scholarly journals Пылевая плазма в тлеющем разряде в магнитном поле до 3000 G

2018 ◽  
Vol 44 (19) ◽  
pp. 66
Author(s):  
Е.С. Дзлиева ◽  
Л.А. Новиков ◽  
С.И. Павлов ◽  
В.Ю. Карасев
Keyword(s):  
Magnetic Field ◽  
Angular Velocity ◽  
Glow Discharge ◽  
Magnetic Fields ◽  
Dusty Plasma ◽  
Drag Force ◽  
Applied Magnetic Field ◽  
Magnetic Trap ◽  
Current Channel ◽  
Angular Velocities

AbstractA glow discharge dusty plasma in a magnetic trap in which the current channel narrows is obtained in moderate magnetic fields up to 3000 G. The results of initial experiments are reported. The formation of stable dusty plasma structures rotating at record-high angular velocities up to 15 rad/s is observed. The dependence of the angular velocity on the strength of the applied magnetic field is measured experimentally. We interpret it quantitatively on the basis of the ion drag force.

scholarly journals Dusty Plasma in Inhomogeneous Magnetic Fields in a Stratified Glow Discharge

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3788
Author(s):  
Elena S. Dzlieva ◽  
Lev G. D’yachkov ◽  
Leontiy A. Novikov ◽  
Sergey I. Pavlov ◽  
Viktor Y. Karasev
Keyword(s):  
Magnetic Field ◽  
Glow Discharge ◽  
Magnetic Fields ◽  
Dusty Plasma ◽  
Inhomogeneous Magnetic Field ◽  
Dust Particles ◽  
Uniform Field ◽  
The Magnetic Field

We study the dynamics of dust particles in a stratified glow discharge in inhomogeneous magnetic fields. Dust structures are formed in standing striations, in which traps for dust particles arise. When a magnetic field is applied, these structures begin to rotate. The observations were carried out in striations near the end of the solenoid, where the region of an inhomogeneous magnetic field begins. With an increase in the magnetic field, the dusty structure can be deformed. The rotation of a dusty structure in an inhomogeneous magnetic field has been studied in detail; it has its own peculiarities in comparison with rotation in a uniform field. We have considered the mechanisms of such rotation and estimated its velocity.

scholarly journals The Magnetic Fields of Pulsars

1974 ◽  
Vol 64 ◽  
pp. 187-187
Author(s):  
D. M. Sedrakian
Keyword(s):  
Magnetic Field ◽  
Angular Velocity ◽  
Magnetic Fields ◽  
Relative Motion ◽  
Kinematic Viscosity ◽  
Charged Particles ◽  
Normal Fluid ◽  
Inertia Effects ◽  
Generation Mechanisms ◽  
Image Position

Two generation mechanisms of magnetic fields in pulsars are considered.If the temperature of a star is more than 108K, the star consists of a normal fluid of neutrons, protons and electrons. Because the angular velocity of pulsars is not constant dω/dt ≠0, inertia effects can occur, and generate magnetic fields through the relative motion of charged particles with different masses. The kinematic viscosity of electrons is 30 times larger than that of protons; hence electrons move with the crust, but the proton-neutron fluid will move relative to the electrons. The magnetic momentum can be calculated by the following formula where Meff = Mp + Mn(Nn/Np), R = radius of the star, σ = conductivity. For typical neutron stars we have dω/dt~ 10-8 s-2, R~106 cm, σ~1029 s-1 and we get a magnetic field of the order of 1010 G.

Magnetically Tailored Arc and Glow Discharge Plasmas for Atomic Spectroscopy

1987 ◽  
Vol 41 (5) ◽  
pp. 833-843 ◽  
Author(s):  
K. Trivedi ◽  
S. Tanguay ◽  
M. Matties ◽  
R. Sacks
Keyword(s):  
Magnetic Field ◽  
Glow Discharge ◽  
Vertical Displacement ◽  
Atomic Spectroscopy ◽  
Radiative Properties ◽  
Current Channel ◽  
Drift Motion ◽  
Magnetic Field Axis ◽  
Discharge Plasmas ◽  
The Magnetic Field

