Showing papers in "Journal of Contemporary Physics-armenian Academy of Sciences in 2016"
TL;DR: In this article, two expansions of the solutions of the biconfluent Heun equation in terms of incomplete Beta functions are presented. But the coefficients of expansions obey four-and five-term recurrence relations, respectively.
Abstract: Considering the equations for some functions involving the first or the second derivatives of the biconfluent Heun function, we construct two expansions of the solutions of the biconfluent Heun equation in terms of incomplete Beta functions. The first series applies single Beta functions as expansion functions, while the second one involves a combination of two Beta functions. The coefficients of expansions obey four- and five-term recurrence relations, respectively. It is shown that the proposed technique is potent to produce series solutions in terms of other special functions. Two examples of such expansions in terms of the incomplete Gamma functions are presented.
14 citations
TL;DR: In this paper, the results of computer simulation of the processes of heat propagation inside the multilayer sensor of thermoelectric detector after absorbing the single photons with the energies 1 keV and 100 eV are presented.
Abstract: The results of computer simulation of the processes of heat propagation inside the multilayer sensor of thermoelectric detector after absorbing the single photons with the energies 1 keV and 100 eV are presented. The variants are considered for different geometries of the sensor which consists of the tungsten absorber and of the thermoelectric layer of the cerium hexaboride. The differences of temporal dependence of the signal arising in the thermoelectric layer when the photon is absorbed in the various areas of absorber are studied in details. The energy resolution and the count rate of the sensor are estimated. It is shown that the multilayer sensors have a number of advantages as compared to the single-layered, and their use is promising in the various fields of science and technology.
10 citations
TL;DR: In this article, the authors presented the results of the computer simulation of heat distribution in the W/(La,Ce)B6/W multi-layer sensor of the thermoelectric detector after the absorption of single photons with the energies 1-100 eV.
Abstract: The results are presented of the computer simulation of heat distribution in the W/(La,Ce)B6/W multi-layer sensor of the thermoelectric detector after the absorption of single photons with the energies 1–100 eV. The influence of the choice of computer simulation parameters on the revealing of the peculiarities of heat transmission processes arising in the sensor of detector depending on the photon energy, the sensor geometry, the absorption area of the absorber surface and the depth of photon thermalization is investigated in details. The energy resolution and the count rate of sensor are evaluated. It is shown that the multi-layer sensor with the thermoelectric (La,Ce)B6 is capable to register a single photon in a wide range of the electromagnetic spectrum at 0.5 K; it has an advantages as compared with the sensor based on the CeB6 with the operating temperature 9 K, and has perspectives to be used in the science and technology.
9 citations
TL;DR: In this paper, LiNbO3-Ho3+ crystals for optical cooling based on the anti-Stokes luminescence in the wavelength range 2000-2200 nm were investigated.
Abstract: The possibilities of LiNbO3-Ho3+ crystals for optical cooling based on the anti-Stokes luminescence in the wavelength range 2000-2200 nm are investigated. The efficiency and cooling temperature under the continuous wave (CW) excitation at the wavelengths 2035-2071 nm by ~100 W power are estimated. It is shown that under the CW excitation at 2035 nm wavelength the maximum cooling temperature is equal to 2.5 K, and at 2071 nm wavelength is equal to 10.9 K.
9 citations
TL;DR: In this article, the possibility of X-ray phase contrast imaging using a three-block interferometer consisting of bi-level Fresnel zone plates is considered, which operates in the amplitude division mode and does not impose strong requirements to spatial and temporal coherences of an initial radiation.
Abstract: The possibility of X-ray phase contrast imaging using already suggested three-block interferometer consisting of bi-level Fresnel zone plates is considered. The interferometer operates in the amplitude-division mode and does not impose strong requirements to spatial and temporal coherences of an initial radiation. The use of the Fresnel zone plates as the interferometer blocks allows one to obtain an optically magnified image of an object and to condense the radiation incident on the tested object.
7 citations
TL;DR: In this paper, the Faraday law of electromagnetic induction for an arbitrarily moving charge is generalized and the expression for the force acting on the charge in an alternating magnetic field is obtained.
Abstract: The Faraday law of electromagnetic induction for an arbitrarily moving charge is generalized and the expression for the force acting on the charge in an alternating magnetic field is obtained. It is shown that besides the Lorentz force perpendicular to the velocity of the particle, the Faraday force parallel to the particle velocity and proportional to it is acting on the charge, too. The equations of motion of the charged particle and the magnetic moment are obtained in the time-varying magnetic field. The problems of induction acceleration of charged particles (betatron) and induction heating of medium (plasma, plasma betatron) are considered.
