摘要:

The self‐consistent rf electric field in ion cyclotron excitation of a multispecies plasma is measured and compared with linear plasma theory. For wave propagation perpendicular to the magnetic fieldBz(kz=0), the rf electric field has minima at major and minor ion cyclotron frequenciesf1,f2, respectively. Nearf&agr;, wheref&agr;is the ion cyclotron frequency of species &agr;, the field is proportional to &Dgr;f=f−f&agr;. The line width aboutf&agr;is proportional tor&agr;≡ the ratio of the ion concentrationn&agr;to the total ion densityn0. As the concentration of minor ion species decreases (r2≲ 10%), the field at frequencies nearf2increases sufficiently to accelerate the minor ions to high energy (≳ 100 eV).

ISSN:0031-9171    

DOI:10.1063/1.862479

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A magnetic flux shell model is described which is suitable for numerical simulations of cylindrically symmetric plasmas. The magnetohydrodynamic equations in magnetic field line coordinates are derived including the effects of finite electrical conductivity and anisotropic heat conductivity. Subsequently, the equations of motion of coaxial plasma shells of constant density, temperature, axial velocity, and axial magnetic field are derived including (a) full radial dynamics and (b) radial pressure balance. Sample simulations of a laser heated solenoid plasma and a &Vthgr;‐pinch reactor are described.

ISSN:0031-9171    

DOI:10.1063/1.862480

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A device which uses an induced Raman or Brillouin scattering process to amplify laser pulses is described. A technique is presented to analyze the amplification of ultrashort laser pulses with effects such as pump depletion included. The results of the examples considered indicate that such a device can be realized with current technology.

ISSN:0031-9171    

DOI:10.1063/1.862481

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The radial width,w, of the boundary layer associated with tearing and twisting modes is always much smaller than equilibrium length scales. However, for the large mode number perturbations which seem particularly relevant to anomalous tokamak radial transport, the poloidal wavelength,k⊥−1, can become short enough to cast doubt on previous analyses, which neglect finite −k⊥wterms. The effect of such terms on prominent electromagnetic eigenmodes is studied here, both analytically and numerically. The two methods agree qualitatively, and show that the growth rates of &Dgr;’‐driven tearing modes are reduced by finitek⊥w, while certain other tearing and twisting mode growth rates are enhanced.

ISSN:0031-9171    

DOI:10.1063/1.862482

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A comparison of the effect of different configurations of the outer conducting surface on the stability of a cylindrical circular plasma of radiusaand lengthLis made. As opposed to the usual configuration of a concentric circular outer conductor, ’’fins’’ or radial conducting surfaces lying on the field lines with the nearest edge a distancecfrom the center of the plasma are considered. The comparison procedure is based upon estimating the difference of the perturbed energy integrals for the various configurations. The usual surface perturbations of the form exp[i(kz±n&Vthgr;)],k∼0 are treated. Fins of zero thickness have no effect on then = 0 mode; however, they do tend to stabilize the importantn = 1 mode. Fora/csufficiently small, radial planes &Vthgr; = 0, &pgr;, and ±&pgr;/2 tend to have the same stabilization effect on then = 1 mode as a concentric outer cylinder of radiusb, whereb∼&sqrt;2c. The interaction between the opposite fins was taken into account.

ISSN:0031-9171    

DOI:10.1063/1.862483

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A magnetohydrodynamic boundary layer analysis is performed treating the effect of the convective term of the equation of motion near the singular surface. The nonlinear equations in this region are separable; the time evolution of the solution is determined by the Riccati equation and nonlinear harmonics are generated at wavenumbers which are multiples of the fundamental. This solution is matched to the linear solution in the outer region yielding modes reminiscent of resistive instabilities which nevertheless are not normal modes of the system.

ISSN:0031-9171    

DOI:10.1063/1.862484

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The Alfve´n‐ion‐cyclotron instability is studied for a model where the ions are confined axially by a quadratic electrostatic well. Comparison between the homogeneous plasma dispersion relation, an effective dispersion relation including the effect of axially bouncing ions, and the complete eigenvalue solution shows that the first two approximate solutions are quite accurate for plasma lengths on the order of the ion gyroradius. The eigenmode with odd electric field symmetry is found to be the most unstable. Comparison is made with a previously reported particle simulation which imposes linear polarization for the electric field. It is found that the linear polarization constraint can give the unphysical result of instability at vanishingly small plasma &bgr;⊥for certain parameters.

ISSN:0031-9171    

DOI:10.1063/1.862485

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Results of particle simulation of the mirror drift cone instability, a high frequency (∼lower hybrid) flute mode with loss‐cone ions, are presented and compared with theory. Possible saturation mechanisms are discussed, and measurements of the diffusion of ions into the loss cone are presented and compared with quasi‐linear theory.

ISSN:0031-9171    

DOI:10.1063/1.862486

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Bounce modes are plasma waves which result from the coherent bounce motion of trapped particles. Such modes can occur in mirror devices when the relative spread in electron bounce frequencies is small. When electron bounce modes have perpendicular wavelengths comparable to typical ion gyroradii and frequencies near the ion gyrofrequency or some harmonic, they couple effectively with the ions and can be destabilized by a loss‐cone ion distribution. A one‐dimensional integral dispersion equation for electron bounce modes in a mirror plasma is derived and solved numerically for the wave eigenfrequencies. Predicted threshold densities for bounce mode instabilities in the Baseball I and Baseball II devices are compared with experimental values. Good agreement is found for Baseball II, but in Baseball I the predicted thresholds are consistently below observed values.

ISSN:0031-9171    

DOI:10.1063/1.862487

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Phase space dynamics of plasma particles in low frequency (&ohgr;≪&ohgr;ci) electromagnetic waves in a low beta inhomogeneous plasma is obtained including the effects of finite ion gyroradius, bounce resonance, and gradientBand diamagnetic drifts. Application of the results to particle flux observations in the magnetosphere is discussed.

ISSN:0031-9171    

DOI:10.1063/1.862496

出版商:AIP    

年代:1979

数据来源: AIP