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Review of Scientific Instruments

Issue 10 • Date Oct 1957

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Displaying Results 1 - 25 of 34
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Neutron Time‐of‐Flight Spectrometer for Use with the Harwell 110‐Inch Cyclotron

    Page(s): 749 - 757
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    A description is given of a neutron time‐of‐flight spectrometer used for energies up to 140 Mev. A 20‐mμsec neutron pulse is obtained by electrostatic deflection of the internal proton beam of the cyclotron onto a thick aluminum target. By timing the neutrons over a 26‐meter flight path an energy spread of 4.2% at 15 Mev is obtained rising to 14% at 140 Mev. The advantages of the technique and possible improvements are discussed. View full abstract»

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  • Gas Scintillation Counter

    Page(s): 758 - 764
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    A systematic investigation of the optimum conditions for the design and operation of a gas scintillation counter has been made. The gases studied were xenon, krypton, argon, helium, and various gas mixtures. Both a 6292 and a quartz window K1306 phototube were used with and without quaterphenyl as a wavelength shifter. Under optimum conditions an energy spread of less than 4% is obtainable for the Po210 α particles. The application of the gas scintillation counter as a fast ``slow neutron detector,'' using the reaction B10(n,α)Li7, and its usefulness as a fast fission detector have been examined and discussed. View full abstract»

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  • Response of an Anthracene Scintillation Counter to 10–120 kev Electrons

    Page(s): 765 - 767
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    Monoenergetic electrons from an electron accelerator were incident on a thin bare anthracene crystal centered on the photocathode of a RCA 6199 photomultiplier. A linear amplifier and single channel analyzer were used to obtain a pulse height distribution at each energy. The pulse height at the maximum of the distribution is a linear function of the incident electron energy with intercepts of 4.5 and 3.5 kev for 0.060‐ and 0.011‐in. thick crystals, respectively. The pulse‐height distribution could be fitted well with a Gaussian. The data indicate a linear relationship between the square of the full width of the pulse‐height distribution at 1/e of the maximum and the electron energy. The average amount of electron energy absorbed in the crystal required to produce a photoelectron at the photocathode is 1.47±0.09 kev/photoelectron for the 0.060‐in. crystal and 1.32±0.13 kev/photoelectron for the 0.011‐in. crystal. View full abstract»

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  • Liquid Tin Solution Calorimeter for Measuring Heats of Formation of Alloys

    Page(s): 767 - 773
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    A liquid tin solution calorimeter has been constructed for determining the heats of formation of alloy phases from the heats of solution of the alloys and of the pure component metals in liquid tin. The design of the calorimeter is presented, and the experimental procedures and calculation methods are described and illustrated with data from representative runs. These indicate that heats of formation of alloy phases may be determined with an average uncertainty of about ±50 cal/g atom. View full abstract»

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  • Apparatus for Measuring Very Low Interfacial Tensions

    Page(s): 774 - 777
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    A pendent drop apparatus for rapidly measuring very low interfacial tensions is described. Interfacial tensions as low as 0.001 d/cm have been measured at 25°C in a water‐oil system. These measurements were made possible through the combined use of small drop‐forming tips, long working distance objectives, electronic flash illumination and Polaroid Land film. Examples of measurements on water‐oil systems are given. The apparatus is designed to provide interfacial tension data as a function of temperature. In addition, the method permits the measurement of interfacial tension as a function of the age of the interface. View full abstract»

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  • Second‐Order Aberrations in a Modified Mattauch‐Type Mass Spectrometer

    Page(s): 777 - 779
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    Control of the energy‐dependendent second‐order aberrations in a Mattauch‐type mass spectrometer is made difficult by the absence of a real image between the object slit and the focal plane in this resolving system. By curving the boundary of the magnetic field and by choosing appropriate relations between the magnetic field boundary curvature and the other parameters involved, it is possible to make both of the energy‐dependent second‐order aberration coefficients vanish simultaneously while retaining the advantages peculiar to this resolving system. View full abstract»

