摘要:

The microwave dielectric constantk′ and loss tangent (tan&dgr;) of rutile have been measured as a function of temperature from 4.2° to 300°K. At low temperatures,k′ approaches the limiting value of 256 in thecdirection and 131 in theadirection. The loss tangent at 4.2°K is 2.5×10−6for pure rutile and increases by an order of magnitude for both 0.12% chromium and 0.2% iron‐doped rutile.

ISSN:0021-8979    

DOI:10.1063/1.1728753

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A method is presented for a statistical analysis of the preferred orientation of a small sample of single crystals. The growth axes of the crystals, as plotted in stereographic projection, are grouped into cells subdividing the standard stereographic triangle and are analyzed in terms of a multinomial distribution subjected to a goodness‐of‐fit test with respect to an assumed distribution. The method is applied to a sample of 31 single crystals of sodium grown in small glass capillaries with a thermal gradient along the capillary axis. An assumed random distribution is subjected to a chi‐square test with the conclusion that it is not random, but has a ⟨111⟩ preferred orientation. The analysis of a smaller sample is exemplified by that of six sodium crystals taken from the literature. A random distribution hypothesis is subjected to a likelihood‐ratio test and is accepted in this case, although visual inspection might lead one to infer a ⟨100⟩ preference. The importance of the orientation of bcc sodium with respect to data on the orientation of fcc lead is also discussed.

ISSN:0021-8979    

DOI:10.1063/1.1728754

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

In chromium chloride the basal dislocations consist of ribbons containing either four or six partials. It is possible to explain this behavior in detail on the basis of the crystal structure.

ISSN:0021-8979    

DOI:10.1063/1.1728755

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The current‐voltage characteristics of germanium tunnel diodes with phonon assisted current predominant have been measured for reverse biases at 297°K. The tunneling exponent is deduced from the data and found to be in agreement with that obtained from high pressure experiments. The value of the pre‐exponential factor obtained from both experiments is much larger than predicted by theory. Calculations of the tunneling current which take into account nonparabolic effects of the energy band structure and the electric field variation with position in the junction are presented and compared with experiment. The results of current‐voltage measurements on germanium diodes with non‐phonon current predominant are also presented and discussed.

ISSN:0021-8979    

DOI:10.1063/1.1728756

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Measurements have been made of the release of ionically pumped helium gas when the metal is bombarded with helium ions. The re‐emitted helium is distinguished from the bombarding helium by the use of a mass spectrometer and by using either He3as the bombarding atom and He4as the trapped atom, or vice versa. The data are presented as a function of: (1) the amount of gas initially trapped, (2) the number of bombarding ions, (3) the initial kinetic energy of the trapped atoms, and (4) the kinetic energy of the bombarding ions. Comparison of these data with those obtained using krypton as the bombarding ion is made and indicates quite different behavior in the two cases. A replacement mechanism is more consistent with the data where helium is the bombarding ion. The corresponding data using krypton had been satisfactorily explained by sputtering of the metal target.

ISSN:0021-8979    

DOI:10.1063/1.1728757

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Direct observation of the effects of fission events has been made in thin films of Al and Pt by transmission electron microscopy.A very thin layer (10 to 20 A thick) of UO2was incorporated between evaporated metal films. The samples were exposed to a total thermal neutron flux of 2.8×1015n/cm2. The fission fragments produced tracks in the matrix, the characteristic appearance of which is strongly influenced by the thickness and the atomic number of the matrix.The mechanism of track formation is discussed from the viewpoint of dissipation of energy by the thermal spike mechanism.

ISSN:0021-8979    

DOI:10.1063/1.1728758

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A unified treatment of the mechanics of deformation and acoustic propagation in porous media is presented, and some new results and generalizations are derived. The writer's earlier theory of deformation of porous media derived from general principles of nonequilibrium thermodynamics is applied. The fluid‐solid medium is treated as a complex physical‐chemical system with resultant relaxation and viscoelastic properties of a very general nature. Specific relaxation models are discussed, and the general applicability of a correspondence principle is further emphasized. The theory of acoustic propagation is extended to include anisotropic media, solid dissipation, and other relaxation effects. Some typical examples of sources of dissipation other than fluid viscosity are considered.

ISSN:0021-8979    

DOI:10.1063/1.1728759

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The current modulation excited by a sinusoidal voltage across a narrow‐gap resonator on an electron beam with a Maxwellian distribution of velocities is treated on the basis of the linearized Boltzmann equation without collisions. The numerical part of the analysis reveals that the current modulation as function of distance has the form of a damped sinusoid, with finite minima, and approaches a constant level at large distances. These results are in qualitative agreement with experimental observations reported elsewhere. The analytical results show that the fast space‐charge wave of monovelocity theory is replaced by a continuum of waves (for &ohgr;p<&ohgr;). This fast‐wave packet decays with distance because of phase mixing, so that only the slow space‐charge wave survives at large distances. Thespatialdecay of the fast‐wave packet is the equivalent in multivelocity beams oftemporalLandau damping in stationary plasmas.

ISSN:0021-8979    

DOI:10.1063/1.1728760

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

This report describes a series of reaction deposition studies directed toward the formation of oriented or epitaxial tungsten films on single‐crystal tungsten by the hydrogen reduction of tungsten hexafluoride at low pressure. In addition, a novel method for controlled etching of tungsten by tungsten hexafluoride for surface pretreatment and as a tool for elucidating metallurgical structure is given. The use of this hexafluoride etching technique for surface pretreatment does not insure oriented deposition, but with the proper control of other factors such as system cleanliness, reactant material purity, deposition rates, etc., oriented or epitaxial deposits have been formed.

ISSN:0021-8979    

DOI:10.1063/1.1728761

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The microwave susceptibility for subsidiary ferrimagnetic resonance with parallel pumping is calculated from the saturation amplitude of the unstable spin waves. The limiting of these runaway magnons is caused by three, four, and higher number magnon interactions. These interactions can lead to a nonlinear (as well as the usual linear) relaxation rate, which can be evaluated using certain approximations. The main features of the results agree with experiment.

ISSN:0021-8979    

DOI:10.1063/1.1728762

出版商:AIP    

年代:1962

数据来源: AIP