bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic Model for Gases with Internal Degrees of Freedom
Authors: Morse T. F.
Published: December 2004

A new model equation has been obtained which permits a kinetic description of gases possessing internal degrees of freedom. The collision term of the model equation is related to the Wang-Chang and Uhlenbeck results for polyatomic gases much in the same manner as the Bhatnagar, Gross, and Krook model is related to the Boltzmann collision integral. A modified perturbation technique utilizing the various time scales of the flow situation has been employed in closing the equations of change. (This has been shown to be asymptotically equivalent to the Chapman-Enskog expansion of the time derivative.) From the model equation and its moments, depending upon the ratio of a ``flow through'' time to the inelastic relaxation time, one directly obtains either the bulk viscosity as a term modifying the pressure tensor, or a relaxation equation for the internal temperature. The model also accounts for the contribution to the heat transfer vector due to the presence of internal degrees of freedom. In this theory, the inelastic relaxation time appears as a parameter of the system. It is hoped that this model may serve the same function for aerodynamic and kinetic boundary value problems for gases with internal degrees of freedom that the Bhatnagar, Gross, and Krook model has for the simple gas.
Composition Dependence of Gaseous Thermal Diffusion Factors and Mutual Diffusion Coefficients
Authors: Mason E. A. , Weissman S. , Wendt R. P.
Published: December 2004

Radioactive tracers are used to measure thermal diffusion factors and mutual diffusion coefficients for several binary gas systems in which one component is present in trace concentration only. The systems are H2–Ar37, T2–Ar, T2–CO2, and T2–N2. These measurements are combined with previous tracer measurements and with earlier measurements on less dilute mixtures to test, over the complete composition range, the theoretical prediction that the reciprocal of the thermal diffusion factor is linear in the mole fraction. The linear relation is found to hold within experimental error. The kinetic theory expressions for the composition dependence are also linear, but do not reliably reproduce the experimental measurements. The implications of these results for the problem of determining intermolecular forces from thermal diffusion measurements are briefly discussed. It is shown that an analogous procedure can be carried out for the composition dependence of the diffusion coefficient, and a new formula for this quantity is derived. This formula can be used to estimate the composition dependence of the diffusion coefficient from measurements of the thermal diffusion factor. This result is checked experimentally.
Spectral Energy Budget in Wall Turbulence
Authors: Lumley J. L.
Published: December 2004

The spectral energy equations are developed for mechanical and thermal wall turbulence; that is, turbulence which obeys similarity relations (not dependent on viscosity) in which the only characteristic length is the distance to the wall. The terms which appear are given physical interpretations relating them to inhomogeneities of intensity and scale. Some tentative conclusions are put forward regarding the spectral energy budget of a more general similar (homogenizable) turbulence.
Initial Phase of the Exploding Wire Phenomenon
Authors: Nash Charles P. , Olsen Clifford W.
Published: December 2004

As an approximation to the behavior of a circuit containing an exploding wire, the differential equation for the discharge of a condenser through a resistive load which increases linearly with time has been solved analytically. The calculations indicate that inductive effects govern the energy consumption in the first pulse for small-diameter wires, while thermodynamic effects are important for large-diameter wires. The importance of the heat of vaporization per unit volume, the resistivity, and the temperature coefficient of resistivity is stressed. Owing to their similarities in these properties, it is predicted, and confirmed experimentally, that gold wires and aluminum wires should display nearly identical first-pulse characteristics.
Secular and Nonsecular Behavior for the Cold Plasma Equations
Authors: Montgomery David , Tidman Derek A.
Published: December 2004

The origin of ``secular'' behavior for the nonlinear cold electron plasma equations is studied. The equations involved are closely related to the Klein-Gordon equation with a small nonlinear term. A method is developed for arriving at perturbation theoretic solutions of this equation, and the method is then applied to the case of the higher-order effects of an electromagnetic wave propagating in the cold electron plasma. An explicit expression for the second order frequency shift is calculated.
Electrostatic Waves in Beam-Plasma Systems
Authors: Lamborn B. N. A. , Lafferty D. L.
Published: December 2004

By describing systems composed of a plasma and a set of moving nonrelativistic charged particle streams by means of collective coordinates, it is possible to discuss the collective interactions of the components of the system. The dispersion relation of an infinite beam-plasma system is found by requiring that the coupled equations of motion of these coordinates have a simultaneous solution. For a finite plasma the interaction is discussed in the limit where the time necessary for a beam particle to traverse the plasma is short. Two types of growing plasma waves are then possible. The first type is due to the coupling of the growing beam modes to the plasma modes. The second type occurs when the frequency of the beam oscillations match the background plasma frequency and leads to a linear growth of the plasma waves.
Diffusion of Charged Particles Across a Magnetic Field in ``Short Circuiting Geometry''
Authors: Schwirzke Fred
Published: December 2004

