摘要:

Starting with the basic plasma kinetic equations correct to second order in the plasma parameter, general formulas for cyclotron and bremsstrahlung emission and absorption are derived. The theory provides a rigorous description of the interaction of plasma and radiation. At equilibrium, Kirchhoff's law is recovered and the theory reduces to previously derived results.

ISSN:0031-9171    

DOI:10.1063/1.1711339

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The solutions of the Simon‐Harris hierarchy of equations for a spatially homogeneous plasma in an external magnetic field are obtained by an operator technique. These solutions are then used to formally derive a Fokker‐Planck equation and what may be interpreted as a radiative transfer equation. Finally the solutions for the limiting case of zero magnetic field are obtained and examined.

ISSN:0031-9171    

DOI:10.1063/1.1711340

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The propagation of low‐frequency electrostatic oscillations perpendicular to a density gradient in a low‐density, fully ionized plasma in a strong magnetic fieldBis studied from the point of view of the linearized macroscopic equations. Two sets of waves are found in the limits where the electrons move freely alongBor not at all alongB. Among these are waves which travel at the electron and ion diamagnetic drift velocities, and a physical description of this phenomenon is given in terms of microscopic motions. The transition between these two sets of modes occurs at angles of propagation very close to 90° toB; to treat this region of angles one must take into account either the electron inertia or the plasma resistivity. Dispersion curves are given for this transition region. In addition, it is found that in a small range of angles one of the cyclotron waves and the wave traveling near the electron drift velocity are unstable and can be excited by the pressure gradient, even if no longitudinal currents exist in equilibrium.

ISSN:0031-9171    

DOI:10.1063/1.1711341

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Instabilities due to resistivity gradients in a low‐pressure plasma are reconsidered using the electrostatic approximation. The fastest growth rate is proportional to &eegr;∥⅓, where &eegr;∥is the resistivity component parallel to the magnetic field. Contrary to earlier belief, heat conductivity along the field lines does not reduce the growth rate appreciably for Stellarator type of data. This mode is strongly localized in a thin layer inside the plasma, and hence may not produce much anomalous diffusion. Comparison is made with the much slower Kadomtsev mode, proportional to &eegr;∥, which is not localized. The effects of finite Larmor radius and Hall current acting in the plane perpendicular to the magnetic field are deduced. The corresponding actions parallel to the magnetic field, which seems to be more important when the plasma pressure is not too low, is not considered.

ISSN:0031-9171    

DOI:10.1063/1.1711342

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

In the last few years experiments were reported which demonstrated propagation of electromagnetic waves through an overdense magnetoplasma, i.e., a plasma whose plasma frequency is greater than the frequency of the probing wave. The interpretation of the experimental results was based on the ``whistler mode.'' The ``whistler mode'' appears in the infinite plane wave solutions of Maxwell's equations for an infinite homogeneous magnetoplasma. In a laboratory plasma, the effects of the boundaries of the plasma may play an important role in determining the propagation properties of the waves. These effects are examined and the analysis shows that the waves may, under certain circumstances, exhibit sufficiently different qualitative and quantitative characteristics to seriously limit the applicability of the infinite medium theory to bounded plasmas. To illustrate this point, the properties of waves propagating in a dense, homogeneous, cylindrical plasma bounded by a conducting wall are examined and compared with the properties of the wave predicted from infinite plane wave theory.

ISSN:0031-9171    

DOI:10.1063/1.1711343

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The approach to equilibrium of the electron and ion components of a plasma has been studied. The interactions between particle pairs are determined in a polarizable plasma, so that collective effects are included at the outset. The pairwise interactions are treated quantum mechanically, in the Born approximation, whereas the collective effects are, in a consistent manner, treated classically. Corrections to previously quoted results, due to the proper inclusion of shielding, as well as quantum effects, are logarithmic.

ISSN:0031-9171    

DOI:10.1063/1.1711344

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

A collisionless field‐free synthesized Cs+plasma stream is impacted on the transverse magnetic field of a C‐electromagnet. The configuration of a ``narrow'' beam is maintained as stream widths (∼4 cm) are small compared to the ion cyclotron radius. The interaction is observed to be unstable when the plasma penetrates or traverses a magnetic field in excess of ∼5 G. The instability is manifested by the appearance of both high (10–100 Mcps) and low (100 kcps) oscillations. It is believed that the instability arises from contrastreaming electron currents generated by a peaked potential structure in the boundary gradient region.

ISSN:0031-9171    

DOI:10.1063/1.1711345

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Calculations are presented which show that a laser pulse delivering powers of the order of 1010W to a liquid or solid particle with dimensions of the order of 10−2cm will produce a hot plasma with temperatures in the range of several hundred eV. To a large extent the plasma temperature is held down by its rapid expansion and cooling. This converts much of the energy supplied into ordered energy of expansion. This ordered expansion energy can amount to several keV per ion. If the expanding plasma can be caught in a magnetic field and its ordered motion converted to random motion this might be utilized as a means for filling controlled thermonuclear fusion devices with hot plasma. Further, it should also be possible to do many interesting plasma experiments on such plasmas.

ISSN:0031-9171    

DOI:10.1063/1.1711346

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Recent observations with the Phoenix high‐energy neutral injection experiment are described. At densities where the electron plasma frequency is greater than the ion cyclotron frequency, strong emission at the ion cyclotron frequency and ½ the ion cyclotron frequency is observed. This is interpreted on the basis of the theory of electrostatic instability developed by Harris and others. Experimentally, the instability results in strong scattering of ions out of the transverse direction but so far as can be observed, there is no actual loss of plasma. Above a density of 5 × 108particles/cm3, accumulation of particles is limited by the development of strong low‐frequency (∼100 kc/sec) oscillations which appear to be anm= 1 displacement of ions and electrons rotating at half the ion precession frequency. This mode is approximately independent of density. During periods of strong emission at the ion cyclotron frequency, however, another mode is observed, the frequency of which is approximately proportional to density. These observations suggest anm= 1 precessional drift instability. The existing theories concerning this low‐frequency instability are fully discussed. We present a new calculation in which the cylindrical plasma shape and the associated boundary conditions are taken into account. Its predictions are in reasonable agreement with the experiment. The electric field inside the plasma is found to be nonuniform even for them= 1 mode, so that finite Larmor radius effects are to be expected for this mode, contrary to common belief. The full equation for the electric potential valid for all densities and including the first order finite Larmor radius effect is presented. However, the finite Larmor radius effect is found to be small at densities around 108particles/cm3, and at magnetic fields above 10 kG.

ISSN:0031-9171    

DOI:10.1063/1.1711347

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

An examination of the stability of the reflex arc discharge against a long wavelengthm= 1 instability has been carried out. In performing the calculation, use was made of the experimental plasma density distribution and the plasma potential distribution as computed by Chen for a hot cathode reflex arc in a strong magnetic field. It is found that the discharge is unstable for helical instabilities with wavelength greater than 1200Rcm, whereRis the discharge radius. The growth rate increases with increasing wavelength. This result is consistent with that of Simon's analysis of a slab geometry with crossed electric and magnetic fields.

ISSN:0031-9171    

DOI:10.1063/1.1711314

出版商:AIP    

年代:1964

数据来源: AIP