摘要:

The experimental observation and theoretical description of a previously unrecognized mechanism for generating electromagnetic emissions and anomalous resistivity from a beam‐plasma interaction which is characteristic of Penning discharges is reported. Very clear emissions were observed from electric field‐dominated bumpy torus plasma near the geometric mean plasma frequency. These emissions are inconsistent with familiar physical mechanisms, and occurred in excellent agreement with the theoretical frequency &ohgr;gm= 0.537(&ohgr;pe&ohgr;pi)1/2. This frequency was derived from a theory based on the interaction of two opposite, interpenetrating electron beams with a heavy ion plasma. The anomalous resistivity associated with this interaction is predicted to several hundred times that of the familiar Buneman or ’’turbulent’’ resistivity. A perturbation procedure is used to obtain analytic expressions for the emission frequency and the anomalous resistivity in the zero temperature case. These results are extended to include the effects of finite ion temperatures on the dispersive properties of the plasma.

ISSN:0031-9171    

DOI:10.1063/1.863538

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The macroscopic equilibrium of relativistic charged particle beams is studied for configurations which are azimuthally symmetric and free of radial divergence. It is proved that in the limit of negligible internal energy all such equilibria are necessarily axially independent. Special radially dependent equilibria are derived.

ISSN:0031-9171    

DOI:10.1063/1.863539

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

One‐dimensional particle simulations of a finite‐length free electron laser show that the convectively‐unstable, short‐wavelength mode is the dominant instability initially for systems long compared with the growth length of the mode. Also, a generalized one‐dimensional linear theory of a finite length system has been derived with all kinetic effects included. Comparison between the unstable modes seen in the simulation and those predicted by this theory are in good agreement. However, the simulations show a significantly higher efficiency than that predicted by the theory when trapping by a single mode is the saturation mechanism. This may be caused by a local dc electric field (space charge fields) that arises self‐consistently as the beam slows down.

ISSN:0031-9171    

DOI:10.1063/1.863540

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The diffusion of ions and electron through a uniform neutral gas was treated with complete wall emission‐absorption boundary conditions. Volumetric ionization and recombination processes were ignored. In the limit of the small ratio of Debye length to channel width (&egr;→0), the problem splits into three regions: anode sheath, cathode sheath, and quasi‐neutral region. The solution is obtained in closed form in each of the three regions and matched in the overlap domains. The unusual feature of this problem is that the boundary conditions are coupled to the solution in a transcendental manner requiring iteration in order to achieve a consistent solution. The degree of surface coverage is an important parameter in determining emission and absorption rates. The results show that ion densities are elevated (above quasi‐neutral levels) in the anode and cathode sheaths tending to enhance electron emission. The quasi‐neutral density at each electrode is the geometric mean of the true charged particle densities at the boundary. Electrical current between the electrodes increases linearly, then saturates sharply with increasing voltage between the electrodes.

ISSN:0031-9171    

DOI:10.1063/1.863541

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Frieman’s derivation of a kinetic equation for a plasma is extended to the case of a plasma in a constant external magnetic field. A uniformly convergent collision term is constructed and a systematic way of dealing with the divergences in the collision term is indicated.

ISSN:0031-9171    

DOI:10.1063/1.863542

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The second law of thermodynamics is shown to place interesting limits on fluctuation amplitudes and on the form of interaction of the turbulence with the plasma in large tokamaks.

ISSN:0031-9171    

DOI:10.1063/1.863543

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A simple theory is developed to describe the density profile of an electromagnetically imploded hollow plasma liner. The model gives a good analytic means of determing density gradient scale length and sheath thickness for use in linear and nonlinear analysis of the Rayleigh–Taylor instability.

ISSN:0031-9171    

DOI:10.1063/1.863517

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The influence of the transverse magnetic field on the growth and decay behavior of weak discontinuities headed by plane and cylindrical wave fronts is analyzed completely, and the various possibilities concerning the evolution of wave forms are characterized.

ISSN:0031-9171    

DOI:10.1063/1.863544

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The force on a plasma which is moving relative to a finite conductivity wall is evaluated assuming that the plasma is distorted by a saturated magnetohydrodynamic mode.

ISSN:0031-9171    

DOI:10.1063/1.863510

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Electron cyclotron waves (whistlers) of large amplitude give rise to nonlinear shift of cyclotron‐resonance velocity. Several effects of the shift on the wave propagation are discussed.

ISSN:0031-9171    

DOI:10.1063/1.863511

出版商:AIP    

年代:1981

数据来源: AIP