摘要:

Calculations are made for the ac losses in a twisted filamentary superconductor by assuming a continuum model with anisotropic conductivity. The Maxwell equations are solved for a long wire of radiusR0and twist lengthL. In terms of the classical skin depth &dgr;, appropriate for the conductivity perpendicular to the filaments, the losses are calculated for an applied magnetic field transverse to the wire axis in the case of (i) a uniform field(2 R0/&dgr;≪1, L/2&pgr;&dgr;≪1), (ii) shielding from surface currents(2 R0/&dgr;≪1, L/2&pgr;&dgr;≫1), and (iii) skin effect(2 R0/&dgr;≫1). Losses are also calculated for the case of a transport current in no applied field. The model can be used in more general cases and has the virtue of giving precise results with a minimum of auxiliary postulates.

ISSN:0021-8979    

DOI:10.1063/1.1663341

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Hysteresis losses in a twisted filamentary superconducting wire are calculated for various cases corresponding to complete penetration of the magnetic field into the wire, shielding of the field by the supercurrents, and shielding due to eddy currents. In general, the wire may be divided into two regions; an outer saturated layer which tends to behave at the higher frequencies like a solid superconductor and the interior where the average parallel electric field vanishes and the wire behaves like a collection of individual filaments.

ISSN:0021-8979    

DOI:10.1063/1.1663342

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Extensive measurements of magnetic bubble mobility in epitaxial Sm0.4Y2.6Ga1.2Fe3.8O12films have shown that is is possible to obtain a uniformity of better than ± 15% over a 1.1 × 1.1‐cm area and an average mobility of 270 cm/sec Oe. This uniformity was obtained in films which were grown under carefully controlled conditions, whereas a variation in the mobility from 170 to 510 cm/sec Oe was observed in other films where the growth parameters were not as carefully controlled. The possibility that the growth rate and growth temperature might influence the mobility was investigated, but no correlation was observed. However, annealing at 1200°C was found to have a beneficial effect on the mobility when the mobility was abnormally low in the as‐grown state. The mobility was also observed to increase by a factor of ∼ 2 over the temperature range 25–80°C, and proton implantation at a dosage sufficient to suppress hard bubbles did not materially affect the mobility. The value of the damping parameter obtained from measurements of wall mobility was found to be in good agreement with the value obtained from measurements of the microwave resonance linewidth.

ISSN:0021-8979    

DOI:10.1063/1.1663343

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Polymeric coatings have been deposited on amorphous chalcogenide films used in laser writing. The coatings are shown to be consistently effective in reducing the power required for crystallization. They are less effective in reducing the amorphising energy.

ISSN:0021-8979    

DOI:10.1063/1.1663344

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A pseudopotential theory for solute‐vacancy binding energies is derived for binary alloys which includes effects of solute‐solute interactions. Using this approach, small binding energies are calculated for impurity‐vacancy interactions in dilute Al&sngbnd;Cu, Al&sngbnd;Mg, Al&sngbnd;Ag, and Pb&sngbnd;In alloys in close agreement with the results of previous high‐temperature equilibrium experiments. Solute clustering is predicted by the model for higher concentrations of solute atoms in aluminum and lead.

ISSN:0021-8979    

DOI:10.1063/1.1663345

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

In most insulators heavy ions produce tracks of radiation‐damaged material which give rise to microscopic channels after appropriate chemical etching. By applying high‐voltage pulses through the irradiated insulator kept between two electrolyte cells containing the etching reagent, these damage tracks cause treeing phenomena. Preliminary results are shown dealing with the treeing production around fission fragment and &agr;‐particle tracks in some organic insulators. Treeing at damage tracks provides a new method for initiating treeing processes and enables us to enlarge damage tracks considerably.

ISSN:0021-8979    

DOI:10.1063/1.1663346

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The de Haas‐van Alphen effect is used to determine the change of the Zn Fermi surface parameters in dilute Zn Cd alloys containing up to 1.2 at.% Cd. Its application in observing the change of the matrix band structure during room‐temperature aging is demonstrated. The presence of local concentration gradients and strain fields in the matrix during precipitation produce strong phase‐smearing effects.

ISSN:0021-8979    

DOI:10.1063/1.1663347

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

To test the suggestion that an enhancement of sputtering occurs in very dense collision cascades, the sputtering yieldper atomwas compared for atomic and molecular ions. In all cases tested, the yieldper atomwas higher for the molecular ions. This effect is the more pronounced the heavier the projectile and the target. In the molecular cases the overlapping cascades have higher energy densities than those initiated by the atomic ions; our results, therefore, support the suggestion of a sputtering enhancement in dense cascades.

ISSN:0021-8979    

DOI:10.1063/1.1663348

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

In a semiconductor in which the effect of mixed conduction is dominant, the determination of carrier mobilities only by Hall measurements is impossible. Magnetoresistance measurements provide the lacking equation which, in conjunction with the expressions forRHand &mgr;nin the mixed conduction region, may be used to determine &mgr;nandb. As the analytical solution is difficult, we solved the system by an approximative method under the main assumption thatb≫1. This method was applied to measurements of semi‐insulating Cr‐doped GaAs (which is a typical example of a semiconductor in which mixed conduction is dominant), with good results. Further application to intrinsic InSb at room temperature, using known data, confirmed the validity of the method.

ISSN:0021-8979    

DOI:10.1063/1.1663349

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A comparison between commonly used expressions for the electron density in the nonparabolic conduction band of Hg1−xCdxTe is made. Calculations are carried out for compositions in the range 0.16≤x≤0.8 and a temperature of 80°K. The effect of the spin‐orbit splitting &Dgr; on electron density is examined.

ISSN:0021-8979    

DOI:10.1063/1.1663350

出版商:AIP    

年代:1974

数据来源: AIP