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Dec 1948

Volume 19, Issue 12, pp. 833-931

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A New Form of Viscometer for Transparent Viscous Liquids

A. A. Elkarim

Rev. Sci. Instrum. 19, 833 (1948); http://dx.doi.org/10.1063/1.1741180 (2 pages)

Online Publication Date: 20 December 2004

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This method is based on the application of Stokes's law, and its aim is to measure the coefficient of viscosity of transparent viscous liquids. The method is to allow air bubbles of maximum diameter to evolve by a manometer system from the bottom to top of a liquid placed in an adjacent adjoining glass cell.

An Autographic Stress Relaxometer

Richard S. Stein and Herman Schaevitz

Rev. Sci. Instrum. 19, 835 (1948); http://dx.doi.org/10.1063/1.1741181 (5 pages) | Cited 1 time

Online Publication Date: 20 December 2004

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An autographic stress relaxometer has been designed and constructed for studying the relaxation of the stress of a polymer film elongated to constant length. The force‐measuring element is a linear variable differential transformer which measures the distortion of a flexible steel ring and drives a recorder. The sample is elongated to the desired length automatically, and the correct length is maintained by means of a second differential transformer.

Optical Measurements of Surface Films. I

Alexandre Rothen and Marjorie Hanson

Rev. Sci. Instrum. 19, 839 (1948); http://dx.doi.org/10.1063/1.1741182 (3 pages) | Cited 14 times

Online Publication Date: 20 December 2004

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Practical information is given concerning the calibration of an instrument called the ellipsometer, which is used to measure thicknesses from one angstrom unit up to many thousands angstrom units of transparent films deposited on polished metal slides. The instrument is a half‐shadow instrument taking advantage of the ellipticity of polarized light reflected from film‐coated metallic surfaces. The half‐shadow is produced by depositing a different thickness of transparent material on the lower and upper part of the slides, or by evaporating directly on the lower part of chromium slides a thin layer of gold.

Some Properties of BF3 in Ionization Chambers

John A. Bistline

Rev. Sci. Instrum. 19, 842 (1948); http://dx.doi.org/10.1063/1.1741183 (5 pages) | Cited 12 times

Online Publication Date: 20 December 2004

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Measurements of the collection of electrons in BF3 due to alpha‐particle ionization pulses are described. Comparison of pulse heights showed that 1.33 as much energy is required to produce an ion pair in BF3 as in argon. The mean drift distance of an electron before capture in BF3 at 76 cm varies from 1.25 cm at an E/P of 5 (volts/cm/cm of Hg) to 7.25 cm at an E/P of 20. The drift velocity is observed and varies from 0.5×106 cm/sec. to 2.5×106 cm/sec. over the range of E/P used. The method of preparation of pure BF3 is described.

The Speeds of Diffusion Pumps for Gases of Low Molecular Weight

J. Blears and R. W. Hill

Rev. Sci. Instrum. 19, 847 (1948); http://dx.doi.org/10.1063/1.1741184 (5 pages) | Cited 6 times

Online Publication Date: 20 December 2004

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The evidence for a general relationship between the speed of a diffusion pump and the molecular weight of the gas being pumped is reviewed. Experiments are described which show that when pumps are operated at their normal ratings, the speeds for hydrogen and helium may be considerably lower than for nitrogen, and it is established that this is due to the relative ease with which the lighter molecules diffuse from the fore‐vacuum to the high vacuum side of the jet. The speeds of diffusion pumps for different gases are not in fixed ratios, but in ratios which depend upon the fore‐vacuum pressure and the heat input to the pump boiler. At heater wattages exceeding twice normal the inverse (M)☒ law may sometimes be obeyed.

A Microwave Gas Discharge Counter for the Detection of Ionizing Radiation

Sanborn C. Brown and John J. McCarthy

Rev. Sci. Instrum. 19, 851 (1948); http://dx.doi.org/10.1063/1.1741185 (10 pages) | Cited 4 times

Online Publication Date: 20 December 2004

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Characteristics of a gamma‐ray counter making use of a 3000‐megacycle gas discharge in a coaxial mode cavity resonator are described. The breakdown of a discharge in gases at these frequencies does not depend upon secondary effects. Since the breakdown is not controlled by positive ions, shorter breakdown and resolving times than those of a Geiger‐Müller counter are realized. In the high frequency discharge, ambipolar diffusion is the controlling factor in loss of electrons. A d.c. clearing field is superimposed on the a.c. field to eliminate electrons rapidly. A quenching agent is present to suppress electron emission from positive ion bombardment of the walls. The discharge is extinguished by reducing the magnetron power electronically. The plateau and sensitivity characteristics are similar to those of a Geiger‐Müller counter.

A Vacuum Spectrograph for the Infra‐Red

Richard M. Badger, Lloyd R. Zumwalt, and Paul A. Giguère

Rev. Sci. Instrum. 19, 861 (1948); http://dx.doi.org/10.1063/1.1741186 (5 pages) | Cited 11 times

Online Publication Date: 20 December 2004

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A description is given of a 1‐meter focus vacuum grating spectrometer for the infra‐red which is distinguished by its versatility and compactness of design. The vacuum container is tubular in form and all optical parts are mounted on a carriage which is readily retractable from the case for adjustment. A novel feature is the use of a sine screw drive which gives a linear wave‐length scale. A representative spectrum tracing is given.

