摘要:

A general expression for the time‐independent transmission coefficient of a double barrier is derived. Unity double barrier transmission is found possible for all energy levels above or below the double barrier potential energy levels. The conditions under which unity transmission occurs are obtained and discussed.Application of the general theory to a piecewise constant potential model indicates that double barrier effects in thin film devices may be most noticeable for a majority of current carriers at energy levels near the maximum potential energy level of the double barrier. The small width of the transmission resonances in the examples considered indicates that double barrier effects would probably not be detected, and if they were detected would probably not be interpreted as such, unless investigation of this particular phenomenon was an objective of the research being conducted.

ISSN:0021-8979    

DOI:10.1063/1.1714294

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A new technique for anomalous skin‐effect studies is described. At low temperatures (∼4°K) it measures both surface reactance and surface resistance over a wide band of frequencies extending to below 100 cps. For the transition region from classical to anomalous behavior, experimental results on high‐purity copper show excellent agreement with theory, assuming diffuse scattering of electrons at the metallic surface. A new numerical table of theoretical values is included.

ISSN:0021-8979    

DOI:10.1063/1.1714295

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A technique is developed for treating each of the waves generated by an arbitrary current source in a partly ionized gas with no steady magnetic field. Starting with Maxwell's equations and three sets of coupled hydrodynamic equations (for the electrons, ions, and neutral molecules), it is shown that one can obtain a separate inhomogeneous wave equation for each type of wave in the plasma, with the source term for the transverse and longitudinal waves dependent, respectively, on the curl and divergence of the current source.

ISSN:0021-8979    

DOI:10.1063/1.1714296

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

It is shown that an electron avalanche travels with a velocityv_ that is dependent upon Townsend's ionization coefficient &agr; and the diffusion coefficient for the electronsD_. Specifically,v_=&mgr;_E+&agr;D_, where &mgr;_ is the electron mobility, and the applied fieldEis assumed constant. Numerical machine calculations have been made to study the effect of diffusion and secondary ionization at the cathode in pulsed Townsend discharges. Illustrative examples show the utility of these calculations in measurements of the Townsend ionization coefficients as well as electron and ion mobilities. It is shown that the diffusion‐broadened avalanche for high values of &agr;d(dis the gap distance) requires more than the electron transit timed/v_ to make a gap crossing.

ISSN:0021-8979    

DOI:10.1063/1.1714297

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

In order to calculate the limiting magnetic field for superconductivity of a type II superconductor, the free‐energy contributions of the Abrikosov mixed state and the electron spin paramagnetism are combined. The solutions which result are applied to the niobium—zirconium alloy system and compared with the available resistive critical field data, as a function of composition. The calculated curve is generally closer to the experimental curve than either the paramagnetic limit orHc2alone, and rather good agreement is obtained for niobium‐rich alloys.

ISSN:0021-8979    

DOI:10.1063/1.1714298

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

An oscillographic study of the ozonizer discharge under normal operating conditions is made and is discussed in the light of known mechanisms active in glass vessels with external electrodes. The investigation is extended to various gases and the features of the breakdown attributable to the glass itself are distinguished from those depending on the nature of the gas.

ISSN:0021-8979    

DOI:10.1063/1.1714299

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

In the presence of a population inversion, fluorescent lifetimes are reduced as a result of stimulated emission. Effective fluorescent lifetimes have been calculated using a Monte Carlo method for ruby rods with Brewster‐angle ends and roughened sides. The calculations take into account the dependence of gain and reflectivity on polarization and the dependence of gain on frequency. The reflection characteristics of the roughened surface are assumed to be those of an ideal diffuse reflector. Results show that effective fluorescent lifetimes are quite insensitive to rod length but strongly dependent on rod diameter. They also indicate the possibility of oscillation in a random mode for rods of sufficiently large diameter.

ISSN:0021-8979    

DOI:10.1063/1.1714300

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

This work is the examination of a cavity mode approach to the mode structure of a laser. Solutions of the vector wave equation for electromagnetic fields in and between perfectly conducting oblate spheroidal cavities are examined for the case of wavelengths much less than cavity dimensions. These solutions are the field modes in Fabry—Perot type resonators with equal‐radius concave spherical mirrors, or with concave—convex spherical mirrors, when the parameters of the oblate spheroids are chosen so that the radii of curvature and spacing on the axis of rotation match those of the resonator mirrors. Expressions for the transverse and longitudinal mode structures are derived. The eigenvalue equations are written, and are solved for the case of the two lowest‐order modes.

ISSN:0021-8979    

DOI:10.1063/1.1714301

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Electrode geometry effects neglected by previous investigators are shown to be significant for electrical breakdown in vacuum for gap lengths 0 to 1 mm exhibiting breakdown at 0 to 60 kV for Al, Cu, and stainless steel electrodes. In particular, data demonstrating curvature, area, and polarity effects are reported. The effects of material transfer, particle inertia, protrusion formation, erosion, and patterned deposits are also reported.

ISSN:0021-8979    

DOI:10.1063/1.1714302

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The solutions of the rate equations describing the Q‐spoiled and pulsed‐transmission‐mode (PTM) operation of a three‐level laser are given. These solutions were carried out in two time regions: (1) the delay time followed by (2) the pulse time. Region (1) was tractable with approximate analytic methods, while in region (2) the equations were solved by analog computer. The effect of the duration of the Q switch on the delay time and on the PTM operation is investigated. It is found that Q‐switch times as long as 20 nsec give satisfactory PTM operation.

ISSN:0021-8979    

DOI:10.1063/1.1714303

出版商:AIP    

年代:1965

数据来源: AIP