scholarly journals Physics of Absorption and generation of Electromagnetic Radiation

2021 ◽  
Author(s):  
Sukhmander Singh ◽  
Ashish Tyagi ◽  
Bhavna Vidhani
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Penetration Depth ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Collision Frequency ◽  
Numerical Examples ◽  
Beam Density ◽  
The Real ◽  
Real Frequency

The chapter is divided into two parts. In the first part, the chapter discusses the theory of propagation of electromagnetic waves in different media with the help of Maxwell’s equations of electromagnetic fields. The electromagnetic waves with low frequency are suitable for the communication in sea water and are illustrated with numerical examples. The underwater communication have been used for the oil (gas) field monitoring, underwater vehicles, coastline protection, oceanographic data collection, etc. The mathematical expression of penetration depth of electromagnetic waves is derived. The significance of penetration depth (skin depth) and loss angle are clarified with numerical examples. The interaction of electromagnetic waves with human tissue is also discussed. When an electric field is applied to a dielectric, the material takes a finite amount of time to polarize. The imaginary part of the permittivity is corresponds to the absorption length of radiation inside biological tissue. In the second part of the chapter, it has been shown that a high frequency wave can be generated through plasma under the presence of electron beam. The electron beam affects the oscillations of plasma and triggers the instability called as electron beam instability. In this section, we use magnetohydrodynamics theory to obtain the modified dispersion relation under the presence of electron beam with the help of the Poisson’s equation. The high frequency instability in plasma grow with the magnetic field, wave length, collision frequency and the beam density. The growth rate linearly increases with collision frequency of electrons but it is decreases with the drift velocity of electrons. The real frequency of the instability increases with magnetic field, azimuthal wave number and beam density. The real frequency is almost independent with the collision frequency of the electrons.

Scattering of circularly polarized electromagnetic waves off a straight electron beam propagating along a constant magnetic field

1991 ◽  
Vol 46 (2) ◽  
pp. 201-207
Author(s):  
Alexander Bogdanov
Keyword(s):  
Magnetic Field ◽  
Nonlinear Dynamics ◽  
Electron Beam ◽  
Electromagnetic Waves ◽  
Electron Beams ◽  
The Other ◽  
Free Electron Lasers ◽  
Circularly Polarized ◽  
Beam Density ◽  
The Stability

The stability of straight field-aligned electron beams, immersed in an external magnetic field of finite magnitude, with respect to the excitation in them of circularly polarized (spiral) electromagnetic waves is a problem calling for detailed investigation, particularly in the context of the study and development of free-electron lasers. Traditionally the problem is treated using the theory of electromagnetic waves scattering off electron-beam density oscillations. This is done, however, without considering the inverse influence of the beam on the dispersion properties of the electromagnetic waves. On the other hand, it is well known that the presence of the beam introduces substantial changes in the characteristics of the electromagnetic waves interacting with the beam, and, moreover, this results in the appearance of radically new types of waves that are entirely absent in free space. The paper is dedicated to the study of the nonlinear dynamics of the interaction of such radically changed electromagnetic waves with the beam density oscillations.

Effect of collisions on the magnetization current in a plasma

1993 ◽  
Vol 50 (2) ◽  
pp. 325-330 ◽  
Author(s):  
G. Brodin ◽  
L. Stenflo
Keyword(s):  
Kinetic Theory ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Collision Frequency ◽  
Generation Mechanism ◽  
Collision Term ◽  
Velocity Dependence ◽  
Magnetization Current ◽  
Nonlinear Magnetization

The generation of a quasi-stationary nonlinear magnetization current in a plasma in the presence of high-frequency electromagnetic waves is considered. A kinetic theory is developed that takes the velocity dependence of the collision frequency into account. The results show that even a small collision term can have a significant effect on the generation mechanism.

