scholarly journals Continuation and stability of rotating waves in the magnetized spherical Couette system: secondary transitions and multistability

2018 ◽  
Vol 474 (2220) ◽  
pp. 20180281 ◽  
Author(s):  
Ferran Garcia ◽  
Frank Stefani
Keyword(s):  
Magnetic Field ◽  
Axial Magnetic Field ◽  
Return Flow ◽  
Rotating Waves ◽  
Periodic Flows ◽  
Moderate Reynolds Number ◽  
Nonlinear Flows ◽  
Spherical Couette ◽  
The Magnetic Field ◽  
Secondary Transitions

Rotating waves (RW) bifurcating from the axisymmetric basic magnetized spherical Couette (MSC) flow are computed by means of Newton–Krylov continuation techniques for periodic orbits. In addition, their stability is analysed in the framework of Floquet theory. The inner sphere rotates while the outer is kept at rest and the fluid is subjected to an axial magnetic field. For a moderate Reynolds number Re  = 10 3 (measuring inner rotation), the effect of increasing the magnetic field strength (measured by the Hartmann number Ha ) is addressed in the range Ha ∈(0, 80) corresponding to the working conditions of the HEDGEHOG experiment at Helmholtz-Zentrum Dresden-Rossendorf. The study reveals several regions of multistability of waves with azimuthal wavenumber m  = 2, 3, 4, and several transitions to quasi-periodic flows, i.e modulated rotating waves. These nonlinear flows can be classified as the three different instabilities of the radial jet, the return flow and the shear layer, as found in the previous studies. These two flows are continuously linked, and part of the same branch, as the magnetic forcing is increased. Midway between the two instabilities, at a certain critical Ha , the non-axisymmetric component of the flow is maximum.

Nonlinear evolution of a wave packet propagating along a hot magnetoplasma column

1987 ◽  
Vol 37 (1) ◽  
pp. 107-115
Author(s):  
B. Ghosh ◽  
K. P. Das
Keyword(s):  
Magnetic Field ◽  
Multiple Scales ◽  
Nonlinear Evolution ◽  
Axial Magnetic Field ◽  
Modulational Instability ◽  
Wave Train ◽  
Dielectric Medium ◽  
Ion Effects ◽  
The Magnetic Field ◽  
Uniform Plasma

The method of multiple scales is used to derive a nonlinear Schrödinger equation, which describes the nonlinear evolution of electron plasma ‘slow waves’ propagating along a hot cylindrical plasma column, surrounded by a dielectric medium and immersed in an essentially infinite axial magnetic field. The temperature is included as well as mobile ion effects for ail possible modes of propagation along the magnetic field. From this equation the condition for modulational instability for a uniform plasma wave train is determined.

scholarly journals DC Glow Discharge in Axial Magnetic Field at Low Pressures

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Shen Gao ◽  
Shixiu Chen ◽  
Zengchao Ji ◽  
Wei Tian ◽  
Jun Chen
Keyword(s):  
Magnetic Field ◽  
Glow Discharge ◽  
Differential Equations ◽  
Axial Magnetic Field ◽  
Glow Discharge Plasma ◽  
Dc Glow Discharge ◽  
Fluid Approximation ◽  
Low Pressures ◽  
Physical Quantities ◽  
The Magnetic Field

On the basis of fluid approximation, an improved version of the model for the description of dc glow discharge plasma in the axial magnetic field was successfully developed. The model has yielded a set of analytic formulas for the physical quantities concerned from the electron and ion fluids equations and Poisson equation. The calculated results satisfy the practical boundary conditions. Results obtained from the model reveal that although the differential equations under the condition of axial magnetic field are consistent with the differential equations without considering the magnetic field, the solution of the equations is not completely consistent. The results show that the stronger the magnetic field, the greater the plasma density.

Schwingung eines Plasmazylinders in einem axialen Magnetfeld II

1960 ◽  
Vol 15 (3) ◽  
pp. 220-226 ◽  
Author(s):  
Klaus Körper
Keyword(s):  
Magnetic Field ◽  
Refractive Index ◽  
External Magnetic Field ◽  
Field Strength ◽  
Axial Magnetic Field ◽  
Surface Current ◽  
The Other ◽  
Plasma Cylinder ◽  
Resonance Frequencies ◽  
The Magnetic Field

Radial oscillations are excited in a homogeneous infinite plasma cylinder in a homogeneous axial magnetic field by a surface current which is homogeneous in the axial and azimuthal directions. The modes of oscillations corresponding to the axial and azimuthal components of current are not coupled, and so they may be analysed separately. The magnetic field in the plasma and vacuum is obtained, and the indices of refraction for both types of oscillations are discussed thoroughly. When the currents are parallel to the external magnetic field, the oscillations are characterized by the refractive index of Eccles. On the other hand, when the current is perpendicular to the magnetic field two resonance frequencies exist, which depend on the density of the plasma and the magnetic field strength. — In the latter case the radial characteristic oscillations of the plasma cylinder in an external magnetic field are considered.