The Electron Multiplier as a Counter for 10‐Kev Protons

J. M. Robson

Rev. Sci. Instrum. 19, 865 (1948); http://dx.doi.org/10.1063/1.1741187 (7 pages) | Cited 9 times

Online Publication Date: 20 December 2004

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Electron multipliers similar to the type described by J. S. Allen are being used as counters for low energy protons. Multipliers with electrodes made from soft beryllium copper count protons in the energy range 5 kev to 10 kev with an efficiency between 80 percent and 100 percent. Efficiencies of about 100 percent have been obtained with a radioactive alpha‐source and about 0.2 percent with a RdTh gamma‐source.

An X‐Ray Diffraction Photometer

C. L. Christ, E. F. Champaygne, R. Bowling Barnes, and C. F. Salzman

Rev. Sci. Instrum. 19, 872 (1948); http://dx.doi.org/10.1063/1.1741188 (7 pages)

Online Publication Date: 20 December 2004

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An automatic recording instrument which permits the direct comparison of the x‐ray diffraction patterns of two separate powder samples has been constructed through suitable modification of a commercial North American Philips Geiger counter x‐ray diffraction spectrometer. Some of the experimental results obtained with the new instrument are shown, and possible applications to qualitative and quantitative analysis indicated.

A Technique for the Making and Mounting of Fine Mesh Screens

H. B. Law

Rev. Sci. Instrum. 19, 879 (1948); http://dx.doi.org/10.1063/1.1741189 (3 pages) | Cited 3 times

Online Publication Date: 20 December 2004

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A new process has been developed for making fine mesh metal screens from glass masters. The master contains grooves corresponding to the screen wires. Metal is sputtered on the master, rubbed off the surface and the remaining metal in the grooves plated to form the screen. Screens from 200 to 1500 meshes per inch have been made with better than 50 percent transmission.
A method of mounting the screens on a ring and subsequent tightening by heat treatment is described.

Constant Temperature Operation of the Hot‐Wire Anemometer at High Frequency

Eli Ossofsky

Rev. Sci. Instrum. 19, 881 (1948); http://dx.doi.org/10.1063/1.1741190 (9 pages) | Cited 12 times

Online Publication Date: 20 December 2004

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Constant temperature operation of the hot‐wire anemometer offers advantages in the study of large velocity fluctuations, of frequency as high as 30,000 cycles per second. To avoid spontaneous oscillations in this type of instrument a carefully designed bridge and amplifier are necessary. Such a design, treating the whole instrument as a feed‐back amplifier, is presented, and minimum requirements for the amplifier proper are found in terms of wire parameters. The thermal noise level of the constant temperature instrument is calculated to be five times higher than that of a comparable constant current instrument because of the additional band width necessary for stable operation.

A Simon‐Type Helium Liquefier with Transfer Siphon

Russell B. Scott and J. Williamson Cook

Rev. Sci. Instrum. 19, 889 (1948); http://dx.doi.org/10.1063/1.1741191 (6 pages) | Cited 6 times

Online Publication Date: 20 December 2004

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A helium liquefier utilizing the Simon expansion process is described. The liquefier is provided with a transfer siphon, so that the liquid produced is delivered into an external cryostat. By locating the expansion valve at the end of the transfer siphon, the cold gas released during the expansion is utilized in precooling the receiver, so that rather high yields are obtained. From the expansion chamber of 400‐cm3 capacity, 310 cm3 of liquid are collected in the receiver.

The Production of Intense Ion Beams in a Mass Spectrometer

Rene H. Bernas and Alfred O. Nier

Rev. Sci. Instrum. 19, 895 (1948); http://dx.doi.org/10.1063/1.1741192 (5 pages) | Cited 10 times

Online Publication Date: 20 December 2004

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A simple 60° mass spectrometer has been built for the production of intense ion beams. Ions are produced by allowing an electron beam collimated by a transverse magnetic field to bombard the vapor issuing from a furnace. By adjusting conditions properly an arc may be struck and total ion currents of 1 to 2 ma could be obtained from the source when the accelerating voltage applied was 15 kev. The collected isotopes were completely resolved, and a total current of 0.3 ma for the several isotopes at the final collector was observed. Because of gas focusing at the operating pressure, space charge effects did not seriously affect the resolution and a resolving power of 1/100 could be obtained. In a 14‐hr. run 6.5 mg of separated zinc isotopes were collected. Preliminary results with magnesium, as well as other solids, indicated that many other substances could be separated without modifying the apparatus. Improvements which would permit higher yields are suggested.

