampule filled with water results in the formation of a disperse water (DW) cloud having a ring shape, which expands rapidly in the radial direction and slowly in the axial direction. Interaction of the DW with a flame produces fire quenching in the interaction zone. Experimental results are used for estimating the requirements and consumptions for creating DW clouds capable of quenching large-scale fires.

Journal ArticleDOI
TL;DR: In this paper, the emission of atomic and cluster ions during the sputtering of a tantalum target by gold cluster ions was experimentally studied for primary ion energies ranging from 6 to 21 keV.
Abstract: The emission of atomic and cluster ions during the sputtering of a tantalum target by gold cluster ions was experimentally studied for primary ion energies ranging from 6 to 21 keV. An increase in the number of atoms in the bombarding cluster ions of gold leads to a considerable increase in the yield of atomic ions of tantalum possessing quasithermal energies. The results provide experimental evidence for the appearance of thermal spikes in the target bombarded with cluster ions, with the corresponding contribution to the emission of atomic ions.

Journal ArticleDOI
TL;DR: In this article, the transient chaos regime in a two-dimensional system with discrete time (Eno map) is considered and it is demonstrated that a time series corresponding to this regime differs from a chaotic series constructed for close values of the control parameters by the presence of "nonregular" regions, the number of which increases with the critical parameter.
Abstract: The transient chaos regime in a two-dimensional system with discrete time (Eno map) is considered. It is demonstrated that a time series corresponding to this regime differs from a chaotic series constructed for close values of the control parameters by the presence of “nonregular” regions, the number of which increases with the critical parameter. A possible mechanism of this effect is discussed.

Journal ArticleDOI
TL;DR: In this paper, the conditions of excitation and the waveguide characteristics were determined in an analytical form for the TM0 mode of a planar waveguide with metal substrate, which has a surface character, in contrast to other (bulk) modes excited in the system.
Abstract: The conditions of excitation and the waveguide characteristics are determined in an analytical form for the TM0 mode of a planar waveguide with metal substrate. This mode has a surface character, in contrast to other (bulk) modes excited in the system. The propagation and damping constants and the energy flux density distributions are compared for the TM0 and TE0 modes.