摘要:

The structure of a very strong detonation wave (a shock wave followed by a thermonuclear reaction zone) propagating through a deuterium‐tritium gas mixture is studied. The shock is sufficiently strong so that it heats the gas to a temperature at which thermonuclear reaction probabilities are large. The characteristic times for collisions and reactions are examined to determine when the von Neumann‐Zeldovich model (separate shock and reaction zone) of detonation structure is applicable. Appropriate nuclear reaction kinetics equations are developed for the reaction zone and the effect of energy loss due to bremsstrahlung is included in the analysis. A set of wave structure equations is derived and solved numerically for several different cases. The physical effects expected from a laboratory fast‐shock experiment are examined briefly.

ISSN:0031-9171    

DOI:10.1063/1.1691950

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The collective processes in a self‐gravitating system with uniform rotation are studied with particular emphasis on the stability of density waves. In addition to the classical Jeans instability, it is shown that the so‐called microinstability can also exist if the distribution is anisotropic and&bgr; ≡ longitudinal dispersion speedtransverse dispersion speed<1 −2212≃ 0.54. The critical wavelength is calculated as a function of &bgr; for nearly transversely propagated modes and is also estimated for the case that waves have arbitrary propagation direction and long wavelength. Finally, the stability of density waves associated with a system in the presence of the Kapteyn‐Eddington star stream is examined.

ISSN:0031-9171    

DOI:10.1063/1.1691951

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

In a cylindrical hydrogenous laboratory plasma source of diameter 21 cm and length 170 cm, the propagation of Alfve´n torsional waves of azimuthal wave field b&thgr;, propagating parallel to a steady magnetic field B0in thezdirection, have been studied. The perturbation ratiob&thgr;/B0has been increased to values as high as 2.6 and found that: (a) As the perturbation ratio is increased the wave rapidly steepens into a shock wave, but at perturbation ratios in excess of 1.2 there is no further reduction in the rise time of the leading edge. (b) The Alfve´n Mach number shows a marked reduction in rate of increase at this perturbation ratio. (c) The attenuation of the wave increases rapidly at this perturbation ratio. (d) There is some evidence of the attenuation energy being expended in particle heating and in the development of a higher‐frequency magnetoacoustic wave traveling radially outwards in the plasma.

ISSN:0031-9171    

DOI:10.1063/1.1691952

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

Mariner II plasma and magnetic‐field data are examined for explicit examples of low‐frequency hydromagnetic waves. From the magnetic‐field data, several sinusoidal waveforms are isolated. One of these clearly satisfies the hydromagnetic equations relating the magnetic‐field variation to the ion‐velocity perturbation for an Alfve´n wave. This result is consistent with Barnes' theoretical prediction that only the Alfve´n mode is not strongly damped in a plasma of moderate or high &bgr;.

ISSN:0031-9171    

DOI:10.1063/1.1691953

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

A theory of low‐frequency drift (universal) instabilities in a nonuniform collisionless plasma is developed for general magnetic field configurations including trapped particle effects, rather than the plane geometry which has previously received most attention. A type of energy principle shows that the special equilibrium distributionF(∈, &mgr;), of interest in minimum‐Bmirror configurations, is absolutely stable to these modes provided∂F/∂∈ < 0together with a second condition on∂F/∂&mgr;. For equilibrium distributions not of this special form, in particular for a Maxwell distribution with a density gradient, the case of axisymmetric toroidal configurations with closed poloidal field lines is considered in detail. Three unstable drift modes are found, a flute‐like mode, a drift‐ballooning mode local to the region of unfavorable curvature, and a drift‐universal mode. Stability criteria and growth rates for the modes are given. The equations also describe a recently discussed low‐frequency trapped‐particle instability.

ISSN:0031-9171    

DOI:10.1063/1.1691954

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The nonlinear effects in weakly turbulent plasmas in the region of particle‐wave resonance are shown to be derivable by determining the response of the plasma to an infinitesimal test wave. The local solutions of the test‐wave responses are examined and the smearing of the particle‐wave resonances and the resulting change in the dispersion relation for the gentle bump instability are determined. The lowest‐order nonlinear transport equation is derived and applied to a weak homogeneous beam.

ISSN:0031-9171    

DOI:10.1063/1.1691955

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

A stochastic (in contrast to kinetic theoretic) approach to the calculation of correlation functions in fully ionized plasmas is investigated. Formally different results are obtained. The question as to whether or not the differences are qualitatively and/or quantitatively significant is raised, but not answered.

ISSN:0031-9171    

DOI:10.1063/1.1691956

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

A plane electromagnetic wave is obliquely incident upon a plasma layer of finite thickness, where the equilibrium plasma is taken to be homogeneous and isotropic. The electric vector of the wave is assumed polarized in the plane of incidence. The specular boundary condition for the distribution function is employed and an exact solution of the coupled Maxwell‐Vlasov equations is derived as an expansion in normal modes, yielding coupled tranverse and longitudinal waves in the plasma region. Temperature effects on the reflection coefficient are investigated.

ISSN:0031-9171    

DOI:10.1063/1.1691957

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

Experiments on shock formation in aQ‐device are described. For equal ion and electron temperatures,Ti = Te, Landau damping prevents shock formation. When the ratioTeTiis made as large as 3‐4 through ion‐neutral atom collisions, shock formation is observed.

ISSN:0031-9171    

DOI:10.1063/1.1691958

出版商:AIP    

年代:1968

数据来源: AIP

摘要:

The dense plasma focus discharge is produced in a hydromagnetic coaxial plasma accelerator. The final heating and compression of the plasma is accomplished by a partial conversion of the stored magnetic energy residing in the region behind the current sheath to plasma energy. The electrical behavior of the discharge is examined to determine the fraction of the initial energy involved in mechanical sheath motion, inductive storage in the accelerator, and Ohmic losses associated with the external and plasma discharge. Many analysis of this kind of datum show no definite correlation between the energy converted and neutron production. Presumably this arises from a lack of information as to how the collapse uses this energy and to the amount of plasma ejected from the dense plasma region during the collapse. From soft x‐ray pinhole and Schlieren photographs, the collapse and the development of the dense plasma is unquestionably a two‐dimensional pinch compression.

ISSN:0031-9171    

DOI:10.1063/1.1691959

出版商:AIP    

年代:1968

数据来源: AIP