摘要:

Much recent work on thermodynamic energy conversion efficiencies is here presentedabinitioand from a unified point of view. New considerations are offered and previous work is analyzed in light of the unified presentation. The energy conversion processes discussed include, for example, the conversion into light in a laser or light-emitting diode and the direct or indirect conversion of solar radiation into work. The thermodynamic limiting efficiencies of these various processes are derived by applying simple balance equations to a generalized energy convertor. The new work includes the distinction between temperatures based on fluxes and temperatures ∂U/∂Sbased on standard thermodynamics, etc., and their application in the correct context. Also the use of standard entropy formulas is justified without relying on thermodynamic equilibrium and the results are then applied to nonequilibrium situations in energy conversion.

ISSN:0021-8979    

DOI:10.1063/1.328187

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Total energy distribution (TED) curves of ions emitted from a gallium liquid metal ion source exhibit full width at half maximum (FWHM) value that increases from 5 to 30 eV with an increasing total current of 1–30 &mgr;A. An energy deficit of 4 eV at threshold supports a field evaporation mechanism of ion formation. The lowest TED FWHM value of 5 eV corresponds to a source angular brightness of 20 &mgr;A/sr.

ISSN:0021-8979    

DOI:10.1063/1.328197

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The deflection and increased divergence of a neutral beam due to a magnetic field perpendicular to the gas‐cell neutralizer has been measured. The hydrogen neutral beam energy was 5.0 keV. The observed neutral beam deflection and divergence were in good agreement with results obtained from solutions of a coupled set of kinetic equations for the transverse velocity distribution functions for energetic ions and neutrals in the neutralizer volume.

ISSN:0021-8979    

DOI:10.1063/1.328198

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

In the measurement of HO concentrations by laser‐excited fluorescence, expansion of the sampled air offers a way to reduce fluorescent and photolytic interference by other species. The decrease in [HO] upon expansion is balanced by an increase in HO fluorescence yield over a wide range of pressures. Background air fluorescence is reduced if the responsible species have fluorescence yields higher than those of HO. Preliminary experiments indicate that most of the fluorescence observed in laboratory air is due to such species. Upon expansion, the suppression of fluorescent interference can be no greater than the reduction in pressure, whereas the suppression of photolytic interference can be no less.

ISSN:0021-8979    

DOI:10.1063/1.328199

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

An experimental observed fact in scattering of electromagnetic waves by dense distribution of discrete scatterers is that the assumption of independent scattering leads to overestimation of scattering effects. To account for this phenomenon in the present paper, the method of coherent potential is applied to the study of multiple scattering of electromagnetic waves by random distribution of discrete scatterers. Comparisons are made with results obtained by using the effective field approximation and the quasicrystalline approximation. Numerical results of the effective dielectric constant and the scattering attenuation rates, as a function of the fractional volume occupied by the scatterers, are illustrated using parameters frequently encountered in the microwave remote sensing of snow and soil moisture. It is shown that the coherent potential method as applied to quasicrystalline approximation is superior to the other approximations in accounting for the overestimation factor.

ISSN:0021-8979    

DOI:10.1063/1.328200

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We will in the present paper derive a general three‐dimensional formalism for electromagnetic scattering from buried inhomogeneities. We will exploit the transition matrix formalism, originally given by Waterman, to electromagnetic scattering in the presence of an infinite surface and a buried bounded inhomogeneity. The analysis explicitly assumes that the sources are located above the ground, but this restriction can easily be relaxed and a parallel derivation can be made for sources located in the ground or inside the buried obstacle. No explicit symmetry assumptions are made for the bounded inhomogeneity or the interface between the halfspaces, except that the interface be bounded by two parallel planes. The scattered field above the ground is calculated in terms of an expansion where the expansion coefficients are solutions of a matrix equation. The expression for the scattered field is separated into a directly scattered term, as if no scatterers were present, and the so called anomalous field, reflecting the presence of the inhomogeneity. We give some numerical examples for a flat interface and an inhomogeneity consisting of one or two buried spheres or a perfectly conducting spheroid.

ISSN:0021-8979    

DOI:10.1063/1.328201

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The transfer of energy between electrons and an electromagnetic field via nonlinear radiation pressure effects is discussed. It is shown that a net transfer of energy from electrons to the interacting field is possible if the field intensity changes with time while its relative spatial distribution is maintained. Ignoring the space‐charge effects an expression is derived for the gain of an amplifying system, based on this concept.

ISSN:0021-8979    

DOI:10.1063/1.328202

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A number of important aspects of the production of annular electron beams by foilless diodes are examined, both theoretically and experimentally. The theories of Ott, Antonsen, and Lovelace (OAL) and Chen and Lovelace (CL) are compared, and the CL theory is extended to include the effect of an axial gap in an approximate fashion. For the case of finite magnetic field strengths, Larmor orbits are examined and radial oscillations of the beam profile are predicted from a beam envelope analysis. Experimental results obtained with both low‐ and high‐impedance sources have been compared with the theory, and based on such studies, the design and construction of an intense hollow beam generator are described. Experimental results obtained with the new diode compare favorably with both the analytic theory and the results of numerical simulations. The device currently produces 2‐MeV electrons at beam currents of 65–70 kA.

ISSN:0021-8979    

DOI:10.1063/1.328203

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A toroidal yoke for an electron‐beam lithography system is compensated for deflection placement errors that normally result from eddy currents generated within the coil windings, as well as driver current settling time and inductive or capacitive coupling within the yoke. Compensation is achieved through the addition of passive conductive material along the outer periphery of the yoke. Both theoretical and experimental results are presented. Agreement is shown to be very good in a specific E‐beam lithography system.

ISSN:0021-8979    

DOI:10.1063/1.328204

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Four general functions are presented which determine self‐consistently the potential minimum position and depth in planar space‐charge‐limited crossed‐field electron guns.

ISSN:0021-8979    

DOI:10.1063/1.328188

出版商:AIP    

年代:1980

数据来源: AIP