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  • Spin Echo Apparatus

    Page(s): 780 - 789
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    A spin echo apparatus is described which can measure nuclear relaxation effects for narrow resonances, convection and diffusion effects, and in some cases, chemical splittings in liquids. This apparatus is assembled mostly from commercial equipment. Commercial units used are identified, and circuit diagrams are given for specially constructed apparatus. Sufficient design information is given to make possible substitutions and improvements to suit the needs of particular projects. Necessary adjustment procedures are described and the relations of instabilities in the apparatus to instabilities in its components are treated. View full abstract»

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  • Precision Thermal‐Conductivity Gas Analyzer Using Thermistors

    Page(s): 789 - 792
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    The characteristics of a thermal‐conductivity gas‐analyzer unit employing thermistors as sensing elements are analyzed theoretically. It is shown that, as a consequence of the fact that thermistors have a negative temperature coefficient of resistance, the sensitivity of the instrument as a function of bridge current exhibits a maximum. The dependence of zero stability on current and cell temperature is approximately related to differences in resistance, temperature coefficient of resistance, and geometry of the reference and sample thermistors. An apparatus suitable for precise trace analyses is described and results obtained with it are presented. It is suggested that the widespread lack of faith in the inherent stability of thermistors for analysis applications is not justified, and has probably been due to insufficient care with current and temperature control. View full abstract»

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  • Optical Autocorrelation Measurement of Two‐Dimensional Random Patterns

    Page(s): 793 - 797
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    A function of two independent variables can be regarded as an image. Using a novel optical technique, the autocorrelation coefficient of such a function is formed as another image. The working principle of the instrument is based on geometrical optics alone, however, the basic equipment was further improved by adopting electronic scanning techniques. Test plates with prescribed autocorrelation functions were made, the equipment was experimentally tested, and was found to operate to satisfaction. View full abstract»

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  • Hermetic Seal for Ferrites

    Page(s): 797 - 799
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    The effects of moisture on the electrical properties of ferrites indicate that the electrical characteristics are adversely affected. The problem concerning the methods for the prevention of moisture absorption by the ferrite element has been solved by coating the surface of the ferrite with a thin layer of glass, thereby effecting a hermetic seal. It was found necessary, however, to first sinter a thin layer of finely ground ferrite surface to reduce porosity, which prevents the flowed glass from being absorbed into the porous ferrite. The glass seal has been shown to have good mechanical and thermal shock properties and yet has negligible effect on the electrical properties of the ferrite. View full abstract»

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  • Coils for the Production of High‐Intensity Pulsed Magnetic Fields

    Page(s): 799 - 807
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    The problem of producing extremely high magnetic fields is briefly reviewed in the light of modern technique. The design, performance, and application of a pulsed-field system capable of more than 750 000 gauss at room temperature is described. The coil comprises a suitably supported, machined, beryllium-copper, helix having an inside diameter of 316in. and a length of about ½ in.; it is connected directly to a 2000 μf, 3 kv bank of surge capacitors by means of a triggered-spark gap. The discharge is oscillatory with a half-period of 120 μsec. Detailed design data and performance characteristics are presented for a large range of similarly constructed coils which afford increased volume and field uniformity at a sacrifice in field intensity. A coil providing transverse access to the field and one suitable for operation in liquid helium are also described. Characteristics of less durable coils constructed of a single strip of conductor are discussed. Brief comments on applications to a broad range of solid-state experiments and some inherent limitations are presented. Finally, the production of modulated pulsed fields, unidirectional fields, and the feasibility of extending the pulse duration are discussed. View full abstract»

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  • Wide‐Band Balun Transformer

