摘要:

A self‐consistent nonlinear theory of the energy and current modulation in a relativistic electron beam propagating through a klystron amplifier is developed. A closed integrodifferential equation for the beam current is obtained, assuming that the beam current is a function of timetand propagation distancez. Properties of the current and energy modulation are investigated from this integrodifferential equation for a broad range of system parameters. Magnitudes of the energy and current modulation are determined in terms of the gap voltage, the cavity frequency, geometric configuration, the beam intensity, and initial kinetic energy of the beam. The modulation amplitude increases, reaches peak, and decreases slowly, as the beam propagates through the amplifier. A simple expression of scaling law for maximum current modulation is obtained. This scaling law could be useful in the design and fabrication of a high‐performance klystron. Nonlinear mode evolution in current profile is also investigated by Fourier decomposing the current modulation obtained from the integrodifferential equation. The mode evolution in a long‐range propagation of an electron beam exhibits various interesting physical properties. For example, the maximum amplitude of the fundamental mode (l=1) occurs at the propagation distance, where all other modes vanish or have a very small amplitude. This property ensures a monochromatic frequency.

ISSN:0899-8221    

DOI:10.1063/1.860852

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Acceleration and heating of an electron beam caused by nonlinear Landau damping of intense electromagnetic waves in a plasma are investigated theoretically based on a velocity‐space diffusion equation. The beat wave, which does not satisfy the dispersion relation, is excited by the nonlinear interaction of two electromagnetic waves and interacts nonlinearly with the electron beam. As the frequency of the beat wave approaches the electron plasma frequency, the rates of acceleration and heating of the electron beam and the beat wave energy density become maximum values, being equal to those by stimulated Raman scattering. The beat wave is an electrostatic mode that can have a phase velocity near the light velocity and is able to accelerate the electron beam to a relativistic energy.

ISSN:0899-8221    

DOI:10.1063/1.860972

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Steady‐state calculations are presented that show that the ion current density extracted off an anode foil in a multistage ion diode is a monotonically decreasing function of the injected current densityJ, going to zero asJgoes to a limiting valueJ1. However,J1can be quite large, going to infinity as the diode voltage approaches the limiting voltageV1from below. Thus, it may not always be practical to inject a beam of current density exceedingJ1. The results presented in this paper can be used to determine the fraction of (typically unwanted) ions extracted from the anode foil whenJ≤J1.

ISSN:0899-8221    

DOI:10.1063/1.860854

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The nonequilibrium properties of strongly coupled plasmas are investigated taking into account reaction and diffusion processes. The starting point is quantum kinetic equations for systems with chemical reactions involving many‐body effects like screening, self‐energy, and medium‐dependent scattering. The influence of these effects on the kinetics of reaction and diffusion processes is discussed. Generalized expressions for the coefficients of impact ionization and diffusion are derived exhibiting a strong density dependence due to the many‐body effects. Solving the reaction‐diffusion equation (RDE) for a dense hydrogen plasma, nonlinear phenomena such as bistability, running ionization fronts, and droplet formation are obtained.

ISSN:0899-8221    

DOI:10.1063/1.860855

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The semilocal kinetic analysis based on appropriate norms of differential operators is able to recover the growth rates of the toroidal ion temperature gradient mode found from the rigorous integral equation formulation.

ISSN:0899-8221    

DOI:10.1063/1.860856

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Nonlinear interaction between intense photons and sound waves in a relativistically hot electron–positron plasma is considered. The modulational instability of a constant amplitude photon is investigated and the formation of polarons (localized photon envelopes trapped in a self‐created density cavity) is discussed. The relevance of this investigation to astrophysical plasmas is pointed out.

ISSN:0899-8221    

DOI:10.1063/1.860863

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

It is shown that purely damped convective cell modes acquire a real frequency in the presence of static charged dust grains in a nonuniform magnetized dusty plasma. The frequency of the two‐dimensional mode is induced by the plasma density gradient and corresponds to charge density waves arising out of the plasma non‐neutrality. The dynamics of weakly interacting finite‐frequency convective cell modes is governed by the generalized Navier–Stokes equation. The presence of the new term arising from the dust inhomogeneity in the latter provides the possibility of a two‐dimensional dipolar vortex solution in dusty plasmas.

ISSN:0899-8221    

DOI:10.1063/1.860864

出版商:AIP    

年代:1993

数据来源: AIP