摘要:

We present a systematic perturbation theory, extendable in principle to all orders of magnitude, for the solution of the equations of motion of an ideal Josephson element shunted by a resistance and driven by a dc current source and a small time‐dependent source. We present second‐order results for the case in which the time dependence is that of a single sinusoid, and these results are compared with other numerical and analytical calculations. Near, but not on, the first constant voltage step where the perturbation theory appears divergent, the current‐voltage characteristic is calculated by means of a nonperturbative adiabatic procedure. The impedance and responsivity agree with earlier results.

ISSN:0021-8979    

DOI:10.1063/1.1662201

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Superconducting critical current densities up to 5.2 × 105A/cm2at 75 kOe and 4.2°K, and up to 4.4 × 105A/cm2at 100 kOe were measured for a 66‐&mgr;m‐thick Nb12Al3Ge deposit made at a rate of 1 &mgr;m/min by high‐rate sputtering. Current‐density‐vs‐transverse‐magnetic‐field curves were either linear or nearly linear, and the current density dropped only 33% over the field range investigated (50–100 kOe). The sample that carried the highest current densities was deposited at 20°C and heat treated one day at 750°C. Current densities for another sample from the same deposit, but heat treated 20 days at 750°C, were about 14% lower than for the sample heat treated one day. The deposits were body‐centered‐cubic (bcc) when deposited at 20°C. Heat treatment at 750°C produced a single metastableA‐15 phase containing grains of 350‐Å diameter; the small grain size presumably accounted for the high current density. Current densities measured with the field perpendicular to the deposit plane were only about 14% lower than with the field parallel to the deposit plane, which indicated theA‐15 phase grains formed by heat treatment at 750°C were nearly equiaxed. The high current density results and the availability of high‐rate sputtering equipment encourage fabrication of practical quantities of sputter‐deposited Nb&sngbnd;Al&sngbnd;Ge superconducting products. Estimated fabrication rates and costs were reasonable.

ISSN:0021-8979    

DOI:10.1063/1.1662202

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

This paper considers the applicability of theoretical equations for the electrical conductivity of homogeneous suspensions of identical nonconducting spheroids to studies of particle behavior in suspensions of practical interest. Results of particle shape and concentration determinations conform to theory up to volume concentrations of 0.6–0.65. The predicted relationship between particle orientation and suspension resistance is verified experimentally. The method is used to study erythrocyte orientation during blood flow in a tube of rectangular cross section. Results are consistent with observations reported by previous investigators and are in qualitative agreement with the theory of Peterlin and Stuart for the orientation distribution of microscopic spheroidal particles in dilute suspensions undergoing shear flow and subject only to thermal agitation.

ISSN:0021-8979    

DOI:10.1063/1.1662203

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Three electron beam deflection yoke models have been built to experimentally test the concept of compensated coil pairs. The yokes were placed in three different conductive tubes. Eddy‐current compensation was achieved, thus verifying earlier computations of the author. In particular, the uncorrected error of the cross‐axial field follows the reciprocal square root of the time following a change in deflection yoke current, and can be neutralized.

ISSN:0021-8979    

DOI:10.1063/1.1662204

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

In studies of surface states at the SiO2&sngbnd;Si interface, an exponential variation of the electron capture cross section with band‐gap energy has recently been observed. In these bias regions, the dispersion parameter &sgr;uswas also observed to tend toward zero. In this paper, it is shown that the &sgr;usvalues inferred from the data reduction may be spurious results, influenced strongly by the energy dependence of the electron capture cross section.

ISSN:0021-8979    

DOI:10.1063/1.1662205

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Polishing anthracene single crystals creates defects which reduce the triplet lifetime not only at the surface but also throughout the bulk. By annealing the crystal, the triplet lifetime can be essentially restored to its initial value.

ISSN:0021-8979    

DOI:10.1063/1.1662206

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The energy spectrum of Na+ions sputtered from NaCl crystals under 20‐keV He+ion bombardment is measured in the energy range from 1 eV to 100 eV using a time‐of‐flight technique. The spectrum behaves like that of neutral atoms sputtered from metals.

ISSN:0021-8979    

DOI:10.1063/1.1662207

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

GaAs/(Ga,Al)As/GaAs transmission photocathodes were fabricated by a multiple layer liquid epitaxy technique using GaAs substrates. The GaAs substrate was subsequently removed by bubble etching. Transmission mode white light sensitivity of 340 &mgr;A/lm and an electron diffusion length of 5 &mgr;m or more can be routinely achieved. The reflection sensitivity was found to be lower than that of a similarly prepared layer grown directly on the GaAs substrate. The spectral response, when analyzed with the yield formula, indicated negligible recombination at the GaAs / (Ga,Al)As interface. Also, despite the almost perfect lattice match between GaAs and AlAs, some bowing of the GaAs / (Ga,Al)As samples was observed, suggesting the presence of internal stresses. A simplified formula is derived for the transmission quantum yield which enables graphic solution of surface recombination velocity at the photocathode input surface and the ratio of photocathode thickness to the electron diffusion length without tedious computer calculations.

ISSN:0021-8979    

DOI:10.1063/1.1662208

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Infrared spectroscopy has been used to study copper impurities in irradiated and unirradiated silicon. No Cu‐associated bands are observed before or after neutron irradiation of the copper‐diffused samples. The presence of Cu impurities in Si does not affect the production of divacancy defects, implying no interaction of Cu with radiation‐induced defects.

ISSN:0021-8979    

DOI:10.1063/1.1662209

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An experimentally simple nuclear magnetic resonance pulse technique is described for measurement of longitudinal and transverse relaxation times. The sequence consists of a Carr‐Purcell train with &pgr; and &pgr;/2 pulses interchanged. The technique offers time savings over traditional methods in cases where relaxation times are long. Experiment times may be halved in some cases. Results obtained with this technique compare well with results obtained using traditional techniques.

ISSN:0021-8979    

DOI:10.1063/1.1662210

出版商:AIP    

年代:1973

数据来源: AIP