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Review of Scientific Instruments

Issue 7 • Date Jul 1959

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Displaying Results 1 - 25 of 36
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Dynamic‐Condenser Magnetic Fluxmeter

    Page(s): 513 - 521
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    This instrument was designed to measure and control the flux density between the poles of an iron‐core electromagnet used in conjunction with a beta‐ray spectrometer. A sensing coil, rotating at 1800 rpm, generates 0.115 v (rms) per gauss. A comparison signal, against which the emf of the coil is bucked, is generated electrostatically by a dynamic condenser. Its rotor plates are shaped to produce a sinusoidal wave form. The amplitude of the comparison signal is determined by a dc voltage applied between two stator sections which are juxtaposed on opposite sides of the rotor shaft. This voltage thus provides a measure of the field strength. An unbalanced condition results in the appearance of a 30‐cps error signal at the stator sections (which are isolated with respect to ac). After amplification and synchronous rectification, this signal indicates the degree and phase of the imbalance. The motor speed is maintained constant by a precision 60‐cps tuning fork. The stability of the fluxmeter is of the order of one part in 2500, as determined by the reproducibility of the positions of internal‐conversion‐electron lines from Bi207 and Cs137 sources. View full abstract»

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  • Use of Capacity‐Controlled rf Energized Ionization Transducer for Balancing Rotors

    Page(s): 522 - 523
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    A rotor‐balancing technique is described in which conventional laboratory equipment may be used. The orbiting motion of a rotating shaft within its own fixed bearings is detected by capacitor probes. After passing through the transducer circuit, the signal is displayed on an oscilloscope. It is therefore possible to obtain the necessary balancing information at operating conditions. View full abstract»

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  • Flux Concentrator for High‐Intensity Pulsed Magnetic Fields

    Page(s): 524 - 533
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    Use of multiturn coil structure in the production of several hundred kilogauss pulsed fields is discussed with specific emphasis on coil life. The magnetic force that shortens the coil life is reduced by introducing a flux concentration device. Into the multiturn coil is inserted a rigid, slotted metal slug that generates induction current in such a way as to shift the magnetic flux from the multiturn to the central vacuum region and serves as a flux concentrator. Electromagnetically and mechanically this scheme is a convenient synthesis of the multiturn and single turn coils. The advantage of this scheme is most apparent for tape‐wound coil structures, and a quantitative analysis of the flux pattern relevant to this coil system is given. An analog computer is employed in solving the time dependence of the field. The results are documented by experimental tests carried out with a 3000‐μf, 4‐kv capacitor bank. View full abstract»

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  • Low‐Noise Hydrophone Preamplifier

    Page(s): 533 - 535
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    The design and performance of a low‐noise hydrophone preamplifier is described. Transistors are used throughout the circuit and it is shown that, although the noise figure is slightly worse than the equivalent circuit using vacuum tubes and transformers, in practice the over‐all performance is superior. View full abstract»

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  • Growth of Large Diameter Silicon and Germanium Crystals by the Teal‐Little Method

    Page(s): 535 - 540
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    The equipment and techniques used to grow 6‐in. diam silicon and germanium crystals are described, and the effect of spin, radiation, and mode of heating on crystal growth from a melt is discussed. View full abstract»

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  • Preparation of Diffusion Couples by Cathodic Sputtering

    Page(s): 541 - 543
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    Apparatus and techniques are described for preparing metal diffusion couples by cleaning the sample surface and depositing an isotope layer by cathodic sputtering. View full abstract»

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  • Mechanical Analog Computer for Solving the Axial Equations of Motion during Bunching in Linear Electron Accelerators

    Page(s): 543 - 547
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    A mechanical analog computer is described which is suitable for the exploratory study of linear accelerator designs in the bunching region, at least in problems of the kind encountered in electron accelerators, where bunching is accomplished in comparatively short intervals and with relatively few phase oscillations. Particle phase is observed directly from a resolver; and particle momentum, particle velocity, and accelerating wave phase velocity are observed simultaneously as linear magnitudes whose relative change during calculation provides useful intuitive guidance in the choice of accelerator parameters. Some calculations are reported which were made with a rough apparatus capable of ∼5% accuracy. View full abstract»

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  • Versatile and Sensitive Vibrating‐Sample Magnetometer

    Page(s): 548 - 557
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    A vibrating‐sample magnetometer, which measures the magnetic moment of a sample when it is vibrated perpendicularly to a uniform magnetizing field, is described. With this instrument, changes as small as 10-5 to 10-6 emu have been detected, and a stability of one part in 104 has been attained. In addition to permitting convenient measurements in the usual laboratory electromagnet, this instrument eliminates or minimizes many sources of error found in other methods. It is simple, inexpensive, and versatile, yet permits precision magnetic moment measurements to be made in a uniform magnetizing field as a function of temperature, magnetizing field, and crystallographic orientation. The mechanical design and detailed operating characteristics are presented. Applications and limitations of the method are outlined. View full abstract»

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  • Low‐Temperature Adiabatic Calorimeter with Automatic Shield Control