The diffusion of plasma across a uniform magnetic field was studied in an experimental apparatus of variable length. Thus, it was possible to confirm, experimentally, the influence of the end walls upon a plasma of finite length in the direction of the field lines; this influence is called ``short circuiting effect.'' By reducing the pressure from 2 × 10−3 to 5 × 10−5 mm Hg, an instability was found, and the diffusion coefficient reached a maximum. The onset of the instability was investigated as a function of pressure, magnetic field strength, and length of the plasma column. The results are compared with the analysis of Guest and Simon about the onset of an instability (similar to that of Kadomtsev and Nedospasov for a positive column) resulting from unequal streaming of ions and electrons to the conducting end walls, a phenomenon which should happen above a critical field or below a critical background pressure.
Slip Instability
Authors: Amsden Anthony A. , Harlow Francis H.
Published: December 2004

A discussion is given concerning the effects of viscosity and large disturbance amplitude on the instability occurring at a slip interface between two parts of an incompressible fluid. In particular it is shown how an analysis by Carrier can be applied to explain the train of small vortices generated at a shearing edge, and comparisons with experimental results are given for a number of examples. In addition, the numerical method of Fromm has been applied to obtain complete solutions of the slip instability problem, and numerous results are presented to show additional comparisons with the linearized theory for viscous fluids, and to show in detail the structure of the late-stage nonlinear flow in which the vortex sheet may tend to ``roll up.''
Production of Fast Molecular Beams Using Gaseous Mixtures
Authors: Klingelhöfer R. , Lohse P.
Published: December 2004

According to Becker and Henkes, relatively fast molecular beams of heavy gases can be produced by having a mixture of the heavy gas and a light acceleration gas expand out of a nozzle and transferring the core of the nozzle flow into high vacuum. By mass spectrometric analysis of the collected beam, the degree of enrichment of the heavy gas is investigated for different argon-hydrogen mixtures and for different inlet pressures. The particle flow density of the molecular beam is obtained by measurement of the pressure head. The acceleration of argon is investigated by a time-of-flight method. For an initial mixture of 1% Ar and 99% H2, the system yields a maximum of 40% for the argon mole fraction in the beam at an inlet pressure of 2 atm. The corresponding flow density is 1.3 × 1017 Ar atoms per cm2 per sec. at a distance of 60 mm from the nozzle; the beam velocity is 2100 m/sec corresponding to a kinetic energy of the argon atoms of about 1 eV.
Collisionless Expansion of Gas Clouds in the Presence of an Ambient Gas
Authors: Bienkowski George
Published: December 2004

The collisionless expansions of spherical and cylindrical gas clouds into an ambient gas are investigated. General expressions for the higher moments are derived and evaluated. The solutions exhibit effects not apparent in previous work on collisionless expansions bounded by vacuum. Mass flow, temperature and velocity exhibit propagating maxima which decay in amplitude and diffuse with time. Time constants for the duration of the expansions are obtained as a rough criterion for possibility of shock formation. Comparisons are made with the Euler solution and a short time collisional solution obtained by numerical integration of the Boltzmann equation with a model collision term.
Runaway Electrons in an Ideal Lorentz Plasma
Authors: Kruskal Martin D. , Bernstein Ira B.
Published: December 2004

The phenomenon of electron runaway under a constant electric field is treated in the simplified model of a Lorentz gas, in which the electrons experience Coulomb collisions with infinitely massive ions only. This model permits a rigorous systematic analysis of the problem, devoid of arbitrary elements, in the limit of weak electric field. The analysis leads to a decomposition of velocity space into three regions. In the first of these, the low velocity domain, the electron distribution function is dominated by collisions and hence almost isotropic; it obeys a diffusion equation driven by the applied field. The second region, one of intermediate velocity, is characterized by quasi-steady flow in velocity space, for which the low velocity region provides the source. Lastly there is a high velocity region, fed by the intermediate region, in which the electrons run away almost freely under the action of the electric field, with only an exceedingly weak diffusion due to collisions. The problem is solved explicitly in the first and third regions and reduced to solving a single ``universal'' partial differential equation in the second region. The runaway rate, number of runaway electrons, and electric current density (average electron velocity) are obtained explicitly.
Effect of Collisions upon Plasma Ion Oscillations
Authors: Kuckes A. F.
Published: December 2004

The coupling between ion oscillations and electric currents introduced by collisional effects was studied. A growth of ion acoustic waves is found which extrapolates to the Vlasov gas value as the collision mean free path and wavelength become comparable. The damping of ion acoustic waves is calculated from the fluid equations. For a plasma confined by a strong magnetic field, convective oscillations can be excited by an electron drift along the magnetic field lines. The growth rate and frequency of these oscillations is compared to stellarator experiments.
Ion Density Measurement in a Barium Plasma by Scattering of Resonance Radiation
Authors: Hofmann Fritz W.
Published: December 2004

A method for measuring local atom or ion densities, based on the scattering of resonance line radiation, is discussed for the case of an optically thin barium plasma confined by a strong magnetic field. The anisotropy of the flux of scattered resonance radiation due to anisotropic illumination and the presence of a magnetic field is examined. Barium ion density measurements on a laboratory plasma are described. It is noteworthy that this method is capable of high spatial resolution, and that light intensity ratio measurements suffice to obtain absolute ion densities. No absolute photometric measurements are required.
Guiding Center Motion and Plasma Behavior in the Bumpy Torus
Authors: Gibson G. , Jordan W. C. , Lauer E. J. , Woods C. H.
Published: December 2004