    Page(s): 808 - 815
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    This paper describes a wide‐band balun transformer which was developed for use with a 200‐Mc band‐width oscilloscope deflection amplifier. The balun has a band width extending from below 50 kc to above 500 Mc. Input impedance data and pulse responses are presented. One balun coil can be used alone as a passive wide‐band pulse inverter. View full abstract»

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  • Mach‐Zehnder Interferometer for Diffusion Measurements in Volatile Liquid Systems

    Page(s): 816 - 821
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    The constructional details and method of operation of an optical diffusiometer are described. The apparatus makes use of a Mach‐Zehnder‐type interferometer, which has not previously been employed for the study of diffusion in liquid systems. The apparatus has been developed for the study of liquid systems whose components are volatile organic solvents. For this purpose a diffusion cell of novel design has been constructed. The diffusiometer has been checked using the system sucrose‐water at 25°C and values of the diffusion coefficient found over six determinations are within 0.2% of the reported value. With volatile liquids, the accuracy claimed is only 1%, although duplicates usually agreed to within 0.5%. View full abstract»

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  • Automatic Plotting of Probe Curves

    Page(s): 822 - 823
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    A simple circuit for automatic plotting of probe curves and diode voltage‐current curves by means of commercial x‐y curve plotters is described. Errors involved and corrections to be applied are discussed. The design of an electrolytic voltage divider for varying the probe voltage is given. View full abstract»

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  • Criterion for Vacuum Sparking Designed to Include Both rf and dc

    Page(s): 824 - 826
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    An empirical relation is presented that describes a boundary between no vacuum sparking and possible vacuum sparking. Metal electrodes and rf or dc voltages are used. The criterion applies to a range of surface gradient, voltage, gap, and frequency that extends over several orders of magnitude. Current due to field emission is considered necessary for sparking, but—in addition—energetic ions are required to initiate a cascade process that increases the emitted currents to the point of sparking. View full abstract»

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  • Method for the Generation of Very Fast Light Pulses

    Page(s): 826 - 827
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    A method is described in which a visible or infrared light beam is repeatedly reflected between a rotating and stationary mirror system. The resulting sweep speed is proportional to the number of such reflections. Light pulses of 4×10-8 sec duration were measured. A considerable increase in the sweep speed appears feasible. Various applications of the system are mentioned. View full abstract»

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  • New Method for Measuring Linear Compressibility of Solids

    Page(s): 828 - 829
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    An apparatus is described for measuring linear compressibility of rods and tubes under hydrostatic pressures to 4000 kg/cm2 and temperatures to 260°C. The measurements are made by means of a linear‐differential transformer located on the outside of the nonmagnetic high‐pressure container. The differential transformer makes it possible to determine the position of a small iron cylinder affixed to the sample. Compressibility of vitreous silica determined by this method was obtained as -ΔV/V=p(26.43–0.0049t) ×10-7+p2(21.8–0.040t)×10-12; compressibility is expressed in relative volume change, p in kg/cm2 and t in °C. View full abstract»

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  • Space Charge Neutralization in the Ionizing Beam of a Mass Spectrometer

    Page(s): 830 - 832
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    A mass spectrometer ion source structure and its mode of operation are described by which the resolved ion current produced from a given gas concentration in the ionizing chamber can be made one to two orders of magnitude larger than is usually obtained in conventional mass spectrometer ion sources. This structure employs an ionizing chamber whose walls are electrically insulated from each other so they can operate at separate potentials which permit positive ions to be trapped in the ionizing electron beam. The resulting partial neutralization of the electronic space‐charge allows the use of a higher current density ionizing beam and also increases the effective ionizing volume from which a stable ion current can be extracted. Inherently this mode of operation produces more fragmentation species because it increases the probability of several successive electron impacts on each particle. View full abstract»

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  • Improved Concave Grating Mounting

    Page(s): 833 - 834
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  • Laboratory‐Scale Solids Metering Device

    Page(s): 837 - 838
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    First Page of the Article
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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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Editor
Albert T. Macrander
Argonne National Laboratory