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Review of Scientific Instruments

Issue 10 • Date Oct 1953

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Displaying Results 1 - 25 of 46
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • The Regular Production of 85 Percent Para Liquid Hydrogen

    Page(s): 899 - 900
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    The storage of liquid hydrogen has become much less troublesome as a result of regularly producing 85 percent para‐liquid instead of ``normal.'' An ordinary liquefaction plant was modified so that the ortho‐ to para‐conversion is catalyzed in the feed gas (at 76°K) and in the liquid within the liquefier. The liquid‐phase conversion causes the full liquefaction rate to drop from 25 to 20.5 liters/hour. Data were also obtained for other liquefaction rates, with and without feed‐gas catalysis. View full abstract»

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  • A Low‐Frequency Oscillator

    Page(s): 901 - 903
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    A low‐frequency simple‐harmonic oscillator, employing a relatively new method of approach, is described. An electronic analog computer of the differential analyzer type is used to solve the differential equation of a mass‐spring system. Three dc operational amplifiers perform the computation and a sinusoidal output is obtained as the solution of the differential equation. Frequency is variable from 0.01 to 100 radians per second in steps of 0.01 radian per second. Distortion is less than 0.1 percent. Maximum output is 90 volts peak into a load of 100 000 ohms. The oscillator is particularly useful in the design and testing of servomechanisms and electronic simulators. View full abstract»

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  • Housing for Co60 Gamma‐Ray Source For Experimental Work

    Page(s): 904 - 906
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    A relatively simple housing for experimental work with multicurie radioactive sources consists of a lead turret on a low table, the volume below the table being shielded on three sides by stationary shielding and in front by a rolling lead door. The source capsule is screwed on to the end of a rod passing through vertical holes in the turret and the table. The source can be positioned in the center of the turret when not in use and, when desired, lowered to any position adjacent to experimental equipment below the table. Using a 40‐curie Co60 source and an annular glass irradiation vessel, an average gamma‐ray intensity of 2×105 r/hr is obtained in a 5‐ml volume of liquid. View full abstract»

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  • Extrapolation Chamber for the Measurement of Beta Sources

    Page(s): 907 - 914
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    Construction and operation of a variable‐spacing, parallel‐plate ionization chamber is described. It has been designed for the measurement of beta‐particle sources of medical and biological interest. It has concentric collecting electrodes of 1, 3, 10, and 30 mm diameter. The air gap in which ionization is measured can be adjusted from 0.04 to 10 mm. Ionization current is measured with a commercial vacuum tube voltmeter which has a full scale sensitivity of 2×10-13 amp. The instrument sensitivity is about 0.4 esu/cc‐sec using a one mm diameter collecting electrode with a collecting air gap of 0.2 mm, and about 4×10-5 esu/cc‐sec using a 30 mm diameter collecting electrode with an air gap of 2 mm. Conditions are described in detail for the determination of ionization per cc in vanishingly small air gaps between polystyrene electrodes, with an accuracy of a few percent. View full abstract»

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  • Nuclear Reactions Between Heavy Nuclei

    Page(s): 915 - 916
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    A method is proposed for using a modified Van de Graaff machine for producing nuclear interactions between heavy nuclei. Negative ions are accelerated from ground to a stripping material in the high potential part of the machine where many electrons are stripped from the ions, and re‐accelerated towards the target material in a grounded end of the machine. View full abstract»

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  • A Minimal Noise Preamplifier for Proportional Counters and Similar Applications

    Page(s): 916 - 919
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    A minimal noise amplifier permitting the recognition of signals of 2μ volts amplitude over a frequency range at 760 kc is described. The device is linear over an input range of 74 db, and is compensated for power supply potential changes by means of negative feedback. View full abstract»

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  • Measurement of the Energy of Isotropic Fast Neutrons with Li6 Loaded Plates

    Page(s): 920 - 924
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    100‐micron E1 and C2 Ilford plates loaded with enriched Li6 were exposed to neutrons from Li7(p, n)Be7 and from H3(p, n)He3. The plates were rotated to mockup isotropic incidence. Neutron energies ranged from 200 to 1500 kev. The plates were faded and developed so as to obtain good triton‐alpha discrimination. Peaks having widths from 100 to 300 kev at half‐maximum were obtained, depending upon neutron energy and selection criteria. View full abstract»

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  • An Automatic X‐Ray Reflection Specimen Holder for the Quantitative Determination of Preferred Orientation

    Page(s): 925 - 928
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    A reflection specimen holder has been developed, which has several new features. A removable jig, which fits into the inner ring, is used for the rapid alignment of the specimen. Two different specimen scanning devices are described, which allow the primary beam to cover successively a large number of grains in the specimen surface while the diffracted intensity is being measured. Since many such time consuming measurements are required for an accurate pole figure, the operation of the instrument and the recording of the data have been made automatic. View full abstract»

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  • Gamma‐Ray Measurements by the Magnetic Analysis of Compton Electrons