Drift surfaces of guiding centers in the Bumpy Torus static magnetic field have been located and analyzed for various torus parameters by making use of the transverse adiabatic invariant μ = p⊥2/B and the longitudinal adiabatic invariant J = ∮ p∥ dl. In addition, the drift equations (for which μ is an invariant) have been solved numerically to investigate limitations on the application of the invariance of J. In general, J is an invariant for the drift equations under adiabatic conditions; however, some special guiding-center trajectories are presented for which the drift per longitudinal period is sufficiently large that the assumption of the invariance of J is not valid. Closed surfaces of constant U = ∮ B−1 dl have been found. These are also surfaces of constant plasma pressure under static equilibrium conditions at low β for a hydromagnetic model. The stability of the equilibrium is discussed.
Turbulence Criteria for a Circumpolar Vortex in a Rotating Gravity Field
Authors: Kao S.-K.
Published: December 2004

An analysis is made of the stability of a circumpolar vortex in a rotating gravity field. Criteria are derived for both the lateral and vertical stabilities of the vortex. It is found that, in the absence of the vertical disturbance, the critical value of the negative lateral velocity shear is smaller than that of the positive lateral velocity shear. Analysis of the vertical stability of the vortex indicates that, in a neutrally stratified fluid, the critical value of the positive velocity shear along the vertical is smaller than that of the negative velocity shear. However, in a thermally stratified fluid, such as the atmosphere, the buoyancy force generally dominates the vertical stability and, therefore, the critical value of the vertical velocity shear.
Propagation of Shock Waves in a Hydrodynamic Conical Shock Tube
Authors: Filler William S.
Published: December 2004

Hydrodynamic shock waves were generated in a conical sector shock tube (7°) driven by a ½g high explosive charge situated at its vertex. Pressure-time histories of the shock waves were obtained with piezoelectric instrumentation. The shape and decay properties of the wave as it progressed down the tube were similar to those of a spherical shock wave generated in free water by a ¼-lb sphere of TNT. The effect of the sector tube in concentrating the explosive energy within a small solid angle is defined by the expression W = Kw sin−2 (½α), where W is the effective weight of charge, w the actual weight of charge used, α the cone half angle, and K an energy loss constant (in this case 0.21). This type of shock tube greatly facilitates the study of explosion hydrodynamic shock waves and their interactions. These results parallel earlier results for a gasdynamic conical shock tube.
Viscous Hypersonic Flow Past a Slender Cone
Authors: Stewartson K.
Published: December 2004

The strong-interaction region in viscous hypersonic flow past a slender cone is considered and expressions for the pressure, shock, skin friction, and heat transfer are derived. An approximate method by which the whole interaction region can be computed is also suggested.
One- and Two-Dimensional Propagation of Alfvén Waves in Inhomogeneous Magnetic Fields
Authors: Plato Guenther
Published: December 2004

It is shown that in an infinitely soft medium where the sound speed is small against the Alfvén speed one-dimensional propagation along a field line with finite curvature is possible only if the gradient of the Alfvén speed in the direction of the principal normal vanishes on that line. However, waves spreading two-dimensionally over certain surfaces always exist. Conditions are derived that the existing waves are without dispersion.
Viscosity of the Isotopes of Hydrogen and their Intermolecular Force Potentials
Authors: Kestin J. , Nagashima A.
Published: December 2004

Measured values of the viscosity are presented for the three isotopes of hydrogen: H2, HD, and D2 at 20°C and at 30°C, all under atmospheric pressure. The ratios of the viscosity of any one pair of the above gases is obtained very accurately, the major source of error being connected with the uncertainties in the knowledge of the impurities present in the gases. On the basis of the Chapman-Enskog theory for the viscosity of gases composed of spherically-symmetrical molecules whose potentials can be represented by the product V(r) = εf(σ/r), it is concluded that all three isotopes have different intermolecular constants. However, the differences which characterize the intermolecular potentials of H2 and D2 are not likely to be large. Calculations which attempt to take into account the differences in the potentials of H2 and D2 by differences in polarizability are not confirmed by the present measurements.
Axially Symmetric Force-Free Plasmoids
Authors: Wells Daniel R.
Published: December 2004

The theory of force-free magnetic fields is applied to equilibrium configurations of an incompressible fluid with axisymmetric motions. It is demonstrated that solutions satisfying collinear force-free flow satisfy the vorticity equation for zero viscosity. Experimental measurements of the magnetic and flow fields of the plasmoids generated by a conical θ-pinch plasma gun are shown to be in agreement with the solutions to these equations.
Theory of Viscous Buckling of Multilayered Fluids Undergoing Finite Strain
Authors: Biot M. A.
Published: December 2004

