On The “Nonresonance” Parametric Cyclotron Radiation

We study the effect of amplification of coherent bichromatic radiation due to its cyclotron parametric interaction with a modulated ensemble of classical electron oscillators. The mechanism of energy exchange between the radiation and the electrons in the absence of partial synchronism of the waves and particles is analyzed. The features of the energy exchange in the course of interaction of the waves with relativistic and nonrelativistic particles are pointed out.     

Double-resonance Semiconductor Superlattice Parametric Oscillator for Generation of Subterahertz Radiation

We report on a subterahertz superlattice parametric oscillator that operated simultaneously at two different harmonic frequencies of a microwave pump field. A pump field (frequency near 100 GHz) was coupled to a GaAs/AlAs superlattice in a resonator for the third and the fifth harmonic. The pump field produced a third harmonic field and this together with the pump field created a fifth harmonic field. A theoretical analysis indicates that the nonlinearity, which is based on the dynamics of miniband electrons, should allow for the upconversion of pump radiation of higher frequency into the terahertz frequency range.      

Polarization Properties of Quantum Cyclotron Radiation

We present a simplified formulae system describing the polarization properties of the quantum cyclotron radiation by a nonrelativistic thermal electron in a very strong magnetic field. In this system, each of the derived quantities, including the Einstein coefficients, the absorption cross sections, and scattering cross sections, as well as the absorption coefficients by plasma, is divided into the perpendicularly and parallelly polarized components. The results, especially the absorption and scattering cross sections of resonant frequency photons, are potentially important in x-ray and γ-ray astronomy, particularly in the study of gamma-ray bursts and pulsars.     

Difference-Frequency Generation of THz Radiation via Parametric Three-Wave Interaction in CdTe and ZnTe Crystals

Difference-frequency generation of terahertz (THz) radiation in a collinear single-crystal scheme with distributed feedback implemented by means of parametric interaction of counterpropagating optical waves in a periodically inhomogeneous medium exhibiting quadratic nonlinearity is investigated. Using ZnTe and CdTe crystals optically pumped at λ = 0.77 and 1.06 μm, respectively, as an example, the possibility of obtaining parametric generation of THz radiation with an optical-to-THz conversion efficiency exceeding 10^–3 (with an extremely narrow line of oscillation of less than 4 GHz for ZnTe and less than 9 GHz for CdTe at 1 THz) is demonstrated in the undepleted-pump-intensity approximation. The obtained results can be used for construction of narrow-band lasers in the THz frequency range with an output power (in the quasicw regime of oscillation) of about 10⁵ W/cm².     

Radiation Spectrum of an Electron Cyclotron Maser

We consider generation of electromagnetic radiation at the electron cyclotron harmonics by energetic-electron beams having the mean momentum parallel, transverse, or oblique to the external magnetic field. This process is most efficient if the characteristic transverse momentum is sufficiently large. The radiation spectrum of the beam moving exactly along the magnetic field is closest to the equidistant one. The angle between the direction of the maximum emission and the magnetic field varies from 70^° for the field-aligned beam to 90^° for the beam whose characteristic momentum is transverse to the magnetic field. In fairly strong magnetic fields, i.e., for _Be >_pe, where _Be and _pe are the electron cyclotron and plasma frequencies, respectively, the radiation is maximum at low cyclotron harmonics and the second harmonic dominates. In the weaker fields (_Be < _pe), higher harmonics, up to fifth or sixth, are generated. Both wave modes are generated, but generation of the ordinary waves is far less efficient than that of the extraordinary waves under the same conditions.     

The Exact Solution of the Eigenvalue Problem for the Parametric Down Conversion Process in the Kerr Medium

The eigenproblem for a class of Hamiltonians of the parametric down conversion process in the Kerr medium is solved. Some physical characteristics of the system are calculated.     

Parametric Instability of Surface Waves on the Second Harmonic of Electron Cyclotron Frequency in a Plasma Layer

The parametric instability of surface waves on the second harmonic of electron cyclotron frequency (SWCF) in a plasma filled dielectric wave guide is examined in a kinetic approximation. The studied surface waves are extraordinary polarized modes and propagate across the external steady magnetic field. The amplitude of the electrical pump wave is assumed to be small. Simple expressions for increments of the parametric instability of the SWCF are calculated. The otained results can be used in controlled fusion researches in order to avoid undesirable regimes of plasma periphery heating in that fusion devices which use the resonance electron cyclotron heating method.     

利用虚光子康普顿散射对同步辐射和回旋辐射的研究

从虚光子的康普顿散射出发,提出了一个同步辐射理论,其波长的计算结果与实验数据很吻合,该理论同时还解释了同步辐射的方向性和宽广的连续光谱等问题,并且当粒子的能量不大时,由该理论可以推出回旋辐射理论     

Modeling Chemically Reactive Flow of Sutterby Nanofluid by a Rotating Disk in Presence of Heat Generation/Absorption

In this article we investigate the flow of Sutterby liquid due to rotating stretchable disk. Mass and heat transport are analyzed through Brownian diffusion and thermophoresis. Further the effects of magnetic field, chemical reaction and heat source are also accounted. We employ transformation procedure to obtain a system of nonlinear ODE's. This system is numerically solved by Built-in-Shooting method. Impacts of different involved parameter on velocity, temperature and concentration are described. Velocity, concentration and temperature gradients are numerically computed. Obtained results show that velocity is reduced through material parameter. Temperature and concentration are enhanced with thermophoresis parameter.     

Cherenkov Radiation in Moving Medium

Cherenkov radiation in uniformly moving homogeneous isotropic medium without dispersion is studied. Formula for the spectrum of Cherenkov radiation of fermion was derived for the case when the speed of the medium is less than the speed of light in this medium at rest. The properties of Cherenkov spectrum are investigated.     

An Experimental Investigation of Second Harmonic Generation in a Cyclotron and Upper Hybrid Resonant Plasma

An experiment is described in which an electromagnetic wave (extraordinary mode) is propagated across a magnetized plasma and second harmonic generation is detected. The generation of the plasma and the second harmonic wave is associated with resonant conditions of electron cyclotron resonance and upper hybrid resonance. By adjusting the intensity of axial magnetic field, the second harmonic generation can be made solely due to the electron cyclotron resonance, the upper hybrid resonance or both. The experiment is qualitatively in agreement with previous similar experiments and can be explained in terms of the spatial variations of the magnetic field intensity and the electron number density. A technique for diagnosing peak number density is developed from the observed second harmonic power characteristics.     

On the Effect of Anomalous Photoabsorption in Parametric X Radiation

The parametric X radiation of relativistic electrons passing through a monocrystal is considered. It is demonstrated that, contrary to widespread opinion, conditions for the effect of anomalous photoabsorption to show up can be realized in the Laue scattering geometry. It is expected that the predicted effect will increase the spectral-angular density of the radiation several times.     

Reconstruction of the Radiation Source Spatial Distribution in a Proportional Scattering Medium

Technical Physics - A new method of image reconstruction for single-photon emission computer tomography (SPECT) in a proportional scattering medium has been suggested. Detector counts have been...