摘要:

Two new and related junction laser resonant structures are described together with their unique spatial output patterns. One of these structures emits a coherent beam in only one direction. The other may oscillate in a variety of spatial modes.

ISSN:0021-8979    

DOI:10.1063/1.1702857

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Experimental studies of field emission and breakdown with nickel cathodes in planar diodes and a cylindrical projection tube are presented. These demonstrate that the currents preceding electrical breakdown are due to field emission from protruding whiskers. An activation of these whiskers can proceed by desorption of gases, and very high electric fields are capable of inducing new intensely emitting whiskers to appear. At critical electrical fields the whiskers disrupt, leaving molten pools at the cathode even in the cylindrical geometry where the anode can play no part in the process. Image disappearance may be caused by the whisker's melting. An estimate of the whisker height can be made from the size of the images in the projection tube. Application of the Fowler‐Nordheim equation enables the current emitting area and the field magnification factor of a protuberance to be estimated. Whisker melting may be the origin of Cranberg's clumps for circuit limited breakdown.

ISSN:0021-8979    

DOI:10.1063/1.1702858

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

An apparatus has been constructed to introduce known amounts of slip between a belt of an insulating material and a rotating, grounded metal roller over which the belt passes. This slip results in frictional generation of electrostatic charge on the belt. The charge generated has been measured at different belt speeds, tensions, angles of wrap of belt around the roller, and at various amounts of slip on the roller. The charge generated per unit area on the belt is correlated with the work per unit area done against the force of friction. A method is presented for obtaining a value of the coefficient of sliding friction between the belt and the roller by the measurement of the charge generated. In addition, evidence of increased charge transfer as a result of frictional heating is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1702859

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Optical Faraday rotation of rare‐earth (III) borate glasses has been investigated at room temperature. The rotation is described in terms of an effective transition wavelength &lgr;twhich is an indicator of the spectral region of the 4fn‐4fn−15dabsorptions mainly responsible for the rotation. An experimental investigation of the magnitude of rotation as a function of rare‐earth (III) ion reveals the importance of the transition wavelengths and the electric dipole matrix elements as parameters affecting the rotation. The borate matrix is found to be more effective than many other environments in the realization of higher Verdet constants.

ISSN:0021-8979    

DOI:10.1063/1.1702860

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

A procedure for uncoupling the charge transport and electric field equations under certain restrictions of dose‐rate limitation and no recombination in a parallel‐plate ion chamber is given. A solution to the first uncoupled transport equation for a flat‐topped ionization pulse, including diffusion, is obtained by finding the appropriate Green's function, and the subsequent current densities and external circuit current are derived. The usual assumption of neglecting diffusion is shown to be valid for most cases involving ion transport by an examination of the general form of the external chamber current. Variations of the external circuit current with the radiation pulse width and the ratio of negative to positive ion mobilities are given. An attempt to ``fit'' an observed record shows marked deviation of the decreasing portion of the signal from the calculated one. This is probably due to the cessation of an appreciable free electron current after irradiation not taken into account by the calculation.

ISSN:0021-8979    

DOI:10.1063/1.1702861

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

A solution of cryptocyanine in methanol has been used as a self‐synchronizing, nondestructive, passive Q‐switch in a ruby laser. A symmetric giant pulse of ∼10 nsec width and 5–10 MW peak power is produced with a standard ruby laser system. This pulse is comparable with pulses generated by other Q‐switching techniques.

