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Nov 1937

Volume 8, Issue 11, pp. 399-454

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Preparation of Large Single Crystals of Sodium Chloride

H. Walther

Rev. Sci. Instrum. 8, 406 (1937); http://dx.doi.org/10.1063/1.1752200 (3 pages) | Cited 2 times

Online Publication Date: 27 December 2004

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An apparatus and a method are described, whereby single crystals of sodium chloride are produced in the form of bars 2 cm in diameter and 30 cm long. The crystal is drawn from the melt by means of a platinum rod which is dipped into it and which is raised and rotated simultaneously by a clock mechanism. An air stream from a circular nozzle surrounding the growing crystal immediately above the surface of the molten salt provides the steep temperature gradient necessary for the continuous growth of the crystal. The orientation of the crystal with respect to the axis of the bar may be chosen at will.

A Simple Knudsen Gauge

A. L. Hughes

Rev. Sci. Instrum. 8, 409 (1937); http://dx.doi.org/10.1063/1.1752201 (4 pages) | Cited 7 times

Online Publication Date: 27 December 2004

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A simple form of Knudsen gauge has been developed in which a thin strip of aluminum leaf is suspended from its upper end in the middle of a glass tube whose axis is vertical. Alongside the aluminum leaf is mounted a platinum strip which can be heated electrically. In the presence of gas at low pressure, the aluminum leaf is pushed away from the heated strip because the molecules hitting it on the side facing the heated strip impart to it more momentum than those hitting it on the other side. The deflection of the aluminum leaf, which can be measured by a microscope with a scale in the eyepiece, is a function of the pressure of the gas, and consequently by suitable calibration, the device may be made to measure pressure. By varying the heating current through the platinum strip a wide variety of sensitivities can be readily obtained. Sensitivities ranging from 1 eyepiece scale division=3.2×10−7 mm to 1 eyepiece scale division=304×10−7 mm have been used. The upper limit at which the gauge will work satisfactorily is approximately 0.01 mm.

Two‐Pulse Oscillator

Ivan A. Getting

Rev. Sci. Instrum. 8, 412 (1937); http://dx.doi.org/10.1063/1.1752202 (2 pages) | Cited 1 time

Online Publication Date: 27 December 2004

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A circuit is described which produces pairs of pulses at any frequency up to about 6000 per second. The members of the pair may be arbitrarily close and of arbitrary amplitude. The circuit is intended for testing resolving powers of pulse‐recording circuits.

A Vacuum Tube Circuit for Scaling Down Counting Rates

E. C. Stevenson and I. A. Getting

Rev. Sci. Instrum. 8, 414 (1937); http://dx.doi.org/10.1063/1.1752203 (3 pages) | Cited 17 times

Online Publication Date: 27 December 2004

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A scaling circuit is described which differs from that of the Wynn‐Williams type in using vacuum tubes instead of thyratrons. Its short resolving time (better than 1/50,000 second), its stability, and its durability over extended periods of operation recommend it for accurate recording of high speed Geiger counter discharges.

Radiation Thermopiles

A. H. Pfund

Rev. Sci. Instrum. 8, 417 (1937); http://dx.doi.org/10.1063/1.1752204 (3 pages) | Cited 6 times

Online Publication Date: 27 December 2004

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Thermopiles of the type to be described have been made for many years. The sole purpose of the present note is to set forth the technique which has been developed for the making of the junction. The theory of thermopiles as well as the construction of other types is covered by a fairly complete bibliography at the end of the paper. In the present procedure of forming the actual ``junction,'' no solder whatsoever is used; furthermore, the number of failures is reduced to a minimum. The mode of mounting is based on a study of those thermopiles which still survive after a long and active life.

An Improved Apparatus for Measuring Surface and Body Temperature

J. D. Hardy and G. F. Soderstrom

Rev. Sci. Instrum. 8, 419 (1937); http://dx.doi.org/10.1063/1.1752205 (4 pages) | Cited 4 times

Online Publication Date: 27 December 2004

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A radiometric device adapted to the measurement of temperatures of black surfaces is described. The precision of the instrument is such that surface temperatures may be measured to ±0.01°C. The apparatus has been used for the measuring of skin temperatures in humans. With the thermoelectric body thermometer, also described the, apparatus is ideal for studying thermal changes in the human body.