High Voltage Pulser for 184‐Inch Cyclotron Electric Deflector

Q. A. Kerns, W. R. Baker, R. F. Edwards, and G. M. Farly

Rev. Sci. Instrum. 19, 899 (1948); http://dx.doi.org/10.1063/1.1741193 (6 pages) | Cited 1 time

Online Publication Date: 20 December 2004

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This paper describes a high voltage pulse generator developed to deflect the beam of the 184‐inch cyclotron at Berkeley, California. The apparatus develops a deflecting potential of 200 kilovolts that rises from 10 percent to 90 percent of peak value in 0.1 microsecond. The unit employs two similar 100 kilovolt water cooled pulse transformers connected symmetrically about ground to the electric deflector bars. Water‐cooled General Electric pulse capacitors are discharged through the two turn primary windings of the pulse transformers by triggering a battery of 16 paralleled Kuthe 5C22 hydrogen thyratrons.
Output voltages are developed across the 17‐turn secondary winding of the pulse transformer. The transformer is mounted in an oil‐filled Lucite case that provides both insulation and compact design.

High Frequency Proton Source

Robert N. Hall

Rev. Sci. Instrum. 19, 905 (1948); http://dx.doi.org/10.1063/1.1741194 (6 pages) | Cited 11 times

Online Publication Date: 20 December 2004

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A proton source employing a 450‐mc/sec. electrodeless discharge in the presence of a magnetic field is described. Ion currents of 400 μa, consisting of over 60 percent protons, are normally obtained, corresponding to a current density due to focused and analyzed protons of 0.03 amp./cm2 at the 1‐mm exit hole. The source requires a hydrogen flow of 30 cc/hr., most of which is prevented from entering the accelerating column by the use of a differential pumping arrangement. The ions diffuse out through the exit hole and are accelerated without the use of a probe, resulting in a well focused, monoenergetic beam accompanied by relatively few stray ions. The experimental results were obtained on a 120‐kv accelerator designed to simulate the initial sections of a typical constant voltage accelerator.

A Study of Small Ether‐Argon Geiger‐Müller Counters

C. V. Robinson and R. E. Peterson

Rev. Sci. Instrum. 19, 911 (1948); http://dx.doi.org/10.1063/1.1741195 (4 pages) | Cited 2 times

Online Publication Date: 20 December 2004

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A variety of ether‐argon mixtures were tried in counters with cathodes ranging in diameter from 0.268″ to 0.038″ and with wires ranging in diameter from 2.3 mils to 0.5 mil. The results suggest an optimum relationship between cathode diameter, wire size, and mixture. Good characteristics were obtained with cathodes as small as 0.067″ in diameter. Small probing counters designed on the basis of this relationship are described.
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Infra‐Red Spectrometer Recording System

John Hovorka and Edward A. Dunlap

Rev. Sci. Instrum. 19, 915 (1948); http://dx.doi.org/10.1063/1.1741196 (2 pages)

Online Publication Date: 20 December 2004

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Abstract Unavailable

A Null‐Reading Fluxmeter

C. C. Lauritsen and T. Lauritsen

Rev. Sci. Instrum. 19, 916 (1948); http://dx.doi.org/10.1063/1.1741197 (1 page) | Cited 8 times

Online Publication Date: 20 December 2004

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Abstract Unavailable

Liquid Helium Depth Gauge

J. R. Feldmeier and B. Serin

Rev. Sci. Instrum. 19, 916 (1948); http://dx.doi.org/10.1063/1.1741198 (2 pages) | Cited 7 times

Online Publication Date: 20 December 2004

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Abstract Unavailable

A Method of Constructing Cu‐Constantan Thermocouples

Howard J. Carter

Rev. Sci. Instrum. 19, 917 (1948); http://dx.doi.org/10.1063/1.1741199 (2 pages) | Cited 1 time

Online Publication Date: 20 December 2004

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Abstract Unavailable

Note on High Pressure Cloud‐Chamber Operation

J. S. Laughlin

Rev. Sci. Instrum. 19, 918 (1948); http://dx.doi.org/10.1063/1.1741200 (2 pages) | Cited 1 time

Online Publication Date: 20 December 2004

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Abstract Unavailable

Vacuum Fittings

C. C. Lauritsen and T. Lauritsen

Rev. Sci. Instrum. 19, 919 (1948); http://dx.doi.org/10.1063/1.1741201 (2 pages) | Cited 1 time

Online Publication Date: 20 December 2004

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Abstract Unavailable

Vapor Pressure Data for Various Substances (A Graphical Presentation)

R. R. Law

Rev. Sci. Instrum. 19, 920 (1948); http://dx.doi.org/10.1063/1.1741202 (3 pages)

Online Publication Date: 20 December 2004

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Abstract Unavailable

The Efficiency of Radiation Shields

A. E. De Barr

Rev. Sci. Instrum. 19, 922 (1948); http://dx.doi.org/10.1063/1.1741203 (1 page)

Online Publication Date: 20 December 2004

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Abstract Unavailable
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Erratum: A Mass Spectrograph for Radioactive Isotopes

Lloyd G. Lewis and Richard J. Hayden

Rev. Sci. Instrum. 19, 922 (1948); http://dx.doi.org/10.1063/1.1741204 (1 page)

Online Publication Date: 20 December 2004

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Abstract Unavailable
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