摘要:

Conventional electrostatic and magnetic lenses were used to focus electron beams in the range of energies 30–70 v, produced by a specially designed experimental tube. The electron distribution in the focused beam was resolved by a series of concentric end collectors and a convention introduced to assess effective beam widths.With near‐symmetrical lenses of the electrostatic type and for energies above 30 v, the beam, if inside the aberration limits of the lens, appears to be acted on as a whole by the field and a definite focus is obtained; for 30‐v beams, on the other hand, there is no unique focus since maximum and minimum values of effective beam width were recorded as the focus voltage was varied. Such a periodic variation might arise from the existence of standing wave patterns in the space charge in front of the cathode.A characteristic feature of the focusing which is most marked in the magnetic case is the disappearance on focus of the Gaussian core of the incident beam distribution. With magnetic lenses having apertures in the ratio 2/1, it was remarkable to find that the smaller aperture lens was the most efficient in bringing beams to a focus. In general, the power of magnetic lenses had to be greatly increased (in the measurements, by a factor of 30) over any expected thin lens performance to achieve a focus. Space charge forces, nonhomocentricity, and potential depression are held to be responsible for the abnormal conditions of focus.

ISSN:0021-8979    

DOI:10.1063/1.1722298

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

Commercial encapsulated siliconp‐njunction diodes were bombarded by 2 Mev electrons from a Van de Graaff generator. The reverse transient current and the static I–V characteristics of the junction were measured before and after varying intervals of the bombardment time. The time dependence of the reverse transient current is in close agreement with theory, and the reciprocal of the minority carrier lifetime, as inferred from these data, is found to be a linear function of the bombardment time. The bombardment also produced marked changes in the static I–V characteristics of the diodes. These data are not in agreement with simplep‐njunction theory. A suggested explanation is that the diode behavior is generally similar to that of ap‐i‐njunction.

ISSN:0021-8979    

DOI:10.1063/1.1722300

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

By taking into consideration both the effects of space‐charge and large‐amplitude scalloping, an analytic solution for periodic‐field beam focusing is obtained through use of successive approximation and Fourier series expansion. The stability limit is then determined by studying a perturbation of the obtained solution. The perturbation results in a Hill's differential equation for the incremental beam radius. This equation yields a stability criterion for periodic‐field beam focusing. It is found that instability starts at some degree of beam scalloping and ends at a higher one, and thus forms an unstable band.

ISSN:0021-8979    

DOI:10.1063/1.1722301

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

The stability of the interface of two superposed streams is studied by extending the theory of Helmholtz stability to include the viscosity and surface tension in the waves. The twouniformlayers of incompressible fluids are of different densities, viscosities and stream velocities. Gravity, Taylor acceleration, and surface tension are taken into consideration. An approximate theory is developed and is valid in three ranges of wave numbers. Neutral stability, rate of growth, and rate of decay are illustrated graphically.

ISSN:0021-8979    

DOI:10.1063/1.1722302

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

Large reproducible changes in work function of oxide cathodes have been observed following step‐like changes in dc current drawn from, as well as to, the coating. One type, with a time constant in the range of 10−2to 1 second, has been reported by others. It appears to be caused by a redistribution of donors by the field set up in the coating. We studied this phenomenon further as a function of temperature, dc current density, coating composition, and barium deposition.We also discovered a second type of transient which follows the first. It has a time constant, in the range from 100 to 104seconds. The amplitude of this change is of the same order as that of the first. The time dependence is in most cases given by a simple exponential. Both amplitude and time constant are a function of the cathode itself as well as its environment. This transient is thought to be caused by a change of the total number of donors. A simple analysis accounting for the exponential form yields values for the donor loss rate.

ISSN:0021-8979    

DOI:10.1063/1.1722303

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

A general solution is obtained to a two‐dimensional problem of the movement of the interface between two immiscible liquids of unequal density in a porous solid, the interface motion being the result of the force of gravity acting on the two liquids. The solution is obtained by direct potential theory methods and employs a method of approximation similar to that used in the linear theory of water waves.It is shown that the elevation of the interface above its equilibrium position satisfies a ``nonoscillatory'' wave equation, i.e., the classical wave equation in which the wave velocity is pure imaginary.The solution of the special case of an initially plane tilted interface is included.

ISSN:0021-8979    

DOI:10.1063/1.1722304

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

The scattering of a plane electromagnetic wave by a perfectly conducting spheroid with small eccentricity is treated by a method of expanding the scattered field directly in a series of spherical vector wave functions. An expression for the first‐order solution of the backscattered field is obtained for arbitrary angles of incidence of a plane wave. The numerical values of echo areas computed from the first‐order expression are shown for various cases, and rough experimental results are also discussed. During this study some mathematical formulas involving the associated Legendre functions have been derived.

ISSN:0021-8979    

DOI:10.1063/1.1722305

出版商:AIP    

年代:1956

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722307

出版商:AIP    

年代:1956

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722308

出版商:AIP    

年代:1956

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1722309

出版商:AIP    

年代:1956

数据来源: AIP