摘要:

Ion cyclotron waves are set up in a toroidal plasma (previously formed by Ohmic heating) contained in the Model C stellarator, and absorbed at local minima in the confining magnetic field. The plasma (1012−1013cm−3) confined in these magnetic mirrors under certain conditions has little interaction with the main body of the plasma; the perpendicular ion temperature can reach several keV, while the electrons remain at less than 100 eV. We can thus reach a regime not yet available to other mirror confinement experiments. The observed cooling of the plasma in the mirrors agrees with the calculated ion‐ion and ion‐electron loss processes and charge exchange. At the highest temperatures and lowest densities, the confinement time in the mirrors is limited to ∼ 1 msec, most likely by charge exchange with a steady influx of neutral hydrogen. We find no evidence for any anomalous particle‐ or energy‐loss process, although several instabilities are predicted by theory to occur.

ISSN:0031-9171    

DOI:10.1063/1.1762187

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The numbers, flow velocities, and temperatures of the positive ions emitted by helium and argon plasmas pulsed into an evacuated region by a plasma gun are determined by a time‐of‐flight analysis on freely expanding ions. Times of plasma release are also calculated. It is shown that the time‐of‐flight technique is applicable even with statistical variations in plasma characteristics observed under apparently identical conditions of plasma production. A slug‐mode description of the average behavior of the gun is seen to agree with the time‐of‐flight analysis if ion recombination is assumed.

ISSN:0031-9171    

DOI:10.1063/1.1762188

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The problem of an electrically conducting, compressible, viscous free jet in the presence of transverse magnetic and electric fields is solved analytically by a perturbation technique. The velocity and temperature profiles are expanded about the nonmagnetic jet solutions, the expansion parameter being the magnetic interaction parameter. The first‐order perturbation solution is obtained in closed form for both the velocity and temperature profiles when a transverse magnetic field interacts with the free jet. Finally, the velocity profiles are obtained in closed form for an electric field transverse to both the jet axis and the magnetic field.

ISSN:0031-9171    

DOI:10.1063/1.1762189

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The stability of relativistic shock waves in an infinitely conducting plasma containing an applied magnetic field parallel to the plane of the shock wave is studied with respect to a disturbance with a wavenumber vector perpendicular to the magnetic field. It is concluded that such disturbances are stable.

ISSN:0031-9171    

DOI:10.1063/1.1762190

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A theory is presented capable of describing the structure of a strong shock in a diatomic gas. Strong shocks in a monatomic gas can be effectively treated using the bimodal distribution function of Mott‐Smith. Relaxation effects are included in the present analysis by replacing the bimodal form with a weighted trimodal distribution function. The three weighting functions are determined to satisfy certain averages of the Boltzmann equation. Logical limitations occur when the trimodal distribution reduces to either a monatomic or a diatomic bimodal distribution. The molecular model under discussion is the rigid convex body of revolution. Specific cases include the loaded sphere and the spherocylinder. Solutions are obtained for slightly loaded spheres by applying a method of matched asymptotic expansions. A computer study is performed at infinite Mach number for a spherocylinder corresponding to a hypothetical ``real'' gas. Comparison with recent shock data suggests the possibility of solidly relating the geometry of a spherocylinder to a nitrogen molecule.

ISSN:0031-9171    

DOI:10.1063/1.1762191

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The use of the Lorentzian scalar electrical conductivity as a basis for constructing a mixture rule for partially ionized gases is extended, and mixture rules for the tensor components of the electrical conductivity are proposed. A comparison with the third Chapman‐Enskog approximation shows that the proposed mixture rules give conductivity values which are within approximately 15% of the more accurate results. A similar comparison for the mean‐free‐path formulas (neglecting ion‐slip) is less favorable. It is concluded that the proposed conductivity formulas provide a satisfactory method for calculating the tensor conductivity for a wide range of electron‐neutral cross sections and magnetic field strengths, and for all degrees of ionization.

ISSN:0031-9171    

DOI:10.1063/1.1762192

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Laminar boundary‐layer heat transfer from a partially ionized monatomic gas to a highly cooled wall with no applied external electric or magnetic fields is analyzed by the similarity solution approach. The gas is assumed to be electrically neutral with ambipolar diffusion by ion‐electron pairs. In addition, equal electron and atom‐ion temperatures are assumed, and sheath effects are not considered. From existing perfect gas similarity solutions, the number of parameters that need to be investigated is reduced to those directly related to ionization effects. Solutions for the limiting cases of a large diffusion rate compared to the net production rate of ions and for local equilibrium are obtained for a range of Prandtl and Lewis numbers. An approximate prediction method that includes variable property considerations is then suggested to account for variable free‐stream velocity and ionization effects in a flow over a highly cooled wall.

ISSN:0031-9171    

DOI:10.1063/1.1762193

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An equation governing the motion of an incompressible fluid flowing axially over a thin paraboloid of revolution is derived. The asymptotic behaviors and an approximate solution are discussed, and numerical solutions computed. From the numerical solutions, an extrapolation towards vanishing boundary thickness is made. It is found that for progressively thin needles, the displacement thickness and drag per unit length diminish very slowly, but eventually become zero as the needle vanishes.

ISSN:0031-9171    

DOI:10.1063/1.1762194

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A new formulation of the multicomponent boundary‐layer problem which is convenient for numerical calculations is developed by a modification of the usual Chapman‐Enskog procedure. The complete set of boundary‐layer equations turn out to be a set of first‐order differential equations and a set of algebraic equations which are linear in the fluxes. The method is extended to include chemically reacting mixtures as well as nonreacting polyatomic molecules. It is shown that the method can be extended to two‐temperature fluids when one of the species has a small mass and to mixtures where it is necessary to retain higher‐order terms in the polynomial expansions used in the Chapman‐Enskog procedure.

ISSN:0031-9171    

DOI:10.1063/1.1762195

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A method of obtaining solutions to nonlinear flow problems by integrating the rate of change of the solution with respect to a suitable parameter is described. The advantage of this method is that the nonlinearity of the problem is confined to a first order equation where it causes little difficulty. The Falkner‐Skan boundary‐layer problem and the problem of flow about a nonlifting airfoil at transonic speeds are used to illustrate the method.

ISSN:0031-9171    

DOI:10.1063/1.1762196

出版商:AIP    

年代:1967

数据来源: AIP