Buoyant Convection During the Growth of Compound Semiconductors by the Liquid-Encapsulated Czochralski Process With an Axial Magnetic Field and With a Non-Axisymmetric Temperature

1996 ◽  
Vol 118 (1) ◽  
pp. 155-159 ◽  
Author(s):  
Nancy Ma ◽  
J. S. Walker
Keyword(s):  
Magnetic Field ◽  
Axial Magnetic Field ◽  
Compound Semiconductors ◽  
Vertical Axis ◽  
Crucible Wall ◽  
Buoyant Convection ◽  
Axisymmetric Part ◽  
Czochralski Process ◽  
Axisymmetric Temperature ◽  
The Magnetic Field

This paper treats the buoyant convection of a molten semiconductor in a cylindrical crucible with a vertical axis, with a uniform vertical magnetic field, and with a non-axisymmetric temperature. Most previous treatments of melt motions with vertical magnetic fields have assumed that the temperature and buoyant convection were axisymmetric. In reality, the temperature and resultant buoyant convection often deviate significantly from axisymmetry. For a given non-axisymmetric temperature, the electromagnetic suppression of the axisymmetric part of the buoyant convection is stronger than that of the non-axisymmetric part, so that the deviation from an axisymmetric melt motion increases as the magnetic field strength is increased. The non-axisymmetric part of the buoyant convection includes relatively strong azimuthal velocities adjacent to the electrically insulating vertical crucible wall, because this wall blocks the radial electric currents needed to suppress azimuthal velocities.

scholarly journals Ion energy increase in laser-generated plasma expanding through axial magnetic field trap

2007 ◽  
Vol 25 (3) ◽  
pp. 453-464 ◽  
Author(s):  
L. Torrisi ◽  
D. Margarone ◽  
S. Gammino ◽  
L. Andò
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Electric Fields ◽  
Axial Magnetic Field ◽  
Ion Beam ◽  
High Vacuum ◽  
Target Surface ◽  
Axial Direction ◽  
Ion Interactions ◽  
The Magnetic Field

Laser-generated plasma is obtained in high vacuum (10−7 mbar) by irradiation of metallic targets (Al, Cu, Ta) with laser beam with intensities of the order of 1010 W/cm2. An Nd:Yag laser operating at 1064 nm wavelength, 9 ns pulse width, and 500 mJ maximum pulse energy is used. Time of flight measurements of ion emission along the direction normal to the target surface were performed with an ion collector. Measurements with and without a 0.1 Tesla magnetic field, directed along the normal to the target surface, have been taken for different target-detector distances and for increasing laser pulse intensity. Results have demonstrated that the magnetic field configuration creates an electron trap in front of the target surface along the axial direction. Electric fields inside the trap induce ion acceleration; the presence of electron bundles not only focuses the ion beam but also increases its energy, mean charge state and current. The explanation of this phenomenon can be found in the electric field modification inside the non-equilibrium plasma because of an electron bunching that increases the number of electron-ion interactions. The magnetic field, in fact, modifies the electric field due to the charge separation between the clouds of fast electrons, many of which remain trapped in the magnetic hole, and slow ions, ejected from the ablated target; moreover it increases the number of electron-ion interactions producing higher charge states.

Investigation of DC Vacuum Arc Interruption Ability with Combined Axial and Radial Magnetic Field

2012 ◽  
Vol 516-517 ◽  
pp. 1791-1797 ◽  
Author(s):  
Mohmmad Al Dweikat ◽  
Yu Long Huang ◽  
Xiao Lin Shen ◽  
Wei Dong Liu
Keyword(s):  
Magnetic Field ◽  
Axial Magnetic Field ◽  
Vacuum Arc ◽  
Axial Component ◽  
Circuit Breakers ◽  
Radial Magnetic Field ◽  
Vacuum Interrupter ◽  
Magnetic Field Simulation ◽  
The Magnetic Field ◽  
Field Influence

DC Vacuum Circuit Breakers based arc control has been a major topic in the last few decades. Understanding vacuum arc (VA) gives the ability to improve vacuum circuit breakers capacity. In this paper, the interaction of a DC vacuum arc with a combined Axial-Radial magnetic field was investigated. The proposed system contains an external coil to produce axial magnetic field (AMF) across the vacuum chamber. The vacuum interrupter (VI) contacts were assumed to be untreated radial magnetic field (RMF) contacts. For this purpose, Finite Element Method (FEM) based Multiphysics simulation of the immerging magnetic field influence on the VA is presented. The simulation shown the ability of the presented system to deflect high DC vacuum arc, also reveals that the vacuum arc interruption capability increases with the rise of the axial component of the magnetic field. Simulation results shown that this method can be applied to improve the interruption capability of the VI.