Three magnetic field-plasma configurations are used to study the interaction of external magnetic fields with analytically useful plasma devices. First, a magnetic field oscillating at 60 Hz and normal to the electric field in a 12-A direct current arc plasma is used to obtain an Ē×B̄ drift motion of the arc current channel. This causes a periodic vertical displacement of the channel. Second, a cw magnetic field is used to alter the structure and radiative properties of a demountable glow discharge lamp that uses a center-post cathode. The magnetic field axis is parallel to the cathode axis, and the lamp is operated in a pseudo-magnetron mode. Third, a damped, oscillatory magnetic field produced by discharging a capacitor through a coil is used to alter the radiative characteristics of several commercial hollow cathode lamps. The magnetic field is parallel to the cathode axis, and again the lamps operate in a pseudo-magnetron mode. In all three systems, the presence of the magnetic field drastically alters the radiative properties of the plasmas.

scholarly journals Physics of magnetized dusty plasmas

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Andre Melzer ◽  
H. Krüger ◽  
D. Maier ◽  
S. Schütt
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Dusty Plasma ◽  
Acoustic Waves ◽  
Dusty Plasmas ◽  
Plasma Properties ◽  
Fundamental Parameters ◽  
Wake Field ◽  
Magnetized Dusty Plasma ◽  
Dust Component

AbstractIn this review, we summarize recent advances in the field of dusty plasmas at strong magnetic fields. Special emphasis is put on situations where experimental laboratory observations are available. These generally comprise dusty plasmas with magnetized electrons and ions, but unmagnetized dust. The fundamental parameters characterizing a magnetized (dusty) plasma are given and various effects in dusty plasmas under magnetic fields are presented. As examples, the reaction of the dust component to magnetic-field modified plasma properties, such as filamentation, imposed structures, dust rotation, nanodusty plasmas and the resulting forces on the dust are discussed. Further, the behavior of the dust charge is described and shown to be relatively unaffected by magnetic fields. Wake field formation in magnetized discharges is illustrated: the strength of the wake field is found to be reduced with increased magnetic field. The propagation of dust acoustic waves in magnetized dusty plasmas is experimentally measured and analyzed indicating that the wave dynamics are not heavily influenced by the magnetic field. Only at the highest fields ($$B> 1$$ B > 1  T) the wave activity is found to be reduced. Moreover, it is discussed how dust-cyclotron waves might be used to indicate a magnetized dust component. Finally, implications of a magnetized dusty plasma are illustrated.

Semiconductor Crystal Growth by the Vertical Bridgman Process With Transverse Rotating Magnetic Fields

2006 ◽  
Vol 129 (2) ◽  
pp. 241-243 ◽  
Author(s):  
X. Wang ◽  
N. Ma
Keyword(s):  
Magnetic Field ◽  
Crystal Growth ◽  
Magnetic Fields ◽  
Applied Magnetic Field ◽  
Rotating Magnetic Field ◽  
Semiconductor Crystal ◽  
Rotating Magnetic Fields ◽  
Electrically Conducting ◽  
Vertical Bridgman ◽  
Bridgman Process

During the vertical Bridgman process, a single semiconductor crystal is grown by the solidification of an initially molten semiconductor contained in an ampoule. The motion of the electrically conducting molten semiconductor can be controlled with an externally applied magnetic field. This paper treats the flow of a molten semiconductor and the dopant transport during the vertical Bridgman process with a periodic transverse or rotating magnetic field. The frequency of the externally applied magnetic field is sufficiently low that this field penetrates throughout the molten semiconductor. Dopant distributions in the crystal are presented.

Erklärung stellarer und planetarer Magnetfelder durch einen turbulenzbedingten Dynamomechanismus

1966 ◽  
Vol 21 (8) ◽  
pp. 1285-1296 ◽  
Author(s):  
M. Steenbeck ◽  
F. Krause
Keyword(s):  
Magnetic Field ◽  
Angular Velocity ◽  
Magnetic Fields ◽  
Cross Product ◽  
Skin Depth ◽  
Electrically Conducting ◽  
Magnetic Stars ◽  
The Magnetic Field ◽  
Component Parallel ◽  
Good Agreement