ISSN:0021-8979    

DOI:10.1063/1.1702862

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Initial measurements on the plasma produced in the Scylla IV theta‐pinch of its electron density, soft x‐ray emission, neutron emission, plasma shape and motion have been carried out as a function of the initial deuterium pressure and bias magnetic field. Interferograms establish electron densities in the range 4 to 7×1016cm−3for the plasma at peak compression and give azimuthally symmetric plasma shapes, which show the absence of the ``rotating flute'' instability as well as the absence of large trapped magnetic fields at peak compression. Streak photographs also indicate gross plasma stability. Shadowgraphs in conjunction with deflection mapping of a grid pattern show sharp plasma boundaries. Soft x‐ray absorption measurements yield plasma electron temperatures in the range 400 to 1200 eV, which are dependent on the magnitude of the reversed bias field and have a gross correlation with the neutron emission. Neutron emissions in the range 107to 2×109per discharge are observed and depend upon the magnitude of the reversed bias field. Neutron collimation experiments yield a plasma length of approximately 70 cm in the 1‐m mirrorless compression coil. The observed electron temperature, neutron emission, and electron density as functions of the bias magnetic field and filling pressure are consistent with the product of the plasma particle energy and the plasma density being a constant, as required for a &bgr;=1 plasma.

ISSN:0021-8979    

DOI:10.1063/1.1702863

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Ag ion conduction currents in &agr; quartz were measured at temperatures between 300° and 550°C with 2.5 V dc applied between Ag electrodes on the inner and outer surfaces of a natural quartz tube. The activation energyHfor this conduction process depends upon the average electric field intensity according to the equationH=H0‐&bgr;E½, whereH0=38 kcal/mole and &bgr;=0.32 kcal/[mole (V/cm)½]. A theory which appears to explain this field dependence postulates the formation of a lattice‐bound negative space charge near the Ag anode. This space charge is formed by the migration of mobile impurity cations away from the anode, leaving behind a net charge due to the presence of substitutional ions such as Al+3. This negative space charge creates electrical field intensities of the order of 105to 107V/cm at the anode surface. This field lowers the height of the 38‐kcal/mole barrier near the anode. Graphs of the available data for Li+and Na+migration indicate that the rate‐limiting step for these processes might also be the surmounting of a potential barrier near the anode‐quartz interface.

ISSN:0021-8979    

DOI:10.1063/1.1702864

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

The dielectric constant and loss factor of natural quartz single crystals have been measured in the temperature range from room temperature to 573°C, and in the frequency range from 50 cps to 100 kc/sec. Parallel to thecaxis a large dispersion in the dielectric constant of the order of &egr;s‐&egr;∞= 500 was observed. Associated with this dispersion is a peak in the loss factor of the order of &egr;″max= 250. The data were analyzed in terms of the Debye equations with a single thermally activated relaxation time. The activation energy is about 16.7 kcal/mole. Perpendicular to thecaxis no peak in &egr;″ was observed, but both &egr;′ and &egr;″ begin to increase at low frequencies and high temperatures.The loss peak parallel to thecaxis was substantially reduced when impurities were removed by electrolysis. The introduction of Ag, Cu, or Na gave rise to new peaks while Li tended to reproduce the original peak. It is concluded that the original loss was due to the motion of Li+ions along structural channels parallel to thecaxis. From the charge transported in electrolysis experiments, it can be inferred that the number of ions involved was about 5×1017per cm3. The observed activation energy is believed to be the Coulomb binding energy between a substitutional Al3+ion and an interstitial Li+ion.

ISSN:0021-8979    

DOI:10.1063/1.1702865

出版商:AIP    

年代:1964

数据来源: AIP

摘要:

Ferromagnetic domain walls tend to move in phase with an alternating stress or magnetic field. This movement is opposed by directionally ordered interstitial atoms. When the time associated with the relaxation process is the order of the period of the moving walls, a phase lag between the applied field and the domain‐wall movement occurs. This phase lag, coupled with normal hysteresis losses, causes a variety of magnetic and magnetoelastic phenomena, among them a strong temperature dependence of the ac magnetic permeability and a broad internal‐friction peak in the temperature range of the Snoek peaks. These phenomena can be interpreted in terms of viscoelastic theory, with a relaxation process (interstitial directional ordering) having a unique activation energy.

ISSN:0021-8979    

DOI:10.1063/1.1702866

出版商:AIP    

年代:1964

数据来源: AIP