The equations of fluid mechanics are applied to the problem of small perturbations upon a finite initial strain-rate of a viscous fluid. The magnitude of the viscosity is such that inertia forces are negligible. General solutions are developed for the time history of buckling of a fluid with an arbitrary number of layers of different viscosities under finite compressive deformation. The effect of gravity is taken into account. Numerical solutions are derived for the single layer. Results are compared with values obtained from the theory of elasticity and viscoelasticity. The interest of the theory lies in its application to problems of folding of geological structures.
Rayleigh-Taylor Instability for Compressible Fluids
Authors: Mitchner M. , Landshoff R. K. M.
Published: December 2004

The stability problem of an accelerating plane interface separating compressible fluids is formulated in general terms. In the limit of small wavelength disturbances, a generalized form of Taylor's value for the growth rate is obtained. For the particular case of constant acceleration and static isothermal equilibrium, the criterion for instability remains the same as for corresponding case of two incompressible fluids, but the growth rate is reduced for longer wavelengths.
Rotating Flows of von Kármán and Bödewadt
Authors: Schwiderski Ernst W. , Lugt Hans J.
Published: December 2004

The rotating flows of von Kármán and Bödewadt are re-examined. Complete sets of boundary data are defined for both problems in accordance with practical flow models. First-order approximations are defined as solutions of ordinary boundary-value problems and equivalent Volterra integral equations. The new solutions depend on three-parameter Reynolds numbers and eliminate discrepancies of the old solutions. Numerical results are displayed for various Reynolds numbers. The critical Reynolds number below which Bödewadt flows are laminar, attached, and nonoscillating is computed.
Gravity Waves due to a Point Disturbance in a Plane Free Surface Flow of Stratified Fluids
Authors: Mei C. C. , Wu T. Yao-tsu
Published: December 2004

The fundamental solution of the gravity waves due to a two-dimensional point singularity submerged in a steady free-surface flow of a stratified fluid is investigated. A linearized theory is formulated by using Love's equations. The effect of density stratification ρ0(y) and the gravity effect are characterized by two flow parameters σ = −(dρ0/dy)/ρ0 and λ = gL/U2, where λ−½ may be regarded as the internal Froude number if L assumes a characteristic value of σ−1. Two special cases of σ and λ are treated in this paper. In the first case of constant σ (and arbitrary λ) an exact mathematical analysis is carried out. It is shown that the flow is subcritical or supercritical according as λ> or <½, in analogy to the corresponding states of channel flows. In addition to a potential surface wave, which exists only for λ>½, there arises an internal wave which is attenuated at large distances for λ>¼ and decays exponentially for λ<¼. In the second example an asymptotic theory for large λ is developed while σ(y) may assume the profile roughly resembling the actual situation in an ocean where a pronounced maximum called a seasonal thermocline occurs. Internal waves are now propagated to the downstream infinity in a manner analogous to the channel propagation of sound in an inhomogeneous medium.
Approximations for Steady-State Isotropic Turbulence
Authors: Kraichnan Robert H.
Published: December 2004

The direct-interaction approximation for turbulence maintained by stationary, isotropic, random stirring forces is formulated in the wavenumber-frequency domain. Further, simplifying approximations are made. The final equations involve the wavenumber energy-spectrum, a characteristic correlation frequency for each wavenumber, and a characteristic response frequency for each wavenumber. A relation is exhibited between the simplified equations and a Fokker-Planck type approximation recently proposed by Edwards.
Some Statistical Properties of the Pressure Field Radiated by a Turbulent Boundary Layer
Authors: Laufer John
Published: December 2004

The radiation field generated by a supersonic turbulent boundary layer is examined. A short description of the experimental technique for measuring the pressure fluctuations is given. One finds that for a given free-stream Mach number the fluctuations scale with the wall shearing stress τw, the nondimensional radiation intensity p′2¯/τw2 increases with Mach number and is two orders of magnitude smaller than the intensity measured on the wall. From the measurements of some statistical properties such as space-time correlation and energy spectrum, one concludes that the streamwise propagation of the radiated pressure is different from that of the wall pressure at lower Mach numbers, and that the radiated field contains relatively much more energy in the low-wavenumber region than does the near field. Some attempt is made to explain these results.
Experiments on Magnetohydrodynamic Shock Waves
Authors: Vlases George C.
Published: December 2004

Differences in the performance of an ``inverse pinch'' electromagnetic shock tube with and without a high degree of preionization are discussed. Only collision-controlled magnetohydrodynamic shock waves are considered. It is found that the flow in the absence of preionization may differ substantially from that when the gas is preheated. Experiments carried out for both cases show qualitative agreement with the theory.
Flux Transport by a Shock Plasma
Authors: Barach J. P. , Lee J. H.
Published: December 2004

A magnetic field of about 50 G is observed to be transported downstream from a sharply localized dc field up to 34 kG interacting transversely with a shock produced plasma flow of velocity up to 2 cm/μsec. The transported flux is found to be antiparallel to the imposed field and to decay exponentially in time as it moves downstream. The decay of the flux gives an estimate of the gas conductivity. The amount of trapped flux is in agreement with an approximate theory in which the decay of the initial trapped flux, the magnetic deceleration of the flow, and the reduction of the conductivity by the magnetic field are considered. The initial trapped flux is found to be proportional to the reduced conductivity and the flow velocity, as expected. However an increase in the imposed field beyond 17 000 G reduces the trapping effect due to reductions in both the conductivity and the exit flow velocity of the plasma. The e-folding time for field decay is roughly 3.5 μsec and does not increase with increasing shock speed.
Thermal Diffusion in Mixtures Containing Carbon Dioxide
Authors: Cozens J. R. , Grew K. E.
Published: December 2004

