摘要:

The radiation output power losses due to the scattering induced by spatial nonuniformities of the medium refraction index are analyzed for an active cavity of the gasdynamic laser. The analysis is based upon the nonlinear equations of chemical kinetics. The attenuation of the coherent radiation power caused by the statistically homogeneous and isotropic flow nonuniformities is treated as a passive loss measured by an extinction coefficient related to the integral scale of the turbulence and the mean‐square fluctuation of the refractive index. A set of straightforward analytical formulas are given for both the coherent and incoherent radiation power as well as for the laser efficiency.

ISSN:0031-9171    

DOI:10.1063/1.861151

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Ion wave turbulence spontaneously excited in a current‐carrying plasma is investigated by the microwave scattering method. The dispersion relation, the wavenumber spectra, and the angular spectra of the ion wave turbulence are determined from the angular distribution of the scattered wave. The wavenumber spectrum has a peak aroundk≃ &ngr;in/vp, and decreases ask−4.8±0.5with increasingk, where &ngr;inis the ion‐neutral collision frequency andvpis the phase velocity of the ion wave. The angular spectrum of the wave energy is found to broaden as the total wave energy,W, increases along the electron drift. The effective collision frequency, &ngr;f, for electrons is also measured by the rf probe method as well as the dc method. An anomalous increase in &ngr;fis observed with the increase inWalong the electron drift. The present experimental results are consistent with the theory of perturbed ion orbits.

ISSN:0031-9171    

DOI:10.1063/1.861152

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A new relativistic electromagnetic computer simulation code, with one spatial dimension, is described which explicitly follows right‐ and left‐going electromagnetic waves by integrating along the characteristics of Maxwell’s equations. To illustrate its suitability for the study of laser‐plasma interactions, simulations are discussed of the heating of plasma by two opposed lasers whose beat frequency drives a local plasma oscillation. Excellent agreement is obtained with analytic theory in the linear‐response regime.

ISSN:0031-9171    

DOI:10.1063/1.861153

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The single‐wave weak cold relativistic two‐stream instability has been studied in one dimension by numerical integration of the equations of motion, energy conservation, and Poisson’s equation. The dynamics is shown to depend only on the single parameterS= &bgr;02&ggr;0(nb/2np)1/3. The nondimensionalized wave energy at initial saturation due to beam trapping,W1= ⟨E2⟩/8&pgr;nbmc2&ggr;0, reaches a maximumW1= 0.09 atS= 0.4 and then decreases withS, but ifS≳0.5 the wave energy is larger at subsequent bounces of the trapped particles, so thatWmaxincreases roughly monotonically withS, reaching 0.11 atS= 3. The drop‐off ofW1(S) is due to a relativistic tendency of beam electrons to bunch in the part of the orbit where the beam electron energy is largest. The self‐consistent nonlinear shifts in wave frequency and amplitude are shown to play an essential role in extracting energy from the beam.

ISSN:0031-9171    

DOI:10.1063/1.861154

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The magnetohydrodynamic stability of a free‐boundary straight plasma column with a slightly elongated rectangular cross section, carrying a uniform axial current, is investigated analytically. Axisymmetric modes (n= 0), for which the circular cross section case is marginally stable (m= 1), are considered. Stability is found for a rigid vertical displacement, in good agreement with numerical results. However, a vertical displacement with a small additionalm= 3 like perturbation, localized near the plasma surface, leads to instability.

ISSN:0031-9171    

DOI:10.1063/1.861155

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

It is shown that a finite disturbance independent of the streamwise coordinate may lead to instability of linear flow, even though the basic velocity does not possess any inflection point.

ISSN:0031-9171    

DOI:10.1063/1.861156

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A remarkably simple method of solution is given for an eigenvalue problem arising in laminar flow in ducts which uses eigenfunctions of the Helmholtz equation. The only computation involved is the determination of zeros of a series to obtain the eigenvalues.

ISSN:0031-9171    

DOI:10.1063/1.861157

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Newcomb’s criterion for convective stability in the presence of a horizontal magnetic field is written in a form which explicitly shows the effect of vertical variations of the magnetic field strength. It is shown that a nonuniform horizontal magnetic field can bedestabilizingas well as stabilizing.

ISSN:0031-9171    

DOI:10.1063/1.861158

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The cold plasma theory of upper hybrid harmonic generation is examined numerically. Inclusion of the density perturbation caused by incident wave pressure gives enhanced harmonic levels (as observed experimentally) and reveals the sensitivity of the theory to the description of the incident fields.

ISSN:0031-9171    

DOI:10.1063/1.861159

出版商:AIP    

年代:1975

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.861160

出版商:AIP    

年代:1975

数据来源: AIP