    Page(s): 557 - 559
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    The design and operation of an adiabatic low‐temperature calorimeter employing a somewhat different design of automatic shield control is described. Thermocouple difference is sensed by a dc μv amplifier, which is followed in the circuit by a recorder‐controller and a Leeds & Northrup Series 60 (current adjusting type) control unit. The output of the latter is used to control the voltage across the shield heaters through a Westinghouse ``Magamp'' saturable reactor. This design has been used successfully with a conventional low‐temperature adiabatic calorimeter (50‐ml sample size). In most cases the recorder showed no variation from zero (±0.002°) during heating and equilibrating periods, while momentary disturbance at ``on'' and ``off'' was less than 0.05°. View full abstract»

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  • Cryostat for Ferrimagnetic Resonance Experiments

    Page(s): 559 - 561
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    A cryostat is described consisting of a glass vacuum insulated inner vessel and a Styrofoam outer vessel. The inner Dewar narrows to a fine tip containing the sample at its lower extremity where it protrudes through the outer vessel, and extends into a microwave cavity. View full abstract»

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  • Preconversion of Oxide Cathodes

    Page(s): 562 - 565
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    It has been shown that the organic contaminants released during the carbonate and binder decomposition of conventional oxide cathodes can be eliminated if the cathode is preconverted in a separate envelope and is then transferred to the final tube as the alkaline‐earth hydroxide. The technique used in accomplishing this lends itself readily to many laboratory applications where tube cleanliness is important. Specific applications to thermionic and secondary emission studies are described. The results indicate a definite reduction in the contamination of tube components and show improved cathode characteristics. View full abstract»

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  • Technique for Measurement of Specific Volume of Liquids at High Pressures and Temperatures

    Page(s): 565 - 567
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    A novel method is described for measuring specific volume of liquids at high temperatures and pressures. The displacement of the two ends of a continuous column of the liquid is measured. One end is maintained at high temperature and pressure while the other is at normal conditions. View full abstract»

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  • High‐Precision Measurement of the Average Value of a Magnetic Field over an Extended Path in Space

    Page(s): 568 - 575
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    A nuclear magnetic resonance experiment which may be used to measure with high precision the average value of a magnetic field over an extended path in space is described. The nuclei, contained in a flowing liquid, are excited at one point and detected at another downstream from the point of excitation. Under proper conditions the average value of the magnetic field along the flow path between points of excitation and detection may be obtained therefrom. Some experimental criteria which must be met in order that this average be correctly obtained are discussed. The results of such an experiment are presented. Although the accuracy of the measurement may be somewhat less than this, line widths of 1 part in 107 have been obtained. View full abstract»

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  • Thermostat Control by Resistance Thermometer

    Page(s): 575 - 576
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    By intercepting on a selenium cell part of the light beam from the galvanometer in the bridge circuit of the resistance thermometer used to measure bath temperature, a signal is obtained which is used to trigger a photo‐relay via a secondary galvanometer. The photo‐relay controls the heating current in the thermostat. Design of the selenium cell mounting and accompanying circuits are described. The device holds a 50‐gal thermostat to 25° within a hunting amplitude of 0.002°C. View full abstract»

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  • Anisotropic Field Plotting in the Electrolytic Tank

    Page(s): 577 - 578
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    A method of solving anisotropic problems in the electrolytic tank has been devised. The resistance of the electrolyte along the two axes is caused to be different by means of a large number of vertical insulating strips. View full abstract»

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  • Low‐Temperature Thermal Noise Thermometer

    Page(s): 578 - 580
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    The design for a relatively simple noise thermometer for use at low temperatures is presented. This thermometer has been used to measure temperatures as low as the lambda point of liquid helium with a least accuracy of 10%. Some of the properties of thermal noise are discussed. View full abstract»

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  • Single‐Crystal Automatic Neutron Diffractometer

    Page(s): 581 - 585
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    An automatic neutron diffraction system for measuring the intensities of all accessible reflections in a zone is described. Crystal and counter setting information is supplied to the instrument on five‐channel punched paper tape. The angular settings are measured by means of analog‐to‐digital converters. All angle information is printed out digitally, together with the diffraction intensity information. View full abstract»

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  • Current Noise and Nonlinearity in Pyrolytic Carbon Films

    Page(s): 586 - 590
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    Measurements of the current noise and nonlinearity in the pyrolytic carbon films of 322 resistors are given. The resistances and the dimensions of the films both varied over a wide range. It is demonstrated that when the dimensions of the films are taken into account their noise and nonlinearity are highly correlated: the noise in a given film can therefore be used to estimate the nonlinearity, and conversely. In many groups of resistors of the same type the resistance change with a given applied voltage varied among resistors by a factor of more than 10, and the noise power for a given current through the resistors varied by a factor of more than 100. In the measurements of nonlinearity the resistance changes were often very small, and, consequently, were easily masked by temperature effects. A measurement method was employed in which the resistors were placed in a balanced bridge, a short high‐voltage pulse was applied to the bridge, and the resistance change was determined from the bridge output voltage. With this technique it was possible to measure resistance changes of the order of 20 ppm with an accuracy of ±3 ppm. View full abstract»

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  • Rubber Sheet Model Studies

    Page(s): 591 - 592
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    First Page of the Article
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  • Metal‐Glass Vacuum Seal for Use at Low Temperatures

    Page(s): 594 - 595
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  • Transistorized Commutator

    Page(s): 595 - 597
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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