Effects of repeated interactions and correlational disintegration on kinetic and transport properties of a non-neutral plasma in strong fields

1990 ◽  
Vol 44 (1) ◽  
pp. 167-190 ◽  
Author(s):  
Alf H. Øien
Keyword(s):  
Magnetic Field ◽  
Particle Transport ◽  
Axial Magnetic Field ◽  
Debye Length ◽  
Electron Plasma ◽  
Larmor Radius ◽  
Equilibration Time ◽  
Cylindrically Symmetric ◽  
Electric Potentials ◽  
Good Agreement

Collisions in a cylindrically symmetric non-neutral (electron) plasma, where the Larmor radius is much smaller than the Debye length, and the consequent particle transport, are studied. The plasma is confined radially by a strong axial magnetic field and axially by electric potentials. Hence two particles may interact repeatedly. Eventually they drift too far away from each other poloidally to interact any more, owing to shear in the E × B drift. The consequent build-up of correlation is limited by correlational disintegration due to collisions with ‘third particles’ between the repeated interactions. A kinetic equation including these effects is derived, and the cross-field particle transport along the density gradient is found. An associated equilibration time is shown to scale as B and to be in good agreement with the experimentally obtained values of Briscoli, Malmberg and Fine.

Anomalous temperature relaxation and particle transport in a strongly non-unifrom, fully in ionized Plasma in a stromg mangnetic field

1995 ◽  
Vol 53 (1) ◽  
pp. 31-48 ◽  
Author(s):  
Alf H. Øien
Keyword(s):  
Magnetic Field ◽  
Particle Transport ◽  
Transport Theory ◽  
Debye Length ◽  
Larmor Radius ◽  
Collision Integrals ◽  
Ion Interactions ◽  
Electrons And Ions ◽  
Temperature Relaxation ◽  
The Magnetic Field

In classical kinetic and transport theory for a fully ionized plasma in a magnetic field, collision integrals from a uniform theory without fields are used. When the magnetic field is so strong that electrons may gyrate during electron—electron and electron—ion interactions, the form of the collision integrals will be modified. Another modification will stem from strong non-uniformities transverse to the magnetic field B. Using collision terms that explicitly incorporate these effects, we derive in particular the temperature relaxation between electrons and ions and the particle transport transverse to the magnetic field. In both cases collisions between gyrating electrons, which move along the magnetic field, and non-gyrating ions, which move in arbitrary directions at a distance transverse to B from the electrons larger than the electron Larmor radius but smaller than the Debye length, give rise to enhancement factors in the corresponding classical expressions of order In (mion/mel).

scholarly journals The K-shell radiation of a double gas puff z-pinch with an axial magnetic field

2003 ◽  
Vol 21 (2) ◽  
pp. 255-264 ◽  
Author(s):  
S.A. CHAIKOVSKY ◽  
A.Yu. LABETSKY ◽  
V.I. ORESHKIN ◽  
A.V. SHISHLOV ◽  
R.B. BAKSHT ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Radiation Source ◽  
Axial Magnetic Field ◽  
Radiation Power ◽  
Plasma Radiation ◽  
Radiation Hydrodynamics ◽  
One Dimensional ◽  
Z Pinch ◽  
Good Agreement

A double shell z-pinch with an axial magnetic field is considered as a K-shell plasma radiation source. One-dimensional radiation-hydrodynamics calculations performed suggest that this scheme holds promise for the production of the K-shell radiation of krypton (hν ≈ 12–17 keV). As a first step in verifying the advantages of this scheme, experiments have been performed to optimize a neon double-shell gas puff with an axial magnetic yield for the K-shell yield and power. The experiments show that the application of an axial magnetic field makes it possible to increase the K-shell radiation power and reduce the shot-to-shot spread in the K-shell yield. Comparisons between the experiments and modeling are made and show good agreement.

A mechanism for Taylor relaxation in Z-pinches. Part 1. Dynamo mechanism

1986 ◽  
Vol 35 (2) ◽  
pp. 295-310 ◽  
Author(s):  
S. K. H. Auluck
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Axial Magnetic Field ◽  
Positive Definite ◽  
Low Energy ◽  
Toroidal Field ◽  
Mhd Equations ◽  
Larmor Radius ◽  
Electron Mass ◽  
Dynamo Mechanism

The dynamo mechanism in an RFP is explained on the basis of new terms in the MHD equations which are proportional to the electron mass and are traditionally neglected. A new azimuthal dynamo current is obtained which is shown to be positive definite. Sustained, spontaneous self-reversal of the toroidal field naturally follows from this. The (F, Θ) curve calculated from this theory under certain assumptions agrees well with experimental data. The theory predicts the presence of large-Larmor-radius particles in the RFP. It also predicts a spontaneous axial magnetic field in linear Z-pinches. Preliminary experiments on low-energy Z-pinches corroborate this prediction.

Dense plasma in Z-pinches and the plasma focus

1981 ◽  
Vol 300 (1456) ◽  
pp. 649-663 ◽  
Keyword(s):  
Magnetic Field ◽  
Plasma Focus ◽  
Axial Magnetic Field ◽  
Ohmic Heating ◽  
Scaling Law ◽  
Three Dimensional ◽  
Power Input ◽  
Larmor Radius ◽  
Mass Motion ◽  
Enhanced Stability