Measurements are reported of the thermal diffusion factor for mixtures of carbon dioxide with argon, with krypton, and with xenon. For the first, the thermal diffusion factor passes through a positive minimum value, and Waldmann's conclusion, from his study of the diffusion thermo-effect, that the thermal diffusion factor increases with decreasing temperature in the range 400–200°K is confirmed. For the other mixtures, the thermal diffusion factor becomes negative as the temperature decreases, and there is no indication of a minimum value in the accessible temperature range.
The Turbulent Boundary Layer in a Compressible Fluid
Authors: Coles Donald
Published: December 2004

A transformation is derived from first principles to reduce the boundary-layer equations for a general compressible two-dimensional flow to incompressible form. For the case of boundary-layer flow of a Newtonian fluid past a smooth wall, but with no other restrictions, it is shown that the combination (ρ∞μ∞/ρwμw) CfReθ is an invariant of the transformation. This result is called the law of corresponding stations. In order to apply the transformation to the problem of the turbulent boundary layer on a smooth wall, it is assumed that the sublayer Reynolds number is unaffected by compressibility or heat transfer provided the density and viscosity are evaluated at a mean sublayer temperature defined by the transformation. Explicit formulas are obtained for the effect of Mach number and heat transfer on surface friction when the fluid is a perfect gas, the pressure is constant, and the stagnation temperature is constant or linear in the velocity. An appendix contains a brief critical discussion of the mean-temperature hypothesis, the laminar-film hypothesis, and other analytical ideas related to the idea of a transformation.
Resonance Oscillations in a Hot Nonuniform Plasma
Authors: Parker J. V. , Nickel J. C. , Gould R. W.
Published: December 2004

A quantitative theory of resonance oscillations, such as observed by Dattner and others, is given. The first two moments of the collisionless Boltzmann equation assuming a scalar pressure are used in conjunction with a physically reasonable radial electron density profile to describe the oscillations of a hot nonuniform plasma cylinder. These equations coupled with Maxwell's equations assuming a scalar potential are solved numerically to yield the frequency spectrum of the plasma wave resonances. It is found that the frequency spectrum depends on the parameter rw2/〈λd2〉 where rw is the radius of the plasma column and 〈λd2〉 is the mean square Debye length of the electron plasma. New experimental observations of dipole and quadrupole spectra for two plasma columns of differing radii are reported and the results of these observations are in good agreement with the theory. The physical mechanism of the resonances is described.
Experimental Demonstration of Hydromagnetic Waves in an Ionized Gas
Authors: Sawyer G. A. , Scott P. L. , Stratton T. F.
Published: December 2004

A regular hydromagnetic oscillation was excited in a linear discharge tube with metal walls. An externally applied axial magnetic field and discharge currents less than 104 amperes were essential to the production of the oscillation. Complete spatial current distributions derived from measurements of the radial and time dependence of the three components of magnetic field showed a helical notch (screw thread) of reduced current density which rotated with uniform angular velocity. The pitch and apparent rotational frequency of the oscillation depended on the gas density, discharge current, and applied axial magnetic field; the right- or left-handedness and rotational sense depended on the relative orientation of the applied axial magnetic field and the self field of the discharge current. The helical regularity could be described as a superposition of hydromagnetic waves traveling in the axial and circumferential directions.
Kinetic Models and the Linearized Boltzmann Equation
Authors: Gross Eugene P. , Jackson E. Atlee
Published: December 2004

Attention is directed to some unsatisfactory features of kinetic theory treatments of problems for which the linearized Boltzmann equation is applicable. The main defects are in the region where nearly free molecular flow conditions prevail. They can be overcome when the problems are treated by simplified kinetic models. In this paper relations between the linearized Boltzmann equation and some models are established. The method is based on a comparison of the eigenvalue spectra of the respective collision operators. Particular attention is paid to inverse fifth molecules. This allows evaluation of the limitations of a given model and shows how more accurate models can be constructed. It is shown how one may overcome the chief shortcomings of approximate solutions of the linearized Boltzmann equation.
Studies of Atomic Recombination of Nitrogen, Hydrogen, and Oxygen by Paramagnetic Resonance
Authors: Marshall Thomas C.
Published: December 2004