Effect of Axial Magnetic Field Strengths on Radial Velocity Field in Liquid Bridge under Microgravity

2012 ◽  
Vol 256-259 ◽  
pp. 1670-1673
Author(s):  
Ru Quan Liang ◽  
Shuo Yang ◽  
Jun Hong Ji ◽  
Ji Cheng He
Keyword(s):  
Magnetic Field ◽  
Liquid Bridge ◽  
Axial Magnetic Field ◽  
Phase Interface ◽  
Mass Conservation ◽  
Inhibitory Effect ◽  
Two Phase ◽  
Conservation Level ◽  
The Magnetic Field ◽  
Field Strengths

This article studies on the effect of magnetic field strengths on the flow field in a liquid bridge under zero gravity. The mass conservation level set method is used to track the two-phase interface. The results show that inhibitory effect of additional axial magnetic field on thermocapillary convection within liquid bridge is obvious, and this kind of inhibitory effect increasing as the magnetic field strength is strengthened.

scholarly journals Ion charge state and energy enhancement by axial magnetic field applied during laser produced plasma expansion

2016 ◽  
Vol 34 (4) ◽  
pp. 606-614 ◽  
Author(s):  
S.A. Abbasi ◽  
A.H. Dogar ◽  
B. Ilyas ◽  
S. Ullah ◽  
M. Rafique ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Charge State ◽  
Impact Ionization ◽  
Axial Magnetic Field ◽  
Debye Length ◽  
Target Surface ◽  
Laser Wavelength ◽  
Electrostatic Model ◽  
Ion Energy ◽  
The Magnetic Field

AbstractThe effects of axial magnetic field on the properties of the ions ejected from Nd:YAG laser (wavelength = 1064 nm, pulse duration = 6 ns) produced expanding Cu plasma were investigated. A plane Cu target, without and with 0.23 T axial magnetic field at its surface, was irradiated in the fluence range of 2–24 J/cm2. The ions emitted along the target surface normal were analyzed with the help of ion collector and time-of-flight electrostatic ion energy analyzer. The integrated ion yield, highest ion charge state, average ion energy, and energy of individual ion charge states were found to increase by application of the magnetic field. The initial parameters of the non-equilibrium plasma such as average ion charge, equivalent potential, electron temperature, electron density, Debye length, and transient electric field were estimated from the experimental results obtained without and with application of the magnetic field. The increase of ion yield and ion charge state by application of magnetic field are most probably due to the trapping of electrons in front of the target surface, which boosts up the electron impact ionization process. The ion energy increment due to the magnetic field is discussed in the frame work of electrostatic model for ion acceleration in laser plasma.

scholarly journals Zur Begrenzung der radialen Ausdehnung des Lichtbogenstromes durch ein axiales Magnetfeld

1970 ◽  
Vol 25 (11) ◽  
pp. 1583-1600
Author(s):  
O. Klüber
Keyword(s):  
Magnetic Field ◽  
Hall Current ◽  
Axial Magnetic Field ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Plasma Radius ◽  
Arc Current ◽  
Field Lines ◽  
The Magnetic Field ◽  
Generally True

Abstract In an arc without external magnetic field the current carrying region is identical with the conducting plasma column. This is no longer generally true if the arc is in an axial magnetic field and if the electrode radius is much smaller than the plasma radius. Radial current components then produce a rotational motion of the plasma and an azimuthal Hall current, and hence electromotive forces which try to suppress the current perpendicular to the magnetic field. In a plasma with finite viscosity the rotation is determined by the Navier-Stokes equation, which is solved here for a homogeneous plasma simultaneously with generalized Ohm's law. The results show that the plasma rotation is always an essential, and often the dominant, mechanism for guiding the arc current parallel to the magnetic field lines.

NUMERICAL INVESTIGATION OF SILICON MELT FLOW IN A SHALLOW ANNULAR POOL UNDER AN AXIAL MAGNETIC FIELD

2007 ◽  
Vol 21 (18n19) ◽  
pp. 3486-3488
Author(s):  
YOU-RONG LI ◽  
DONG-MING MO ◽  
LAN PENG ◽  
SHUANG-YING WU
Keyword(s):  
Magnetic Field ◽  
Steady Flow ◽  
Axial Magnetic Field ◽  
Three Dimensional ◽  
Melt Flow ◽  
Radial Temperature ◽  
Annular Pool ◽  
Silicon Melt ◽  
Surface Patterns ◽  
The Magnetic Field

In order to understand the effect of the magnetic field on surface patterns on semi-conducting silicon melt in industrial Czochralski furnaces, we conducted a series of unsteady three-dimensional numerical simulations of silicon melt flow in a shallow annular pool under the axial magnetic field for the magnetic field strength from 0 to 0.1T. The pool is heated from the outer cylindrical wall and cooled at the inner wall. Bottom and top surfaces are adiabatic. When the magnetic field is weak, the simulation can predict various three-dimensional oscillatory flows depending on the radial temperature difference. With the much larger magnetic field, three-dimensional flow becomes axisymmetric steady flow. Details of flow and temperature disturbances are discussed and the critical magnetic field strengths for the onset of axisymmetric steady flow are determined.

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