6 citations
TL;DR: In this article, the energy spectrum and the wave functions of the single-electron states in the spherical core/shell/shell nanolayer were considered in the regime of strong quantizations.
Abstract: In a spherical core/shell/shell nanolayer the single-particle states were considered in the regime of strong quantizations. The relation between the geometrical dimensions of the corresponding components of a sample are chosen in such a way that the differences between the characteristics of materials form a quantum well for the charge carriers in the middle layer. The adequate approximate approaches are suggested to determine analytically the energy spectrum and the wave functions of the single-electron states in the spherical nanolayer. A comparison of the results of the analytical and the numerical calculations is performed. The interval values of the ratio between the layer thickness and its radius at which the results of proposed approximations coincide with the satisfactory accuracy with the results of numerical calculations are determined.
5 citations
TL;DR: In this article, the gas response test measurements of all studied nanocomposite structures carried out in air/target gas mixture showed that the most and at one time selective response to butanol vapor exposure in comparison to other mainly toxic and harmful gases such as acetone, toluene, formaldehyde, dimethylformamide, and others is observed for samples obtained by hydrothermal synthesis with 1:4 and 1:200 weight ratios of the nanocomposition components.
Abstract: Gas sensing characteristics of multi-walled carbon nanotubes coated with tin dioxide nanoparticles nanocomposite thick-film structures (MWCNTs/SnO2) prepared using hydrothermal synthesis, sol–gel technique and their combined process were investigated. Gas response test measurements of all studied nanocomposite structures carried out in air/target gas mixture showed that the most and at one time selective response to butanol vapor exposure in comparison to other mainly toxic and harmful gases such as acetone, toluene, formaldehyde, dimethylformamide, and others is observed for samples obtained by hydrothermal synthesis with 1:4 and 1:200 weight ratios of the nanocomposite components, respectively. These sensors are characterized by relatively short response and recovery times about 12 and 100 s, respectively, as well as low operating temperatures in the range of 150–200°C.
5 citations
TL;DR: In this article, the possibility of creating free electron lasers without inversion (FELWI) is shown to have threshold character with respect to the intensity of wave to be amplified, and a description of threshold conditions is given in the single-particle approach.
Abstract: The possibility of creating free electron lasers without inversion (FELWI) is shown to have threshold character with respect to the intensity of wave to be amplified. A description of threshold conditions is given in the single-particle approach. It is shown that as the observation threshold of amplification without inversion is rather high, and the possibility of experimental realization of FELWI may be essentially impeded
5 citations
TL;DR: In this paper, the results of numerical calculations of integral (spatial) coefficients of transmission and reflection are given as functions of incident wave intensity for fixed thickness of the crystal for two-beam diffraction of a narrow incident beam.
Abstract: Diffraction of a spatially inhomogeneous X-ray wave was theoretically studied in a crystal with cubic nonlinear response to the strength of an external electric field. Using numerical calculations in case of two-beam diffraction of a narrow incident beam, the intensity distributions on the output surface of the crystal was investigated depending on the thickness and intensity of the incident beam. The results of numerical calculations of integral (spatial) coefficients of transmission and reflection are given as functions of incident wave intensity for fixed thickness of the crystal.
5 citations
TL;DR: In this paper, the properties of the electron gas in cylindrical nanolayer have been investigated and the dependence of mean energy, mean magnetization and mean magnetic susceptibility on the values of magnetic field is obtained.
Abstract: Diamagnetic properties of the electron gas in cylindrical nanolayer have been investigated. The dependence of mean energy, mean magnetization and mean magnetic susceptibility on the values of magnetic field is obtained. Comparison of these dependencies with the case, when the electron gas is localized in the cylindrical quantum dot, is carried out. In a nanolayer, the character of an effect of size quantization on the magnetic properties of the electron gas has been revealed.
TL;DR: In this paper, the work of the frequency reference of atomic transitions is demonstrated, based on the application of the spectrum of a selective reflectance (SR) from the boundary of atom vapors with the use of nano-cell (NC) with the thickness L ~ λ/2, where λ is the laser wavelength equal to 780 nm.
