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1
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Gaussian Beam Diffraction and Self-Focusing in Weakly Anisotropic and Dissipative Nonlinear Plasma

100%
Berczynski P., Berczynski S., Kravtsov Y.
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vol. 125
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issue 1
39-45
EN
The paper presents a simple and effective method to calculate polarization and diffraction of the Gaussian beam in nonlinear and weakly dissipative plasma. The presented approach is a combination of quasi-isotropic approximation of geometric optics with complex geometrical optics. Quasi-isotropic approximation describes the evolution of polarization vector reducing the Maxwell equations to coupled ordinary differential equations of the first order for the transverse components of the electromagnetic field. Complex geometrical optics describes the Gaussian beam diffraction and self-focusing and deals with ordinary differential equations for Gaussian beam width, wave front curvature, and amplitude evolution. As a result, the quasi-isotropic approximation + complex geometrical optics combination reduces the problem of diffraction and polarization evolution of an electromagnetic beam to the solution of the ordinary differential equations, which enable to prepare fast and effective numerical algorithms. Using combined complex geometrical optics/quasi-isotropic approximation for weakly anisotropic plasma, we assume that nonlinearity of anisotropy tensor is small and we restrict ourselves to considering only isotropic nonlinearity. The quasi-isotropic approximation effectively describes the evolution of microwave and IR electromagnetic beams in polarimetric and interferometric measurements in thermonuclear reactors and the complex geometrical optics method can be applied for modeling of electron cyclotron absorption and current drive in tokamaks.
2
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Acousto-Electric Interaction in Magnetised Piezoelectric Semiconductor Quantum Plasma

100%
Ghosh S., Muley A.
Acta Physica Polonica A
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2016
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vol. 130
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issue 6
1401-1405
EN
Amplification of an acoustic wave is considered in magnetised piezoelectric n-type semiconductor plasma under quantum hydrodynamic regime. The important ingredients of this study are the inclusion of quantum diffraction effect via the Bohm potential, statistical degeneracy pressure, and externally applied magnetostatic field in the momentum balance equation of the charged carriers. A modified dispersion relation is derived for evolution of acoustic wave by employing the linearization technique. Detailed analysis of quantum modified dispersion relation of acoustic wave is presented. For a typical parameter range, relevant to n-InSb at 77 K, it is found that the non-dimensional quantum parameter H reduces the gain while magnetic field enhances the gain of acoustic wave. The crossover from attenuation to amplification occurs at (ϑ₀/ϑₛ)=1 and this crossover point is found to be unaffected by quantum correction and magnetic field. It is also found that the maximum gain point shifts towards lower drift velocity regime due to the presence of magnetic field while quantum parameter H shifts this point towards higher drift velocity. Numerical results on the acoustic gain per radian and acoustic gain per unit length are also illustrated. Our results could be useful in understanding acoustic wave propagation in magnetised piezoelectric semiconductor in quantum regime.
3
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Simple Microwave Technique for Non-Destructive Testing of Electrical Properties of Magnetized Materials

100%
Laurinavičius L.
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vol. 125
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issue 2
205-207
EN
New technologies allow obtain low-dimensional structures, thin films, monocrystal samples of modern semiconductor materials. Electrical parameters of semiconductors should be tested by non-destructive simple methods to provide the high quality of new electronic devices. The principle of operation of proposed compact microwave meter is based on magnetic vortex oscillation and magnetoplasmic wave excitation technique in semiconductors placed in strong magnetic field. A high frequency field is interacting with charge carriers of semiconductor sample and contactless measurements of density N and mobility μ of free charge carriers of semiconductors can be realized. Microwave technique for non-destructive testing electrical properties of semiconductor materials is described. Simple microwave meter consists of constant magnetic field source, high frequency generator, transmitting-receiving antenna and indicator. In semiconductor specimen placed in constant and alternating magnetic fields a vortex current and magnetoplasmic microwave are excited. The response signals are measured to find a value of density N and mobility μ of free charge carriers in testing materials. Experimental parameters of measured n-InSb, CdHgTe, BiSb specimens are presented.
4
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Non-Equilibrium Plasma Instabilities