The three-body volume recombination coefficient for neutral atoms A of nitrogen, oxygen, and hydrogen in their parent molecular gases M has been measured over a pressure range of one to ten millimeters at 300°K. The observations fit a reaction of the form A+A+[M]→ lim k1(A)A2*+[M],where k1(A), the rate constant, is found to be, respectively, k1(N) = 1.5 × 10−32 cm6/sec, k1(O) = 0.45 × 10−32 cm6/sec, and k1(H) = 6.5 × 10−32 cm6/sec. These determinations have an experimental fluctuation of ± 20%. Observations of the electron spin resonance (ESR) signal from the ground state of the atoms allowed direct determination of the atomic density. Measurements were made in a stream of flowing gas which carried the atoms through the ESR detection cavity. An atomic concentration of 1014 − 1016 cm−3 could be obtained in a CW electrodeless discharge. Surface recombination was inhibited by coating wall surfaces with a thin film of concentrated H2SO4. The work also includes some preliminary measurements of surface atomic recombination coefficients.
Approximate Theory of Viscosity and Thermal Conductivity in Dense Polyatomic Fluids
Authors: Sather Norman F. , Dahler John S.
Published: December 2004

Formulas are derived for the collisional contributions to the pressure tensor and heat-flux vector in fluids composed of molecules which interact with impulsive forces. An approximation scheme is then employed to obtain ``zero-order'' estimates of the viscosity and thermal conductivity coefficients for various molecular models. The models considered are rough spherical and rigid convex molecular ``cores'' surrounded by potential staircases. The viscosity and thermal conductivity coefficients determined for the special case of cores surrounded by a square-well attractive potential are found to vary approximately as T1/2 eA/T at ordinary liquid temperatures. Calculations are also presented of the variations of the transport coefficients with molecular shape and eccentricity parameters.
Compressibility and Intermolecular Forces in Gases. II. Nitrous Oxide
Authors: Schamp H. W. , Mason E. A. , Su K.
Published: December 2004

The compressibility of nitrous oxide (N2O) has been measured with high precision from 0° to 150°C and over a density range of about 18 to 180 amagat. The agreement with results of others using somewhat different experimental techniques is good. The virial coefficients are calculated, and the intermolecular potential of nitrous oxide calculated from the second virial coefficient for several forms of force laws, both spherical and nonspherical. A comparison with the physically similar molecule carbon dioxide is made.
Scattering of Electromagnetic Waves by a Nonequilibrium Plasma
Authors: Rosenbluth M. N. , Rostoker N.
Published: December 2004

Incoherent scattering is determined by the spectral density of electron-density fluctuations. This quantity has previously been calculated for a plasma in thermal equilibrium. We have extended the theory to include spatially homogeneous nonequilibrium states of a hot plasma. An elementary derivation of the previous results and the new results is given in terms of dressed test particles. Numerical calculations have been carried out for a plasma with hot electrons and cold ions, and for a plasma in which the electrons have a net drift relative to the ions.
Equilibrium Solutions of a Plane Electron Beam in a Plasma
Authors: Lundgren Thomas S. , Chang Chieh-Chien
Published: December 2004

Equilibrium solutions of an electron beam injected into a plasma are considered. This is a preliminary step in studying the stability of the so-called ``E layer'' of the Astron thermonuclear reactor. The model consists of a plane sheet of streaming electrons in a homogeneous plasma. Equilibrium solutions are obtained from the collisionless Boltzmann equations for three fluids: one of stream electrons, another of plasma electrons, and a third of plasma ions. Two important cases are treated in this manner: cold plasma and cold beam. The distribution of beam electrons, plasma ions, and plasma electrons are disclosed.
Hydromagnetic Stability of Toroidal Equilibria with an Externally Imposed Rotational Transform
Authors: Johnson John L. , Greene John M. , Weimer Katherine E.
Published: December 2004

A simple ``single-term'' stability criterion is obtained for hydromagnetic equilibria with multipolar fields. It replaces an earlier criterion in which it is necessary to evaluate the ratio of two infinite determinants. It corresponds to the criterion recently developed for arbitrary equilibria by Mercier, Bineau, and ourselves but is tailored to a specific geometry.
Precursor Effects and Electron Diffusion from a Shock Front
Authors: Wetzel Lewis
Published: December 2004

Recent experiments have disclosed electrical effects well ahead of an advancing shock front. Certain of these effects have been attributed to the diffusion of electrons through the shock front from the ionized region behind it. The diffusion hypothesis is examined in terms of a simple heuristic model, in which the diffusion is assumed to take place from a plane electron source moving with the shock velocity. According to this model, there is no true electron ``front,'' as has been suggested by some experiments with ionizing shocks. However, a transient in the electron distribution may give rise to a virtual front in certain experimental situations. Under reasonable assumptions, the existing observations of precursor fronts by Weymann are found to be consistent with the predictions of the model.
Axisymmetric Shocks in the Newtonian Limit for Nonrigid Boundaries
Authors: Zadoff Leon N.
Published: December 2004

The natural generalization of the snowplow equation in two-dimensional axisymmetric or Cartesian geometries is a Newtonian approximation in which the possibility of surface deformation is admitted. Such a general Newtonian approximation has been derived from the Lagrangian fluid equations, using an ideal-gas model in the limit of strong shock and high density ratio across the shock front. In one dimension the result reduces properly to the snowplow equation. In two dimensions, if the surface is constrained and the motion steady, the result consists of the ``Newtonian plus Busemann'' terms. The general result contains in addition a Coriolis term. The general theory is applied to the evaluation of the pressure on the surface of a conical plasma whose vertex angle is decreasing uniformly with time. Although the results are derived for an ideal-gas model, they are applicable whenever dissociation and ionization are taking place behind a strong shock front.
Experimental Investigation of the Equilibrium Interface Technique
Authors: Copper John A.
Published: December 2004

The equilibrium-interface technique has been suggested as a possible shock-tunnel driver method. If this technique is workable, reservoir enthalpy levels can be increased substantially over those obtainable with the tailored-interface technique without any physical modification of the shock tube. In order to determine the feasibility of the equilibrium-interface technique as a shock-tunnel driver method, experiments were performed in a shock tube, utilizing a cold helium driver over the shock Mach number range 3.29 to 7.26.

