摘要:

A technique for replicating optically selected areas is described. It requires no special equipment beyond an optical microscope with a vertical illuminator, and yields a replica with the area of interest placed at an easily recognizable position with respect to the electron microscope grid.

ISSN:0034-6748    

DOI:10.1063/1.1720526

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A technique has been evolved to generate hydrostatic and uniaxial stress regimes, using a Teflon cell as a container in a conventional piston‐cylinder device. Details of the technique and calibration procedure are described. The possibility of using high resistivity as‐grown n‐GaAs for pressure measurement is indicated. Piezoresistive effects in oriented n‐Si plates were used to determine the nature of stress distribution in the pressure medium. The usefulness of the technique to semiconductor studies is pointed out.

ISSN:0034-6748    

DOI:10.1063/1.1720527

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Since the discovery of high field superconductors, it has been possible to generate high magnetic fields with lightweight, compact superconducting solenoids. In most cases, these magnets are operated in conventional liquid helium Dewars which are heavy and unwieldy and usually offer only vertical access to the magnetic field, which makes them very inconvenient for many uses, such as with optical research instrumentation. A system is described in which the magnet and cryostat are integrated into a single light weight package which weighs only 13.6 kg and provides horizontal access to magnetic fields in excess of 50 kG with working bores of 3.80 cm at temperatures near 4.2°K and 2.54 cm at room temperature for periods up to 12 h between fillings. Due to its over‐all configuration, the magnetic field is highly accessible and allows spectroscopic measurements to be made conveniently at 50 kG. Also, the system can be easily transported while it is filled with liquid helium.

ISSN:0034-6748    

DOI:10.1063/1.1720528

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The Argonne 7.7 m bent crystal gamma‐ray spectrometer is combined with a lithium drifted Ge diode detector to perform high resolution gamma‐ray spectroscopy on complicated neutron capture gamma‐ray spectra. The system combines the energy precision of the bent crystal spectrometer with the high resolution of the Ge diode. The system is most useful in the 1–3 MeV energy range where both the precision and energy resolution obtained by the combined system frequently are from 3 to 10 times those of either the bent crystal or the Ge diode used individually. A 50‐fold improvement in the signal‐to‐background ratio is obtained through the use of the combined system. The use of the system is illustrated by113Cd(n,&ggr;)114Cd spectra. The Argonne system is compared with other possible crystal diffraction arrangements and with coincidence and anticoincidence techniques for improving the quality of the (n,&ggr;) measurements. The application of the Argonne system to the comparison of (n,&ggr;) transisions with gamma transitions following radioactive decay is discussed. New values for the strong gamma transition associated with the decay of137Cs and60Co are quoted along with a more precise value (1294.35±0.30 keV) for the gamma ray associated with the decay of41A. Improvements in the Argonne system are described and a proposed extension of the system for precision energy measurements in the 2–5 MeV range is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1720529

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A simple and rapid automatic method for measuring the Seebeck coefficient of semiconductors is described. Provided that errors due to sample mounting and contacting are negligible, 1% accuracy can be achieved.

ISSN:0034-6748    

DOI:10.1063/1.1720530

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An approximate mathematical analysis of wall loading and energy dissipation is presented in lieu of comprehensive (and expensive) destructive testing, with the aim of extending previously published maximum peak current ratings for a given lamp type to flashtubes having various length/diam ratios and operating in multisection LC discharge lines (pulse forming networks). A second peak current rating, independent of pulse duration, is tentatively established in an attempt to predict failures from excessive current buildup rates.

ISSN:0034-6748    

DOI:10.1063/1.1720531

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An inertial impaction sampling device was developed for the purpose of collecting samples of liquid droplet clouds dispersed in a wind tunnel. The device is based on Stoker's smoked slide technique, which enables one to determine the diameters of impacting droplets by measuring the diameters of the impressions left in a soot coating on a glass slide. Incorporated into the sampler design is a rotary shutter mechanism which momentarily exposes eleven slides to the droplet cloud. The exposure time of the shutter can be adjusted so that it is commensurate with the density of the droplet cloud.

ISSN:0034-6748    

DOI:10.1063/1.1720532

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An apparatus for depositing thin layers of two substances in a given ratio is described. It consists of a servomechanism which controls the rate of vaporization of one of the substances with respect to the other. The performance of the installation is evaluated.

ISSN:0034-6748    

DOI:10.1063/1.1720533

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The essential component of the apparatus is a semiconductor loaded E plane ``T'' waveguide junction. The scattered wave produced by the induced anisotropy is measured. The principal result is that the apparatus directly determines the complex amplitude of the off‐diagonal element of the apparent susceptibiltiy. The technique can be used to measure effective mass at higher temperatures than is possible with the cyclotron resonance absorption cavity technique. It can also be employed to determine the mobility of powdered or irregular samples.

ISSN:0034-6748    

DOI:10.1063/1.1720534

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The standard Keˆ pendulum was modified to accommodate sheet specimens. Redesign of the specimen clamps, support rods, and inertia member made it possible to handle sheet specimens 125 mm in gauge length and 6 mm in width. Because deformation was found to distort the Snoek peak, specimens were prepared by spark machining or milling rather than by shearing. The close similarity of the background damping level and the Snoek peak height and shape for sheet and corresponding wire specimens, as well as the low amplitude dependence observed in the sheet specimens, demonstrated the acceptability of the pendulum modifications and specimen shape.

ISSN:0034-6748    

DOI:10.1063/1.1720535

出版商:AIP    

年代:1967

数据来源: AIP