Many of the earliest experiments in controlled thermonuclear fusion research were Z -pinches. However these pinches were found to be highly unstable to the m = 0, the m — 1 (kink), and the Rayleigh-Taylor instability. The addition of an axial magnetic field and the removal of end losses by proceeding to a toroidal geometry has led to the class of discharges known as tokamaks and the reversed field pinch. But, at fusion temperatures and with practical values of applied magnetic field this restricts the plasma density to 10 20 to 10 21 m- 3 , thereby requiring a containment time of several seconds and a plasma radius of about 1 m. Meanwhile studies of the plasma focus, which after its three-dimensional compression closely resembles a Z -pinch, have shown that a plasma of density 10 25 m- 3 and temperature 1 keV can be achieved in a narrow filament of radius 1 mm. It has enhanced stability properties which might be attributable to the effects of finite ion Larmor radius. Its neutron yield in deuterium can be as high as 10 12 per discharge, with a favourable empirical scaling law, but the thermonuclear origin of the neutrons is doubtful because of the evidence of centre-of-mass motion and the formation of electron and ion beams. The development of high voltage, high current pulse technology has permitted the reconsideration of the Z -pinch to attain dense fusion plasmas which might be stabilized by scaling the ion Larmor radius to be comparable with the pinch radius. Experiments at Imperial College show that the plasma remains stationary for about twenty Alfven radial transit times, limited only by the period of the current waveform. Theory indicates that a dense compact Z -pinch can satisfy Lawson conditions with a power input dependent on the enhanced stability time, or, if stable, with ohmic heating balancing axial heat losses. Preliminary results on a laser-initiated Z -pinch are also presented.

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 Can Resistive Kink Instabilities Drive Simple Loop Flares?

1989 ◽  
Vol 104 (2) ◽  
pp. 305-308
Author(s):  
M. Velli ◽  
G. Emaudi ◽  
A.W. Hood
Keyword(s):  
Magnetic Field ◽  
Boundary Conditions ◽  
Growth Rates ◽  
Axial Magnetic Field ◽  
Small Region ◽  
Coronal Loops ◽  
Simple Loop ◽  
Cylindrically Symmetric ◽  
Line Tying ◽  
Kink Instability

SummaryA detailed analysis of the kink instability in finite length (inertially line-tied), cylindrically symmetric coronal loops is presented. The correct line-tying boundary conditions within the framework of ideal and resistive magnctohydrodynamics are discussed, and the growth rates of unstable modes and corresponding eigenfunctions are calculated. Resistive kink modes are found to be unstable in configurations where the axial magnetic field undergoes an inversion, resistive effects being confined to a small region around the loop vertex.

Electron plasma oscillations at arbitrary Debye lengths

1991 ◽  
Vol 45 (3) ◽  
pp. 407-414 ◽  
Author(s):  
B. Lehnert
Keyword(s):  
Debye Length ◽  
Normal Modes ◽  
Density Perturbation ◽  
Electron Plasma ◽  
Difficult Problem ◽  
Magnetized Plasma ◽  
Larmor Radius ◽  
Plasma Oscillations ◽  
Phase Mixing ◽  
Fluid Behaviour

A solution is presented for electron plasma oscillations in a thermalized plasma, at arbitrary ratios of the Debye length AλD and the perturbation wavelength λ. The limit λD≪λ corresponds to the conventional fluid-like theory of small particle excursions, whereas λD≫λ corresponds to the free-streaming limit of strong kinetic phase mixing due to large particle excursions. A strong large-Debye-distance (LDD) effect already appears when λD ≳ λ. The initial amplitude of the fluid-like contribution to the macroscopic density perturbation then becomes small compared with the contribution from the free-streaming part. As a consequence, only a small fraction of the density perturbation remains after a limited number of kinetic damping times of the free-streaming part. The present analysis can be considered as a first exercise in an attempt to tackle the far more difficult problem of large-Larmor-radius (LLR) effects in a magnetized plasma. The analysis further shows that a representation in terms of normal modes of the form exp (— iωt) leads to amplitude factors of these modes that are related to each other and that depend on the combined free-streaming and fluid behaviour of the plasma. Consequently, these modes are coupled and cannot be treated as independent of each other.

THE VLASOV–POISSON SYSTEM WITH STRONG MAGNETIC FIELD IN QUASINEUTRAL REGIME

2003 ◽  
Vol 13 (05) ◽  
pp. 661-714 ◽  
Author(s):  
F. GOLSE ◽  
L. SAINT-RAYMOND
Keyword(s):  
Magnetic Field ◽  
Space Variable ◽  
Debye Length ◽  
Time Variable ◽  
Larmor Radius ◽  
Incompressible Euler Equation ◽  
Variable Control ◽  
Self Consistent ◽  
Constant External Magnetic Field ◽  
Incompressible Euler

Consider the motion of a gas of electrons with a background of ions, subject to the self-consistent electric field and to a constant external magnetic field. As the Debye length and the Larmor radius vanish at the same rate, the asymptotic current density is governed by the 2D1/2 incompressible Euler equation. Establishing limit requires to overcome various difficulties: compactness with respect to the space variable, control of large velocities, oscillations in the time variable. Yet, for particular initial data, the simultaneous gyrokinetic and quasineutral approximation is completely justified.

Spontaneous generation of magnetic field in an imploding plasma

1984 ◽  
Vol 32 (3) ◽  
pp. 349-357 ◽  
Author(s):  
S. K. H. Auluck
Keyword(s):  
Magnetic Field ◽  
Axial Magnetic Field ◽  
Equations Of Motion ◽  
Field Configuration ◽  
Spontaneous Generation ◽  
Centripetal Acceleration ◽  
Cylindrically Symmetric ◽  
Order Of Magnitude ◽  
Reversed Field ◽  
Metallic Liner

Spontaneous generation of an axial magnetic field is predicted when the usually neglected centripetal acceleration term is properly taken into account in the two-fluid equations of motion for a cylindrically symmetric imploding plasma. An order-of-magnitude calculation is presented to illustrate spontaneous generation of a reversed-field configuration in a plasma imploded by a metallic liner.

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