In a foregoing paper 1 the effects of a turbulent motion on magnetic fields were investigated. Especially turbulence was treated under the influence of CORIOLiS-forces and gradients of density and/or turbulence intensity. It was shown that on these conditions the average cross-product of velocity and magnetic field has a non-vanishing component parallel to the average magnetic field. Here we give the consequences of this effect for rotating, electrically conducting spheres.At first a sphere rotating with constant angular velocity is investigated. The quadratic effect provides for dynamo maintainance of the magnetic fields. A field of dipol-type has the weakest condition for maintainance. Applications to the magnetic field of the earth show a good agreement with the conceptions of the physical state of the earth’s core.For a second model differential rotation is included. We have also dynamo maintainance. Since we have to assume that generally the angular velocity is a function decreasing with the distance from the centre of the sphere, the calculations show that we have a preferred self-excited build-up of a quadrupol-type field. This model may be applicable to magnetic stars.Finally we look for dynamo maintainance of alternating fields. We consider the skin-depth to be small compared with the radius of the sphere, then we have plane geometry. The existence of periodical solutions is proved. Applications to the general magnetic field of the sun, which has a period of 22 years, are discussed.

Experimental Investigation of Magnetically-Induced Thermal Conductance Variations in a Ferromagnetic Nanofluid

2011 ◽  
Author(s):  
Alexander M. Gardner ◽  
Indira Seshadri ◽  
Ganpati Ramanath ◽  
Theodorian Borca-Tasciuc
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
Experimental Investigation ◽  
Magnetic Fields ◽  
Thermal Resistance ◽  
Applied Magnetic Field ◽  
Thermal Conductance ◽  
Flow Characteristics ◽  
Test Apparatus ◽  
The Subject

Ferrofluids have been the subject of great interest in engineering because of their unique flow characteristics under magnetic fields (Rosensweig, 1987). However, there are limited experiments which show the potential of ferrofluids to undergo controlled changes in thermal conductivity (Philip et al., 2008) under magnetic fields. The purpose of this experiment is to investigate thermal transport in ferrofluids. A test apparatus was designed and the thermal resistance of a commercially available ferromagnetic fluid within a test cell was measured as a function of the applied magnetic field.

scholarly journals Magnetic field frequency optimisation for MFL imaging using QWHE sensors

2020 ◽  
Vol 62 (7) ◽  
pp. 396-401
Author(s):  
J M Watson ◽  
C W Liang ◽  
J Sexton ◽  
M Missous
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Strength ◽  
Power Consumption ◽  
Applied Magnetic Field ◽  
Magnetic Particles ◽  
Permanent Magnets ◽  
Low Frequency ◽  
Step Size ◽  
Lift Off

Magnetic particle and other magnetic flux leakage (MFL)-based methods for the detection and evaluation of surfacebreaking flaws in ferromagnetic materials typically use high-strength (∼0.5 T RMS) low-frequency (≤50 Hz) magnetic fields. The rationale behind this is the ready availability of strong permanent magnets and mains power for highstrength electromagnets. This high field strength is needed to saturate the sample and compensate for the insensitivity of magnetic particles, silicon Hall sensors, coils and other magnetic transducers. Consequently, the frequency of the applied magnetic field is typically limited to ≤50 Hz and does not consider the frequency response of the material under test (some MFL applications use this low frequency to detect subsurface or flaws on the backwall). In this study, a probe consisting of a quantum well Hall-effect (QWHE) sensor, an illuminating electromagnet and sensor circuitry was controlled using an automated XYZ scanner with an x-y measurement step size (ie magnetic image pixel size) of 100 microns. This probe was used to apply magnetic fields of various frequencies (DC to 1 kHz) and field strengths (5 mT to 100 mT) to ascertain a frequency and field range best suited to detecting 10 mm- and 11 mm-long longitudinal surface-breaking toe cracks in ground mild steel welds. A lift-off distance of <1 mm was controlled using a proximity laser and a z-direction motor module to autonomously control the probe lift-off and conform to sample geometry. This study found that an applied magnetic field with a frequency of 800 Hz and a field strength of 10 mT RMS was optimal under the constraint of power consumption, based on the ratio of MFL responses from the two flaws and the weld. It was found that other frequency field combinations had comparable or higher detection but were discounted as they had substantially higher power consumption.

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