The oblique reflexion of long wireless waves from the ionosphere at the places where the Earth's magnetic field is regarded as vertical

1952 ◽  
Vol 244 (887) ◽  
pp. 469-503 ◽  
Keyword(s):  
Magnetic Field ◽  
Differential Equations ◽  
Electromagnetic Waves ◽  
Hypergeometric Functions ◽  
Collision Frequency ◽  
Path Difference ◽  
Stratified Medium ◽  
Graphical Form ◽  
Confluent Hypergeometric Functions ◽  
Ionization Density

The calculation of reflexion coefficients for long wireless waves incident obliquely on the ionosphere requires an exact solution of the differential equations governing the propagation of electromagnetic waves in the ionosphere. Equations are developed for the electromagnetic field in a horizontally stratified medium of varying electron density, the presence of a vertical external magnetic field and also the collision frequency of the electrons with neutral molecules being taken into account. Provided certain inequalities hold amongst these ionospheric characteristics, the ionosphere splits up effectively into two regions, in each of which the differential equations of wave propagation approximate to simpler forms. If a model ionosphere is chosen in which the ionization density increases exponentially with height/and the collision frequency is assumed constant over the range of height responsible for reflexion, the equations for the two regions can be solved exactly. The solution for the lower region is expressed in terms of hypergeometric functions, and that for the upper region in terms of generalized confluent hypergeometric functions. Exact expressions in terms of factorial functions can then be deduced for the reflexion coefficients of both regions separately. Moreover, these coefficients can be combined, with due allowance for the path difference between the two regions, to give the overall reflexion coefficients for the effect of the ionosphere as a whole on an incident wave. A suitable definition is given for the apparent height of reflexion in terms of the phase of the reflected wave. The results of the theory are illustrated in graphical form for a particular model ionosphere approximating to the 'tail’ of a Chapman region, and a brief comparison with experimental observations concludes the paper.

scholarly journals Sealing by soldering of microblock packages made of diamagnetic alloys using high-frequency heating

2018 ◽  
pp. 3-8
Author(s):  
V. L. Lanin ◽  
Yu. N. Grishchenko
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Penetration Depth ◽  
High Frequency ◽  
Skin Layer ◽  
Magnetic Core ◽  
Power Lines ◽  
Hf Heating ◽  
Field Penetration Depth ◽  
Field Penetration

The main difficulties of application of high-frequency (HF) heating for sealing by soldering of microblock packages made of aluminum alloys is the low efficiency of heating, long processing time and considerable heating of the internal electronic module while sealing. The purpose of this study was to use effectively the physical phenomena of HF heating in order to optimize the HF heating parameters of sealing by soldering using fusible solders of microwave microblock packages made of diamagnetic alloys. Effects of HF heating (superficial, proximity and concentration of power lines) of the electromagnetic field are applied to sealing using soldering of microwave microblock packages made of diamagnetic alloys. The optimized parameters of HF heating provide energy efficiency and productivity of sealing: frequency of the electromagnetic field and the inductor design. When soldering microelectronic devices containing electronic parts sensitive to the electric field component, the energy of electromagnetic field in the package should be significantly lower than the energy of elements degradation, in which case the skin layer reaches the field penetration depth which is equal to 4 package thickness values. In order to increase the HF heating efficiency, there should be a concentration of the inductor current on the package surface facing the inductor, which is done by using a ferrite magnetic core. Using a ferrite magnetic core inside the inductor concentrates tension of magnetic field due to concentration of power lines of magnetic field in 1,2-1,3 times. The optimal frequency range for HF soldering is 0,4—2,0 MHz when at electromagnetic field penetration depth into the material of the package equal to 4 thickness values of the skin layer, the field strength is 152 times weaker in comparison with the surface.

Field variation of the superconducting penetration depth

1950 ◽  
Vol 203 (1073) ◽  
pp. 210-223 ◽  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Penetration Depth ◽  
Critical Field ◽  
High Frequency ◽  
Cylindrical Specimen ◽  
Sudden Increase ◽  
Field Variation ◽  
Steady Magnetic Field ◽  
Small Change

