摘要:

Three distinct saturation mechanisms occurring in ferrite frequency doublers are described. An approximate nonlinear equation of motion, including the effect of the reaction field, is obtained and solved for a particular case. The effects of the system parameters on conversion efficiency are discussed. Restrictions on the validity of the analysis due to transverse and longitudinally pumped spin waves are examined.

ISSN:0021-8979    

DOI:10.1063/1.1728465

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Current noise measurements of the organic semiconductor polyacrylonitrile pyrolyzed in nitrogen at temperatures from 550° to 900°C reveal conductivity fluctuations similar to those attributed to carrier fluctuations in inorganic semiconductors. The current noise spectra exhibit characteristic time constants of 10−2, 3×10−4, and 5×10−5sec which are independent of pyrolysis temperature and are tentatively associated with the molecular structure leading to conductivity. The observed noise magnitude suggests the existence of a large number of independent sub‐volumes which increase in size with treatment temperature. Samples pyrolyzed above 700°C exhibit 1/fnoise that may be indicative of a different molecular structure.

ISSN:0021-8979    

DOI:10.1063/1.1728466

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

This brief preliminary report shows by a simple experiment that major flux changes in tape‐wound, magnetic‐amplifier‐type cores begin near the core's inner perimeter and progress outward, at power frequencies, as has been predicted [R. C. Barker, Trans. Am. Inst. Elec. Engrs.79‐I, 482 (1960), with accompanying discussion]. It also shows, when the core is operated on a minor hysteresis loop, that at the start of every odd half‐cycle of excitation additional small inward‐progressing flux changes occur near the outer boundary of the region in which flux was reversed during the preceding even half‐cycle. This reduces slightly the hysteresis loss in the odd half‐cycles, and the resulting energy unbalance causes the minor loop to cling to one end of the major loop—a phenomenon well known in rectangular‐loop materials. The cause of the energy unbalance was hitherto unknown, however. The method used for the experiments is observation of the voltage that appears between two probes touched to the side of the core when the core is excited by a conventional winding. This method is known to other investigators but scantily reported in the literature. It is not analyzed here, but some experimental justification is given.

ISSN:0021-8979    

DOI:10.1063/1.1728467

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A one‐dimensional analysis is given on the minority carrier transport characteristics of a transistor base region containing an arbitrary drift field distribution. This field is assumed to enhance—or retard—the motion of minority carriers between an emitter and collector junction, thereby modifying the influence of bulk recombination mechanisms. Base region transport efficiency is established in terms of the transistor current gain when an ideal emitter junction is assumed. Applications of this analysis are demonstrated by establishing the base region transport efficiency for diffused transistors. Two types of structures have been analytically investigated: the alloy‐diffused transistor, containing a diffused collector junction and an alloy‐type emitter; and the double‐diffused transistor constructed entirely by diffusion techniques. For practical semiconductor devices, a comparison of these two structures has shown negligible differences in their base region transport efficiency and, furthermore, the drift mechanisms within these diffused devices have little influence upon their one‐dimensional current gain.

ISSN:0021-8979    

DOI:10.1063/1.1728469

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The light pulses associated with the halogen‐quenched Geiger‐Mu¨ller discharge of three commercially available end‐window counters have been observed with a photomultiplier. Two of the counters were geometrically identical and filled to approximately the same pressure with neon and argon, respectively. The third tube was physically larger and contained neon. An individual light pulse, the duration of which is very much shorter than the corresponding normal voltage pulse, has a reproducible and distinctive shape. The amplitude of the light pulse and reciprocal of its risetime increase approximately linearly with increasing overvoltage. Arguments are given that relate the rise time to the velocity of propagation of the discharge. The smaller of the two neon tubes displayed double pulses over its entire Geiger region while the other tubes seemed entirely free of this phenomenon.

ISSN:0021-8979    

DOI:10.1063/1.1728470

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A normalization of practical quantities has yielded systematic forms for performance calculations of an idealized couple composed of temperature‐independent parameters. The normalized quantities can be expressed by only three parameters at most instead of six, i.e., normalized current and two types of normalized temperature difference. Effects of contact resistance, current ripple, and heat leak on practical quantities are also considered as functions of the same parameters. Proposed graphs herein of performance quantities and their variations with above effects are given respectively, including no fixed parameters. The temperature difference normalized by its maximum is recommended as ``figure of performance'' as a criterion for an operating couple.

ISSN:0021-8979    

DOI:10.1063/1.1728471

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An ordered structure is found in interstitial solid solutions as dilute as 0.1 at. % nitrogen in tantalum. On the basis of the symmetry of the ordered structure, tetrahedral rather than the usual octahedral sites are considered appropriate for the nitrogen atoms. The effect of the ordered structure on the properties of the solid solution are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1728472

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The contributions to the elastic shear constants of beryllium at 0°K were calculated on the basis of an energy band model for this metal proposed by Herring and Hill. The results are compared with those obtained assuming nearly‐free‐electron and free‐electron behavior for the valence electrons. It was found that the valence electron contribution was very sensitive to the shape of the energy bands and hence the Fermi contribution to the elastic shear constants was strongly dependent upon the energy band model chosen. On the basis of the model proposed by Herring and Hill the elastic shear constants of beryllium, like the alkali metals, are predominantly determined by the electrostatic energy of the ion‐cores.

ISSN:0021-8979    

DOI:10.1063/1.1728473

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The relative efficiencies and decay times of alpha particle induced scintillations of CaWO4and CdWO4were investigated as a function of temperature in the range 10° to 375°K. Their behavior at intermediate and high temperatures is in agreement with that expected from the Mott‐Seitz‐Kro¨ger configurational coordinate model. Values ofEQ, thermal quenching energy, of 0.34 and 0.31 ev were found for CaWO4and CdWO4, respectively. As the temperature was decreased below 60°K, an increase in the decay times and a decrease in the relative efficiencies were found. This behavior can be explained qualitatively by assuming the existence of a trapping level.

ISSN:0021-8979    

DOI:10.1063/1.1728474

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Silicon surface‐barrier photodiodes have been fabricated and the steady‐state and time‐varying photoresponse have been measured. The photodiodes are operated in the reverse‐bias, or photoconductive mode at room temperature and do not require encapsulation. The average steady‐state photosensitivity is 0.31 &mgr;a/&mgr;w (&lgr;=5461 A) and 0.065 &mgr;a/&mgr;w (&lgr;=2537 A) with approximately 50 A of gold on the sensitive area. With no gold on the sensitive area, the photosensitivity is 0.37 &mgr;a/&mgr;w and 0.13 &mgr;a/&mgr;w, respectively. The photoresponse is uniform over the sensitive area (0.1 to 2.5 cm2) to within a few percent, depending on the wavelength. The high‐frequency cutoff is limited by the photodiode capacitance and load resistance. Cutoff frequencies greater than 100 kcps have been obtained. The operating characteristics of these devices are reported for six wavelengths lying in the range of approximately 0.2 to 0.6 &mgr;. The possibility of using photodiodes of this type in combination with a scintillator crystal for detecting charged particles is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1728475

出版商:AIP    

年代:1962

数据来源: AIP