摘要:

The radiation characteristics of a flanged parallel‐plate waveguide in an anisotropic plasma medium are treated as a boundary value problem. Numerical results are presented on the effect of the anisotropic medium on the radiation pattern, the reflection coefficient, and the input impedance for the TEM‐ and TM01‐wave incidence.

ISSN:0021-8979    

DOI:10.1063/1.1663620

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

An electron‐beam probe has been developed to measure the potential profile of a plasma within a spherical grid structure which was designed to trap charged particles. The potential was obtained from observed deflections of a collimated beam of electrons incident upon the device at selected impact parameters. The beam consisted of conversion electrons of 62.2 and 84.2 keV from a Cd109source. Deflections of the beam through the plasma were measured relative to the beam trajectory without voltage applied to the grids. A movable detector allowed angular resolution to within 0.08 deg for maximum deflections of 7 deg. The inversion of the nonlinear singular integral relating potential and deflection is accomplished in an iterative manner with appropriate series expansions about the singular points. Simulations using postulated potential profiles show this procedure to give accuracy typically better than 4% with 20 deflection samples. Beam deflection measurements in spherical electrostatic systems without plasma show this probe technique to be very accurate. For a variety of experimentally controlled plasma parameters, no measurable departures from electrostatic potential profiles were observed.

ISSN:0021-8979    

DOI:10.1063/1.1663621

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A theoretical model is developed to describe the behavior of an ion‐injection electrostatic confinement device. It is assumed that there is a shallow potential well in the center. Distribution functions, which are consistent with atomic processes occurring and with mechanisms leading to particle angular momentum, are obtained for ions and electrons. Using these distribution functions, Poisson's equation is solved to obtain potential and density profiles. By varying the experimental parameters, the conditions needed to go from a shallow potential well to a deep potential well are studied. The most important problems are found to be nonspherical focusing through grid construction asymmetry, and neutralization by electrons. Deeper wells are produced by increasing ion perveance, improving spherical symmetry, and reducing pressure.

ISSN:0021-8979    

DOI:10.1063/1.1663622

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Analytical results have been derived for the lossless infinite parallel‐plane waveguide inhomogeneously loaded with a ferrite‐dielectric composite medium. It is found that the existing mode is a hybrid mode composed of all six field components. The magnetic property of ferrite in this composite medium is masked by the presence of a dielectric. It has been shown that this study represents a good approximation for the complicated microstrip transmission lines fabricated out of this composite medium.

ISSN:0021-8979    

DOI:10.1063/1.1663623

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The interaction of an electromagnetic wave at a planar interface between a dielectric and a moving magnetized ferrite medium has been considered for arbitrary angles of incidence. The ambient magnetic field has been assumed normal to both the plane of incidence and the direction of motion of the ferrite medium. The modified form of Snell's law of refraction is derived and the possibility for total reflection of the incident wave is discussed. The expressions for the phase and the group velocities, the equivalent refractive indices of the moving medium, and the reflection and the transmission coefficients for both an incidentEwave and an incidentHwave have been obtained. It is found that two modified Brewster angles can exist for the case of an incidentHwave and that, unlike the case of an incidentEwave, the various reflection and transmission properties for an incidentHwave are independent of the ferrite anisotropy. Numerical results on the angles of refraction, critical angles for total reflection, and power transfer coefficients for incidentEandHwaves are presented for several values of the translational velocity of the ferrite medium, the ambient magnetic field strength, and the saturation magnetization. It is revealed that substantial changes in the reflection and propagation characteristics appear only for velocities within a factor of 5 of the velocity of light.

ISSN:0021-8979    

DOI:10.1063/1.1663624

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Based on experimental shock data of Al'tschuler, Anderson, and Kormer, an equation of state from Zel'dovich is used to estimate thermodynamic characteristics of a porous aluminum target, after impact by iron or aluminum projectiles, in the impact velocity range ∼8–20 km s−1, which produces shock pressures in the range 0.4–8Mbar. The initial target distention,m=&rgr;0/&rgr;00, is varied from 1 to 3. It is found that projectile and target pressures and the projectile thermal energy are monotonically decreasing functions ofm. The thermal energyE′retained in the relaxed target is a monotonically increasing function ofm. The electronic fraction of thermal pressure ranges from a few percent for a nonporous target at 8 km s−1up to 20% at 20 km s−1andm=3. Within the ranges of target density, &rgr;0i, and target distention,m, considered in this study, and in the impact velocity rangeVi=8–16 km s−1, the relative effectiveness of these parameters in producing target heatE′(erg/g) can be roughly characterized by the relationE′∝∼&rgr;0i0.47 m1.49 Vi2.13. The minimum velocity that will produce significant target vaporization in aluminum‐aluminum impact decreases from 18.4 to 7.9 km s−1asmis changed from 1 to 3, whereas that for iron‐aluminum impact drops from 14.0 to 7.4 km s−1.

ISSN:0021-8979    

DOI:10.1063/1.1663625

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Permeation, diffusion, and solubility of three gases (helium, deuterium, and neon) were measured in vitreous boric oxide. Results indicate that these parameters are especially sensitive to the thermal history of the glass. If experimental times are comparable to structural relaxation times, anomalous results may be obtained.

ISSN:0021-8979    

DOI:10.1063/1.1663626

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Methods of applying laser interferometry to measure particle velocity history at the interface between a shocked specimen and a transparent window material are discussed. Particular emphasis is given to diffusely reflecting interface surfaces, to shock‐induced light polarization shifts which can occur in the window material, and to a transient loss of fringe contrast which occurs whenever the reflecting surface velocity is spattially nonuniform. It is shown that the loss of finge contrast can be used to provide time‐resolved measurements of the spatial variations in particle velocity.

ISSN:0021-8979    

DOI:10.1063/1.1663627

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

In this paper, we present a method of analysis by which the Maxwellianized electron cascade equations are coupled to the fluid‐mechanics conservation equations for the purpose of investigating the effect of a shock‐induced flow field on breakdown. A particular example of breakdown initiated behind a previously existing blast wave in argon is investigated. It is shown that the breakdown process may be hindered by the rapid hydrodynamic cooling due to geometrical expansion of the mass element under consideration.

ISSN:0021-8979    

DOI:10.1063/1.1663628

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Monte Carlo calculations have been performed to determine the spatial distribution of energy dissipated in a 4000‐Å‐thick film of polymethyl methacrylate (PMMA), due to an incident electron beam. The calculations were performed for 5‐, 10‐, and 20‐keV electrons on a silicon substrate and also for 20‐keV electrons on copper and gold substrates. The effect of varying the beam diameter from 250 to 3000 Å was evaluated. A detailed comparison is made between the Monte Carlo results and analytic models used to predict the energy dissipated. The plural scattering model is found to be in good agreement with the Monte Carlo calculations, whereas discrepancies are found with the multiple scattering model. The large‐angle backscattering model is found to have several important limitations. Energy dissipation is calculated for the exposure of dots, isolated lines, and arrays of closely spaced lines—geometries that are of significance in electron beam lithography.

ISSN:0021-8979    

DOI:10.1063/1.1663629

出版商:AIP    

年代:1974

数据来源: AIP