摘要:

A method of measuring magnetic field strengths is described which utilizes the incremental permeability of a small Permalloy core. Alternating‐current excitation is used which in turn permits amplification and hence a relatively high sensitivity and accuracy.

ISSN:0034-6748    

DOI:10.1063/1.1740906

出版商:AIP    

年代:1947

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1740907

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

Water drops and water‐alcohol drops formed in a Wilson cloud chamber were photographed with periodic illumination and their velocity was measured. The drop size was determined by means of Stokes' law, and the square of the radius of the drop was found to vary linearly with time as soon as the drop was large enough to register photographically. A 60‐cycle neon light that moved with constant velocity during the exposure was turned on by the expansion valve. This light was photographed on the same frame, and its flashes were used to establish the zero of the time scale for the drop images. It was observed that the straight line obtained from the experimental points intersected the time axis about 0.1 sec. after the zero. This fact seems to indicate that the rate of growth of the drops is smaller during the first 0.1–0.2 sec. and then reaches a constant value. The slope of the straight part of the curve was found to be about 7.5×10−6cm2/sec. for water and 4.4×10−6cm2/sec. for water‐alcohol.

ISSN:0034-6748    

DOI:10.1063/1.1740908

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

A sensitive boron trifluoride ionization chamber for the detection of weak neutron sources is described. Its efficiency for Ra‐Be neutrons is about 2 percent with a background of 15 c/min.

ISSN:0034-6748    

DOI:10.1063/1.1740909

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

One method of determining particle energies in nuclear research depends upon the measurement of pulses produced by the particles in an ionization chamber. The Pulse Analyser is an instrument which analyses the electrical pulses from the chamber into a number of classes according to their amplitude and hence produces an energy spectrum of the particles. It has the following features: (1) every pulse is counted ensuring the highest accuracy for a given time; (2) some indication of the final result appears while the experiment is in progress; (3) the number of pulses within a certain amplitude range is recorded by a mechanical counter, eliminating most of the labor required for obtaining results. Problems of design are discussed, and a brief survey of the ways in which they are treated in five different Pulse Analysers is given. One of these instruments, built by the authors, is described in detail. This Analyser is designed for slowly rising pulses (up to 1 millisecond in duration) and for low counting rates (up to a few hundred per minute). It has 20 identical channels, each channel recording the pulses within an amplitude range that can be varied from 0.1 to 10 volts. The performance of the Analyser is discussed and some typical results obtained with it are given.

ISSN:0034-6748    

DOI:10.1063/1.1740910

出版商:AIP    

年代:1947

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1740891

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

A method of using an electrical network to solve a determinental or secular equation has been devised (i.e., to determine the characteristic values of a real, symmetrical matrix). By plugging suitable coils and condensers into a panel board, a network is assembled which has for its description at resonance an equation identical with the secular determinant. The circuit consists ofnjunction points, each connected to every other through fixed reactive admittances equal to the corresponding off‐diagonal terms of the matrix, and each connected to ground through a fixed admittance equal to the negative of the sum of the constant part of the diagonal term and the off‐diagonal terms in the same row or column. In addition each junction is connected to ground through a variable admittance which represents the unknown in the equation; these latter admittances are equal for all of the junction points. While the network is excited with alternating current from a constant current source of constant frequency, the variable admittances are all altered simultaneously by the same amount until all the maxima of the electromotive forces of the junction points with respect to ground have been found. The values of the variable admittances at the several maxima constitute the desired roots. Usually an accuracy of better than one percent is obtained.

ISSN:0034-6748    

DOI:10.1063/1.1740892

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

The design of a vortex tube of good efficiency in which the expansion of a gas in a centrifugal field produces cold is described. The important variables in construction and operation are discussed and data for several tubes under various operating conditions are given. Low pressure gas, 2 to 11 atmospheres, enters the tube and two streams of air, one hot and the other cold, emerge at nearly atmospheric pressure. The cold stream may be as much as 68°C below inlet temperatures. Efficiencies and applications are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1740893

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

A four‐channel electronic switch and amplifier designed for direct connection to the deflection plates of commercial oscilloscopes are described. The system permits the simultaneous presentation of four signals and responds uniformly to d.c. voltages and a.c. voltages with frequencies up to 100 Kc. It may be used for visual observation in this range, for film recording of the wave form of individual cycles up to 1 Kc frequency, and for recording the modulation on carrier signals with frequencies up to 100 Kc. A discussion of the principles, circuit, and results are given.

ISSN:0034-6748    

DOI:10.1063/1.1740894

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

A device is described which was developed for the rapid computation of rays in a medium in which the index of refraction or speed is a function of only one rectangular coordinate. It was used during the war for the computation of sound fields in water in the ray approximation, and hence is called the sonic ray plotter. It could also be applied to the ray approximation solution of the problem of the propagation of radar signals in a stratified atmosphere, since it is possible to transform the curvature of the earth into an additional refractive index that depends only on the height above a plane earth.

ISSN:0034-6748    

DOI:10.1063/1.1740895

出版商:AIP    

年代:1947

数据来源: AIP