摘要:

The dispersion relation for propagation of an electromagnetic wave between two semi‐infinite slabs of plasma is found under the assumption of infinite magnetic field along the slabs. Provided the plasma frequency is above the applied frequency, a fast wave solution exists, with a sinusoidal field distribution in the free‐space region between the plasma slabs, and exponential decay into the slabs. A complex plasma frequency is introduced to account for collision losses in the plasma, and substituting this complex plasma frequency into the dispersion relationship, the attenuation constant of the wave is found. The imaginary part of the plasma frequency is computed from collision theory and found to give damping considerably smaller than that obtained with metal guides. An application to high‐field linear accelerators is treated in detail.

ISSN:0021-8979    

DOI:10.1063/1.1728877

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The filamentary maser action in a ruby is explained as caused by minute randomly distributed variations in index of refraction. Relations are derived for the density of filaments and their size in terms of a Fourier resolution of the inhomogeneities. These are so small that it seemed that thermal motion might play a part, but this is shown to be orders of magnitude too small at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.1728878

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The prior restriction to conservative motion of the electrons has been removed, but scattering has still been neglected. The rate of energy loss has been used to derive the stationary distribution over a range of energy (or momentum) and canonical angular momentum for an arbitrary magnetic field distribution. A necessary ingredient is the retardation of the electrons; the radiative component of this has been estimated, but not included; the dynamical friction component, arising from motion through a uniform, fully ionized plasma, has been used as the sole contributor to energy loss. This friction also affects the canonical angular momentum and the latter's change in one cycle relative to the energy change has been formulated. Maxwell's equation connecting magnetic field with current density, applied to the stationary distribution, has permitted the formulation of the relation between field and the other variables. This completes the number of relations required to determine the magnetic field (eigenfunction) arising from a given rate of electron injection (eigenvalue): The trajectory equations have been derived.It has been necessary to picture physically the complete evolution of a trajectory from injection to stopping, both to understand what the mathematics says and to devise an adequate machine program. When field reversal occurs, then just before the electrons die, the electron swarm divides into two counter‐rotating eddies. Two iterative solution techniques have been used to calculate the field distributions for a range of initial energies, field strengths, and injection rates. A striking result is that once reversal of field occurs by increasing the injection rate, it is generally true that the reversed field varies little, but the layer becomes progressively thinner as the injection rate increases further. At some rate the layer thickness passes through zero and thereafter the injection radius lies not at the apocenter of the initial trajectory but at the pericenter, the layer protruding from its prior position.For full‐energy radii of gyration which are less than about one‐third the injection radius, anomaolus solutions appear which are unstable. A number of aspects of the problem of incorporating anElayer into a thermonuclear device are briefly discussed, namely, the effect of scattering, the possibility of two‐beam instability, the injection of the electrons, effects of end reflection in a finite‐length layer, electrodynamic effects, and plasma diamagnetism.

ISSN:0021-8979    

DOI:10.1063/1.1728879

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Tunnel emission into vacuum is obtained from thin‐film sandwiches of (a) aluminum‐alumina‐aluminum and (b) aluminum‐alumina‐platinum. The alumina layer is made by oxidizing an evaporated film of aluminum in air. Cesium processing, to lower the work function, results in an increase of emission of five orders of magnitude.

ISSN:0021-8979    

DOI:10.1063/1.1728880

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The dissolution and growth behavior of lithium fluoride crystals in aqueous solutions containing long‐chain fatty acids as step‐poisons has been investigated. Both positive crystals (whiskers and platelets) and negative crystals (etch‐tunnels) can be grown, respectively, from supersaturated and undersaturated solutions of lithium fluoride containing identical concentrations of stearic acid (∼2×10−6N). Dissolution behavior in stagnant environments is of particular interest for etch‐tunnels some 0.5 &mgr; in diameter and more than 100 &mgr; in length (negative whiskers) have been observed. Two types of etch‐tunnel can be distinguished; those nucleated at a surface defect—such as a cleavage step or the point of emergence of a dislocation (Dtype)—and those nucleated at apparently random points on the crystal surface (Rtype). Metallographic observations reveal that dislocations are not essential to negative crystal growth and it is proposed that tunnels grow simply because dissolution is less efficiently inhibited at the end of a tunnel than at the external surface of the crystal. This is a consequence of the reduced number of poison molecules available to inhibit kink and step motion at the end of a tunnel because of their slow rate of diffusion in a stagnant environment. Vigorous agitation of the environment suppresses etch‐tunnel formation.