Pressure histories were measured at the end of the driven tube; this pressure was found to reach an equilibrium condition for the complete shock Mach number range investigated. From the pressure histories the equilibrium pressure, time to reach equilibrium, and test time were determined. Measured equilibrium pressures were compared with those predicted from the measured shock Mach number. From the measured equilibrium pressure the equilibrium enthalpy level was computed. The maximum equilibrium enthalpy was more than six times the reservoir enthalpy produced using the tailored-interface technique.
Equilibrium and Stability of Helical Hydromagnetic Systems
Authors: Greene John M. , Johnson John L. , Kruskal Martin D. , Wilets Lawrence
Published: December 2004

A formalism for representing helically invariant hydromagnetic systems is introduced. Such systems are the most general two-dimensional configurations in three-dimensional space, since they include translation-invariant and rotation-invariant configurations as special cases. Expressions for the magnetic field and, when the system is in equilibrium, the current are given in terms of an appropriate nonorthogonal coordinate system. An energy integral is given which forms the basis of a numerical relaxation procedure for obtaining equilibria. The relationship between this formalism and that in which the equilibrium problem is reduced to solving a partial differential equation for the stream function is established. The necessary and sufficient condition for the stability of helically invariant systems with respect to localized displacements is obtained.
One-Dimensional Plasma Model at Thermodynamic Equilibrium
Authors: Eldridge O. C. , Feix M.
Published: December 2004

The one-dimensional motion of a number of plane charged sheets is followed with an electronic computer. The energy in the electric field is computed for cases where the number of particles in a Debye length vary from 1/4 to 10. These results agree with an exact theory given by Lenard. The Fourier components of the field energy and of the square of the current density are measured by averaging over a long time interval. These results are compared with values predicted by the linearized Vlasov equation.
Radio Emission by Electrons in the Fine-Structure Electric Fields of Shock Waves
Authors: Tidman D. A.
Published: December 2004

The structure of shock waves in fully ionized hydrogen in the absence of a magnetic field has been investigated by Greenberg and Trève using the Mott-Smith distribution for the protons and a local Maxwellian for the electrons. They find that large charge-separation effects occur inside the shock due to the electron-proton mass difference, thus giving rise to strong stationary electric-field oscillations in the shock transition. This behavior is typical of other theories of plasma shock structure. The radio noise emitted by electrons in the plasma accelerated in these electric fields is now calculated. In traversing the electric oscillations inside the shock, those electrons with a few times the thermal energy radiate like an assembly of oscillators at frequencies capable of propagating ahead of the shock. Although the particular shock-wave model of Greenberg and Trève has been adopted for the purposes of the numerical discussion, the parameters of the radiation calculation are readily adjusted for possible changes in the shock-wave model which more detailed treatments of shock structure may bring. The application of this process to Type II solar radio bursts is discussed. Assuming that such shock waves are produced by a solar flare expanding into the corona, a sufficiently high intensity of radio emission is found to provide an alternate possible interpretation for this source of solar noise.
Nonthermal Impurity Radiation from a Spherical Plasma
Authors: Cuperman S. , Engelmann F. , Oxenius J.
Published: December 2004

The steady-state energy loss of a homogeneous and isothermal spherical plasma due to de-excitation radiation of impurity ions, assumed to have two energy levels only, is investigated without making the assumption that this radiation is thermal. A method developed by R. N. Thomas is adopted which consists in solving simultaneously the equation of radiative transfer and the equations for the rate of change of the occupation numbers of the energy levels. Analytical methods for calculating the source function obtained in this way are indicated.
Particle Behavior in a Static, Asymmetric, Magnetic Mirror Geometry
Authors: Gibson G. , Jordan W. C. , Lauer E. J.
Published: December 2004

The motion of a charged particle in an asymmetric mirror geometry has been studied. The asymmetric geometry for these studies is constructed by giving equal but opposite tilts to the two identical, coaxial coils of a symmetric geometry in which the coils are spaced about one coil mean diameter apart. (This is equivalent to one section of a ``bumpy torus.'') A model for describing a particle's motion in this geometry is presented. It is based on the guiding-center drift surfaces determined theoretically from the longitudinal and transverse adiabatic invariants and the invariance of the magnitude of the momentum. The results of the experimental investigations are successfully interpreted in terms of the model.
Theory of Electrolytes
Authors: Cohn Jack
Published: December 2004

