摘要:

An ion optical system suitable for extracting dense ion beams from gas discharges is described. A study of the beam forming characteristics of the system was performed by using an automatic trajectory tracer with space‐charge simulation. Experimental measurements show that the extraction system operates satisfactorily over a wide range of current densities; total mercury‐ion beam currents in excess of 1 A have been achieved. An empirical method of estimating perveance as a function of geometry, based on electrolytic tank measurements, is in agreement with experimental results.

ISSN:0021-8979    

DOI:10.1063/1.1709059

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A quadrupole mass spectrometer was used to measure the desorption rate of oxides produced by adsorption of oxygen on GaAs polar {111} crystal planes. The results suggest that oxygen is adsorbed dissociatively at Ga surface atoms and is desorbed as Ga2O in a first‐order process with an activation energy of 54±4 kcal/mole from the (111) face and 42±4 kcal/mole from the (1¯1¯1¯) face. In agreement with previous work, O2sticking probability was∼10−4at low coverage; however, no activation energy for adsorption was detected for the (111) face. Desorption of Ga2O from the (1¯1¯1¯) surface showed evidence of an additional, weaker binding state not present on the (111) surface.

ISSN:0021-8979    

DOI:10.1063/1.1709060

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An axial or inverse pole figure represents the density of a fiber axis over the crystallographic triangle for the crystal system. This function can be represented by a series over this triangle and the coefficients are defined by a least‐squares solution. In a second method, the values of the density at a collection of points over the triangle can be calculated without using a series. Both these methods are easier to set up, have much greater flexibility in the data selection and weighting, and give impoved results over those obtained by using Legendre polynomials. Expressions for calculating the standard deviation for all three cases are given.

ISSN:0021-8979    

DOI:10.1063/1.1709061

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A comparison of the fine structures at theKabsorption edges of copper, nickel, and zinc in several alloys demonstrates that the rigid‐band model is strictly obeyed by copper‐zinc and nickel‐zinc solid solutions. The density of 3dholes in nickel declines progressively with increasing zinc concentration, vanishing at 30 at.% Zn according to a plot of the integrated absorptions in the corresponding energy region of the NiKedge. A similar systematic decline in the 4shole density at copper atoms takes place with increasing zinc content. A shift to lower energies of the initial rise in the ZnKedge in both alloy systems is ascribed to the emergence of 4sholes at zinc atoms. Although the initial rise of the copperKedge does not shift with alloying, the rest of the absorption spectrum shifts to lower energies with increasing zinc content. No shifts in the fine structure at the nickelKedge are observed.

ISSN:0021-8979    

DOI:10.1063/1.1709062

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Films of As2Se3and Sb2Se3and their mixtures have been studied by electron microscopy and diffraction. On heating amorphous As2Se3films no change occurs, but the Sb2Se3films and mixtures of Sb2Se3and As2Se3transform to give small single crystals. These crystals have theircaxes parallel to the substrate and give mainly (010) and (100) planes normal to the beam. Rate of nucleation is independent of temperature, indicating nucleation from predetermined nucleation centers. Growth rate increases with increasing temperature, but involves very little migration of material, implying that surface migration is very slow.

ISSN:0021-8979    

DOI:10.1063/1.1709063

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The low‐pressure plane‐wave test in metals provides more sensitive measurements of the effects of strain rate on plastic behavior than rod‐wave tests. Since strain‐rate effects are due to the motion of dislocations in these materials, such tests should lead to an increased understanding of dislocation dynamics. Two current theories of dislocation mechanics are studied in the context of plane‐wave propagation: the Gilman relation in which the dislocation velocity is proportional to the negative exponential of the reciprocal of the resolved shear stress, and the activation‐energy model in which dislocation velocity is proportional to the exponential of the shear stress. These theories are applied to the problem of attenuation of the elastic precursor wave and the results compared with published experimental data. It is shown that both fit the presently available data and cannot be resolved by low‐pressure plastic‐wave tests. The analytical results, however, suggest the appropriate value of impact pressure above which the two theories predict different results for tests of thin specimens.

ISSN:0021-8979    

DOI:10.1063/1.1709064

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The propagation of an electromagnetic wave in an anisotropic conductor in the presence of a static magnetic field is discussed. The medium is described by a general tensor relation between the current density and the electric field. In the isotropic, uncompensated limit the wave is known as the helicon. The infiniteslab boundary‐value problem is solved and the resistivity tensor elements are related to experimentally measurable quantities.

ISSN:0021-8979    

DOI:10.1063/1.1709065

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

This paper reports recent observations on the performance of continuous ruby lasers and compares them with theoretical computations of threshold, power output, and efficiency. The theoretical model includes effects due to scattering, temperature,2Elevel splitting, and excited‐state absorption. It is used to compute numerically the optimized output coupling for various pump levels and the corresponding power outputs. Experimentally, power outputs of up to 2.4 W and incremental (above threshold) efficiencies of ∼0.11% were observed. Some experiments on the effects of differing crystal diameters and cooling water temperatures and flow rates were performed. Good agreement was obtained between the observed and computed dependence of power output and efficiency on various laser parameters. The agreement is of significance primarily because it implies that the theoretical model can be used in optimizing the design of continuous ruby lasers, and in predicting their performance. Results of rough calculations of projected performance are given.

ISSN:0021-8979    

DOI:10.1063/1.1709066

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The field distributions and propagation constants of the lowest‐order modes of anisotropic dielectric waveguide models, which are relevant to electro‐optic diode modulators, are derived. Smoothly varying dielectric constant models yield results that are essentially identical to discontinuous‐dielectric‐constant models. The relative intensities of the two modes representing the two polarizations are shown to vary greatly with position. Models where the dielectric constant is asymmetric about the junction plane yield similar results for the propagation constants provided the asymmetry is small. The field distributions, however, can be markedly affected by even small asymmetries. For larger asymmetries no discrete modes can propagate for parameter values typical of GaP electro‐optic diode modulators. Absorption differences inside and outside of the waveguide are shown to play a minor role in determining the mode characteristics, at least for GaP diodes. The variation with voltage of the various mode parameters depends on whether the dielectric discontinuities which produce the mode confinement are fixed or move with the junction boundaries. The crystalline orientation dependence is explored by considering individually the junction field in the [111], [100], and [110] directions with the light beam traveling in specific perpendicular directions. The wavefronts of the two lowest‐order modes do not coincide when anisotropic absorption or arbitrarily oriented strains are present; the phase difference between the modes will then depend upon the lateral position of measurement.

ISSN:0021-8979    

DOI:10.1063/1.1709067

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709068

出版商:AIP    

年代:1967

数据来源: AIP