摘要:

A simple analytic model is developed to describe the plasma parameters produced at peak compression when gas‐filled spherical shell targets are imploded by the ablation pressure produced by irradiation with constant laser power. The range of validity of the model is discussed and, in particular, the constraints due to preheating by hot electrons. Comparison with numerical simulation verifies the accuracy of the model. The implications of the scaling of compressed plasma parameters with target and laser parameters are discussed.

ISSN:0031-9171    

DOI:10.1063/1.863769

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Electrostatic radiation from a monopole antenna in a magnetoplasma is studied theoretically in the frequency range between the electron gyrofrequency and its second harmonic. The scalar potential created by a point source is calculated numerically using the least‐damped‐root approximation, which involves considering only two roots of the dispersion equation, corresponding to the oblique mode and to the cyclotron harmonic mode. The potential distribution can be understood as being due both to interference between these two modes and to diffraction of the cyclotron harmonic mode alone. Theoretical spatial distribution fit the experimental data. In particular, the theory confirms that cyclotron harmonic waves should be detectable in all directions from the source, as was observed experimentally. A good agreement with experimental data is shown by theoretical curves of constant phase and of constant amplitude. An approximate analytical model of the potential distribution is presented, and is compared with the numerical model and with experimental data. Finally, it is shown how such data can be interpreted to yield the electron density and temperature.

ISSN:0031-9171    

DOI:10.1063/1.863770

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The filamentation instability properties of a relativistic hollow electron beam confined in axial flow by a uniform magnetic field, in the absence of background plasma, in a pipe are investigated via the Vlasov–Maxwell equations. The instability is found to be have two sidebands, one with a spectrum of positive wavenumberskand the other with a spectrum of negative wavenumbers. The spectral pointk= 0, associated with the diokotron instability, is excluded from the two unstable sidebands of the filamentation instability. Only in the limit of zero axial beam flow (&ggr;→1), does the diokotron instability become asymptotically part of the filamentation instability spectrum. In this limit, the two sidebands of the filamentation instability merge asymptotically and symmetrically toward the diokotron instability spectral point,k= 0, in agreement with the basic driving physical mechanisms and geometry configurations for these two distinct and different instabilities.

ISSN:0031-9171    

DOI:10.1063/1.863771

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A stationary spectrum of high‐frequency Langmuir wave turbulence is found to be unstable with respect to Alfve´n wave perturbations. This instability seems to explain some magnetic pulsation phenomena in the magnetosphere.

ISSN:0031-9171    

DOI:10.1063/1.863772

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A Hamiltonian formulation of the guiding‐center drift in arbitrary, steady‐state, magnetic and electric fields is given. The canonical variables of this formulation are simply related to the magnetic coordinates. The modifications required to treat a large class of ergodic magnetic fields using magnetic coordinates are explicitly given in the Hamiltonian formulation.

ISSN:0031-9171    

DOI:10.1063/1.863773

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A comment on a note on Poisson’s equation for pressure in a turbulent flow is presented. (AIP)

ISSN:0031-9171    

DOI:10.1063/1.863774

出版商:AIP    

年代:1982

数据来源: AIP