摘要:

The digital trigger circuit described in this paper allowed us to trigger digital data acquisition equipment accurately. Its main feature is a noise suppression circuit which introduces only a small phase shift and permits us to reject noise very close to the frequency range of the measured signal. The level of the rejected noise signal as well as the trigger level are adjustable with thumbwheel switches. The performance of the trigger circuit is demonstrated with a disturbed sine wave as input signal. An analog equivalent circuit with noise rejection characteristics similar to those of the pseudo‐filter is described.

ISSN:0034-6748    

DOI:10.1063/1.1134134

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A new technique has been developed to bond LaB6to rhenium under a high temperature arc. Such a bond exhibits remarkable stability even when reheated to the emission temperatures above 1500°C, and thus presents a convenient method for making compact, high intensity electron sources for SEM and other applications.

ISSN:0034-6748    

DOI:10.1063/1.1134135

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A system is described which is entirely composed of commercially available instruments. The construction of a rotating cell with two compartments is described in detail. It is furthermore shown that a differential amplifier, although applicable in most cases, cannot be used in the case of small signals on a large background because of its small dynamic range. This difficulty can be overcome by incorporating a lock‐in amplifier in the system.

ISSN:0034-6748    

DOI:10.1063/1.1134136

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A technique has been devised for electronically eliminating background signals in chopped infrared measuring systems by subtracting a reference signal of proper frequency, phase, and amplitude from the background signal. Subsequently acquired point‐source or distant‐small‐source signals are converted to dc voltage levels which are directly related to incident flux. The system, based on operational amplifier principles, permits measurements of weak radiant emissions in the far ir under signal‐to‐noise conditions beyond the capabilities of previous field portable instruments.

ISSN:0034-6748    

DOI:10.1063/1.1134137

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Operation of an automatic data acquisition system, with an on‐line minicomputer, in the 0.4–3 K temperature range is described and illustrated by results obtained on pure copper. The temperature scale was set up using both3He vapor pressure thermometry and the NBS superconductive fixed point device. On the basis of specific heat measurements on pure Cu and Cu alloys, it appears that the temperatures assigned by the NBS to the superconducting transition temperatures of cadmium and zinc are too close. The required adjustment is within their assigned uncertainty limits.

ISSN:0034-6748    

DOI:10.1063/1.1134138

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An electrical technique that uses the peaks and troughs of a sine wave source voltage is employed to measure the relative capacitance of a dynamic admittance cell containing cyclohexane at 2.1 and 6.3 GPa. Parameters for the linear shock‐particle velocity equation of motion of the liquid are deduced, and a procedure for measuring the shock temperature of selected materials is proposed. A model for shock electrification is given indicating that electrification is a consequence of a normal‐state material undergoing a species change. Cyclohexane is an unusual material under shock loading in that it does not exhibit a species change in the pressure range considered.

ISSN:0034-6748    

DOI:10.1063/1.1134139

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Two devices for the direct measurement of the anelastic properties of metals in a reactor are described. First, a resonant cavity system has been adapted for the in‐pile determination of dimensional changes, with application to strain relaxation measurements at and above room temperature. Second, an inverted torsion pendulum operated at 130 Hz at a constant amplitude has been devised for the study of internal friction in metals exposed to a fast neutron flux. The relevant detection systems and the mechanical arrangements for both apparatus are given, together with typical recorded curves.

ISSN:0034-6748    

DOI:10.1063/1.1134140

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A simple circuit is presented which allows a signal with over 100 dB of dynamic range to be recorded on a modest tape recorder. No pilot track is necessary, and the same curcuit in a different mode is used on replay to reproduce the original dynamic range. There is no spectral distortion of the recorded signal, and calibration of reference levels is unnecessary.

ISSN:0034-6748    

DOI:10.1063/1.1134141

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A microwave system for very sensitive dielectric measurements on high‐loss liquids over the frequency range 8–26.5 GHz is described which depends on the cavity resonance perturbation method. Equations for the resonance perturbation by a thin capillary in cylindrical as well as in rectangular cavities are derived, demonstrating the dependence of the real and imaginary part of &egr; on both the resonance frequency shift and the change in resonance width of the cavity. The microwave generator with high frequency stability (1 part in 108) is frequency modulated at one or two frequencies. The use of phase sensitive detection allows &egr; measurements on water to within 1%, as well as dielectric difference measurements on aqueous solutions to within 0.005 in &Dgr;&egr;′ and &Dgr;&egr;″(1 part in 104or better). Details of cavity constructions are given and some measurements on water and on dilute aqueous solutions are reported.

ISSN:0034-6748    

DOI:10.1063/1.1134142

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A transient pressure–volume–temperature (PVT) experimental technique for determining true bulk gas temperature during gas discharge from a vessel to the atmosphere is described. The bulk temperature obtained is valid no matter how nonuniform gas temperature is inside the vessel and accounts for all modes of heat transfer during discharge.

ISSN:0034-6748    

DOI:10.1063/1.1134143

出版商:AIP    

年代:1975

数据来源: AIP