摘要:

Germanium single crystals pile‐irradiated at 20°C and 1014to 1017n/cm2etch differently from similar crystals which have not been irradiated. The irradiated crystals when etched with CP‐4 show a finer surface granulation. This difference in etching behavior is reduced on annealing. Kinematic studies indicate an activation energy for the annealing process between 1.6 and 1.8 ev. The etching behavior of silicon single crystals shows a similar change on pile irradiation. The present work, though preliminary in nature, suggests a new experimental approach to the study of radiation damage.

ISSN:0021-8979    

DOI:10.1063/1.1722759

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Water‐tank observations of the flow phenomena associated with boundary‐layer transition have revealed that a two‐dimensional discrete vortex line, which is considered to be the consequence of an amplified perturbation wave, has a strong tendency, in shear flows, to form three‐dimensional vortex loops with a marked transverse wavelength. The formation and development of the vortex loop is found to be the essential feature preceding the creation of a turbulent spot which takes place near the top of the vortex loop and near the outer edge of the boundary layer. This formation and development provides the guiding principle of laminar‐to‐turbulent transition in wakes and jets as well as in the boundary layer.

ISSN:0021-8979    

DOI:10.1063/1.1722760

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

General equations governing the hydrodynamic behavior of an ideal compressible fluid in which chemical reactions and internal relaxations proceed are formulated. For one‐dimensional flow the equations are transformed to characteristic form, in which the ``frozen'' or high‐frequency sound velocity plays a role analogous to the unambiguous sound velocity in the nonreactive case.

ISSN:0021-8979    

DOI:10.1063/1.1722761

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Measurements of the intrinsic tensor permeability [&mgr;] of unsaturated Ni ferrite at 9300 mc, using cavity perturbation techniques, have revealed an anomalous resonance for negative (anti‐Larmor) circularly polarized fields. The resonance has a line width of 70 oe and occurs very near the coercive force which is 13.2 oe. The usual resonance for positive (Larmor) circularly polarized fields occurs at 2750 oe. An interesting consequence of the low‐field resonance is that below saturationK″ is negative, whereK=K′−iK″is the off‐diagonal component of [&mgr;]. Above saturationK″ is positive. The change in sign ofK″ is shown not to violate energy considerations.These effects are explained by a theory involving rf demagnetizing poles on Bloch walls based on a model with a physically probable domain structure. The theory extends the Polder‐Smit mechanism in unmagnetized media to include applied dc fields and circularly polarized rf fields. It is applicable to all ferrites, both mono‐ and polycrystalline, having domain walls free to move in dc fields of the order of the coercive force. Since the anomalous resonance depends upon the domain structure and appears to occur generally, it is a probe of considerable usefulness for the study of magnetization processes and high‐frequency phenomena in ferrites.

ISSN:0021-8979    

DOI:10.1063/1.1722762

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

An equation relating the potential applied to and the current flowing in a liquid dielectric has been derived. The theoretical equation predicts that beyond a certain threshold potential the current is independent of the applied potential and is proportional to the number of ions produced per unit volume per unit time.Measurements of the number of ions produced in cyclohexane as a function of temperature and water concentration were made. It was found that in the pure state about 200 ions/cm3‐sec were produced, while in the water saturated cyclohexane at 50°C about 1.6×105ions per cm3per sec were produced. It was concluded that the conductance in the pure state was due to ionization by cosmic radiation.When the cyclohexane was saturated with water, a large increase in the conductivity was observed as the cyclohexane passed through the freezing point. This behavior corresponds to an increase in the dielectric constant as noted by Seyer and Barrow.

ISSN:0021-8979    

DOI:10.1063/1.1722763

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The generation of the deposit spot patterns from low‐index planes at lower and higher ion energy is explained by mechanical double and triple collisions of the perpendicularly incident ions with lower and upper surface atoms of the target plane. The effective collision spheres are assumed to be determined by the largest closed electronic shells of the ion and the target atom with radii smaller than the radii of the largest electronic orbits of these shells. A second factor has to be taken into account for the explanation of the shape and other features of the single spots of the patterns. This is the attenuating influence of the different electron densities in the paths of the ion within the lattice, because the largest closed electronic shells exceed the size of the collision spheres and produce the highest electron density in close‐packed rows of the lattice.These two concepts are sufficient to explain the number and arrangements of the spots in the patterns of low‐index planes, the specific shape of the single spots, the alterations of the spot patterns connected with higher ion energy or with accidental deviations of the prepared crystal plane from the ideal crystallographic plane, the deviation of the symmetry axis of the single spots in (110) fcc patterns from the diagonal direction of the unit area, and finally the different shape and size of the single spots in (111) spot patterns of silver and copper.

ISSN:0021-8979    

DOI:10.1063/1.1722764

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Equations are derived for the impurity distribution which arises by evaporation of impurities from the surface of a homogeneously doped semiconductor. The rate of evaporation is assumed to be proportional to the surface concentration. When a rectifying metal contact is made to a semiconductor with such an impurity distribution, the dependence of capacitance on the applied voltage can be used to determine the proportionality constant between rate of evaporation and surface concentration.

ISSN:0021-8979    

DOI:10.1063/1.1722765

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Some experimental results are presented of the flow generated by the explosion of a sphere of high‐pressure gas. Glass spheres of 1, 2, and 5‐in. diam containing air, He, or SF6at overpressures up to 21 atmos were used to produce a spherical analog of the shock tube. The results show that the shock sphere may be applied to the study of explosions, implosions, and spherical wave interaction under controlled and known initial conditions.

ISSN:0021-8979    

DOI:10.1063/1.1722766

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

Diffraction of a wave by an aperture of any shape in a thin screen is treated by a new method—``the geometrical theory of diffraction.'' This is an extension of geometrical optics which accounts for diffraction by introducing new rays called diffracted rays. They are produced when incident rays hit the aperture edge and they satisfy the ``law of diffraction.'' A field is associated with each ray in a quantitative way, by means of the optical principles of phase variation and energy conservation. In addition ``diffraction coefficients'' are introduced to relate the field on a diffracted ray to that on the corresponding incident ray.By this method a simple formula is obtained for the field diffracted by any aperture. It yields the field in the aperture, the diffraction pattern and the transmission cross section. Explicit formulas and numerical results are given for slits and circular apertures. The accuracy of the results increases as the wavelength decreases, but they are useful for wavelengths even as large as the aperture dimensions.

ISSN:0021-8979    

DOI:10.1063/1.1722767

出版商:AIP    

年代:1957

数据来源: AIP

摘要:

The magnetostriction of oriented polycrystalline MnBi was found to be higher than any published value for a metal. A value of −250×10−6was measured parallel to a field of 22 000 oersteds oriented perpendicular to thecaxis of the aligned hexagonal crystallites. This field magnetized the specimen to only slightly more than half of saturation. A tentative value of −800×10−6for the magnetostriction at saturation was obtained by plotting the magnetostriction as a function of (B‐H)2and extrapolating to saturation. Magnetic anisotropy constants ofK1=9.1×106ergs per cm3andK2=2.6×106ergs per cm3were obtained by fitting a calculated curve to the experimental magnetization curve.

ISSN:0021-8979    

DOI:10.1063/1.1722768

出版商:AIP    

年代:1957

数据来源: AIP