摘要:

A transient increase of the temperature of the surface of a type II superconductor cooled in a static magnetic field causes flux expulsion and enhances the final diamagnetic moment. It is argued that a net paramagnetic current is induced at the surface of the specimen during the initial cooling in a static magnetic field. Quenching of this surface current by a heat pulse permits flux expulsion.

ISSN:0003-6951    

DOI:10.1063/1.1755071

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Room‐temperature values for all six independent elastic coefficients (at constant electric field) and all four independent piezoelectric stress coefficients have been determined from ultrasonic velocity measurements on a single‐crystal specimen of lithium tantalate grown by the Czochralski technique. The two independent dielectric constants at constant strain were derived from low‐frequency measurements on thin plates of lithium tantalate, in conjunction with the relevant elastic and piezoelectric data. The numerical results have been used to map the deviation of the elastic energy flux vector from the wave propagation direction for plane elastic wave propagation in theYZcrystallographic plane.

ISSN:0003-6951    

DOI:10.1063/1.1755072

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The characteristics of the current convective instability in a hollow plasma column are described. Langmuir probe measurements of the radial form of the perturbed electron density reveal that the rotating helix is concentrated towards the outer wall of the discharge vessel. The instability has been shown to occur at a lower critical magnetic field for a hollow plasma cell than for a regular positive column cell of the same dimensions. Neither of these features are considered in previous theoretical work. For both the regular and the hollow positive column, the use of measured electron density profiles in numerically evaluating a stability criterion is shown to give improved agreement between theory and experiment.

ISSN:0003-6951    

DOI:10.1063/1.1755073

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Zeeman effect studies of the 118.65 &mgr;m line of a CW water‐vapor laser have shown that the levels involved in the transition have lifetimes between 0.04 and 0.4 &mgr;sec and the same total angular momentum, and that the transition has an effective magnetic moment of about 3/4 of a nuclear magneton. These results were obtained by a new spectroscopic technique making explicit use of the saturation behavior of the laser oscillator. This technique enables lifetimes, angular momenta, and magnetic moments to be determined with magnetic field splittings of the order of or less than a tenth of the natural width of the transition.

ISSN:0003-6951    

DOI:10.1063/1.1755074

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Light‐emittingp‐njunctions are scanned by an acoustic domain traveling at sound velocity in CdS at room temperature. The light elements are heterojunctions formed by depositingp‐Cu2S onn‐CdS. The acoustic domain is generated in CdS by applying a bias electric field which gives the electrons a drift velocity greater than the shear sound velocity. When the acoustic domain is in the vicinity of ap‐njunction, part of the acoustic energy is transformed into light. As the domain travels between consecutive light elements it replenishes its lost acoustic energy from the bias electric field.

ISSN:0003-6951    

DOI:10.1063/1.1755075

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Experimental results of Raman‐Nath scattering of light by ultrasonic surface and volume waves in quartz are presented. The experiments indicate that the presented method will be a valuable tool for studying the effect of discontinuities upon surface wave propagation. It also appears that the phase velocity of the sound waves may be determined with good accuracy.

ISSN:0003-6951    

DOI:10.1063/1.1755076

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The effect of amplitude of the ultrasonic pulse on the attenuation of pure and impure single crystals of superconducting tin has been studied for the strained as well as annealed specimens. It has been found that small amplitude favors oscillations and the temperature‐dependent attenuation is strongly dependent on the strain content of the specimen and slightly on amplitude.

ISSN:0003-6951    

DOI:10.1063/1.1755077

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The temperature dependence and the absolute sign of the electro‐optic coefficients in single‐crystal LiNbO3were measured in the temperature range of 20°‐250°C using a vibrating‐mirror Michelson interferometer. The linear electro‐optic effect in LiNbO3is related through a simple model to the quadratic electro‐optic effect in paraelectric perovskites. The measured magnitude, sign, and the temperature dependence of the electro‐optic effect in this crystal are consistent with this model.

ISSN:0003-6951    

DOI:10.1063/1.1755078

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The nonlinear coefficientd31of K.6Li.4NbO3is equal tod31of LiNbO3. Also, the serious problem of optically induced refractive‐index inhomogeneities which has been observed in many nonlinear materials, notably LiNbO3, is not observed in this new material. The electro‐optic half‐wave voltage of this new material is 930 V.

ISSN:0003-6951    

DOI:10.1063/1.1755079

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A novel point tunneling technique for superconductors is reported. This technique employs the intrinsic barrier layer formed between a degenerate GaAs point and the superconducting metal surface. Excellent agreement between theoretical and experimental conductance curves is obtained for polycrystalline lead.

ISSN:0003-6951    

DOI:10.1063/1.1755080

出版商:AIP    

年代:1967

数据来源: AIP