Abstract: On an example of the D2-line of the Rb atoms the work of the frequency reference of atomic transitions is demonstrated, based on the application of the spectrum of a selective reflectance (SR) from the boundary of atom vapors with the use of nano-cell (NC) with the thickness L ~ λ/2, where λ is the laser wavelength equal to 780 nm. When changing the thickness of the nano-cell near the thickness L ~ λ/2, we observe the inversion of sign of the SR slope profile which is positive when L λ/2. In the case when the incidence angle of the laser beam on the surface of the nano-cell is close to the normal, in real-time it is possible to form the derivative of the SR which represents a resonance peak with ~35 MHz spectral linewidth and located at the atomic transition. The phenomenon of oscillation of the sign of slope while changing the nano-cell thickness from L ~ λ/2 up to L ~ 3/2λ is demonstrated. The practical application of the SR is noted.
TL;DR: In this paper, it was shown that the recorded interference pattern formed at the output surface of the analyzer crystal (the third block of interferometer) is the X-ray interferometric hologram (generally the Fresnel one) of the object under investigation.
Abstract: The X-ray interferometric Fresnel holography was proposed and theoretically investigated. It was shown that under definite conditions the recorded interference pattern formed at the output surface ofthe analyzer crystal (the third block of interferometer) is the X-ray interferometric hologram (generally the Fresnel one) of the object under investigation. Further reconstruction of an image is performed with the help of visible light or a numerical method. As an example the recording of a Fresnel hologram of the simplest case of one-dimensional object, a narrow slit, and the reconstruction of an image by means of visible light were considered. This method may be used in X-ray microscopy and realized using synchrotron sources ofX-ray radiation, as well as X-ray free electron lasers.
TL;DR: In this article, an expression for the thermal linear expansion coefficients and thermal conductivities of amorphous dielectrics above the Debye temperature is given. But this is for the compounds of the chemical composition corresponding to the rare-earth magnesium hexaaluminates taken as an example.
Abstract: Expressions for estimation of the thermal linear expansion coefficients and of the thermal conductivities of amorphous dielectrics above the Debye temperature are obtained. It is shown that for the compounds of the chemical composition corresponding to the rare-earth magnesium hexaaluminates taken as an example these parameters for amorphous compounds are less than for polycrystalline.
TL;DR: The obtained results allow us to determine the proximity of the physical properties of the bone transplantation material Cerabone® with the natural bone matrix.
Abstract: The refractive indices n(ω) and absorption coefficients α(ω) of the jawbone and the human bone substitute Cerabone® were determined in vitro by the terahertz (THz) time-domain spectroscopy (TDS) in a wide frequency range from 0.2 to 2.5 THz. It is shown that the refractive index of the human jawbone changes between the values of 2.075 and 2.157, and of the Cerabone® between 2.4 and 2.65. The absorption coefficient of the human jawbone increases depending on the frequency from 1.7 cm–1 to 178.5 cm–1, showing several resonance absorption lines at the values greater than 1.6 THz. The absorption coefficient of Cerabone® increases from zero to 80 cm–1, and the resonance absorption occurs at 1.7 THz. The obtained results allow us to determine the proximity of the physical properties of the bone transplantation material Cerabone® with the natural bone matrix.
TL;DR: In this paper, the penetration of the microparticle (electron) through the δ-potential barriers which are embedded into the quantum wire of cylindrical shape with the characteristic effect of dimensional quantization in the transverse direction is considered.
Abstract: The penetration of the microparticle (electron) through the δ-potential barriers which are embedded into the quantum wire of cylindrical shape with the characteristic effect of dimensional quantization in the transverse direction is considered. The analytical expressions for the amplitudes of the multichannel scattering, which are valid for the barriers consisting of one and two δ-potentials located at some distance from each other are obtained. It is shown that the multichannel scattering turns into the one-dimensional, if the initial energy of the longitudinal motion of electron is not sufficient to excite the higher channels of scattering. In this case, the obtained formulas for the scattering amplitudes coincide with the well-known expressions for the one-dimensional scattering. The obtained solutions satisfy the conservation law of the number of particles, which is the indirect proof of the validity of derived formulas.
TL;DR: In this article, the authors investigated the possibility of formation of a coherent dark state in the five-level system in the entire volume of the medium in an adiabatic pulse propagation and showed that the dark state formation is independent on the value of the first two-photon detuning from the resonance.
Abstract: The possibility of formation of a coherent dark state in the five-level system in the entire volume of the medium in an adiabatic pulse propagation is investigated. It is shown that the dark state formation is independent on the value of the first two-photon detuning from the resonance, which may be changed during the propagation in the medium. In the case of the M-type system with the equal strengths of oscillators at the extreme transitions it is shown that the self-phase modulation does not influence the coherent effects while in the ladder-type system it may lead to the destruction of the dark state. The estimation of the length of the medium in which the propagation effects are negligible is obtained.
