摘要:

The attenuation of electron oscillations in a fully ionized plasma with a small amount of Coulomb scattering is investigated by means of the Fokker‐Planck equation. In the present treatment, dynamical coefficients with the proper velocity dependence are utilized in contrast to previous work based upon simplified collisional models. The use of transform methods leads to a modified Landau dispersion integral from which follow the temporal damping decrement for ion‐electron collisions: &ggr;i= [&ngr;coll/3(2&pgr;)½] [1 + 4 (k rD)2]; and the corresponding electron‐electron decrement: &ggr;e= [&ngr;coll/3(&pgr;½)] [1 + 3.85 (k rD)2], where &ngr;collis the electron collision frequency,kis the oscillation wavenumber, andrDis the Debye correlation length.

ISSN:0031-9171    

DOI:10.1063/1.1724511

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The case of one‐dimensional geometry for the transition region separating a uniform plasma from its confining magnetic field is considered. The magnetic‐field profile within the boundary layer is determined by the current distribution, i.e., by the paths of the ions and electrons. The paths of these particles, on the other hand, are determined by the fields in which they move. An exact, self‐consistent solution of Maxwell's equations and the equations of motion of the particles is obtained. A detailed analysis is made for a hydrogen plasma. These results are then compared with those of a plasma whose positive constituent is the proton and whose negative constituent has a mass which approaches zero and a speed which approaches infinity in such a way that the energy remains finite. The transition layer thickness for these two plasmas agree to one part in 106. It is shown that this latter case is equivalent to treating the electrons of the hydrogen plasma in the guiding‐center approximation.

ISSN:0031-9171    

DOI:10.1063/1.1724512

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The general theory for high‐temperature plasmas, in the presence of an external uniform magnetic field, is developed by means of a Laplace‐transform technique. The dispersion relations for the longitudinal and the transverse oscillations, for a relativistic Maxwellian distribution with mass motion as well as for a non‐Maxwellian distribution in the absence of magnetic field are derived. The stability of two streams is investigated in detail both in the nonrelativistic and in the extreme relativistic limits. The longitudinal and the transverse modes are uncoupled only when the stream velocity and the wave velocity are parallel.

ISSN:0031-9171    

DOI:10.1063/1.1724513

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The dispersion relations and the problem of the stability of two streams, in the presence of an external magnetic field, are discussed by using the general theory developed in an earlier paper [B. Buti, Phys. Fluids6, 89 (1963).] For wave propagation parallel to the magnetic field, a relativistic Maxwellian distribution with mass motion is used; and for wave propagation in a direction perpendicular to the magnetic field, an isotropic non‐Maxwellian distribution is employed. In the latter case, gaps in the frequency spectrum occur.

ISSN:0031-9171    

DOI:10.1063/1.1724494

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The steady‐state energy loss of a homogeneous and isothermal spherical plasma due to de‐excitation radiation of impurity ions, assumed to have two energy levels only, is investigated without making the assumption that this radiation is thermal. A method developed by R. N. Thomas is adopted which consists in solving simultaneously the equation of radiative transfer and the equations for the rate of change of the occupation numbers of the energy levels. Analytical methods for calculating the source function obtained in this way are indicated.

ISSN:0031-9171    

DOI:10.1063/1.1724495

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

A mean containment time &tgr; of many seconds has been observed for a significant fraction of the energetic (≤ 2.2‐MeV) positrons emitted from Ne19isotropically and uniformly in a mirror geometry with mirror ratioRin the range 1.1–3.7. Long‐time containment has been observed for particles that escape through a mirror at radial distances for which the particle orbits do not encircle the axis, as well as for those that escape on or near the axis. The dependence of &tgr; on theZof the scattering gas, the gas pressure, the positron energy, the coil current, and the diameter and separation of the coils has been investigated. Most of the data were obtained with the two mirror coils separated one coil mean diameter. For sufficiently small values of &lgr; (the ratio of the maximum orbit diameter on axis to the coil mean diameter), &tgr; is independent of &lgr; and its dependence upon the above parameters agrees with the predictions of scattering theory. Also, the fraction of particles trapped as a function of the mirror ratio agrees with calculations based on the loss cone concept. These results demonstrate that the particles ``behave adiabatically'' if &lgr; is less than about 1/10. For larger values of &lgr; the observed &tgr;'s are shorter. Results obtained with probes are in agreement with the prediction that the intersections of particle drift surfaces with the plane midway between the mirror coils are concentric circles centered on the axis. In the cusped field resulting from opposite currents in two coils separated by one coil mean radius, containment times of several seconds have been observed at radial distances where the field is of sufficient strength that ``adiabatic behavior'' is expected. Near the axis, however, no long‐time (> 0.5‐sec) containment has been observed.

ISSN:0031-9171    

DOI:10.1063/1.1724497

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The motion of a charged particle in an asymmetric mirror geometry has been studied. The asymmetric geometry for these studies is constructed by giving equal but opposite tilts to the two identical, coaxial coils of a symmetric geometry in which the coils are spaced about one coil mean diameter apart. (This is equivalent to one section of a ``bumpy torus.'') A model for describing a particle's motion in this geometry is presented. It is based on the guiding‐center drift surfaces determined theoretically from the longitudinal and transverse adiabatic invariants and the invariance of the magnitude of the momentum. The results of the experimental investigations are successfully interpreted in terms of the model.

ISSN:0031-9171    

DOI:10.1063/1.1724498

出版商:AIP    

年代:1963

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.1724499

出版商:AIP    

年代:1963

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.1724500

出版商:AIP    

年代:1963

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.1724501

出版商:AIP    

年代:1963

数据来源: AIP