摘要:

The small‐amplitude motion of a relativistic beam passing through plasma is studied using transport theory. For the equilibrium state, a relativistic Maxwellian velocity distribution is obtained. The linearized Boltzmann equation is used to relate beam and plasma density and current perturbations to perturbations in the electromagnetic field. Approximate criteria are obtained to justify the neglect of static fields. Finally, these general results are specialized to those of a uniform beam.

ISSN:0031-9171    

DOI:10.1063/1.1706120

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The stability of a uniform relativistic beam of particles injected into a plasma is studied using the previously developed linear transport theory. Velocity distribution in the beam and electron‐ion collisions in the plasma are considered. For wave propagation in the beam direction, an exact treatment is given, while for oblique angles between plasma waves and the beam two kinds of perturbation theory are developed. We find that the two electromagnetic modes of beam‐plasma oscillation are always stable, but that growing electrostatic oscillations are possible for long enough wavelengths. For short wavelengths or high temperatures this mode is also stable. Boundary effects and the effects of static fields are not considered.

ISSN:0031-9171    

DOI:10.1063/1.1706121

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The anisotropic diffusion of ions and electrons in a nonmultiplying partially ionized plasma lying in a strong uniform magnetic field has been analyzed to zero and first order in the parameter &OHgr;−1, where &OHgr;2is the ratio of the reduction of transverse electron mobility to the reduction of transverse ion mobility due to the magnetic field. This obviates the need for an earlier erroneous assumption. Potential distribution and electron and ion current flows have been formulated for two‐dimensional flow, using a lowest‐harmonic charged‐particle distribution in a rectangular space and various wall‐current conditions. The encroachment of sheaths inward from the walls has not been considered on the basis that, in principle, the charged‐particle concentration could always be assumed to be large enough to keep this complication small.

ISSN:0031-9171    

DOI:10.1063/1.1706122

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

A plasma stream was directed from a field‐free region along the axis of symmetry into a magnetic field of biconical cusped geometry. No evidence was found to support the hypothesis that a directed plasma stream can not penetrate a magnetic field whose value exceedsBc2= 12&pgr;&rgr;v2, where &rgr; is the plasma density andvits directed velocity. As the plasma penetrated the magnetic field, the plasma and field were found to intermix. Large quantities of the plasma which entered the containment region through one point cusp were found to leave promptly through the second point cusp and through the line cusp. Bombardment of the vacuum chamber walls in the vicinity of the line cusp generated sufficient secondary ions to mask any small scale plasma trapping. However, there was no evidence of gross trapping of the injected plasma.

ISSN:0031-9171    

DOI:10.1063/1.1706123

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

Plane steady shock waves and solitary waves in a hydrogen plasma without external magnetic fields are studied using a simple kinetic theory model to describe the plasma. This model uses a Mott‐Smith distribution for the protons and a local Maxwellian distribution for the electrons. Charge separations occur inside the shock front because of the proton‐electron mass difference. The proton and electron densities, and the electric field, have an oscillatory fine structure with characteristic length ∼10M&lgr;D, whereMis the Mach number and &lgr;Dthe Debye length, going through the shock. In these oscillations, the densities overshoot their final Rankine‐Hugoniot condition values. The distance in which the oscillations decay to 1/e, which we take as the shock width, is ∼4&lgr;, where &lgr; is the mean free path in the unshocked gas, in the range of Mach numbers considered. There are no continuous solutions for this model above Mach 2.19. The peak electric fields inside the shock are large; in a plasma of &lgr;/&lgr;D= 2 × 104, the electric field reaches 2.2 × 106v/cm in a Mach 2.1 shock. The large‐amplitude solitary waves, which are the basic ingredient of the fine structure of the shock, are studied separately, and a heuristic picture is presented of the growth of these solitary waves, which is due to the coupling between the bulk flow of the plasma and the internal electric fields generated by charge separation. The rate of decay of these solitary waves is estimated.

ISSN:0031-9171    

DOI:10.1063/1.1706124

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The stability of two Maxwellian components of a plasma, which have different drift velocities, is investigated by means of a graphical solution of the dispersion relation. The graphical technique has the advantage of exhibiting the content of the dispersion relation in a transparent manner. By this method we determine the region of instability as a function of the perturbation wavelength &lgr; and the relative velocity of the components, and show how this region depends on the ratio of the Debye lengths and plasma frequencies. In the case of an electron‐proton plasma we obtain the maximum growth rate as a function of &lgr; and the critical drift velocity as a function of the temperature ratios. The structure of the unstable region is also indicated by a few lines of constant growth rate.

ISSN:0031-9171    

DOI:10.1063/1.1706125

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The correlation function for the electric field in a fully ionized plasma is derived, and its application to the problem of finding the force on a charge moving slowly through a plasma is described. The correlation function is evaluated for a plasma with and without a magnetic field, and this function is then converted to the spectrum of the mean‐square fluctuation in the random electric field. The application of the generalized fluctuation‐dissipation theorem gives the mean force on a slowly moving test charge. The relation of this to other treatments is briefly discussed.

ISSN:0031-9171    

DOI:10.1063/1.1706126

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

At certain times during Ohmic heating in hydrogen and deuterium discharges in the B‐3 stellarator, it was observed that over a wide range of experimental conditions the plasma current decreased abruptly (current inhibition) following a period of increasing current and decreasing charged particle density. It is suggested that this may be a manifestation of an electrostatic instability.

ISSN:0031-9171    

DOI:10.1063/1.1706127

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The dyadic Green's function for hydromagnetic waves in a uniform, fully ionized, perfectly conducting, pressureless fluid is obtained. The electromagnetic field consists of two modes, one that propagates isotropically and one that propagates along the field lines. The radiation rate from some simple model current distributions is derived from the Green's functions. If the source contains a current along the constant static field, then the radiation along the field lines through the source is very intense. This last result also holds in the nonuniform static field of an infinitely long straight wire.

ISSN:0031-9171    

DOI:10.1063/1.1706128

出版商:AIP    

年代:1960

数据来源: AIP

摘要:

The microwave cavity method for the measurement of various parameters of a cold plasma in the presence of a static magnetic field is examined. Emphasis is placed on the determination of the limits of validity of the perturbation theory for various mode configurations of a cylindrical cavity coaxial with a plasma column and coaxial with the static magnetic field. The classes of modes examined are those which in the absence of the magnetic field reduce to the TM0m0, TM1mn, TE1mn, and TE0mnmodes. For the TM0m0and TE0mnmodes, exact expressions for the cavity frequency shifts are obtained. These expressions are then expanded in appropriate power series to obtain the limits of validity of the perturbation method. For the TE0mnmodes the perturbation theory must be modified to account for the polarization of the plasma. In the absence of a magnetic field, the TM1mnas well as the TE1mnmodes are degenerate in their resonant frequencies. The presence of a magnetic field removes the degeneracy and causes the resonant frequency to be double‐valued. An experimental test of the validity of the perturbation method can be had by comparing the two resonant frequencies. The relation is given between the characteristics of the various modes and the propagation of plane waves in infinite uniform plasmas.

ISSN:0031-9171    

DOI:10.1063/1.1706129

出版商:AIP    

年代:1960

数据来源: AIP