TL;DR: In this paper, a molecular-statistical theory of phase transitions in lyotropic liquid crystals, which describes the phase transitions between the isotropic (micellar), nematic and lamellar phases was developed.
Abstract: A molecular-statistical theory of phase transitions in lyotropic liquid crystals, which describes the phase transitions between the isotropic (micellar), nematic and lamellar phases was developed. The equations describing the dependence of parameters of orientation and translational long-range order on the concentration were obtained. It was shown that depending on the values of the model microscopic constants, the nematic phase–lamellar phase transition can be both of the first and the second order. The influence of intensive and low intense γ-radiation on the phase transitions mentioned herein was considered. It was shown that the irradiation changes the model constants responsible for the phase transitions. On this basis, it can be assumed that the γ-radiation influences the course of the dependence of the long-range order parameters on concentration as well as it changes the values of the critical concentrations of the phase transitions and even the phase transition order.
TL;DR: In this article, two-coordinate sensitive IR photodetectors based on locally irradiated (n)CdTe-InSb heterojunction formed by the pulsed laser deposition of CdTe thin layer were fabricated, and it was shown that they have linear output characteristics.
Abstract: Photosensitivity of locally irradiated (n)CdTe–(p)InSb heterojunction formed by the pulsed laser deposition of CdTe thin layer was investigated. Two-coordinate sensitive IR photodetectors based on such heterojunction were fabricated, and it was shown that they have the linear output characteristics. The measured value of coordinate sensitivity is about 30 nA/μm.
TL;DR: In this paper, it was shown from the mathematical point of view that the problem is equivalent to a spheroidal hydrogen atom in a parabolic potential with the cylindrical symmetry.
Abstract: In a uniformly charged prolate spheroidal Thomson hydrogen atom the electron states have been investigated. It has been shown from the mathematical point of view that the problem is equivalent to a spheroidal hydrogen atom in a parabolic potential with the cylindrical symmetry. In the framework of adiabatic approximation, the energy of ground state has been calculated. Comparison with the case of uncharged spheroidal quantum dot has been made, and the analytical form of wave function of electron has been also obtained.
TL;DR: In this paper, the two-crystal X-ray diffraction from reflecting atomic planes of a single crystal with AT-cut was experimentally considered in the Laue geometry, when both the crystals are simultaneously in the field of bulk acoustic waves.
Abstract: The two-crystal X-ray diffraction from (1111) reflecting atomic planes of quartz single crystal with AT-cut was experimentally considered in the Laue geometry, when both the crystals are simultaneously in the field of bulk acoustic waves. It is shown that as a result of spatial modulation of reflected beam an odd number of parallel X-ray beams is obtained.
TL;DR: In this paper, it was shown that at the dynamical diffraction of spherical X-ray wave on a short period superlattice, a focusing of satellites occurred both at different depths of the super lattice and at different distances from the crystal in vacuum.
Abstract: It was shown that at the dynamical diffraction of spherical X-ray wave on a short period superlattice, a focusing of satellites occurred both at different depths of the superlattice and at different distances from the crystal in vacuum depending on the structural factors of the superlattice. Based on the obtained results a method for investigation of a superlattice by means of dynamical diffraction focusing of a spherical X-ray wave was proposed. The method is based on the measurement of focal distances of different satellites.
TL;DR: In this paper, the Fourier transform method was used to reconstruct the X-ray interferometric Young fringes and the reconstruction of an object image as an object by means of the intensity distribution on the hologram.
Abstract: An X-ray interferometric Fourier holography was proposed and theoretically investigated. X-ray Interferometric Young fringes and the reconstruction of an object image were investigated by the Fourier transform method. It was shown that on the output surface of the analyzer crystal (the third plate of the interferometer) the interference pattern of two slits gives X-ray interferometric Young fringes. An expression for the period of X-ray interferometric Young fringes was obtained. The subsequent reconstruction of the slit image as an object is conducted by means of the Fourier transform method of intensity distribution on the hologram. Three methods for reconstruction of the function of complex transmission of the object are presented: an analytical one–the approximate method, the iteration method and the step-by-step approach. As examples a recording of X-ray interferometric Fourier hologram and the reconstruction of the function of complex amplitude transmission of a beryllium circular cylinder are given.