A new approach is devised for the study of thermodynamic systems composed of particles interacting with Coulomb forces, specifically applied to solutions of strong electrolytes (composed of ions of equal size). A method is constructed for the evaluation of the average number density as a function of position about an ion expressed as a series of terms dependent on the average potential about the ion. The problem is formulated in such a manner that averages of quantities are found by the method of steepest descents. The electrolyte equation is found in first approximation to be similar to the nonlinearized Debye-Hückel equation, containing, however, terms referring to the ion size. When the ionic fractional volume is much less than one this equation becomes the nonlinearized Debye-Hückel equation. In the limit of small concentrations it is also shown that the equation governing the electrolyte is precisely the nonlinearized Debye-Hückel equation. The electrolyte equation is briefly discussed in higher-order approximations.
Condensed Presentation of Transport Coefficients in a Fully Ionized Plasma
Authors: Shkarofsky I. P. , Bernstein Ira B. , Robinson B. B.
Published: December 2004

A presentation of transport coefficients in a fully ionized plasma in terms of effective collision, gyration, and oscillation frequencies is given. It has the virtue of reducing the task of presenting the data to the tabulation of certain dimensionless functions of restricted variation. Moreover the quantities involved are directly related to the reciprocals of the coefficients usually considered, for instance to the resistivity rather than the conductivity.
Analysis of the Transition Region between a Uniform Plasma and its Confining Magnetic Field. II
Authors: Hurley James
Published: December 2004

The case of one-dimensional geometry for the transition region separating a uniform plasma from its confining magnetic field is considered. The magnetic-field profile within the boundary layer is determined by the current distribution, i.e., by the paths of the ions and electrons. The paths of these particles, on the other hand, are determined by the fields in which they move. An exact, self-consistent solution of Maxwell's equations and the equations of motion of the particles is obtained. A detailed analysis is made for a hydrogen plasma. These results are then compared with those of a plasma whose positive constituent is the proton and whose negative constituent has a mass which approaches zero and a speed which approaches infinity in such a way that the energy remains finite. The transition layer thickness for these two plasmas agree to one part in 106. It is shown that this latter case is equivalent to treating the electrons of the hydrogen plasma in the guiding-center approximation.
Stability of an Electrostatically Supported Fluid Column
Authors: Reynolds John M.
Published: December 2004

An analytical and experimental study has been made of the cylindrical interface between two dielectric liquids under the influence of electrostrictive forces and surface tension. The analysis indicates that, for ``high''-frequency applied fields such an interface can be stable. For stability, the applied voltage must be great enough to suppress surface tension effects and lower than some analytically determined critical value. For voltage greater than this critical value, experiments indicate that the interface is deformed in an unusual manner.
Hypersonic Low Density Wakes
Authors: Chuan Raymond L. , Yang H. T.
Published: December 2004

Under conditions of high speed and gas rarefaction the character of the wake behind a body changes significantly from its behavior at normal densities. Experimental studies at M ≃ 6 and 8 with spheres and cylinders have clearly established the transition from the shock-expansion-neck-recompression type of wake to a completely merged type of flow field. At the extremely low-density end of the transition the wake structure shows qualitative agreement with that predicted by a free-molecule theory based on the two-stream, line-of-sight principle.
Spectral Study of the Luminosity Produced during Coalescence of Oppositely Charged Falling Water Drops
Authors: Miller A. H. , Shelden C. E. , Atkinson W. R.
Published: December 2004

An experimental study was made of the luminosity that accompanies the coalescence of oppositely charged falling water drops in order to establish which of several possible mechanisms was responsible for the luminosity. Spectrograms which show excitation of the N2 2P and N2+ 1N systems when the drops fall through air, and which fail to show these systems when the drops fall through CO2, establish that for the range of parameters studied, dielectric breakdown of the gas through which the drops fall is the process responsible for the luminosity. Oscillographic studies showed that the production of luminosity and the transfer of charge occurred simultaneously and lasted less than 14 nsec. These observations, showing the importance of dielectric breakdown in effecting charge transfer, contrast with much that appears in the literature that stresses the importance of the bulk dielectric relaxation time and of surface tension as parameters that govern the rate at which charge is lost by water surfaces under slightly different circumstances. Typical conditions resulting in luminosity of the type studied are: drops radius ∼500 μ, drop charge ∼50 × 10−12 C, relative approach velocity of main body of drops ∼10 cm/sec, and bulk dielectric relaxation time for water of the quality used 10−5 sec.
Transition Flow through Short Circular Tubes
Authors: Sreekanth A. K.
Published: December 2004

The mass flow of nitrogen gas through short circular tubes was measured in the transition flow regime with the length-to-diameter ratios varied between 0.005 and 1 and with pressure ratios across the tubes varied between 1 and 20. The range of Knudsen numbers (ratio of upstream mean free path to the diameter of the tube) covered was between 0.1 to 1.7. Comparisons are made of the measurements with existing theories, and a semiempirical equation is developed to correlate the measured data at all of the pressure ratios, Knudsen numbers, and length-to-diameter ratios covered in the present study.