摘要:

Internal conversion cascading in fragments from thermal‐neutron‐induced fission of235U was studied through the measurement of the x rays emitted by the fragments. Two high‐resolution Si(Li) semiconductor detectors were used to measure the x rays which are emitted when internal conversion occurs during the deexcitation of a fragment nucleus. The energies of the two coincident x rays and the kinetic energy of a fission fragment, if present, were recorded event by event as three‐parameter data. The yield of x rays was obtained for the events when two or more x rays were emitted from the same element for the cases of fission and nonfission coincidences and for the events when both fission fragments emitted one or more x rays in coincidence with fission. The yield of x rays from the different elements produced in fission was also measured for single x‐ray fission detections. From the results of the experiment, it was found that the odd‐Zelements of the heavy‐fragment region had a higher proportion of their x rays emitted in multiple‐emission events than did the even‐Zelements. An increase in the single‐x‐ray yield per fragment aboveZ=57 was observed for the even‐Zelements 58 and 60. This rise was not present in the multiple‐x‐ray yields and hence was attributed to the possible enhancement of single low‐energy transitions in the even‐even nuclei of these two elements. It was also observed that, on the average, for a given element split x‐ray emission is anticorrelated; there is a preference for x‐ray emission from one or the other of the two complementary fission fragments.

ISSN:0021-8979    

DOI:10.1063/1.325549

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The time‐dependent impedance behavior of large‐aspect‐ratio pinched electron‐beam diodes with no external magnetic field is investigated using two pulsers having 0.4–1.0 MV voltage, and the experimental results are compared to predictions from a time‐dependent computer code which incorporates several important mechanisms that affect diode impedance. A discussion of these mechanisms includes experimental evidence of their existence and their effects on the observed diode impedance. A simple model for the current is used in a time‐dependent analysis of the data in order to demonstrate qualitative effects. The rise time of the electric field, the cathode‐plasma velocity, the time‐dependent generation of ion sources from the anode, and the special diode geometries (tapered cathodes) are shown to affect the diode impedance in good agreement with theory.

ISSN:0021-8979    

DOI:10.1063/1.325550

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Lasing spectra of a transverse‐mode‐stabilized AlGaAs laser of a channeled‐substrate planar structure have been investigated. These lasers, which oscillate in the fundamental transverse mode, reproducibly operate in a single longitudinal mode. In addition, their linewidth is as narrow as or smaller than 30 MHz when the injection current is ∼1.2 times above threshold. The intensity distribution and excitation dependence of a nonlasing longitudinal mode have been found to be more complicated than expected from a simple theory: sizable dips have been observed in the envelope function, and nonlasing modes have been found to decrease as the injection current is increased above threshold. Furthermore, hysteresis has invariably been observed in the lasing‐wavelength–vs–device‐temperature (or dc current) characteristics. These behaviors are believed to reflect a slightly inhomogeneous nature of the gain spectrum because of a finite thermalization time of injected carriers, as discussed recently by Yamada and Suematsu.

ISSN:0021-8979    

DOI:10.1063/1.325551

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We discuss the propagation of nonlinear optical pulses in dispersive media in the presence of inhomogeneities. Two kinds of inhomogeneities are considered, one arising due to radial variation of the refractive index of the medium and the other due to boundary conditions at the medium boundary, i.e., at the radius of an optical fiber. The wave equation is solved in the presence of these effects, taking an average of the radial dependence. It is shown that inhomogeneities have a remarkable influence on the dispersive properties of the medium, and even at normal dispersion, ’’light’’ pulses can be used for soliton transmission. Numerical results are obtained for a Nd : glass laser (&lgr;=1.06 &mgr;m) propagating in SiO2glass.

ISSN:0021-8979    

DOI:10.1063/1.325552

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A novel nonvolatile semiconductor memory called the light‐activated storage device (LASD) is reported. It consists of a thin metal–silicon‐dioxide–silicon (MOS) structure with the SiO2layer ion implanted with impurities such as As or P which create light‐sensitive traps. The sites resulting from the implantation are charged (’’write’’ operation) by using light and a moderate‐voltage bias to photoinject carriers from the metal or silicon contacts into the SiO2where some of the carriers are trapped on these sites as they traverse the oxide layer. It is discharged (’’erase’’ operation) by using light and a low‐voltage bias to photoionize these trapped charges while blocking photoinjection from the contacts with the internal field of the trapped charges. The ’’write’’ and ’’erase’’ properties of this structure are investigated as a function of the ion used (As or P), ion fluence, ion energy, and oxide thickness. The LASD is shown to have reproducible cycling properties and excellent charge retention.

ISSN:0021-8979    

DOI:10.1063/1.325553

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

TE‐TM mode conversion was studied in LPE‐grown garnet films with high Faraday rotation (up to 1800 °/cm at 1.15‐&mgr;m wavelength) and positive uniaxial anisotropy. High conversion ratios (80–90&percent;) were found for several modes. The phase matching is satisfactorily explained by the birefringence in the film resulting from the misfit stress.

ISSN:0021-8979    

DOI:10.1063/1.325554

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The optical‐storage effect in evaporated films of arsenic trisulfide (As2S3) has been investigated. The physical and chemical aspects of the films were studied using a combination of etching, x‐ray diffraction, ir spectroscopy, and annealing experiments. This study of the As2S3optical‐storage medium has culminated in the development of a physical model involving three well‐defined states for the medium.

ISSN:0021-8979    

DOI:10.1063/1.325555

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Observation of the electrical characteristic of the glow discharge allows easy study of the influence of additives and contaminants. Moreover, when arcing occurs, interesting information is obtained by observing the damping of the arc current. The efficacy of the low‐ionization organic additive to prevent arcing is confirmed, and the deleterious influence of oxygen contamination is demonstrated. This result accounts for the technical rule of preventing air from entering the discharge vessel. Increased output peak power is observed, resulting from the use of a suitable additive.

ISSN:0021-8979    

DOI:10.1063/1.325536

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A new method for determining refractive‐index changes in Ti‐diffused LiNbO3optical waveguides is reported. The measurement process was as follows: (1) Diffusion profiles and Ti concentrations in LiNbO3optical waveguides were measured by an x‐ray microanalyzer. (2) Ti concentrations in the samples were converted into refractive‐index changes using calibration curves which gave the relation between Ti concentrations and refractive‐index changes. The calibration curves were obtained from highly Ti‐diffused LiNbO3samples, as well as Ti‐doped LiNbO3single crystals. As an example, the maximum refractive‐index changes of a Ti‐diffused LiNbO3optical waveguide made at 1000 °C for 10 h were determined to be &Dgr;ne=1.05×10−2and &Dgr;no=7.7×10−3.

ISSN:0021-8979    

DOI:10.1063/1.325537

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A new method is proposed for the multiplication of the mass transport effect of thermal diffusion and is applied to gas compression using thermal energy without any machinery. Experiments were carried out for compression of air using a highly porous material as a diffusion medium in order to confirm the principle of the method.

ISSN:0021-8979    

DOI:10.1063/1.325538

出版商:AIP    

年代:1978

数据来源: AIP