摘要:

When a plasma is confined by magnetic fields inside a cylindrical conducting wall, the configuration of equilibrium can have either circular symmetry or helical symmetry. Thus, a sharp‐boundary screw pinch can have a circular or helical interface between the plasma and the vacuum. Each possesses the same amounts of total plasma mass, axial magnetic flux in plasma, axial magnetic flux in vacuum, and total azimuthal magnetic flux. It is shown that in the neighborhood of a point of bifurcation there are stable long‐wavelength helical equilibria. The equivalent circular equilibria with the same plasma mass and magnetic fluxes are unstable.

ISSN:0031-9171    

DOI:10.1063/1.1694376

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An analytic theory, embodying an axially‐dependent breakdown model, is presented to explain the focusing experienced by an intense relativistic electron beam upon its injection into a gently‐tapered, metallic guide tube (cone) filled with a neutral gas. The mechanism of cone focusing is thereby believed to be identified for the first time. The theory predicts the relative efficiency, relative fluence gain, energy loss along the cone, pressure variation, and cutoffs, with full dependence on the beam, cone, and neutral gas parameters. The theory is in good agreement with experiment. It is emphasized that the axially‐dependent nature of the breakdown must be considered to explain the focusing; in addition, it is shown why image charges, image currents, or specular reflections can not explain the focusing.

ISSN:0031-9171    

DOI:10.1063/1.1694377

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The envelope of the adiabatic trajectory solution for particle motion that occurs in cone focusing of intense relativistic electron beams is investigated. Comparisons with exact trajectory envelopes (obtained numerically) show that the adiabatic envelope is an excellent approximation under a wide variety of circumstances. Consequently, several important effects are disclosed: (1) The axial dependence of the breakdown (and not the radial dependence) is explicitly shown to determine the focusing, (2) increasing the cone angle rapidly leads to increased losses, (3) angular momentum created by scatter in the anode foil typically should not cause significant losses, and (4) increase of the beam temperature along the cone axis is demonstrated. A novel explanation of “adiabatic envelope conservation” is included.

ISSN:0031-9171    

DOI:10.1063/1.1694378

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The common occurrence of electron temperatures of a few hundred electron volts in&thgr;‐pinch experiments is shown by simple analytic arguments to be rather tightly determined by a balance between energy gained from collisions with the much higher‐temperature ions and thermal conduction to material walls. It is also shown that electron thermal conduction should not cause a greater loss of energy from straight&thgr;pinches of any length than ion end loss unless rather large magnetic mirror ratios can be obtained. This applies in particular to straight&thgr;‐pinch fusion feasibility experiments and fusion reactors. Also several suggestions are presented for reducing end losses and heating plasma columns.

ISSN:0031-9171    

DOI:10.1063/1.1694379

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Velocity distribution functions of both the electron and the proton component of the magnetospheric plasma are measured in 62 logarithmically spaced steps from 50 eV to 50 keV by an instrument carried upon the ATS‐5 spacecraft in circular synchronous orbit (6.6 earth radii). Oscillations which appear to be collisionless drift waves having periods of several minutes or longer are found in this data. Linearized wave theory can be use to predict the theoretical perturbation distribution functionfTin terms of the perturbing fields and the equilibrium distribution functionF. The functional dependence of the theoretical perturbation distribution functionfTupon particle energy can then be compared with that of the measured perturbationfM. The linear wave theory is found to predict correctly a change in the sign offMwhich occurs at a critical particle energyE*and the relative magnitude offMover the entire energy range.

ISSN:0031-9171    

DOI:10.1063/1.1694380

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Similarity solutions for strong cylindrical blast waves, under a constant axial current, and valid for small times, are obtained. The medium is of low constant pressure and follows an inverse power law for density.

ISSN:0031-9171    

DOI:10.1063/1.1694381

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The ion Mach number seen by the ion shock embedded in a collisional shock propagating in an electron proton gas is found to reach a limiting value of 2.66 as the free stream Mach number goes to infinity.

ISSN:0031-9171    

DOI:10.1063/1.1694382

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An analytical investigation of the current driven ion wave instability in a collisional plasma, taking account of the background temperature variations, has been carried out.

ISSN:0031-9171    

DOI:10.1063/1.1694383

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Electron plasma waves propagating perpendicular toB0in a weakly magnetized uniform plasma are observed above the upper hybrid frequency. Dispersion and damping follow classic laws. Application to high precision plasma diagonstics is pointed out.

ISSN:0031-9171    

DOI:10.1063/1.1694384

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An attempt is made to clarify the differences in the nonlinear plasma interaction of two fixed-phase wavepackets from that of two random-phase packets, and present a simple interpretation which is in agreement with the available experimental results.

ISSN:0031-9171    

DOI:10.1063/1.1694385

出版商:AIP    

年代:1973

数据来源: AIP