A Simplified Hydrogen Liquefier

J. E. Ahlberg, I. Estermann, and W. O. Lundberg

Rev. Sci. Instrum. 8, 422 (1937); http://dx.doi.org/10.1063/1.1752206 (5 pages) | Cited 4 times

Online Publication Date: 27 December 2004

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By using a ``twisted tube'' heat interchanger, it has been possible to build a small hydrogen liquefier of great simplicity and efficiency, which can be operated from commercial hydrogen cylinders without the use of a compressor and delivers about one liter of liquid hydrogen per hour.

Quantity Heads for the Air‐Driven Ultracentrifuge

Ralph W. G. Wyckoff and J. B. Lagsdin

Rev. Sci. Instrum. 8, 427 (1937); http://dx.doi.org/10.1063/1.1752207 (3 pages) | Cited 3 times

Online Publication Date: 27 December 2004

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Abstract Unavailable

Simple Circuit for Generator Voltage Stabilization

Paul Kirkpatrick and Keith Harworth

Rev. Sci. Instrum. 8, 430 (1937); http://dx.doi.org/10.1063/1.1752208 (2 pages)

Online Publication Date: 27 December 2004

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The output voltage of an a.c. or d.c. generator may be rendered invariant to changes in speed by exciting the field from a storage battery bucked by an auxiliary d.c. generator which is driven at the same speed as the principal generator.

A Method for Magnetic Spectrograph Calculations

F. T. Rogers

Rev. Sci. Instrum. 8, 432 (1937); http://dx.doi.org/10.1063/1.1752209 (5 pages)

Online Publication Date: 27 December 2004

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A method is presented for calculating the kinetic energies of charged particles from magnetic spectrograph data. The method is of some generality in that it is valid for a magnetic field which may depart appreciably from perfect uniformity, provided only that the field focus the particles properly. It is suggested that, although the method is quite lengthy, it might be of use for calculations based on measurements of the highest precision and for calculations of ordinary precision based on data taken with a magnetic field which is not at all uniform.

The Adjustment of a Crystal for Oscillation X‐Ray Photographs

Otis P. Hendershot

Rev. Sci. Instrum. 8, 436 (1937); http://dx.doi.org/10.1063/1.1752210 (3 pages) | Cited 6 times

Online Publication Date: 27 December 2004

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Abstract Unavailable

A Simple Quartz Fiber Electrometer

C. C. Lauritsen and Thomas Lauritsen

Rev. Sci. Instrum. 8, 438 (1937); http://dx.doi.org/10.1063/1.1752211 (2 pages) | Cited 4 times

Online Publication Date: 27 December 2004

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Abstract Unavailable

Cloud Chamber for Nuclear Disintegration Studies

H. R. Crane

Rev. Sci. Instrum. 8, 440 (1937); http://dx.doi.org/10.1063/1.1752212 (5 pages) | Cited 1 time

Online Publication Date: 27 December 2004

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Construction of an entirely automatic cloud chamber particularly adapted to the study of the high energy electrons produced in artificial disintegration experiments is described. Air core coils which are capable of producing magnetic field strengths up to 4000 gauss at the time of expansion are used. An incandescent light source, using three 1000‐watt projection bulbs furnishes sufficient light for ⅕ second camera exposure.

Axial Magnetic Suspensions

F. T. Holmes

Rev. Sci. Instrum. 8, 444 (1937); http://dx.doi.org/10.1063/1.1752213 (4 pages) | Cited 31 times

Online Publication Date: 27 December 2004

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A vertical ferromagnetic needle can be supported in macroscopic equilibrium by magnetic forces alone. One method using a variable magnetic field is described and shown to have considerable latitude in details of application. A 6 g rotor having a moment of inertia of about 0.8 g cm2 was suspended in this manner. It was spun at about 1200 rev./sec., its behavior indicating that with suitable driving arrangements much higher speeds should be attainable. At 600 rev./sec. with driving torque zero it exhibited a deceleration of about 2×10−3 rev./sec.2. A suspended element weighing about ¾ g showed torsion constants, depending on adjustments, down to 7×10−6 dy cm/rad.

An Oil‐Immersed Generating Voltmeter

Harold A. Thomas

Rev. Sci. Instrum. 8, 448 (1937); http://dx.doi.org/10.1063/1.1752214 (2 pages) | Cited 2 times

Online Publication Date: 27 December 2004

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An oil‐immersed generating voltmeter has been constructed and tested. Its chief advantages compared to one operated in air are compactness and increased sensitivity due to the higher dielectric constant. Dimensions of the parts of the instrument are included.
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