摘要:

A 110–118‐GHz receiver based on a superconducting quasiparticle tunnel junction mixer is described. The single‐sideband noise temperature is as low as 68±3 K. This is nearly twice the sensitivity of any other receiver at this frequency. The receiver was designed using a low‐frequency scale model in conjunction with the quantum mixer theory. A scaled version of the receiver for operation at 46 GHz has a single‐sideband noise temperature of 55 K. The factors leading to the success of this design are discussed.

ISSN:0003-6951    

DOI:10.1063/1.94455

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Thin amorphous films of the superconducting metallic glass (Mo0.6Ru0.4)82B18were annealed for 1 h at various temperaturesTAup to 650 °C. The structural relaxation caused by the isochronal annealing well below the crystallization temperature leads to a decrease of the critical temperatureTcand to an increase of the electrical resistivity &rgr;. Subsequently the films were irradiated with high energetic sulphur ions below 30 K. It is shown that the structural effects induced by the heat treatment are opposite to the irradiation effects and can be reversed by the ion irradiation. After high dose irradiation the saturation values of &rgr; andTcindicate that the structural states of the amorphous films are identical for all samples independently of the initial stage of relaxation. The experimental results confirm our former interpretation of the irradiation effects in this compound as a smearing of the structure factorS(k).

ISSN:0003-6951    

DOI:10.1063/1.94456

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The chemical composition of bronze‐processed Nb3Sn at grain boundaries and its variation as a function of distance from the grain boundary were determined using Auger electron spectroscopy. The composition at the grain boundary was 44.1, 30.6, and 25.4 at. % for Nb, Sn, and Cu, respectively, and approached to the bulk value (∼75 at. % Nb and ∼25 at. % Sn) at ∼20 A˚ into the grain, as determined by a depth‐profiling method.

ISSN:0003-6951    

DOI:10.1063/1.94457

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Preparation of high quality single crystal Nb tunnel junctions based on Nb/Nb2O5/Pb structures is reported.Vmvalues of 30±10 mV were obtained. The average specific capacitance of these junctions is 0.020±0.002 pF/&mgr;m2. From measurements of the oxidation rate, the conductance at high voltage bias, and observations of the tunneling behavior, we show that some characteristics previously associated with oxidized niobium barriers are not intrinsic and are significantly improved when the underlying niobium film is single crystal.

ISSN:0003-6951    

DOI:10.1063/1.94458

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The magnetic and structural properties of rapidly quenched FePr(BSi) alloys are presented. The samples are usually magnetically soft in the as‐quenched state. However, large coercive fields in the range of 5–20 kOe are developed upon heating the samples to a temperature around 700 °C. The best properties have been obtained on a Fe76Pr16B5Si3sample with a maximum energy product (BH)m&bartil;12 MGOe. This value is much better than that of AlNiCo and makes these materials outstanding as cobalt‐free permanent magnets.

ISSN:0003-6951    

DOI:10.1063/1.94459

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We have found that transverse field annealed ribbons of Metglas 2605 SC exhibit shear modulus variations, &Dgr;&mgr; effect, larger than 50 and transverse coupling coefficient about 0.99. Excited in standing torsional wave the peak resonant frequency has been measured as a function of the applied tensile stress when a constant dc current was flowing through the ribbon. A simplified model has been developed in order to explain the appearance of such giant values, one order of magnitude larger than any other previously reported. It has been found that the symmetrical distribution of shear strain concerning the longitudinal and transverse ribbon axes is the main source of the magnetoelastic effects enhancement.

ISSN:0003-6951    

DOI:10.1063/1.94460

出版商:AIP    

年代:1983

数据来源: AIP