The high-frequency technique developed previously has been used to investigate the dependence of the penetration depth in superconducting tin on the strength of the applied field. A steady magnetic field was applied transverse to a thin cylindrical specimen forming part of a 3 cm. resonator, any resulting change in penetration depth being revealed as a shift in the resonant frequency. The change was greatest close to the transition temperature (3.72° K), but even here it amounted to no more than 3% at the critical field strength. As the temperature was lowered the effect became smaller at first, reaching a very low value at 3° K, and then increased once more to about 2 % at 1.7° K. The effect of a steady magnetic field on the high-frequency resistance was also studied, though not in great detail. Above 3° K the resistance decreases slightly until at a field strength rather greater than ½ H c a sudden increase announces the formation of the intermediate state. At lower temperatures the effect of the steady field is to increase the resistance slightly. It is suggested that the very small change in penetration depth even at the critical field strength is evidence of the existence of long-range order in the superconducting state over a distance of 10 -4 cm. or more, and the very sharp resistance transition in pure superconductors is adduced as further evidence of this hypothesis.

PROPAGATION OF ELECTROMAGNETIC WAVES ALONG A THIN PLASMA SHEET

1960 ◽  
Vol 38 (12) ◽  
pp. 1586-1594 ◽  
Author(s):  
James R. Wait
Keyword(s):  
Magnetic Field ◽  
Surface Wave ◽  
Plasma Sheet ◽  
Electromagnetic Waves ◽  
Uniform Magnetic Field ◽  
Collision Frequency ◽  
Conducting Plane ◽  
Waveguide Type ◽  
Trapped Surface ◽  
Thin Plasma

It is shown that a thin ionized sheet will support a trapped surface wave. The effect of a constant and uniform magnetic field is to modify the phase velocity and polarization of the surface wave. The essential features are illustrated by numerical results for selected values of the electron density, collision frequency, and gyro frequency. The effect of locating the plasma sheet near and parallel to a conducting plane is also considered. In this situation other modes of a waveguide type are possible in addition to the surface wave.

scholarly journals Effect of heating of frozen colostrum in two-resonator installation

2021 ◽  
Vol 935 (1) ◽  
pp. 012026
Author(s):  
G Novikova ◽  
I Ershova ◽  
M Prosviryakova ◽  
O Mikhailova ◽  
V Storchevoy ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Penetration Depth ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Raw Material ◽  
Dielectric Parameters ◽  
Field Exposure ◽  
Ultra High Frequency ◽  
Significant Difference ◽  
High Frequency Electromagnetic Field

Abstract The study is aimed at the effect substantiation of voluminous heating of the cattle frozen colostrum in the two-resonator installation. The methodology is based on the theory of the electromagnetic field, the laws of thermodynamics and the results of physical modeling. The colostrum dielectric parameters were analyzed in the temperature range from -12 °C to +40 °C. The theoretical studies were carried out for changes finding out in the absorption coefficient of the electromagnetic field and the penetration depth of the electromagnetic waves 12.24 cm long during defrosting/heating of the cow colostrum with the fat content of 6.4%. It is found that the penetration depth of the electromagnetic field into the frozen raw material at negative temperatures range (0.2-1.0 cm) is less than that at the colostrum positive temperatures (1.0-2.17 cm). With such significant difference in the dielectric characteristics of the frozen and thawed colostrum and in their penetration depths of the ultra high frequency electromagnetic field, the rate of their heating is considerably different. The developed continuous-flow ultra high frequency electromagnetic generator contains two voluminous resonators. They provide the colostrum being in different physical states with different doses of the ultra high frequency electromagnetic field exposure.

Electron-cyclotron absorption by inhomogeneous current-carrying plasmas

1994 ◽  
Vol 52 (2) ◽  
pp. 195-214 ◽  
Author(s):  
C. J. H. Cavalcanti ◽  
R. S. Schneider ◽  
L. F. Ziebell
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Electron Cyclotron ◽  
Wave Frequency ◽  
Cyclotron Absorption ◽  
Homogeneous Background ◽  
Electron Cyclotron Waves ◽  
The Magnetic Field

We consider effects of inhomogeneity on the absorption of high-frequency electromagnetic waves, propagating at arbitrary angles relative to the magnetic field, by current-carrying plasmas. An inhomogeneous current is assumed to be immersed in an otherwise homogeneous background, and the absorption of fundamental electron-cyclotron waves is discussed, with emphasis on the dependence of the inhomogeneity effect on wave frequency and angle of propagation.

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