100%
Petit J., Geffray J.
Acta Physica Polonica A
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2009
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vol. 115
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issue 6
1170-1172
EN
Low magnetic Reynolds non-thermal plasmas are sensitive to the Velikhov electrothermal instability when the Hall parameter exceeds the local critical value. Then the instability quickly grows and highly reduces the performance of MHD converters. After operating (International MHD Meeting, Warsaw 1968) the first high power density two-temperature - but short duration - MHD Faraday generator, using a first stabilization method, we presented a better one in the beginning of the eighties that was demonstrated through low pressure experiments (French Academy of Sciences, 1981; and 8th International MHD meeting, Moscow 1983). This second method was based on a non-uniform B-field and electrical tensor conductivity. It is time now to rebuild MHD activities all over the world as deserved, corresponding to progress of today's techniques. Different applications of this instability cancellation are presented.
5
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The Effects of Relativistic Warm Plasma Waveguide and High Frequency Electrical Field on Beam-Plasma Interaction

100%
El-Shorbagy K.
Acta Physica Polonica A
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2007
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vol. 112
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issue 1
41-48
EN
The paper is concerned with investigation of the influence of an intense high frequency electric field and relativistic warm plasma waveguide on electrostatic oscillations of nonuniform bounded plasma. The stabilizing effect of a strong high frequency (pump) electrical field on beam-plasma interaction in a cylindrical relativistic warm plasma waveguide is discussed. A new mathematical technique "separation method" was applied to the two-fluid plasma model to separate the equations, which describe the system, into two parts, time and space parts. Plasma electrons are considered to have a relativistic, thermal velocity. It is shown that a high frequency electric field has no essential influence on dispersion characteristics of unstable surface waves excited in a relativistic warm plasma waveguide by a low-density electron beam. The region of instability is only slightly narrowing and the growth rate decreases by a small parameter and this result was reduced comparing to cold, nonrelativistic plasma. Also, it is found that the plasma electrons did not affect the solution of the space part of the problem.
6
Content available remote

Terahertz Detection of Quantum Cascade Laser Emission by Plasma Waves in Field Effect Transistors

100%
Teppe F., Consejo C., Torres J., Chenaud B., Solignac P., Fathololoumi S., Wasilewski Z., Zholudev M., Dyakonova N., Coquillat D., El Fatimy A., Buzatu P., Chaubet C., Knap W.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
930-932
EN
We report on the resonant detection of a 3.1 THz radiation produced by a quantum cascade laser using a 250 nm gate length GaAs/AlGaAs field effect transistor at liquid nitrogen temperature. We show that the physical mechanism of the detection is related to the plasma waves excited in the transistor channel. The detection is enhanced by increasing the drain current and driving the transistor into saturation regime. These results clearly show that plasma wave nanometer-size transistors can be used as detectors in all-solid-state terahertz systems where quantum cascade lasers act as sources.
7
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Microwave Radar for Non-Destructive Express Testing of Electrical Properties of Semiconductor Materials

100%
Novickij J.
Acta Physica Polonica A
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2011
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vol. 119
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issue 4
537-541
EN
Microwave radar for non-destructive express testing of electrical properties of semiconductor materials which consists of pulsed magnet, transmitting and receiving antennas, high frequency generator, pulsed modulator and digital oscilloscope is described. In semiconductor specimen placed in pulsed magnetic field a magnetoplasmic wave is excited and propagated through the specimen. Delay time and attenuation of transmitted and reference signals are measured to find a value of concentration and mobility of free charge carriers in semiconductors. Experimental data of testing of InSb, n-InSb specimens are presented and acceptable for express testing correspondence of results was achieved.
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