TL;DR: It was shown that the proposed coding technique significantly simplifies the main program code by reducing its size, as well as making it more readable and easily modifiable.
Abstract: An advantage of implementation of object-oriented programming principles in numerical simulation in hard X-ray optics was considered. The suggested approach was demonstrated on the example of two-beam X-ray interferometer with the refracting prism. It was shown that the proposed coding technique significantly simplifies the main program code by reducing its size, as well as making it more readable and easily modifiable.
TL;DR: In this paper, a set of ordered sequences of the activities of 232Th, 235U and 238U series radionuclides is used to determine the ordering of nuclide activities by solving a system of Bateman-Rubinson differential equations.
Abstract: The method of standard sets is considered without use of a reference sample. In this method a set of ordered sequences of the activities of 232Th, 235U and 238U series radionuclides is used. The ordering of nuclide activities is determined by solving a system of Bateman–Rubinson differential equations. The calculated activities of nuclides are arranged in the form of a table of standards. The table of standards serves as an internal mathematical reference (the reference sample).
TL;DR: In this article, the results of investigations of nuclear reactions on separated isotopes of lead (206Pb, 207Pb and 208Pb) and tin (118Sn) isotope performed using the method of induced activity are given.
Abstract: Nuclear reactions at the interaction of particles with heavy targets were studied using the method of induced activity. This method permits an investigation of the mechanism of residual nuclei formation in a wide range of nuclear masses beginning from light nuclei up to the nuclei with masses near to the target mass. The results of investigations of nuclear reactions on separated isotopes of lead (206Pb, 207Pb, 208Pb) and tin (118Sn) isotope performed using the method of induced activity are given.
TL;DR: In this paper, a step-wise phase mask (SPM) was used to provide phase matching for all the spectral components of a terahertz pulse by providing the effective conversion of laser radiation in the terahethertz region, which can be applied in the time-domain spectroscopy, the imaging of hidden objects and etc.
Abstract: A new scheme for the efficient generation of broadband terahertz radiation via optical rectification of femtosecond laser pulses in the single-domain lithium niobate crystal equipped with the step-wise phase mask (SPM) is investigated. It is shown that using the SPM one can provide the phase matching for all the spectral components of a terahertz pulse by providing the effective conversion of laser radiation in the terahertz region. The angular distribution of spectral components, as well as the temporal shape of terahertz pulses in the wave zone is studied. These results can be applied in the time-domain spectroscopy, the imaging of hidden objects, and etc.
TL;DR: In this article, the results of measurements on the search for the cluster decay of 252Cfnucleus with the emission of the bound state of eight neutrons are presented, and the value of an upper limit of the partial probabilities for this process is obtained, which contradicts to the result ofthe recently published work, in which the possible existence of octaneutron was declared.
Abstract: The results ofmeasurements on the search for the cluster decay of 252Cfnucleus with the emission ofthe bound state of eight neutrons are presented. The value of an upper limit ofthe partial probabilities for this process is obtained, which contradicts to the results ofthe recently published work, in which the possible existence of octaneutron was declared. Based on the results of our measurements, the estimations for the upper limits ofpartial probabilities for the emission of 20C, 24O, 28Ne, 32Mg, 36Si, 40S, 40P, and 40Si clusters are given. The estimation for the upper limit of the partial probability of 250Cf decay with the emission of the bound state of six neutrons is also obtained.
TL;DR: In this paper, the identification of tagging jets in the Higgs boson production process with a following decay of a Higgs particle to τ-leptons (VBF H→τ−τ+) at the endcup region of the upgraded CMS detector at large amount (140) of additionally imposed pp-interactions is given.
Abstract: The procedure of identification of tagging jets in the Higgs boson production process with a following decay of the Higgs boson to τ-leptons (VBF H→τ−τ+) at the endcup region of the upgraded CMS detector at large amount (140) of additionally imposed pp-interactions is given. The efficiency and purity of tagging jets selection at the CMS endcup region are estimated.
TL;DR: In this article, a description of FNAL E866 experimental data on pA → J/ψX processes is given in the model of intermediate leading states, and the agreement attained with experimental data is an argument in favor of the model used and of the validity of its generalization to the case of nucleus-nucleus interactions.
Abstract: A description of FNAL E866 experimental data on pA → J/ψX processes is given in the model of intermediate leading states. The agreement attained with experimental data is an argument in favor of the model used and of the validity of its generalization to the case of nucleus–nucleus interactions.