摘要:

New analysis is presented using a unipolar ion‐mobility conduction model in planar geometry which solves for the transient behavior of the bulk electric field and space‐charge distributions as a function of time and space, as well as the resulting time dependence of the terminal quantities of voltage and current. The charge‐conservation quasilinear partial differential equation is solved using Lagrange's method with the method of characteristics. The analysis is generalized to handle any physically allowed initial and boundary conditions for any type of applied excitation. Special cases are examined of the turn‐on transient with the application of a step voltage or current, contrasting the behavior between space‐charge‐limited conditions where the emitter electric field is zero to those where the emitter field is nonzero. Much of the analysis yields closed‐form expressions.

ISSN:0021-8979    

DOI:10.1063/1.1663610

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A detailed numerical analysis has been made with respect to the cross slip behavior of a pair of passing screw‐type superlattice dislocations on parallel slip planes in a simple B2‐type superlattice. It is found that below some critical interplanar spacing, cross slip will always occur with mutual annihilation of the two dislocations. This critical spacing in turn establishes the maximum stress required to pass both dislocations past one another (i.e., the maximum strengthening). It is found that the maximum passing stress increases linearly with increasing antiphase boundary energy.

ISSN:0021-8979    

DOI:10.1063/1.1663611

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The complex dielectric constant frequency spectra of vapor‐deposited amorphous Se&sngbnd;Bi and Se&sngbnd;Bi&sngbnd;As films were measured as a function of heat treatment near the glass transition temperature. The observed dielectric dispersions have been attributed to interfacial polarization arising from a layering of alternate high‐bismuth and low‐bismuth amorphous phases parallel to the surface of the film. Theoretical equations based on this interfacial polarization model have been used to reproduce the observed dielectric behavior. The model can correctly fit the observed loss peak frequencies and amplitudes and the increase of the peak frequencies with increasing time of heat treatment for lower‐bismuth‐concentration films (<5.0 at.% Bi). At higher bismuth concentrations conducting paths must be proposed in order to account for the very large dispersion peaks and low‐frequency dielectric constants which are observed. These paths occur either through individual high‐bismuth layers or through the bulk of the film. The addition of arsenic to the low‐bismuth‐concentration films increases the over‐all conductivity and causes a conductivity maximum with heat treatment in the high‐conductivity layers. In the high‐bismuth‐concentration films the arsenic tended to stabilize the amorphous phases of the film.

ISSN:0021-8979    

DOI:10.1063/1.1663612

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The frequency shifts andQchanges of a resonant microwave cavity were utilized as a basis for determining microwave susceptibilities and loss tangents for solids and liquids. The method employed consisted of varying the depth of penetration of a continuous cylindrical sample of the material into a cavity operating in the TM010mode with the resonant frequency and quality factor determined at each incremental setting of the perturbing sample. The perturbation of the cavity was achieved by advancing the sample into the cavity along the symmetry axis by employing a micrometer drive appropriately calibrated for depth of penetration of the sample. A differentiation method was used to obtain the half‐power points of the cavity resonance profile at each depth of penetration. The perturbation techniques for resonant cavities were used to reduce the experimental data obtained to physical parameters for the samples. The probing frequency employed was near 10 GHz.

ISSN:0021-8979    

DOI:10.1063/1.1663613

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

To control the collector temperature of an electrostatic probe, we have studied and built a cooling circuit to cool by convection; we have considered two possibilities for the cooling liquid—with and without phase conversion. We give the corresponding thermic study and the cooling effects on the experimental results, obtained from a simple Langmuir probe and a grid probe. The cooling is indispensable at all temperatures for a probe with a positively biased grid. We find that the reemission current varies when the collector is still negative.

ISSN:0021-8979    

DOI:10.1063/1.1663614

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The results of a comprehensive diode study conducted using a pulsed high‐current electron accelerator are reported. Time‐dependent analysis of right‐cylindrical graphite cathodes has shown evidence of the field emission character of the cold‐cathode diode. The effects of cathode whiskers or microprojections on the diode response have been observed. Within a few nanoseconds after the voltage is applied to the diode, the whiskers explode to form cathode flares. The observed diode perveance throughout the remainder of the pulse can be explained in terms of the expansion of the plasma cathode formed by the merger of many cathode flares. Cathode plasma velocities ranged from approximately 2 to 3 cm/&mgr;sec. The observed diode behavior was consistent with that predicted by previous studies of high‐voltage vacuum breakdown.

ISSN:0021-8979    

DOI:10.1063/1.1663615

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A semiclassical impact parameter method has been used to calculate the Gaunt factors, cross sections, and rates for electron‐impact excitations between selected states of the hydrogenlike and heliumlike ions of aluminum. These results are compared to the ``universal'' values suggested by Allen. For the resonance transitions, agreement with Allen's values becomes poorer as the charge on the target increases. Agreement is good for the nonresonant transitions.

ISSN:0021-8979    

DOI:10.1063/1.1663616

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Two assumptions made in a previous treatment of this subject are circumvented—that the mean free time is constant and that the ion temperature is independent of position. The results are applied to drift tube analysis for errors in the interpretation of the drift velocity due toN−2effects.

ISSN:0021-8979    

DOI:10.1063/1.1663617

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The dependence on the ratio of the electric field to the neutral particle number density of reaction rate constants measured in drift tubes can be approximated asymptotically near zero field by the logarithm of the relative speed distribution of an ion and a neutral molecule, evaluated at the threshold velocity. This approximation adequately represents the field dependence of the rate constant into the region where experimental measurements of the rate constant can be obtained, allows a quick determination of the threshold velocity from rate constant measurements, and gives a consistency check on proposed ion‐molecule relative speed distributions.

ISSN:0021-8979    

DOI:10.1063/1.1663618

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

By inserting a grid in a beam‐generated plasma column, single waves can be produced as a result of the beam‐plasma instability exciting a finite‐length cavity mode. The oscillation frequency is found to increase with beam velocity, in contrast to the frequency‐velocity relationship of the wave with the maximum growth rate. The nonlinear evolution of the beam‐generated wave and satellites due to a test wave are observed.

ISSN:0021-8979    

DOI:10.1063/1.1663619

出版商:AIP    

年代:1974

数据来源: AIP