    Page(s): 929 - 937
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    A magnetic spectrometer has been constructed which can be used to determine photon intensities and energies over an energy range of approximately 0.2 to 12 Mev. Over this energy range, the detection efficiency of the spectrometer is such that a monoenergetic photon flux density of the order of 105 photons per cm2 will produce one count. The instrument measures the momentum distribution of Compton electrons ejected from a thin beryllium foil into a small solid angle in the direction of the incident photon beam. A method of converting these measurements to corresponding photon intensities and energies is presented. The calculations necessary to convert to photon intensities are based on the Klein‐Nishina formula, and include the effects of scattering and energy loss of the electrons in the foil. The spectrometer was calibrated from (a) the line shapes produced when the gamma‐rays from the radioactive sources Cs137 (0.661 Mev) and Na24 (1.37 Mev, 2.76 Mev) were incident on the foil, and (b) the intensity measurements of these sources, obtained with an ionization chamber. View full abstract»

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  • A Direct‐Reading Rate Meter for High‐Intensity Penetrating Radiation

    Page(s): 938 - 943
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    Inherent technical difficulties in the measurement of x‐ray intensities from 100 to 5000 r/minute, at exciting potentials between 400 and 2000 KVP (kilovolts peak), have been investigated. Extending the ranges of conventional condenser‐electrometer dose meters by use of absorbing media not only increases energy dependence, but is also found to cause an apparent displacement in effective geometrical location of the ionization chamber. 250‐r, 1000‐r and 2500‐r condenser chambers have proved susceptible to serious errors from dielectric leakage, which increase rapidly with chamber range above 100 r and with radiation energy above 200 KVP. Associated measurements of voltage saturation indicate that no error from this source need be expected for full‐scale exposure times exceeding two seconds. A direct reading circuit has been developed to combine the known wavelength characteristics of ``air wall'' thimble‐type chambers with the linear current response of a portable d'Arsonval galvanometer. A 25‐r Victoreen chamber, remotely read through lengths up to 70 feet of polyethylene coaxial cable, shows linear calibration from 35 to 5500 r/minute with over‐all reproducibility to the order of ±1.5 percent. Ionization readings correspond, within the accuracy of chamber volume determination, to the definitive value of esu/cc second. View full abstract»

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  • The Development of a Fine‐Focus Flash X‐Ray Tube

    Page(s): 944 - 948
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    Analysis of image quality indicates that a significant improvement in the technique of flash radiography might be attained through reduction of focal spot size. Existing requirements on such targets are already severe. Nevertheless it has been possible, through a novel conical design, to obtain a measured focal spot one millimeter square in a sealed‐off flash tube operating at 100 kilovolts. View full abstract»

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  • Method for Obtaining Streaming Orientation and Simultaneous Determination of Dielectric Properties in Macromolecular Solutions

    Page(s): 949 - 954
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    A method has been devised for the measurement of the dielectric constant and the specific conductance of aqueous solutions undergoing streaming with velocity gradients between 0 and 10 000 sec-1. The solution to be investigated is placed in the annular space between two concentric cylinders forming the measuring cell. Electrodes are inserted in the walls of the cylinders of which the outer is fixed and the inner is rotated. Two types of cells are used; the electrical field in one case being perpendicular to and in the other case parallel with the stream lines. The impedance of the cell with the solution investigated is determined with a specially constructed Schering bridge making measurements possible in the frequency range 0.05 to 5 megacycles per second and at specific conductances of 1 to 200 μmho per centimeter. The advantage of the bridge circuit employed is that the conductance of the cell is balanced by a variable air condenser, making possible an accuracy of 0.1 percent in the values for both conductance and dielectric constant. Excellent mechanical and electrical stability and a low interference level are necessary for high accuracy. Experiments with solutions of sodium thymonucleate show that the current interpretation of the dielectric properties of macromolecules must be revised. The term streaming dielectric investigations is suggested as a suitable name for studies with the type of instrument described. View full abstract»

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  • An Integrating Photometer for X‐Ray Intensity Measurements

    Page(s): 955 - 960
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    X‐ray diffraction spots on films vary in area and are uneven in density. An instrument is described, which, after calibration against a standard intensity scale imprinted on the film, scans the spot by a light ray, and transforms transmitted light pulses into linear functions of intensity by electronic means. A figure, proportional to the intensity of the spot, is obtained on a mechanical counter. The integrating process is fully automatic, and measurement of one spot takes about a minute. Reproducibility depends on the relative intensity of the measured spot, and can be raised up to 1 percent. View full abstract»

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  • Development of a High‐Fidelity Preamplifier for Use in the Recording of Bioelectric Potentials with Intracellular Electrodes

    Page(s): 960 - 967
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    In the intracellular recording of action potentials, the fidelity of recording is limited by the resistance and capacitance of the ultramicroelectrode required for making connection to the intracellular contents, and by the characteristics of the input circuit of the amplifier. The cathode follower circuit conventionally used to minimize the time constant of the recording system is discussed and its shortcomings are analyzed. An improved circuit involving positive feedback is presented. The measurement of the recording system time constant is discussed. View full abstract»

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  • Repairing Ionization Gauge Tubes

    Page(s): 985 - 986
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  • A Proportional Counter Spectrometer for Neutrons

    Page(s): 986 - 987
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  • Ratio Recording in Isotopic Analysis

    Page(s): 987 - 989
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  • Cutting Tool for Alkali Metals

    Page(s): 989
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  • Oil Manometer for Ultra‐High Vacuum Systems

    Page(s): 989 - 990
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Aims & Scope

Review of Scientific Instruments, published by the American Institute of Physics, is devoted to scientific instruments, apparatus, and techniques.

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Meet Our Editors

Editor
Albert T. Macrander
Argonne National Laboratory