摘要:

The plasma physics of thermionic converters is discussed in an attempt to develop a coherent physical picture of this aspect of the converter in all regions of operation. Emphasis is placed on the presentation of simple physical models consistent with experimental data: The usefulness of certain characteristic features of theI–Vcurve, in determining the physical processes governing converter operation, is pointed out. Nine regions of converter operation are identified by these features of theI–Vcurve and are discussed. The importance of two parameters of converter operation, the pressure—spacing productpd, and the relative amount of emitter‐surface ion generation &bgr;, in controlling converter behavior is emphasized. The particular values ofpdand &bgr; control which of the nine regions of converter operation appear on a particularI–Vcurve.

ISSN:0021-8979    

DOI:10.1063/1.1710144

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

This paper is concerned with the determination of the quantum statistics of the photoelectric detection, and theE‐field detection of multiple‐mode superposed chaotic and coherent radiation. The GlauberP‐representation is utilized extensively, and results are obtained by a fully quantum‐mechanical treatment. The generating function, the mean, and the variance of the photocount statistics are derived for illumination times of arbitrary duration and for modes of arbitrary statistical interdependence. For short illumination times, the complete photocount distribution is obtained. The distribution has the same form as that for a single mode of superposed chaotic and coherent radiation. The multiple‐mode distribution, however, is nonstationary. The difference between experimental determinations of the mean and variance which utilize periodic sampling and those which utilize random sampling is derived. A method for determining theP‐representation for modulated fields is described, and the detection statistics are derived. The statistics of theEfield are found to be Gaussian, and it is found that for multiple‐mode classical statistics and quantum statistics differ.

ISSN:0021-8979    

DOI:10.1063/1.1710145

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The impedances and the noise generated in the Narda model N821B metal bolometers with direct current passing through them are measured over the frequency range of 1 to 100 kc/sec. The impedance measurements indicate that the impedance of the bolometer consists of resistive part and capacitive‐reactance part. This agrees withI&Dgr;Veffect discussed by Becking and van Vliet. The noise measurements indicate that large amounts of noise over Johnson noise are associated with the temperature‐fluctuation noise and 1/fnoise in the bolometer when direct current is passed through it. For a bias current lower than 6 mA, the temperature‐fluctuation noise predominates and the observed noise has spectral distribution in agreement with the theoretical results obtained by Milatz and van der Velden. For a higher current (8.7 mA), the observed noise shows 1/fcharacteristics.

ISSN:0021-8979    

DOI:10.1063/1.1710146

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A model for the nucleation of magnetic domain walls in single‐crystal window‐frame samples of ferrite is presented. It is assumed that the wall exists prior to the application of an external field and that it is attracted to the surface by an effective pressure due to surface tension and interaction with surface defects. This pressure is nonconservative since it depends on the direction of wall motion as well as position. Using this model it is possible to explain the experimental dependence of wall velocity on time and of nucleation time on applied field.

ISSN:0021-8979    

DOI:10.1063/1.1710147

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A self‐decoration effect has been observed in thermally etched polycrystalline lithium ferrite. Each decoration is generally characterized by a geometric symmetry which apparently is related to and indicative of the crystallographic orientation of the surface on which it is found. An explanation for the formation of these decorations is proposed.

ISSN:0021-8979    

DOI:10.1063/1.1710148

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The two‐stage, green‐edge fluorescence at 4.2°K of single crystals of CdS excited by laser‐produced red light was examined. The green‐edge emission was found to be very similar to that produced by ultraviolet excitation. However, a green‐edge shift to longer wavelengths, as well as no evidence of a blue‐edge emission, was found. These effects could be explained by the existence of a distant‐pair recombination process for the green‐edge emission, and a low rate of free electron—hole production.

ISSN:0021-8979    

DOI:10.1063/1.1710149

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Data on the paramagnetic susceptibilities of the rare‐earth‐zinc intermetallic compounds, NdZn2, SmZn2, GdZn2, TbZn2, HoZn2, and YbZn2, in the 77° to 300° K region, are presented. The susceptibility obeys the Curie—Weiss law for all the compounds except YbZn2. YbZn2has a susceptibility which is negative at room temperature but positive at lower temperatures. The data obtained from the paramagnetic region for the other compounds, except GdZn2, yield effective magnetic moments in agreement with the theoretical moments for the corresponding free tripositive ions. The reason for the anomalous value for GdZn2is not understood.

ISSN:0021-8979    

DOI:10.1063/1.1710150

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The collection of charge in a silicon detector was studied for ionizing radiation of alpha and beta particles. In particular, the characteristics were studied for the case wherein the space‐charge width of the detector is less than range of the ionizing particle. In this case there may be charge collection due to diffusion of electrons or holes to the edge of the space‐charge region. The factors related to this type of collection are combined in a function termed the back‐collection factor which is defined in an integral equation relating number of electron—hole pairs collected as a function of space‐charge width. The back‐collection factor is considered a function of distance from edge of space‐charge region and amplifier‐integration time. A method to calculate the back‐collection factor as a series expansion is presented. Experimental data for 8.78‐ and 5.48‐MeV alpha particles was analyzed to determine the range of back‐collection and the form of its dependence on distance and integration time. The range of back‐collection varies from 33 to 50 &mgr; for integration time 0.1 to 5.0 &mgr;sec for 8.78‐MeV alphas in silicon. Similarly, for 5.48‐MeV alphas it varies from 16 to 52 &mgr;. Beta particles required a different treatment because of their distribution of curved trajectories in a solid. The effect of this distribution in trajectories was considered in relation to the response of a silicon detector when space‐charge width is less than range. It was noted that the previous experimental work by Aguet al.on absorption of electrons in aluminum foils of varying thickness should be in agreement with the count rate at full energy for a silicon detector when the albedo is included in the calculations. Experimental measurements were made on the number of electrons at full energy as a function of space‐charge width for 264‐keV conversion electrons from203Hg and these were shown to be in agreement with Agu's data. The results support the view that solid‐state detectors may be used to measure ionization effects within the solid from which they are constructed.

ISSN:0021-8979    

DOI:10.1063/1.1710151

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A simple dislocation‐enhanced diffusion model is proposed to explain the anomalous diffusion of phosphorus and boron in silicon. Jogs created by dislocation intersections undergo climb and emit vacancies as they are carried into the crystal on gliding diffusion‐induced dislocations. It is shown that the resulting increase in the vacancy concentration may be fully adequate, when occurring in conjunction with the field‐aided diffusion mechanism, to explain the enhanced diffusion.

ISSN:0021-8979    

DOI:10.1063/1.1710152

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

It has recently been reported that the enhancement of the rate of diffusion of phosphorus in silicon in the high concentration range is substantially reduced when the surface concentration is increased beyond a critical value. In this paper it is shown that this effect is consistent with a model which explains the anomalous diffusion by the generation of excess vacancies from edge jogs during the glide of diffusion‐induced dislocations into the crystal.

ISSN:0021-8979    

DOI:10.1063/1.1710153

出版商:AIP    

年代:1967

数据来源: AIP