摘要:

Two techniques have been devised for the exploration of electrostatic and magnetic fields where conventional methods fail. Both use electron lens systems to magnify the deflecting effect of the fields on electron beams. One technique is the electron optical analog of the ``Schlieren'' method; the other involves deformed shadows of a thin obstruction.For several reasons the ``Schlieren'' patterns obtained experimentally thus far have been interpreted only qualitatively. The patterns obtained by the shadow method, however, have been used for quantitative evaluation of field strengths. Experimental patterns of both types, produced by the fields of magnetized recording wires, are shown.The shadow method is theoretically applicable to the quantitative evaluation of a wide variety of electric and magnetic fields. It utilizes formulas based on relations between field distribution and electron deflection, and between the latter and the geometrical parameters of a focusing system. Such formulas are derived and applied to several simple types of field.An application of the theory to the magnetized wires used in the experiments yields relations from which each field distribution is evaluated by fitting a line to experimentally determined points. The theory also predicts the geometrical properties of the experimental patterns.The agreement between theory and experiment is sufficiently good to justify the underlying theoretical assumptions and approximations.

ISSN:0021-8979    

DOI:10.1063/1.1698303

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

Threshold detectors (In115, Ag107, and C12) were used to determine the relative intensities of neutrons at various distances inside a large water tank. Neutrons with energies up to 30 Mev were produced by (d, n) reactions. At distances in the water >20 cm the ``half‐thickness'' of water was found to be almost independent of neutron energy (about 8 cm).

ISSN:0021-8979    

DOI:10.1063/1.1698304

出版商:AIP    

年代:1949

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1698305

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

An experimental investigation of dielectric rod as wave guide indicates that the guiding effect is retained even when the rod is only a fraction of a wave‐length in diameter. The greater part of the guided energy is then outside the dielectric, so that a very low loss wave guide results. Measurements of performance made at 1.25 cm indicate attenuations down to 0.004 decibel per meter in polystyrene rod, and show good agreement with theoretical predictions. A resonator utilizing the dielectric‐rod wave guide is described, in which a maximumQof approximately 53,000 was observed.

ISSN:0021-8979    

DOI:10.1063/1.1698306

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

Analysis of the non‐radiative modes propagated along a circular dielectric rod is accompanied by a discussion of dielectric loss. The attenuation for the three lowest modes in polystyrene is computed and agrees with the experimental data of Chandler given in the preceding paper.

ISSN:0021-8979    

DOI:10.1063/1.1698307

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The traveling‐wave amplifier is a typical structure where E‐M waves and electrons, traveling with approximately the same velocity, exhibit a strong interaction. The problem has usually been discussed for the case of weak waves with approximations corresponding to a small signal theory. It is interesting to state the limitations of this theory and to discuss the behavior of such tubes for strong signals. It seems that the amplified wave obtained in the case of small signals is progressively distorted until a final stage is reached where no further amplification is possible. The type of final distorted wave depends essentially upon all the details of the structure. In many cases where a complete investigation was possible, some strange types of shock waves were obtained, with a complete bunching of the space charge. A similar solution also applies to the linear accelerators or to the synchrotrons.

ISSN:0021-8979    

DOI:10.1063/1.1698308

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The quasi‐equilibrium distribution of a disperse phase,B, within a polycrystalline second phase,A, is investigated by methods of statistical thermodynamics. PhaseBis assumed to consist of spherical particles of uniform size within theAcrystals, and of lenticular particles of uniform size at the boundaries between twoAcrystals. The concentration (Mf) ofBat the grain boundaries ofAis found to be related to the sizes (r1andr2) of theBparticles at and away from grain boundaries, in terms of the interfacial energies (&ggr;aaand &ggr;ba), the temperature (T), the over‐all concentration (M), and the size of theAcrystals (R), byMf1−MfMw1−Mw−r13/r23=exp−&ggr;aar12kT9&pgr;Z−(9&pgr;/2)13(3Z3+2&pgr;)(r1/r2)3Z3−4&pgr;,wherew=1−2.66fr1R(Z−(&pgr;/3)Z−2)whereZ=2&pgr;(4(&ggr;ba/&ggr;aa)+1)3(2(&ggr;ba/&ggr;aa)−112.Temperature will significantly affect the distribution only if &ggr;aar12is of the order ofkT, or if &ggr;ba/&ggr;aa∼½.

ISSN:0021-8979    

DOI:10.1063/1.1698309

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

A technique of specimen preparation especially suited to the study of polymeric molecules and aggregates is presented. With slight modifications it is applicable to the preparation of replicas of a wide variety of surfaces where the action of heat, pressure, and solvents must be minimized. The method owes its superiority to the use of an aluminum‐beryllium alloy of high strength, low scattering power and nearly amorphous structure. A layer of evaporated hydrophilic material facilitates the separation of the metal film from the mounting surface. Micrographs are presented showing certain applications of the method.

ISSN:0021-8979    

DOI:10.1063/1.1698310

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The quantitative evaluation of the constituents of mixtures from x‐ray powder diffraction patterns has been highly successful in certain cases, but has been found subjected to limitations as an analytical tool of more general use. These arise from a number of effects which interfere with a simple interpretation of the patterns. The paper discusses the basic aspects of these interferences, in particular of those which result from superpositions of lines, and develops a method which takes account of them. The method is adapted to meet such cases where the constituents or impurities which interfere with the regular patterns are unknown.

ISSN:0021-8979    

DOI:10.1063/1.1698311

出版商:AIP    

年代:1949

数据来源: AIP

摘要:

The resistivity and the total emissivity of commerical titanium have been measured over the temperature range from room temperature to 1400°K. The resistivity at 20°C is 78.6 microhm cm. Above this temperature it increases to a flat maximum of 182 microhm cm at the temperature of the hexagonal‐body‐centered cubic transformation. The total emissivity is about 0.31 at low temperatures and there is some indication that it shows a maximum near the transition temperature. The spectral emissivity and the brightness temperature scale are also determined over the range of 1000°K–1400°K.

ISSN:0021-8979    

DOI:10.1063/1.1698312

出版商:AIP    

年代:1949

数据来源: AIP