摘要:

A simple modification to an RCA EMU3G electron microscope is described which makes it possible to obtain transmission pseudo‐Kossel patterns. These were analyzed to obtain accurate lattice constants for a hexagonal beryllium‐4.4 wt% copper alloy.

ISSN:0034-6748    

DOI:10.1063/1.1720968

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

This paper describes a technique for the measurement of sound velocities to pressures of 100 kbar, utilizing ultrasonic pulse techniques in which variations in transit time together with independent measurements of sample length changes are taken into account. This arrangement permits measurements to be made through and above transformations in samples under pressure and frees the apparatus from stringent parallelism requirements applicable to other interferometry techniques. The accuracy of the velocity measurements at high pressure is 1%. Results obtained in this system on gold are in good agreement with predictions based on low pressure single crystal measurements.

ISSN:0034-6748    

DOI:10.1063/1.1720969

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A simple laser method of measuring projectile displacement in a light gas gun is described in which some of the problems encountered in the use of microwaves to determine displacement are avoided.

ISSN:0034-6748    

DOI:10.1063/1.1720970

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The design, construction, and performance of a laser frequency control system using two optical discriminators to achieve both long and short term frequency stability are described. The design philosophy emphasizes the active rather than the passive approach to stabilization; consequently, the system should be applicable to situations where intrinsic stability is difficult to achieve by mechanical or thermal techniques alone.

ISSN:0034-6748    

DOI:10.1063/1.1720971

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The fundamental concepts of the Thomson heat and the basic equations governing the heat flows associated with its generation are presented. From these considerations, two different approaches to the direct measurement of the Thomson coefficient are demonstrated. The methods include a nonequilibrium technique in which the measurements are based on the initial temperature changes associated with the application of a potential gradient to a metal specimen in a thermal gradient and a technique in which the equilibrium temperature difference associated with the reversal of current flow form the basis for the calculation of the Thomson coefficient. The latter case leads to a very simple equation relating the Thomson coefficient to the change in equilibrium temperature associated with reversal of current flow. A simple calorimeter was designed and utilized to test the validity of the analysis and to compare these results with the electric current variation technique which was reported previously. The Thomson coefficients for nickel were observed as −32 ±12% &mgr;V/deg (40.1°C); −40.0±5% &mgr;V/deg (20°C) and −58.0±2% &mgr;V/deg (10°C). Those for lead were observed as −0.36±11% (41.0°C) and −0.31±3% (20°C).

ISSN:0034-6748    

DOI:10.1063/1.1720972

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A simple form of accelerometer using interference fringes of a Fabry‐Perot system is described, in which accelerations as small as 10−5msec−2(10−6g) can be measured. The variations in the light flux transmitted by the vibration‐sensitive interferometer due to relative plate displacements as small as 0.25 nm (10−8in.) are photodetected and finally displayed as a waveform on an oscilloscope. A frequency analyzer in the detection system enables any chosen harmonic component to be studied and measured. The unit can be calibrated readily in terms of the wavelength of light during measurement for any given frequency. The unit has been used to measure low vibration levels in laboratory rooms where the amplitude and frequency range of the main disturbances usually were in the ranges 0–0.05 &mgr; (0–2 &mgr;in.) and 0–50 Hz, respectively.

ISSN:0034-6748    

DOI:10.1063/1.1720973

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Measurement of the absolute temperature of microwave noise sources under field conditions is usually achieved at the expense of tedious rf attenuation measurements and the incorporation of cryogenic equipment in the measurement system. Measurement accuracy is determined by the precision to which the effects of passive rf attenuation are known. The technique described does not require this knowledge of the effects of rf attenuation on instrument calibration. The feasibility of this technique has been established by tests performed with a modified Dicke radiometer. The technique establishes the radiometer indicator output zero as a direct reading of absolute zero and provides calibration of the indicator scale directly in degrees Kelvin. Laboratory calibration of an appropriately modified radiometer and measurement of noise temperature near absolute zero are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1720974

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The construction and performance of an electron diffraction camera suitable for the examination of crystalline regions of a few hundred A˚ngstroms extension is described. Goniometric control of the angle of incidence is available under conditions of low contamination. Brief descriptions are given of applications to (a) problems of symmetry including the direct determination of noncentrosymmetric groups, (b) the determination of thickness to an accuracy of one unit cell, (c) the refinement of structure potentials, (d) the measurement of the angular dependence of absorption, (e) the collection of structural data from thin crystals, and (f) the study of imperfect crystals.

ISSN:0034-6748    

DOI:10.1063/1.1720975

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A simple apparatus is described which provides tensile strength data for fine fibers in the 5–5000 g ultimate load range. The tester features a rapid fiber mounting system, visual or strip chart readout, and a constant strain rate.

ISSN:0034-6748    

DOI:10.1063/1.1720976

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Sealing techniques are described for joining windows of lithium fluoride, magnesium oxide, and quartz to Pyrex glass, FN glass, quartz, and silver. These seals withstand repeated bakeouts at 300–350°C and can be used in ultrahigh vacuum systems.

ISSN:0034-6748    

DOI:10.1063/1.1720977

出版商:AIP    

年代:1967

数据来源: AIP