ISSN:0021-8979    

DOI:10.1063/1.1728881

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Hall measurements on manganese‐doped gallium arsenide reveal a single acceptor level for this impurity with an ionization energy of 0.1 ev. The ionization energy and segregation coefficient,ks=0.05, appear to be independent of concentration over the rangeNA=6×1017−1×1020/cm3.

ISSN:0021-8979    

DOI:10.1063/1.1728882

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The output power level of an optical maser is dependent on the level of inversion which can be reached. Using a technique in which the optical feedback is modulated by a shutter disk, an enhancement of the output power level of a pulsed ruby optical maser was observed. The higher level of output power occurred for only a short pulse. An explanation is given and the observed effect compared to the expected value.

ISSN:0021-8979    

DOI:10.1063/1.1728883

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The sputtering yield of gold bombarded by low energy (20–100 ev) helium, neon, and argon ions has been measured by the increase in electrical resistance of a thin gold film. It has been shown that for neon and argon the yield decreases rapidly with decreasing ion energy from 100 to 40 ev; below 40 ev the decrease is less rapid and no definite threshold has been found. With 40‐ev neon ions the yield is proportional to the ion current density, but with argon ions of this energy the yield is independent of the current: For currents greater than 100 &mgr;a/cm2neon is more efficient than argon in sputtering gold. To explain the variation of yield with ion current for low energy neon ions it is suggested that the sputtering may take place by a two‐stage process: the first stage being the creation of defects in the gold by the ions, and the second stage, ejection of gold atoms from the neighborhood of these defects.

ISSN:0021-8979    

DOI:10.1063/1.1728884

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A technique has been developed to pull single crystals of volatile materials using standard pulling apparatus. This has been accomplished by covering the surface of the material to be pulled with a substance that is liquid at the pulling temperature. Crystals of PbTe and PbSe were pulled using molten B2O3as the surface liquid.

ISSN:0021-8979    

DOI:10.1063/1.1728885

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The spatial distribution of atoms ejected from low index planes of Cu, Ni, Au, Al, Ge, and Si have been studied for bombardment by Hg+, Ne+, and Ar+ions of energies up to 800 ev. In addition, the atom ejection for Hg+‐ion bombardment of various Ge planes (12° apart) belonging to the [110] zone has been investigated in detail. For the fcc crystals, ejection was observed in ⟨110⟩ directions at all energies, in⟨100⟩ directions at higher energies, and in ⟨411⟩ directions under certain conditions. The ejection in the ⟨110⟩ and ⟨100⟩ directions are interpreted to be the result of focusons intercepting the surface with sufficient energy to cause a surface atom to be ejected. It is shown that a reasonable interpretation of the atom ejection in ⟨411⟩ directions is that a ⟨110⟩ focuson may intercept and eject a surface atom which is in a twin position rather than a normal position. For ion bombardment of Ge and Si atom ejection is observed in ⟨111⟩ and ⟨100⟩ directions. A possible interpretation is that many of the natural interstitial positions are filled near the surface as a result of the bombardment and that the structure resembles more that of a bcc structure. The systematic deviation in ejection directions from the associated crystallographic direction observed for the Hg+‐ion bombardment of various Ge surfaces suggests that the atomic collisions resulting in atom ejection for Ge and Si occur in the outer few surface layers.

ISSN:0021-8979    

DOI:10.1063/1.1728886

出版商:AIP    

年代:1962

数据来源: AIP